(c) The Computer Language Company Inc. 1981-1993 All rights reserved. Ver. 6.21, 2nd Quarter 1993 REMEMBER... USE ACRONYMS!  If you can't find a term, look up its acronym. Try ISO, rather than International Standards Organization.  BE SURE TO LOOK UP LESSONS!  浜様様様様様様様様様様様様様様様様様様様様様様様融  THIS VERSION OF THE GLOSSARY HAS BEEN  DESIGNED FOR USE ON A BBS  藩様様様様様様様様様様様様様様様様様様様様様様様夕  敖陳陳陳陳 Beginning of Glossary Text 陳陳陳陳陳朕 A/D converter (Analog to Digital Converter) Device that converts continuously varying analog signals from instruments that monitor such conditions as movement, temperature, sound, etc., into binary code for the computer. It may be contained on a single chip or can be one circuit within a chip. See modem and codec. Contrast with D/A converter. A/UX Apple's version of UNIX for the Macintosh. It is based on AT&T's UNIX System V with Berkeley extensions. A20 PC address line that points beyond one megabyte. For downward compatibility with 8086/8088s, this line is gated in 286s and up and is controlled by circuitry on the motherboard. When disabled, it keeps the machine in Real Mode (under 1MB). When enabled, the CPU can address beyond 1MB (Protected Mode). The HMA (high memory area) can also be accessed in Real Mode when this line is turned on. There are 32 address lines on a 386DX (A0-A31), 24 on a 386SX and 286 (A0-A23). A: Designation for the first floppy disk drive in a PC. ABC (Atanasoff-Berry Computer) First electronic digital computer. Completed in 1942 by Iowa State Professor John Atanasoff and graduate student Clifford Berry, it embodied the input, memory and arithmetic unit of future computers. John Mauchly, cobuilder of the ENIAC, visited Atanasoff in 1940 and corresponded with him. Although Eckert and Mauchly are considered the creators of the first electronic digital computer, Atanasoff and Berry are acknowledged contributors. In 1990, nearly 50 years after his invention, 87-year-old Atanasoff was awarded the National Medal of Technology. abend (ABnormal END) Also called a crash or bomb, occurs when the computer is presented with instructions or data it cannot recognize or the program is reaching beyond its protective boundary. It is the result of erroneous software logic or hardware failure. When the abend occurs, if the program is running in a personal computer under a single-task (one program at a time) operating system, such as DOS, the computer locks up and has to be rebooted. Multitasking operating systems with memory protection halt the offending program allowing remaining programs to continue. If you consider what goes on inside a computer, you might wonder why it doesn't crash more often. A mainframe's memory can easily contain over 300 million storage cells (bits). Within every second, millions of these cells change their state from uncharged to charged to uncharged. If only one cell fails, the computer can abend. ABI (Application Binary Interface) Specification for a particular hardware platform and operating system. It details the machine language of the CPU family as well as the calls between the application and the operating system. abort (1) To exit a function or application without saving any data that has been changed. (2) To stop a transmission. About the Glossary In 1981, "The Computer Glossary" started out as a 330-term compendium to Alan Freedman's computer literacy seminars. By 1989, the 4th edition contained 3,500 terms and 400 illustrations and won the "Best Reference Book of the Year" award from Computer Book Review. The 5th edition was introduced in both print and electronic form. The 6th edition contains over 5,400 terms. This disk version has more than 6,000 terms and is updated quarterly. To upgrade, look up "Order Form."  USE ACRONYMS! To save index space, most terms in this Glossary are entered by their acronyms. Look up ZBR, not zone bit recording.  A Note from the Author My goal is to keep the Glossary informative, interesting, accurate and timely. I invite your suggestions on new and existing terms. Please write or fax me. Alan Freedman THE COMPUTER LANGUAGE COMPANY 5521 State Park Road Point Pleasant, PA 18950-0265 FAX 215/297-8424 above the line See "IBM COBOLs" in COBOL. ABR (AutoBaud Rate detect) Analysis of the first characters of a message to determine its transmission speed and number of start and stop bits. absolute In programming, a mathematical function that always returns a positive number. For example, ABS(25- 100) yields 75, not -75. absolute address Explicit identification of a memory location, peripheral device, or location within a device. For example, memory byte 107,443, disk drive 2 and sector 238 are absolute addresses. The computer uses absolute addresses to reference memory and peripherals. See base address and relative address. absolute vector In computer graphics, a vector with end points designated in absolute coordinates. Contrast with relative vector. absolute zero Theoretical temperature at which molecular activity ceases (-273.15 C, -459.67 F). abstract data type User-defined data type in object-oriented programming. See object-oriented programming. AC (Alternating Current) Common form of electricity from power plant to home/office. Its direction is reversed 60 times per second in the U.S.; 50 times in Europe. Contrast with DC. accelerator Key combination used to activate a task. See accelerator board. accelerator board Add-in board that replaces the existing CPU with a higher performance CPU. See graphics accelerator. acceptance test Test performed by the end user to determine if the system is working according to the specifications in the contract. access To store data on and retrieve data from a disk or other peripheral device. See access arm and access method. access arm Mechanical arm that moves the read/write head across the surface of a disk similar to a tone arm on a phonograph. The access arm is directed by instructions in the operating system to move the read/write head to a specific track on the disk. The rotation of the disk positions the read/write head over the required sector. access charge Charge imposed by a communications service or telephone company for the use of its network. access code (1) Identification number and/or password used to gain access into a computer system. (2) Number used as a prefix to a calling number in order to gain access to a particular telephone service. access line Line from a customer site to a telephone company's central office. access method Software routine that is part of the operating system or network control program which performs the storing/retrieving or transmitting/receiving of data. It is also responsible for detecting a bad transfer of data caused by hardware or network malfunction and correcting it if possible. Tape Access Methods With tapes, the sequential access method is always used for storing data, which places the next block of data after the previous one. Disk Access Methods For disks, indexed access methods are widely used to keep track of records and files. The index is a table of contents for each file or each record within the file. The sequential method is also used when retrieval of individual records is not required. The indexed sequential method, or ISAM, combines both methods by providing an index that is kept in sequential order. For fastest retrieval, the direct access method uses a formula to convert the record's identifying field, such as account number, into a physical storage address. Communications Access Methods Communications access methods, such as IBM's TCAM and VTAM, transfer data between a host computer and remote terminals. These routines prepare the data for transmission by placing the data into frames with appropriate control codes. These methods reference layers 3, 4 and 5 of the OSI model. LAN access methods, such as CSMA/CD (Ethernet) and token passing (Token Ring), transfer data to and from connected computers on the network. These methods reference layers 1 and 2 of the OSI model. access time (1) Memory access time is how long it takes for a character in memory to be transferred to or from the CPU. In a personal computer, fast RAM chips have an access time of 70 nanoseconds or less. (2) Disk access time is an average of the time it takes to position the read/write head over the requested track. Fast personal computer hard disks have access times of 18 milliseconds or less. Mainframe disks can be less than one millisecond. This is a common speed measurement, but disk performance is influenced by channel speed (transfer rate), interleaving and caching. account number Number assigned to an employee, customer, vendor or product for identification. Although it may contain only numeric digits, it is often stored as a character field, so that parts of the account number can be searched independently. For example, the number could contain a territory code, and records could be selected by state or region. accounting machine Early office machine used to compute and prepare invoices and payroll, etc., using magnetic stripe ledger cards or punched cards. accumulator Hardware register used to hold the results or partial results of arithmetic and logical operations. ACD (Automatic Call Distribution) Routing of an incoming telephone call to the next available operator. ACE (Advanced Computing Environment) Open standard (announced 1991) based on Intel 386 and MIPS R3000/R4000 hardware and Windows NT and ACE UNIX operating systems. ACE was conceived to allow users to migrate from Intel-based PCs to MIPS RISC architecture, which is licensed to several manufacturers. For information, contact ACE Program Manager at MIPS, 408/524-7000. ACF (Advanced Communications Function) Official product line name for IBM SNA programs, such as VTAM (ACF/VTAM), NCP (ACF/NCP), etc. ACK (ACKnowledgment code) Communications code sent from a receiving station to a transmitting station to indicate that it is ready to accept data. It is also used to acknowlege the error-free receipt of transmitted data. Contrast with NAK. ACM (Association for Computing Machinery) Membership organization founded in 1947 dedicated to advancing the arts and sciences of information processing. In addition to awards and publications, ACM also maintains special interest groups (SIGs) in the computer field. Address: 1515 Broadway, New York, NY 10036, 212/869-7440. acoustic coupler Device that connects a terminal or computer to the handset of a telephone. It contains a shaped foam bed that the handset is placed in, and it may also contain the modem. ACS (Asynchronous Communications Server) Communications server that manages a pool of modems. It directs outgoing messages to the next available modem and directs incoming messages to the appropriate workstation. active addressing LCD technology that improves passive matrix screen contrast. See LCD. active matrix LCD technology used in color screens for laptops. See LCD. active star Network topology that provides regeneration of signals in the central hub. Contrast with passive star. See hub. ACTOR Object-oriented programming language for PCs from The Whitewater Group Inc., Evanston, IL. It runs under Windows and has a Pascal-like syntax to ease the transition to object-oriented languages. actuator Mechanism that causes a device to be turned on or off, adjusted or moved. The component that moves the head assembly on a disk drive or an arm of a robot is called an actuator. AD/Cycle (Application Development/Cycle) SAA-compliant software from IBM that provides a system for managing systems development. It provides a structure for storing information about all phases of an information system including systems analysis and design, database design and programming. ad hoc query Non-standardized inquiry. A query composed to answer a question as the need arises. Ada High-level programming language developed by the U.S. Department of Defense along with the European Economic Community and many other organizations. It was designed for embedded applications and process control but is also used for logistics applications. Ada is a Pascal-based language that is very comprehensive. Ada was named after Augusta Ada Byron (1815- 1852), Countess of Lovelace and daughter of Lord Byron. She was a mathematician and colleague of Charles Babbage, who was developing his Analytical Engine. Some of her programming notes for the machine have survived, giving her the distinction of being the first documented programmer in the world. The following Ada program converts Fahrenheit to Celsius: with Text_IO; procedure Convert is  package Int_IO is new Text_IO.Integer_IO(Integer);  Fahrenheit : Integer; begin  Text_IO.Put_Line("Enter Fahrenheit");  Int_IO.Get(Fahrenheit);  Text_IO.Put("Celsius is ");  Int_IO.Put((Fahrenheit-32) * 5 / 9);  Text_IO.New_Line; end Convert;  ADABAS DBMS from Software AG, Reston, VA, for IBM mainframes, VAXes, various UNIX platforms and OS/2 PCs. It is an inverted list DBMS with relational capabilities. A 4GL called NATURAL, text retrieval, GIS processing, SQL and distributed database functions are also available. Introduced in 1969, it was one of the first DBMSs. ADAPSO See ITAA. adapter Device that allows one system to connect to and work with another. Display adapters and network adapters are really controllers, not adapters. See host adapter and expansion bus. adaptive compression Data compression technique that dynamically adjusts the algorithm used based on the content of the data being compressed. adaptive equalization Transmission technique that dynamically adjusts its modulation method based on the quality of the line. adaptive routing Ability to select a new communications path to get around heavy traffic or a node or circuit failure. ADB (Apple Desktop Bus) Macintosh communications port for keyboards, mice, trackballs, graphics tablets and other input devices. ADC See A/D converter. ADCCP (Advanced Data Communications Control Procedure) ANSI communications protocol that is similar to the SDLC and HDLC protocols. add-in, add-on Refers to hardware modules, such as printed circuit boards, that are designed to be plugged into a socket within the computer. adder Elementary electronic circuit that adds the bits of two numbers together. address (1) Number of a particular memory or peripheral storage location. Like post office boxes, each byte of memory and each disk sector has its own unique address. Programs are compiled into machine language, which references actual addresses in the computer. (2) As a verb, to manage or work with. For example, "the computer can address 2MB of memory." address bus Internal channel from the CPU to memory across which the addresses of data (not the data) are transmitted. The number of lines (wires) in the address bus determines the amount of memory that can be directly addressed as each line carries one bit of the address. For example, the 8088 CPU has 20 address lines and can address 1,048,576 bytes. The 68020 has 32 address lines and can address four gigabytes. Various swapping and switching techniques can be added to the hardware that allow a computer to use more memory than is directly addressable by its address bus. See EMS.  敖陳陳陳陳朕 敖陳陳陳陳朕  団陳陳1陳陳調  CPU 団陳陳2陳陳調 RAM  団陳陳4陳陳調  団陳陳8陳陳調  団陳16陳陳調  団陳32陳陳調  団陳64陳陳調  団陳128陳陳調  Address Bus address mode Method by which an instruction references memory. An indexed address is modified by the contents of an index register before execution. An indirect address points to another address. Ultimately, in order to do any actual processing, the instruction must derive real, or absolute addresses, where the required data is located. address register High-speed circuit that holds the addresses of data to be processed or of the next instruction to be executed. address space Total amount of memory that can be used by a program. It may also refer to virtual memory, which includes memory and disk. For example, the 386 can address 4GB of physical memory and 64TB of virtual memory. address translation Transforming one address into another. For example, assemblers and compilers translate symbolic addresses into machine addresses. Virtual memory systems translate a virtual address into a real address. addressable cursor Screen cursor that can be programmed to move to any row or column on the screen. ADE (Application Development Environment) IBM approach for developing applications that will run in all SAA environments. The development software is client/server based; the main functions reside in the host. ADF (Application Development Facility) IBM programmer- oriented mainframe application generator that runs under IMS. ADMD (ADministrative Management Domain) Public e-mail service. See X.400. Adobe fonts See PostScript. Adobe Type Manager PostScript font utility for the Macintosh and Windows from Adobe Systems. It scales Type 1 fonts into screen fonts and prints them on non-PostScript dot matrix and HP laser printers. Rather than downloading the font to the printer, it sends a bitmap of the entire page of text to the printer. ATM technology is built into OS/2 and NeXTstep, and was originally developed to provide WYSIWYG screen fonts for the Mac. See PostScript. ADP (1) (Automatic Data Processing) Synonymous with data processing (DP), electronic data processing (EDP) and information processing. (2) ADP, Inc. Nationwide computer services organization that also provides international communications services. ADP system (Automatic Data Processing system) Same as computer system. ADPCM (Adaptive Differential PCM) Advanced PCM technique that converts speech to 32 or 16 Kbits/sec. Instead of coding an absolute measurement at each sample point, it codes the difference between samples and can dynamically switch the coding scale to compensate for variations in amplitude and frequency. ADRS (A Departmental Reporting System) IBM mainframe report writer. ADS (AutoCAD Development System) Allows C routines to be run from within AutoCAD. ADT (Asynchronous Data Transfer) Transmission technique used in ISDN PBXs that dynamically allocates bandwidth. See also abstract data type. AdvanceNet Network strategy from HP that incorporates OSI and SNA network architectures. In 1983, HP was the first major vendor to make a commitment to OSI. AdvanceNet also supports MAP, Starlan 10, Ethernet and X.25 packet switching networks. AFE (Apple File Exchange) Macintosh utility that converts data files between Mac and PC formats. It also includes a file translator between IBM's DCA format and MacWrite; however, MacLink Plus Translators can be used for additional capability. AFIPS (American Federation of Information Processing Societies Inc.) Organization founded in 1961 dedicated to advancing information processing in the U.S. It was the U.S. representative of IFIP and umbrella for 11 membership societies. Dissolved in 1990 and superseded by FOCUS. AFP (AppleTalk Filing Protocol) Client/server protocol used in AppleTalk communications networks. In order for non-Apple networks to access data in an AppleShare server, their protocols must translate into the AFT language. AFS Distributed file system for large, widely-dispersed UNIX networks from Transarc Corp., Pittsburgh, PA. It is noted for its ease of administration and expandability and stems from Carnegie-Mellon's Andrew File System. agent Software routine that waits in the background and performs an action when a specified event occurs. For example, agents could transmit a summary file on the first day of the month or monitor incoming data and alert the user when a certain transaction has arrived. See workflow automation. AI (1) (Artificial Intelligence) Devices and applications that exhibit human intelligence and behavior including robots, expert systems, voice recognition, natural and foreign language processing. It also implies the ability to learn or adapt through experience. In the future, everything we now know and think about a computer will change. By the turn of the century, you should be able to converse with the average computer. Future systems will ask you what help you need and automatically call in the appropriate applications to aid you in solving your problem. In the 1990s, the AI buzzword will be abused to the hilt as it will refer to any and all advancements. However, the acid test of AI was defined in the 1940s by the English scientist, Alan Turing, who said, "A machine has artificial intelligence when there is no discernible difference between the conversation generated by the machine and that of an intelligent person." Note: The term intelligence refers to processing capability; therefore, every computer is intelligent. But, artificial intelligence implies human-like intelligence. An ironic twist in terminology. (2) (Application Interface) Programming interface for IBM's 8514/A. AIIM (Assn. for Information and Image Management) Membership organization that promotes and advances the development of systems that store, retrieve, integrate and manage images of documents. Founded in 1943, it provides periodicals, industry studies, educational programs and expositions. Address: 1100 Wayne Ave., Suite 1100, Silver Spring, MD 20910, 301/587-8202. AIX (Advanced Interactive eXecutive) IBM's version of UNIX for 386-based PS/2s, RTs and mainframes. It is based on AT&T's UNIX System V with Berkeley extensions. ALC (Assembly Language Coding) Generic term for IBM mainframe assembly languages. Aldus Persuasion Desktop presentation program for the Mac from Aldus Corp., Seattle, WA. It is used to create output for overheads, handouts, speaker notes and film recorders and provides sophisticated transition features (fades, gravel, swipes, etc.). algebraic expression One or more characters or symbols associated with algebra; for example, A+B=C or A/B. ALGOL (ALGOrithmic Language) High-level compiler language that was developed as an international language for the expression of algorithms between people and between people and machines. ALGOL-60 (1960) was simple and widely used in Europe. ALGOL-68 (1968) was more complicated and scarcely used, but was the inspiration for Pascal. The following example changes Fahrenheit to Celsius:  fahrenheit  begin  real fahr;  print ("Enter Fahrenheit ");  read (fahr);  print ("Celsius is ", (fahr-32.0) * 5.0/9.0);  end  finish algorithm Set of ordered steps for solving a problem, such as a mathematical formula or the instructions in a program. alias (1) Alternate name used for identification, such as for naming a field or a file. (2) Phony signal created under certain conditions when digitizing voice. aliasing In computer graphics, the stair-stepped appearance of diagonal lines. See anti-aliasing. All-In-1 Office systems software from Digital for the VAX series. It provides a menu to all of Digital's office systems programs, including word processing, appointment calendars and e-mail systems. allocate To reserve a resource such as memory or disk. See memory allocation. Alpha Family of advanced RISC-based, 64-bit CPUs from Digital. First model introduced early 1992 is the 150MHz 21064-AA, considered equivalent to a Cray-1 on a single chip. Alpha AXP computer systems use the Alpha CPU and run under Windows NT, OpenVMS and OpenOSF operating systems. alpha channel High-order eight bits in a 32-bit graphics pixel used as a separate layer to mask an area for editing or creating special effects (textures, montages, etc.). alpha test First test of newly developed hardware or software in a laboratory setting. The next step is beta testing with actual users. alphageometric See alphamosaic. alphamosaic Very-low-resolution display technique that uses elementary graphics characters as part of its character set. alphanumeric Use of alphabetic letters mixed with numbers and special characters as in name, address, city and state. The text you're reading is alphanumeric. Altair 8800 Microcomputer kit introduced in 1974 from Micro Instrumentation and Telemetry Systems. It sold for $400 and used an 8080 microprocessor. In 1975, it was packaged with Microsoft's MBASIC. Although computer kits were advertised earlier by others, an estimated 10,000 Altairs were sold, making it the first commercially successful microcomputer. alternate routing Ability to use another transmission line if the regular line is busy. AlterNet See UUNET. Alto Xerox personal computer that pioneered the mouse/icon environment. Developed at PARC, it was the progenitor of Xerox's Star and Apple's Lisa and Mac. Designed in 1973 with 128K RAM, 608x808 screen, 2.5MB removable hard disk and built-in Ethernet. About 1,000 Altos were in use by 1979. ALU (Arithmetic Logic Unit) High-speed CPU circuit that does calculating and comparing. Numbers are transferred from memory into the ALU for calculation, and the results are sent back into memory. Alphanumeric data is sent from memory into the ALU for comparing. The results are tested by GOTOs; for example, IF ITEMA EQUALS ITEMB GOTO UPDATE ROUTINE. AM (Amplitude Modulation) Transmission technique that blends the data signal into a carrier by varying (modulating) the amplitude of the carrier. See modulate. AM386 Low-power, 386-compatible chips from Advanced Micro Devices. AM386DXL chips are Intel 386DX compatible, and AM386SXL chips are Intel 386SX compatible. ambient Surrounding. For example, ambient temperature and humidity are atmospheric conditions that exist at the moment. Amdahl (Amdahl Corp., Sunnyvale, CA) Computer manufacturer founded in 1970 by Gene Amdahl, chief architect of the IBM System/360. In 1975, Amdahl installed its first IBM-compatible mainframe, the 470/V6. Although not the first to make IBM- compatible mainframes, it succeeded where others failed. Today, Amdahl offers a full range of mainframe products. Dr. Amdahl left the company to form Trilogy in 1979 and now heads Andor Corp., a manufacturer of products for large IBM mainframe installations. American Bell AT&T trade name used after divestiture. Federal court order later prohibited its use. AMI BIOS Popular PC-compatible ROM BIOS from American Megatrends, Inc., Norcross, GA. Ami Pro Windows word processing program from Lotus that includes desktop publishing features. It allows for the creation of presentation-quality charts and graphs. Ami was one of the first full-featured word processors for Windows and was originally developed by Samna Corp. Amiga Personal computer series from Commodore that runs under the AmigaDOS operating system, uses the 68000 CPU family and features the Workbench window- oriented user interface. The Amiga 500 is geared for home use and includes built-in speech synthesis, stereo sound and color graphics. The Amiga 2000 is designed for office applications, including CAD and desktop publishing. It has optional PC compatibility and NTSC video processing. The Amiga 3000 (68030) provides enhanced graphics and Workbench interface. amp (AMPere) Unit of electrical current in a circuit. Volts measure the force or pressure behind the current. Watts are a total measurement of power derived from multiplying amps times volts. amplitude Strength or volume of a signal, usually measured in decibels. amplitude modulation See AM. analog Representation of an object that resembles the original. Analog devices monitor conditions, such as movement, temperature and sound, and convert them into analogous electronic or mechanical patterns. For example, an analog watch represents the planet's rotation with the rotating hands on the watch face. Telephones turn voice vibrations into electrical vibrations of the same shape. Analog implies continuous operation in contrast with digital, which is broken up into numbers. Advantages and Disadvantages Of Analog Techniques Traditionally, audio and video recording has been analog. Sound, which is continuously varying air vibrations, is converted into analogous electrical vibrations. Video cameras scan their viewing area a line at a time and convert the infinitely varying intensities of light into analogous electrical signals. The ability to capture the subtle nature of the real world is the single advantage of analog techniques. However, once captured, modern electronic equipment, no matter how advanced, cannot copy analog signals perfectly. Third and fourth generations of audio and video recordings show marked deterioration. By converting analog signals into digital, the original audio or video data can be preserved indefinitely and copied over and over without deterioration. Once continuously varying analog signals are measured and converted into digital form, they can be stored and transmitted without loss of integrity due to the accuracy of digital methods. The key to conversion is the amount of digital data that is created from the analog signal. The shorter the time interval between samples and the more data recorded from that sample, the more the digital encoding reflects the original signal. analog channel In communications, a channel that carries voice or video in analog form as a varying range of electrical frequencies. Contrast with digital channel. analog computer Device that processes infinitely varying signals, such as voltage or frequencies. A thermometer is a simple analog computer. As the temperature varies, the mercury moves correspondingly. Although special-purpose, complex analog computers are built, almost all computers are digital. Digital methods provide programming flexibility. analog monitor Video monitor that accepts analog signals from the computer (digital to analog conversion is performed in the video display board). It may accept only a narrow range of display resolutions; for example, only VGA or VGA and Super VGA, or it may accept a wide range of signals including TV. See multisync monitor and RGB monitor. Contrast with digital monitor. analysis See systems analysis & design. analyst See systems analyst. Analytical Engine Programmable calculator designed by British scientist, Charles Babbage (mid 1830s). Although never completed due to lack of funds and constant redesign, it was a major advance and contained the principles of the stored program computer. Babbage's colleague, Augusta Ada Byron, daughter of the poet Lord Byron, explained the machine's concepts to the public. See Ada. AND, OR & NOT Fundamental operations of Boolean logic. AND is true if both inputs are true, OR is true if any input is true, and NOT is an inverter; the output is always the opposite. See Boolean search, chip and gate.  AND OR NOT  Inputs Output Inputs Output Input Output  敖陳陳陳堕陳陳 敖陳陳陳堕陳陳 敖陳陳堕陳陳  0 0 0 0 0 0 0 1  0 1 0 0 1 1 1 0  1 0 0 1 0 1 青陳陳祖陳陳  1 1 1 1 1 1  青陳陳陳祖陳陳 青陳陳陳祖陳陳  ANDF (Architecture Neutral Distributed Format) See OSF. angstrom Unit of measurement equal to approximately 1/250 millionth of an inch (.1 nanometer). It is used to measure the elements in a chip. ANI (Automatic Number Identification) Telephone service that provides the telephone number of the incoming call. animated graphics Moving diagrams or cartoons. Often found in computer-based courseware, animated graphics take up far less disk space than video images. anisotropic Refers to properties, such as transmission speed, that vary depending on the direction of measurement. Contrast with isotropic. anode In electronics, positively charged receiver of electrons that flow from the negatively charged cathode. anomaly Abnormality or deviation. It is a favorite word among computer people when complex systems produce output that is inexplicable. ANSI (American National Standards Institute) Membership organization founded in 1918 that coordinates the development of U.S. voluntary national standards in both the private and public sectors. It is the U.S. member body to ISO and IEC. Information technology standards pertain to programming languages, EDI, telecommunications and physical properties of diskettes, cartridges and magnetic tapes. Address: 11 West 42 St., New York, NY 10036, 212/642-4900. ANSI character set ANSI-standard character set that defines 256 characters. The first 128 are ASCII, and the second 128 contain math and foreign language symbols, which are different than those on the PC. See extended ASCII. ANSI terminal Display terminal that follows commands in the ANSI standard terminal language. Uses escape sequences to control the cursor, clear the screen and set colors, for example. Communications programs often support the ANSI terminal. ANSI.SYS See DOS ANSI.SYS. answer only modem Modem capable of answering a call, but not initiating one. anti-aliasing In computer graphics, a category of techniques that is used to smooth the jagged appearance of diagonal lines. For example, the pixels that surround the edges of the line are filled in with varying shades of gray or color in order to blend the sharp edge into the background. See dithering. Antifuse PLD technology from Actel Corp. that works the opposite of typical programmable chip methods. Instead of creating open circuits (blowing the fuse), connections are made between elements. antivirus Program that detects and removes a virus. ANVIL Family of CADD/CAM software packages from Manufacturing and Consulting Services Inc., Scottsdale, AZ. ANVIL products include 2 1/2-D and 3-D mechanical engineering systems for PCs, workstations, minis and mainframes. APA (All Points Addressable) Refers to an array (bitmapped screen, matrix, etc.) in which all bits or cells can be individually manipulated. APCUG (Assn. of Personal Computer User Groups) Non-profit organization dedicated to fostering communication among and between user groups and between user groups and vendors. Address: Suite 700, 1730 M St. N.W., Washington, DC 20036. aperture card Punched card that holds a frame of microfilm. API (Application Program Interface) Language and message format used by a program to activate and interact with functions in another program or in the hardware. See interface. APL (A Programming Language) High-level, interactive scientific language noted for its brevity and matrix generation capabilities. Developed by Kenneth Iverson in the mid 1960s, it runs on micros to mainframes and is often used to develop mathematical models. It is primarily an interpreted language, but compilers are available. APL uses unique character symbols and requires special software or ROM chips to enable the computer to display and print them. APL is popular in Europe. APM (Advanced Power Management) API from Intel and Microsoft for battery-powered computers that lets programs communicate power requirements to slow down and speed up components. The 386SL takes full advantage of APM. Apollo (Apollo Systems Div. of HP) Formerly Apollo Computer, Inc., this maker of high-performance workstations became a division of HP in 1989. Founded in 1980, it pioneered networked workstations. app See application. app code (APPlication code) Instructions in a program that actually process data. APPC (Advanced Program-to-Program Communications) High- level communications protocol from IBM that allows a program to interact with another program. It supports client/server and distributed computing by providing a common programming interface across all IBM platforms for communications over a variety of transport protocols. It provides commands for managing a session, sending and receiving data and transaction security and integrity (two-phase commit). APPC software is either part of or optionally available on all IBM and many non-IBM operating systems. Since APPC has only supported SNA, utilizing SNA's LU 6.2 protocol for session establishment, APPC and LU 6.2 have been considered synonymous. In time, APPC will support other industry protocols, such as TCP/IP and OSI. APPC commands have differed across platforms. Under SAA, the CPI-C interface defines a standard set of APPC verbs. append To add to the end of an existing structure. Apple (Apple Computer, Inc., Cupertino, CA) Manufacturer of personal computers and the industry's most fabled story. Founded in a garage by Steve Wozniak and Steve Jobs and guided by Mike Markkula, Apple blazed the trails for the personal computer industry. Today, Apple makes more personal computers than any other single company. Apple was formed on April Fool's Day in 1976. After introducing the Apple I at the Palo Alto Homebrew Computer Club, 10 retail stores were selling them by the end of the year. In 1977, it introduced the Apple II, a fully- assembled computer with 4K RAM for $1,298. Its open architecture encouraged third-party vendors to build plug-in hardware enhancements. This, plus sound and color graphics, caused Apple IIs to become the most widely used computer in the home and classroom. They were also used in business primarily for the innovative VisiCalc software that was launched on it. In 1983, Apple introduced the Lisa, the forerunner of the Macintosh. Lisa was aimed at the corporate market, but was soon dropped in favor of the Mac. As a graphics-based machine, the Mac was successful as a low-cost desktop publishing system. Although praised for its ease of use, its slow speed, small screen and closed architecture didn't excite corporate buyers. Since the advent of the Mac II in 1987, that has changed. Macs offer large screens, open architecture and color. Numerous entry-level and high-speed models have been added and widely accepted. In 1991, Apple surprised the industry by announcing an alliance with IBM to (1) fully integrate Macs into IBM enterprise networks, (2) develop the PowerPC with Motorola, a single- chip version of IBM's RS/6000 architecture, (3) develop PowerOpen, an industry standard UNIX (OSF/1 compliant) that runs AIX and Mac applications on the PowerPC, (4) form Taligent, Inc. to develop and license an object-oriented operating system for the PowerPC, Motorola 68xxx and Intel x86 families with compatibility with AIX, OS/2 2.0 and System 7, (5) form Kaleida Labs, Inc. to develop and license multimedia software, tools and scripting languages for a diverse variety of computers and consumer electronic gear. Apple II Personal computer family from Apple that pioneered the microcomputer revolution and has been widely used in schools and home. It uses the 8-bit 6502 microprocessor running at 1MHz, an 8-bit bus and runs under Apple's DOS or ProDOS operating system. AppleSoft BASIC is built into ROM and always available. With a Z80 microprocessor board plugged in, Apple IIs can run CP/M programs, such as dBASE II. As of the end of 1992, the Apple IIe and a IIe card for the Mac LC are the only Apple II models still in the product line. APPLE II AND II+ Introduced in 1977, the Apple II came with 4K RAM and hooked up to a TV and cassette tape recorder. A floppy disk was available in 1978. In 1979, an enhanced II+ came with 48K of RAM. Screen resolution is 280x192x6. APPLE IIe AND IIc In 1983, the "e"nhanced Apple IIe was introduced with four cursor keys (not two) and 128K of RAM. In 1984, the IIc portable was launched with a sleek design, but limited expandability. APPLE IIGS Introduced in 1986 and discontinued in 1992, the IIGS is faster and adds enhanced graphics and sound (GS). It runs standard Apple II software, but requires GS software to use its enhancements. Specs: 2.8MHz 16-bit 65C816 CPU, 320x200x256 screen, 15 sounds, AppleTalk. APPLE III Yes, there was an Apple III in 1980, intended for business users. It was not 100% compatible with the II and never caught on. Apple key Original name of the Command key. Apple menu Menu at the top left side of a Macintosh screen that is always available to provide access to desk accessories. AppleShare Software from Apple that turns a Macintosh into a file server. It works in conjunction with the Mac operating system and can coexist with other Macintosh applications in a non-dedicated mode. AppleShare PC Software for PCs from Apple that allows a PC to connect to an AppleTalk network. It requires a LocalTalk PC Card from Apple for ISA PCs, or a LocalTalk Card from DayStar Communications for Micro Channel PCs. AppleSoft BASIC Apple's version of BASIC that comes with Apple II models. It is installed in firmware and is always available. applet Small application, such as a utility program. AppleTalk OSI-based LAN from Apple introduced in 1985. It supports Apple's proprietary LocalTalk access method as well as Ethernet and Token Ring. The AppleTalk protocol and LocalTalk access method are built into all Macs, IIGS's and LaserWriters. With products from Apple and others, AppleTalk can run in PCs, VAXs and UNIX workstations. AppleWorks Integrated software package for Apple IIs from Claris Corp. Introduced in 1983 by Apple, it combines word processing, file management, spreadsheet, business graphics and communications. application (1) Specific use of the computer, such as payroll, inventory and billing. (2) Same as application program and software package. application developer Individual that develops a business application and usually performs the duties of a systems analyst and application programmer. application development language Same as programming language. application development system Programming language and associated utility programs that allow for the creation, development and running of application programs. DBMSs are often full application development systems, which include a programming language, query language, report writer and the capability to interactively create and manage database files. application framework (1) Building blocks of an application. (2) Class library that provides the foundation for programming an object-oriented application. application generator Software that generates application programs from descriptions of the problem rather than by traditional programming. It is at a higher level and easier to use than a high-level programming language. One statement or descriptive line may generate a huge routine or an entire program. However, application generators always have limits as to what they can be used for. Generators used for complex program development allow if-then-else programming to be expressed along with the simpler descriptive entries. application layer In communications, the interaction at the user or application program level. It is the highest layer within the protocol hierarchy. See OSI model. application notes Instructions and recommendations from the vendor provided in addition to the normal reference manuals. application package Software package that is created for a specific purpose or industry. application processor Computer that processes data in contrast with one that performs control functions, such as a front end processor or database machine. application program Any data entry, update, query or report program that processes data for the user. Contrast with system program. application program interface See API. application program library Application programs used by an organization. application programmer Individual who writes application programs in a user organization. Most programmers are application programmers. Contrast with systems programmer. APPN (Advanced Peer-to-Peer Networking) Extensions to IBM's SNA communications that provide necessary enhancements for distributed computing. It provides intermediate node routing (routing a message from one computer to another), dynamic network services (automatic reconfiguration of a network) and improved administration. It makes use of LU 6.2 protocols and is implemented in SNA Node Type 2.1. APT (Automatic Programmed Tools) High-level programming language used to generate instructions for numerical control machines. Arago dBASE IV-compatible DBMS and compiler (Arago Quicksilver) originally developed by WordTech Systems. In 1992, the technology was acquired by Borland. arbitration Set of rules for allocating machine resources, such as memory or peripheral devices, to more than one user or program. ARC, ARC+Plus (1) PC compression programs from System Enhancement Associates, Inc., Clifton, NJ. ARC was one of the first compression utilities to become popular in the early 1980s. ARC+Plus provides enhanced features and speed. (2) ARC extension previously used by PKWARE Inc. in its PKARC program. (3) (Advanced RISC Computing) Open system specification based on the MIPS R3000 and R4000 CPUs. It includes EISA and TURBOchannel buses. architecture See computer architecture, network architecture and software architecture. archive (1) To copy data onto a different disk or tape for backup. Archived files are often compressed to maximize storage media. (2) To save data onto the disk. archive attribute File classification that indicates whether the file has been updated since the last backup. ARCNET (Attached Resource Computer NETwork) Local area network introduced in 1968 by Datapoint Corp. It was the first LAN. It uses a token passing access method at 2.5 Mbits/sec with a distributed star topology for up to 255 nodes. In 1989, 20 Mbits/sec versions were introduced. It supports coax, twisted pair or fiber optic cable. Adapters allow it to connect to mini and mainframe networks. Ardis (Advanced National Radio Data Service) Joint venture of IBM and Motorola that provides wireless data transmission in the 800MHz FM band. It covers most U.S. metropolitan areas with over 1,000 base stations. areal density Bits per square inch of disk surface (BPI x TPI). arg See argument. argument In programming, a value that is passed between programs, subroutines or functions. Arguments are independent items, or variables, that contain data or codes. When an argument is used to customize a program for a user, it is typically called a parameter. arithmetic coding Statistical data compression method that converts strings of data into single floating point numbers between 0 and 1. arithmetic expression (1) In mathematics, one or more characters or symbols associated with arithmetic, such as 1+2=3 or 86. (2) In programming, a non-text expression. arithmetic logic unit See ALU. arithmetic operators Symbols for arithmetic functions: + add, - subtract, * multiply, / divide. See precedence. arithmetic overflow Result from an arithmetic calculation that exceeds the space designated to hold it. arithmetic underflow Result from an arithmetic calculation that is too small to be expressed properly. For example, in floating point, a negative exponent can be generated that is too large (too small a number) to be stored in its allotted space. ARP (Address Resolution Protocol) TCP/IP protocol used to obtain a station's physical address from its logical IP address. ARP requests are broadcast onto the network. Reverse ARP, or RARP, is used by a diskless workstation to obtain its logical IP address. Responding to a RARP broadcast from the workstation, a RARP server sends back the IP address. ARPANET (Advanced Research Projects Agency NETwork) Research network funded by DARPA (originally ARPA) and built by BBN, Inc., in 1969. It pioneered packet switching technology and was the original backbone and testbed for the now-gigantic Internet. In 1983, the military communications part of it was split off into MILNET. ARQ (Automatic Repeat Request) Method of handling communications errors in which the receiving station requests retransmission if an error occurs. array Ordered arrangement of data elements. A vector is a one dimensional array, a matrix is a two- dimensional array. Most programming languages have the ability to store and manipulate arrays in one or more dimensions. Multi-dimensional arrays are used extensively in scientific simulation and mathematical processing; however, an array can be as simple as a pricing table held in memory for instant access by an order entry program. See subscript. array element One item in an array. array processor Computer, or extension to its arithmetic unit, that is capable of performing simultaneous computations on elements of an array of data in some number of dimensions. Common uses include analysis of fluid dynamics and rotation of 3-D objects, as well as data retrieval, in which elements in a database are scanned simultaneously. See vector processor and math coprocessor. artificial intelligence See AI. artificial language Language that has been predefined before it is ever used. Contrast with natural language. AS (Application System) IBM mainframe 4GL that runs under MVS. It was originally designed for non- computer people and includes commands for planning, budgeting and graphics. However, a programmer can also produce complex applications. It also provides computer conferencing. AS/400 (Application System/400) IBM minicomputer series introduced in 1988 that supersedes the System/36 and System/38. System/36 programs run in the AS/400 in System/36 mode after they have been recompiled. System/38 programs run intact in System/38 mode. After recompilation, System/38 programs will run in native AS/400 mode, which takes advantage of all system resources. The AS/400 serves in a variety of networking configurations: as a host or intermediate node to other AS/400s and System/3x machines, as a remote system to mainframe-controlled networks and as a network server to PCs. The AS/400 offered the widest range of connectivity in an IBM introduction. ascender The part of lowercase b, d, f, h, k, l, and t, that extends above the body of the letters. ASCII (American Standard Code for Information Interchange) Pronounced "ask-ee." A binary code for data that is used in communications, most minicomputers and all personal computers. ASCII is a 7-bit code providing 128 character combinations, the first 32 of which are control characters. Since the common storage unit is an 8- bit byte (256 combinations) and ASCII uses only 7 bits, the extra bit is used differently depending on the computer. For example, the PC uses the additional values for foreign language and graphics symbols (see ASCII chart below). In the Macintosh, the additional values can be user-defined. In the Mac version of this Glossary, the PC symbols are designed into the font used for the definitions. See ASCII chart and hex chart. ASCII chart 浜様様様様様様様様様様様様様様様僕様様様様様様様様 Standard ASCII Extended ASCII The first 32 characters are (IBM PC) control codes. 0 Null 33 ! 81 Q128 174 220 楮 1 Start of heading 34 " 82 R129 175 221 欹 2 Start of text 35 # 83 S130 176 鯵222 涅 3 End of text 36 $ 84 T131 177 嘘223 澪 4 End of transmit 37 % 85 U132 178 桶224 犧 5 Enquiry 38 & 86 V133 179 崖225 畉 6 Acknowledge 39 ' 87 W134 180 干226 盧 7 Audible bell 40 ( 88 X135 181 騎227 禳 8 Backspace 41 ) 89 Y136 182 恭228 篋 9 Horizontal tab 42 * 90 Z137 183 軍229 綺 10 Line feed 43 + 91 [138 184 験230 羣 11 Vertical tab 44 , 92 \139 185 抗231 膾 12 Form feed 45 - 93 ]140 186 些232 荳 13 Carriage return 46 . 94 ^141 187 山233 藝 14 Shift out 47 / 95 _142 ｳ188 竺234 蟶 15 Shift in 48 0 96 `143 189 蹴235 觝 16 Data link escape 49 1 97 a144 190 廠236 貂 17 Device control 1 50 2 98 b145 191 審237 躡 18 Device control 2 51 3 99 c146 192 棲238 邵 19 Device control 3 52 4100 d147 193 然239 鏈 20 Device control 4 53 5101 e148 194 続240 雕 21 Neg. acknowledge 54 6102 f149 195 坦241 餾 22 Synchronous idle 55 7103 g150 196 蝶242 鮑 23 End trans. block 56 8104 h151 197 迭243 鷓 24 Cancel 57 9105 i152 198 導244 25 End of medium 58 :106 j153 199 燃245 26 Substitution 59 ;107 k154 200 罰246 27 Escape 60 <108 l155 201 紐247 28 File separator 61 =109 m156 202 奮248 29 Group separator 62 >110 n157 203 乏249 30 Record separator 63 ?111 o158 204 務250 31 Unit separator 64 @112 p159 205 由251 32 Blank space 65 A113 q160 206 粒252 66 B114 r161 ヽ207 漏253 67 C115 s162 208 亞254 68 D116 t163 ３209 儚255 69 E117 u164 こ210 匈 70 F118 v165 コ211 啌 71 G119 w166 Τ212 坡 72 H120 x167 С213 娚 73 I121 y168 ┳214 岾 74 J122 z169 215 彝 75 K123 {170 216 愕 76 L124 |171 217 抒 77 M125 }172 218 擲 78 N126 ~173 219 朿 79 O127  80 P 藩様様様様様様様様様溶様様詫様様瞥様様詫様様詫様様 ASCII file Data or text file that contains characters coded in ASCII. Text files (not created in a word processor), batch files and source language programs are ASCII files. Contrast with binary file. ASCII Files for Data Conversion Database files and word processing documents generally contain proprietary codes and binary numbers, which are not true ASCII characters. However, most applications can import and export ASCII files, which provides a common denominator for converting one format to another. ASCII protocol Simple form of transmitting ASCII data which implies little or no error checking. ASCII sort Sequential order of ASCII data. In ASCII code, lower case characters follow upper case. True ASCII order would put the words DATA, data and SYSTEM into the following sequence: DATA SYSTEM data Ashton-Tate Software company founded in 1980 by Hal Lashlee and George Tate to market dBASE II. Borland acquired it in 1991. ASIC (Application Specific Integrated Circuit) Custom chip designed for a specific application. It is designed by integrating standard cells from a library. ASIC design is faster than designing a chip from scratch, and design changes can be made more easily. askSam Text management system for PCs from askSam Systems, Perry FL. It holds unstructured text as well as standard data fields. The product is noted for its flexible text retrieval and hypertext capabilities. ASM (1) (Association for Systems Management) International membership organization founded in 1947 with over 10,000 administrative executives and specialists in information systems. It sponsors conferences in all phases of administrative systems and management and serves business, education, government and the military. Address: 24587 Bagley Rd., Cleveland, OH 44138, 216/243-6900. (2) File extension for assembly language source programs. ASN.1 (Abstract Syntax Notation.1) Rules for defining data structures transmitted over an OSI network. aspect ratio Ratio of width to height of an object. ASPI (Advanced SCSI Programming Interface) SCSI standard developed by Adaptec. See SCSI and CorelSCSI. assembler Software that translates assembly language into machine language. Contrast with compiler, which is used to translate a high-level language, such as COBOL or C, into assembly language first and then into machine language. assembly language Programming language that is one step away from machine language. Each assembly language statement is translated into one machine instruction by the assembler. Programmers must be well versed in the computer's architecture, and, undocumented assembly language programs are difficult to maintain. It is hardware dependent; there is a different assembly language for each CPU series. In the past, control programs (operating systems, database managers, etc.) were written in assembly language to maximize the machine's performance. Today, C is often used instead. Like assembly language, C can manipulate the bits at the machine level, but it is also portable to different computer platforms. There are C compilers for most computers. Although often used synonomously, assembly language and machine language are not the same. Assembly language is turned into machine language. For example, the assembly instruction COMPARE A,B is translated into COMPARE contents of memory bytes 2340-2350 with 4567-4577 (where A and B happen to be located). The physical binary format of the machine instruction is specific to the computer it's running in. Assembly languages are quite different between computers as is evident in the example below, which takes 16 lines of code for the mini and 82 lines for the micro. The example changes Fahrenheit to Celsius.  HP 3000  begin  intrinsic read,print,binary,ascii;  array buffer(0:17);  array string(0:3);  byte array b'string(*) = string;  integer ftemp, ctemp, len;  move buffer:= "Enter Fahrenheit ";  print (buffer,-30,%320);  len:=read (string,-4);  ftemp:= binary(b'string,len);  ctemp:= (ftemp-32) * 5 / 9;  len:= ascii(ctemp,1-,b'string);  move buffer:= "Celsius is ";  move buffer(14) := string, (-len);  print (buffer,-32,%0);  end  IBM PC (x86 family) (Only 15 of the 82 lines are shown here.)   cseg segment para public 'CODE'  assume cs:cseg,ds:cseg  start:  jmp start1  msgstr db 'Enter fahrenheit '  crlf db 13,10,'$'  nine db 9  five db 5  outstr db 'Centrigrade is $'  start1: push ds  push cs  pop ds  mov dx,offset cseg:msgstr  mov ah,9  int 21h  (67 more lines are required!) assignment statement In programming, a compiler directive that places a value into a variable. For example, COUNTER = 0 creates a variable named counter and fills it with zeros. The VARIABLE NAME = VALUE syntax is common among programming languages. associative storage Storage accessed by comparing the content of the data stored in it rather than by addressing predetermined locations. ASSP (Application Specific Standard Part) ASIC chip originally designed for one customer and then released to the general public. asymmetric modem Full-duplex modem that transmits data in one direction at one speed and simultaneously in the other direction at another speed. For example, data flows at high-speed in one direction while acknowledgement is returned at low speed in the other. Contrast with ping pong. asymmetric multiprocessing Multiprocessing design in which each CPU is dedicated to a specific function. Contrast with symmetric multiprocessing. asymmetric system (1) System in which major components or properties are different. (2) In video compression, a system that requires more equipment to compress the data than to decompress it. asynchronous (1) Unsynchronized events, for example, the time interval between event A and B is not the same as B and C. (2) Able to initiate a transmission at either end. (3) In SNA, refers to independent events rather than concurrent events. For example, if one user sends mail to a party who is not available, the ability to forward the mail at a later time is considered asynchronous. (4) Starting the next I/O operation before the current one is completed. (5) In SCSI, the acknowledgment of each byte of data transferred. Contrast with synchronous. asynchronous protocol Communications protocol that controls an asynchronous transmission, for example, ASCII, TTY, Kermit and Xmodem. Contrast with synchronous protocol. asynchronous transmission Transmission of data in which each character is a self-contained unit with its own start and stop bits. Intervals between characters may be uneven. It is the common method of transmission between a computer and a modem, although the modem may switch to synchronous transmission to communicate with the other modem. Also called start/stop transmission. Contrast with synchronous transmission.  asynchronous  transmission: a bc d efg hi j kl m  synchronous  transmission: abcedefghijklm AT (Advanced Technology) IBM's first 286-based PC, introduced in 1984. It was the most advanced machine in the PC line and featured a new keyboard, 1.2MB floppy and 16-bit data bus. AT-class machines run considerably faster than XTs (8088- based PCs). See PC. AT bus Refers to the 16-bit bus introduced with the IBM AT. See ISA. AT class Refers to PCs that use the 286 CPU and the 16-bit AT (ISA) bus. AT command set Series of machine instructions used to activate features on an intelligent modem. Developed by Hayes Microcomputer Products, Inc., and formally called the Hayes Standard AT Command Set, it is used entirely or partially by most every modem manufacturer. AT is a mnemonic code for ATtention, which is the prefix that initiates each command to the modem. See Hayes Smartmodem. AT interface See AT bus. AT keyboard 84-key keyboard provided with the PC AT. It corrected the non-standard placement of the PC's return and left shift keys. See PC keyboard and Enhanced keyboard. AT&T (American Telephone & Telegraph Company) Largest long distance communications carrier in the U.S. Once the largest corporation in America, it was relieved of its operating telephone companies on 1/1/84, by Federal court order. It has gone through a major change from the world's largest monopoly to a competitive enterprise. Its ventures into the PC market have been modest, but in 1991, it acquired NCR, a seasoned computer company. ATA Interface specification for IDE drives. Also used for PCMCIA solid state disks. Atari (Atari Computer, Sunnyvale, CA) Manufacturer of personal computers originally founded in 1972 by Nolan Bushnell and famous for its "Pong" video games. In 1976, it was sold to Time Warner, Inc., and in 1984 was sold to Jack Tramiel and investors. Within six months, the 520ST was introduced, the first personal computer designed for MIDI applications. Its product line, aimed at providing quality computing at affordable prices, includes the 1040STE, TT030 workstation and Portfolio palmtop. ATE (Automatic Test Equipment) Machines that test electronic systems, primarily chips. See EDA and DTA. ATM (1) (Automatic Teller Machine) Special-purpose banking terminal that allows users to make deposits and withdrawals. It can be a stand-alone unit or online to a central computer system. ATMs are activated by inserting a magnetic card (cash card or credit card) in the machine that contains the user's identification number. (2) (Asynchronous Transfer Mode) High-speed packet switching technique suitable for MANs and broadband ISDN transmission. It uses cell relay transmission. (3) See Adobe Type Manager. atom In list processing languages, a single element in a list. atomic Indivisible. An atomic operation, or atomicity, implies an operation that must be performed entirely or not at all. For example, if machine failure prevents a transaction to be processed to completion, the system will be rolled back to the start of the transaction. See two-phase commit. attached processor Additional CPU connected to the primary CPU in a multiprocessing environment. It operates as an extension of the primary CPU and shares the system software and peripheral devices. attenuation Loss of signal power in a transmission. attribute (1) In relational database management, a field within a record. (2) For printers and display screens, a characteristic that changes a font, for example, from normal to boldface or underlined, or from normal to reverse video. (3) See file attribute. audio Range of frequencies within human hearing (approx. 20Hz at the low to a high of 20,000Hz). Traditional audio devices are analog, because they handle sound waves in an analogous form. Radios maintain the audio signal as rippling waves from antenna to speaker. Sound waves are "carved" into plastic phonograph records, and audio tape records sound as magnetic waves. Audio is processed in a computer by converting the analog signal into a digital code using various techniques, such as PCM. audio board Same as sound card. audio response See voice response. audiotex Voice response application that allows users to enter and retrieve information over the telephone. In response to a voice menu, users press the keys or answer questions to select their way down a path of choices. It is used for obtaining the latest financial quotes as well as for ordering products. It is also built into interactive systems that allows databases to be changed. See VIS. audiovisual Audio and/or video capability. audit Examination of systems, programming and datacenter procedures in order to determine the efficiency of computer operations. audit software Specialized programs that perform a variety of audit functions, such as sampling databases and generating confirmation letters to customers. It can highlight exceptions to categories of data and alert the examiner to possible error. Audit software often includes a non-procedural language that lets the auditor describe the computer and data environment without detailed programming. audit trail Record of transactions in an information system that provides verification of the activity of the system. The simplest audit trail is the transaction itself. If a person's salary is increased, the change transaction includes the date, amount of raise and name of authorizing manager. A more elaborate audit trail can be created when the system is being verified for accuracy; for example, samples of processing results can be recorded at various stages. Item counts and hash totals are used to verify that all input has been processed through the system. authoring program Software that allows for the development of tutorials and CBT programs. authorization code Identification number or password that is used to gain access to a local or remote computer system. Authorware Macintosh authoring program from Authorware, Inc., Minneapolis, MN. Courseware developed on the Mac can be converted to the PC. auto (AUTOmatic) Refers to a wide variety of devices that perform unattended operation. auto answer Modem feature that accepts a telephone call and establishes the connection. See auto dial. auto attendant Voice store and forward system that replaces the human operator and directs callers to the appropriate extensions or voice mailboxes. auto bypass Ability to bypass a terminal or other device in a network if it fails, allowing the remaining devices to continue functioning. auto dial Modem feature that opens the line and dials the telephone number of another computer to establish connection. See auto answer. auto line feed Feature that moves the cursor or print head to the next line when a CR (carriage return) is sensed. PCs put a LF (line feed) after the CR and don't use this feature. The Mac uses only a CR, thus auto line feed causes the CR to move the output device to the next line. auto logon Performing the complete log-on sequence necessary to gain entry into a computer system without user intervention. auto resume Feature that lets you stop working on the computer and take up where you left off at a later date without having to reload applications. Memory contents are stored on disk or kept active by battery and/or AC power. AutoCAD Full-featured CAD program from AutoDesk Inc., Sausalito, CA, that runs on PCs, VAXs, Macs and UNIX workstations. Originally developed for CP/M machines, it was one of the first major CAD programs for personal computers and became an industry standard. Many software packages import and export graphics files in DXF, AutoCAD's external file format. autocoder IBM assembly language for 1960s-vintage 1400 and 7000 series computers. AUTODIN (AUTOmatic DIgital Network) Worldwide communications network of the U.S. Defense Communications System. AUTOEXEC.BAT (AUTOmatic EXECute BATch) DOS batch file that executes when the computer is started. The OS/2 counterpart is STARTUP.CMD. See DOS AUTOEXEC.BAT. autoflow Wrapping text around a graphic image or from one page to the next. AutoLISP AutoCAD language used to create customized menus and routines. automata theory Open-ended computer science discipline that concerns an abstract device called an "automaton," which performs a specific computational or recognition function. Networks of automata are designed to mimic human behavior. automatic data processing Same as data processing. automatic feature negotiation Ability of a modem to determine and adjust to the speed, error control and data compression method of the modem at the other end of the line. automation Replacement of manual operations by computerized methods. Office automation refers to integrating clerical tasks such as typing, filing and appointment scheduling. Factory automation refers to computer-driven assembly lines. autosave Saving data to the disk at periodic intervals without user intervention. autosizing Ability of a monitor to maintain the same rectangular image size when changing from one resolution to another. autostart routine Instructions built into the computer and activated when it is turned on. The routine performs diagnostic tests, such as checking the computer's memory, and then loads the operating system and passes control to it. autotrace Routine that locates outlines of raster graphics images and converts them into vector graphics. AUX (AUXiliary) DOS name for the first connected serial port. See DOS device names. See also A/UX. auxiliary memory High-speed memory bank used in mainframes and supercomputers. It is not directly addressable by the CPU, rather it functions like a disk. Data is transferred from auxiliary memory to main memory over a high-bandwidth channel. See auxiliary storage. auxiliary storage External storage devices, such as disk and tape. AVC (Audio Visual Connection) Multimedia software from IBM that works in conjunction with IBM's Audio Capture and Video Capture boards for the PS/2. It allows users to integrate sound and pictures into applications and includes an authoring language. AVI (Audio Video Interleaved) Windows multimedia video format from Microsoft. It interleaves standard waveform audio and digital video frames (bitmaps) to provide reduced animation at 15 fps at 160x120x8 resolution. Audio is 11,025Hz, 8-bit samples. avionics Electronic instrumentation and control equipment used in airplanes and space vehicles. Award BIOS Widely-used PC-compatible ROM BIOS from Award Software, Inc., Los Gatos, CA. By 1991, over 20 million Award BIOS's have been installed. awk (Aho Weinberger Kernighan) UNIX programming utility developed in 1977 by Aho, Weinberger and Kernighan. Due to its unique pattern-matching syntax, it is often used in data retrieval and data transformation. DOS versions are also available. AXP Family of computer systems from Digital that use the Alpha CPU chip. azimuth Trajectory of an angle measured in degrees going clockwise from a base point. A disk azimuth alignment test checks for the correct positioning of the read/write head to the track. B/ISDN (Broadband/ISDN) See ISDN. B protocol File transfer protocol from CompuServe. Quick B is a faster version only for downloading. The latest versions of B will automatically select Quick B. b-spline In computer graphics, a curve that is generated using a mathematical formula which assures continuity with other b-splines. B-tree (Balanced-tree) Technique for organizing indexes. In order to keep access time to a minimum, it stores the data keys in a balanced hierarchy that continually realigns itself as items are inserted and deleted. Thus, all nodes always have a similar number of keys. B+tree is a version of B-tree that maintains a hierarchy of indexes while also linking the data sequentially, providing fast direct access and fast sequential access. IBM's VSAM uses this. B1 DOD computer security levels. See NCSC. B: Designation for the second floppy disk drive in a PC. back-end CASE CASE tools that generate program code. Contrast with front-end CASE. back end processor Same as database machine. back up To make a copy of important data onto a different storage medium for safety. backbone In communications, the part of a network that handles the major traffic. It may interconnect multiple locations, and smaller networks may be attached to it. backfilling Assigning EMS memory to conventional memory in XTs and ATs in order to let DESQview run more programs concurrently. Motherboard chips are disabled and EMS chips are assigned the low memory addresses. background (1) Non-interactive processing in the computer. See foreground/background. (2) Base, or backdrop, color on screen. For example, in the DOS version of this Glossary, the text color is white on a blue background. background ink Highly reflective OCR ink used to print the parts of the form not recognized by a scanner. background noise Extraneous signal that has crept into a line, channel or circuit. background processing Processing in which the program is not visibly interacting with the user. Most personal computers use operating systems that run background tasks only when foreground tasks are idle, such as between keystrokes. Advanced multitasking operating systems let background programs be given any priority from low to high. backing storage Same as auxiliary storage. backlit LCD screen that has its own light source from the back of the screen, making the background brighter and characters appear sharper. backplane (1) Reverse side of a panel or board that contains interconnecting wires. (2) Printed circuit board, or device, containing slots, or sockets, for plugging in boards or cables. See bus. backslash See DOS backslash. backsolver See solver. backspace (1) To move the screen cursor one column to the left, deleting the character that was in that position. A backspace to the printer moves the print head one column to the left. (2) To move to the previous block on a magnetic tape. backup Additional resources or duplicate copies of data on different storage media for emergency purposes. See backup types. backup & recovery Combination of manual and machine procedures that can restore lost data in the event of hardware or software failure. Routine backup of databases and logs of computer activity are part of a backup & recovery program. See checkpoint/restart. backup copy Disk, tape or other machine readable copy of a data or program file. Making backup copies is a discipline most computer users learn the hard way-- after a week's work is lost. backup disk Disk used to hold duplicate copies of important files. Floppy disks and disks cartridges are used for backup disks. backup power Additional power source that can be used in the event of power failure. See UPS. backup tape See tape backup. backup types Selection of files for backup purposes. A full backup backs up all selected files. A differential backup backs up selected files that have been changed. This is used when only the latest version of a file is required. An incremental backup backs up selected files that have been changed, but if a file has been changed for the second or subsequent time since the last full backup, the file doesn't replace the already-backed-up file, rather it is appended to the backup medium. This is used when each revision of a file must be maintained for backup. Backus-Naur form Also known as Backus normal form, it was the first metalanguage to define programming languages, developed by John Backus and Peter Naur in 1959. backward chaining In AI, a form of reasoning that starts with the conclusion and works backward. The goal is broken into many subgoals or sub-subgoals which can be solved more easily. Known as top-down approach. Contrast with forward chaining. backward compatible Same as downward compatible. bad sector Segment of disk storage that cannot be read or written due to a physical problem in the disk. Bad sectors on hard disks are marked by the operating system and bypassed. If data is recorded in a sector that becomes bad, file recovery software, and sometimes special hardware, must be used to restore it. BAK file (BAcKup file) DOS and OS/2 file extension for backup files. BAL (1) (Basic Assembly Language) Assembly language for the IBM 370/3000/4000 mainframe series. (2) (Branch And Link) Instruction used to transfer control to another part of the program. ballistic gain Trackball or mouse feature that changes cursor travel relative to hand speed. The faster the ball is moved, the farther the cursor is moved. baloon help On-screen help displayed in a cartoon-style dialogue box that appears when the pointer (cursor) is placed over the object in question. balun (BALanced UNbalanced) Device that connects a balanced line to an unbalanced line; for example, a twisted pair to a coaxial cable. A balanced line is one in which both wires are electrically equal. In an unbalanced line, such as a coax, one line has different properties than the other. band (1) Range of frequencies used for transmitting a signal. A band is identified by its lower and upper limits; for example, a 10MHz band in the 100 to 110MHz range. (2) Contiguous group of tracks that are treated as a unit. (3) Printing element in a band printer. band pass filter Electronic device that prohibits all but a specific range of frequencies to pass through it. band printer Line printer that uses a metal band, or loop, of type characters as its printing mechanism. The band spins horizontally around a set of hammers. When the desired character is in front of the selected print position, the corresponding hammer hits the paper into the ribbon and onto the character in the band. bandwidth Transmission capacity of a computer channel, communications line or bus. It is expressed in cycles per second (Hertz), the bandwidth being the difference between the lowest and highest frequencies transmitted. The frequency is equal to or greater than the bits per second. Bandwidth is also often stated in bits or bytes per second. See video bandwidth. bank Arrangement of identical hardware components. bank switching Engaging and disengaging electronic circuits. Bank switching is used when the design of a system prohibits all circuits from being addressed or activated at the same time, requiring that one unit be turned on while the others are turned off. BAPC (Business Applications Performance Corp.) Nonprofit organization founded in 1991 that develops benchmarks for PC software. bar chart Graphical representation of information in the form of bars. See business graphics. bar code Printed code used for recognition by a scanner. Traditional one-dimensional bar codes use the bar's width as the code, but encode just an ID or account number. Two-dimensional systems, such as PDF 417 from Symbol Technology, hold 1,800 characters in an area the size of a postage stamp. See UPC. barrel distortion Screen distortion in which the sides bow out. Contrast with pincushioning. barrel printer Same as drum printer. base (1) Starting or reference point. (2) Component in a bipolar transistor that activates the switch. Same as gate in a MOS transistor. (3) Multiplier in a numbering system. In a decimal system, each digit position is worth 10x the position to its right. In binary, each digit position is worth 2x the position to its right. base address Starting address (beginning point) of a program or table. See base/displacement and relative address. base alignment Alignment of a variety of font sizes on a baseline. base/displacement Machine architecture that runs programs no matter where they reside in memory. Addresses in a machine language program are displacement addresses, which are relative to the beginning of the program. At runtime, the hardware adds the address of the current first byte of the program (base address) to each displacement address and derives an absolute address for execution. base font Default font used for printing if none other is specified. baseband Communications technique in which digital signals are placed onto the transmission line without change in modulation. It is usually limited to a few miles and does not require the complex modems used in broadband transmission. Common baseband LAN techniques are token passing ring (Token Ring) and CSMA/CD (Ethernet). In baseband, the full bandwidth of the channel is used, and simultaneous transmission of multiple sets of data is accomplished by interleaving pulses using TDM (time division multiplexing). Contrast with broadband transmission, which transmits data, voice and video simultaneously by modulating each signal onto a different frequency, using FDM (frequency division multiplexing). Baseband (interleaves signals)  烝烝烝烝烝烝烝烝烝烝烝烝烝烝烝烝烝烝烝  data(1) data(2) data(3) data(1)  樛樛樛樛樛樛樛樛樛樛樛樛樛樛樛樛樛樛樛  Broadband (true simultaneous)  烝烝烝烝烝烝烝烝烝烝烝烝烝烝烝烝烝烝烝烝  data(1)xxxxxxxxxxxxxxxxxxxxxxxxxxx  陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳  voice(1)xxxxxxxxxxxxxxxxxxxxxxxxxx  陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳  data(2)xxxxxxxxxxxxxxxxxxxxxxxxxxx  陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳  data(3)xxxxxxxxxxxxxxxxxxxxxxxxxxx  樛樛樛樛樛樛樛樛樛樛樛樛樛樛樛樛樛樛樛樛  baseline Horizontal line to which the bottoms of lowercase characters (without descenders) are aligned. See typeface. baselining tool Network monitor that analyzes communications usage in order to establish routine traffic patterns. BASIC (Beginners All purpose Symbolic Instruction Code) Programming language developed by John Kemeny and Thomas Kurtz in the mid 1960s at Dartmouth College. Originally developed as an interactive, mainframe timesharing language, it has become widely used on small computers. BASIC is available in both compiler and interpreter form. As an interpreter, the language is conversational and can be debugged a line at a time. BASIC is also used as a quick calculator. BASIC is considered one of the easiest programming languages to learn. Simple programs can be quickly written on the fly. However, BASIC is not a structured language, such as Pascal, dBASE or C, and it's easy to write spaghetti code that's difficult to decipher later. The following BASIC example converts Fahrenheit to Celsius:  10 INPUT "Enter Fahrenheit "; FAHR  20 PRINT "Celsius is ", (FAHR-32) * 5 / 9  BASIC in ROM BASIC interpreter stored in a read only memory chip that is available to the user at all times. BAT file (BATch file) File of DOS or OS/2 commands, which are executed one after the other. It has a .BAT extension and is created with a text editor. See DOS batch file and DOS AUTOEXEC.BAT. batch Group, or collection, of items. batch data entry Entering a group of source documents into the computer. batch file (1) File containing data that is processed or transmitted from beginning to end. (2) File containing instructions that are executed one after the other. See BAT file. batch file transfer Consecutive transmission of two or more files. batch job Same as batch program. batch operation Some action performed on a group of items at one time. batch processing Processing a group of transactions at one time. Transactions are collected and processed against the master files (master files updated) at the end of the day or some other time period. Contrast with transaction processing. Batch and Transaction Processing Information systems typically use both batch and transaction processing methods. For example, in an order processing system, transaction processing is the continuous updating of the customer and inventory files as orders are entered. At the end of the day, batch processing programs generate picking lists for the warehouse. At the end of some period, batch programs print invoices and management reports. batch program Non-interactive (non-conversational) program such as a report listing or sort. batch session Transmitting or updating an entire file. Implies a non-interactive or non-interruptible operation from beginning to end. Contrast with interactive session. batch stream Collection of batch processing programs that are scheduled to run in the computer. batch system See batch processing. batch terminal Terminal set up for transmitting or receiving blocks of data, such as a card reader or printer. batch total Sum of a particular field in a collection of items used as a control total to ensure that all data has been entered into the computer. For example, using account number as a batch total, all account numbers would be summed manually before entry into the computer. After entry, the total is checked with the computer's sum of the numbers. If it does not match, source documents are manually checked against the computer's listing. batteries See lead acid, NiCad, nickel hydride and zinc air. baud (1) Signalling rate of a line. It's the switching speed, or number of transitions (voltage or frequency changes) that are made per second. Only at low speeds are bauds equal to bits per second; for example, 300 baud is equal to 300 bps. However, one baud can be made to represent more than one bit per second. For example, the V.22bis modem generates 1200 bps at 600 baud. (2) Commonly (and erroneously) used to specify bits per second for modem speed; for example, 1200 baud means 1200 bps. See previous paragraph. baud rate Redundant reference to baud. Baud is a rate. baudot code Pronounced "baw-doh." One of the first standards for international telegraphy developed in the late 19th century by Emile Baudot. It uses five bits per character. BBS (Bulletin Board System) Computer system used as an information source and message system for a particular interest group. Users dial into the BBS, review and leave messages for other users as well as communicate to other users on the system at the same time. BBSs are used to distribute shareware and may provide access (doors) to other application programs.  BOARDWATCH MAGAZINE  NATIONAL LIST OF  ELECTRONIC BBSs AND ONLINE INFORMATION SERVICES (Copied with permission) BOARDWATCH MAGAZINE 5970 S. Vivian Street Littleton, CO 80127 Information 303/973-6038 Subscriptions 800/933-6038 By modem (N81) 303/973-4222 65' North (DESQview utilities) 907/452-1460 ADA 9X Project (Ada language) 800/232-9925 ADA Information Clearinghouse 703/614-0215 Advanced Data Services Inc. 301/695-9116 American Cybernetics 602/968-1082 ANARC (World/Radio/TV handbook) 913/345-1978 APCUG - Assn. of PC User Groups 408/439-9367 Applied Modeling Research (EPA models) 919/541-1325 Aquila (Fidonet/Interlink/Metronet) 708/820-8344 Ashton-Tate Technical Support 408/431-2275 AST Technical Support 714/727-4723 AT&T Support (PC 6300 & other models) 908/769-6397 ATI Support (modems & video cards) 416/756-4591 Attention to Details (utilities/ASP) 714/681-6221 Audiophile Network (high-end audio) 818/988-0452 Automobile Consumer Services (prices) 513/624-0552 AviTechnic 1:261/662 301/252-0717 BBS America (DFW online newsletter) 214/680-3406 BBS Press Service (INFOMAT Online) 913/478-9239 Best Friends (multiline social) 714/828-7093 Big Sky Telegraph (educ/econ Montana) 406/683-7680 Bird Info Network (exotic birds) 303/423-9775 BMUG (Mac support) 415/849-2684 Boardwatch Magazine Online Info 303/973-4222 Boca Research Support BBS 407/241-1601 Book BBS (info on 3000+ computer books)215/657-6130 Borland Download BBS 408/439-9096 Bruce's Bar & Grill (social) 203/236-3761 Bucks Telematics 273/201 215/493-5242 C.A.R.L. Library Service (Colorado) 303/863-1350 CAD/Engineering Service 1:116/32 615/824-4938 Canada Remote Systems 416/798-4713 Capital PC User's Group BBS 301/738-9060 Castle Tabby 107/4122 (Apple, MAC) 908/988-0706 Celebration Station (games chat) 207/374-5161 Census Bureau Office Automation 301/763-4576 Census Bureau Personnel Division 301/763-4574 Channel 1 (45-line PC Board sys) 617/354-8873 Chicago SysLink (TRS 80 support) 312/622-4442 chinet (UNIX Systems Internet mail) 312/283-0559 ClassiComputerFieds (classified ads) 317/359-5199 Clean Air (health, smoking topics) 408/298-4277 Cleveland Freenet (city info) 216/368-3888 CocoNet (San Diego entertainment) 619/456-0815 Comm-Post, The 104/666 303/534-4646 Community News Service (entertainment) 719/520-5000 Compact Audio Disk Exchange (buy/sell) 415/824-7603 CompuCom Support (9600 bps - $279 ) 415/499-7711 Computer Garden (treasure hunting) 301/546-1508 Computerized BBS (Ward Christensen) 708/849-1132 Computing Canada Online (PC newspaper) 416/497-5263 Corporate Data Exchange (CDX)(PR news) 609/683-4422 CrossTalk Technical Support 404/740-8428 CTC IEEE Employment Database (resumes) 508/263-3857 Cul-de-Sac Bar & Grill (ham radio) 508/429-1784 Dante Project (Divinia Comedia) 603/643-6310 Dark Side of the Moon (DOS & UNIX) 408/245-7726 Data Core (25 line major BBS) 213/842-6880 DataLink RBBS System (NOAA satellite) 214/394-7438 Dawg Byte (ANSI Art Club 1:116/29) 615/385-4268 Denver Exchange 104/909 (gay, lesbian) 303/623-4965 DragonNet 386/451 (major BBS) 409/765-5459 East Bay X-Change 372/888 803/556-7485 Echo (Unix CAUCUS conferencing) 212/989-8411 Economic Bulletin Board (statistics) 202/377-3870 Ed Hopper's BBS (home of uuPCB) 713/997-7575 Electric Ideas Clearinghouse 206/586-6854 Energy Info Admin E-Publications 202/586-8658 eSoft Product Support (Bread Board) 303/699-8222 Event Horizons (graphics image lib.) 503/697-5100 Exchange BBS (gay/bi/lesbian) 713/521-2191 EXEC-PC (largest BBS in US, 100 lines) 414/789-4210 Executive Network (interlink netmail) 914/667-4567 Eye Contact (gay issues, chat) 415/255-5972 Falken Support (software) 703/803-8000 Far West (Western Canada Galacticomm) 604/381-3934 FAX/Satellite (NOAA Weather) 619/224-3853 FCC Public Access Link 301/725-1072 Federal Job Information Center 313/226-4423 FEDLINK ALIX II (federal libraries) 202/707-4888 Fido Software 1:125/111 415/863-2739 Fido Tech Stand (info for Holland) 31-30-735900 FOG City 125/10 (gay community) 415/863-9697 Fred the Computer (Weirdnet Newswire) 508/872-8461 FreeBoard (desktop pub. 1:264/212) 804/744-0797 FSBBS Prototype System (FSUUCP & FSBBS)805/543-8227 Fun Connection (entertainment, news) 503/753-8431 Gateway Comm. (NetWare, TCP/IP util.) 714/863-7097 GDP Technologies (PC shareware) 303/673-9470 Gilmore Systems (support MAGNUM BBS) 818/706-9805 GLIB (gay/lesbian information) 703/578-4542 Greenpeace Environet (ecological) 415/512-9108 Hayes Microcomputer (modem support) 800/874-2937 Heartland Free-net 309/674-1100 Herpnet/Satronics (reptile, amphibian) 215/698-1905 HH Info-Net (windows, OS/2) 203/246-3747 HOLLIS (Harvard online library) 617/495-9500 Hysterics (Amiga 1:163/109) 613/231-7144 IBM National Support Center 404/835-5300 Inbound/Outbound/Teleconnect 212/989-4675 Index Systems (Atlanta BBS) 404/924-8414 Infinity World (8-line galacticomm) 606/271-6556 InfoHost Demo BBS 201/288-7792 Infolink for Upper East Tenn. 615/434-2552 Inns of Court (LAN related files) 214/458-2620 Intel PCEO Support 503/645-6275 Invention Factory (shareware catalog) 212/431-1194 Investor's Online Data (stocks) 206/285-5359 JAG-NET (Navy Judge Advocate General) 703/325-0748 JDR Microdevices (hardware catalog) 408/559-0253 JEPP/LINK (pilot weather service) 800/767-7000 JOBBS (job listings technical) 404/992-8937 Keith Graham Shareware (utilities) 914/623-0039 KIMBERELY (prime rate, T-bills, etc.) 612/340-2489 King's Market 104/115 (writer's area) 303/665-6091 LANtastic (tech. support) 602/293-8065 Late Night (GENESIS software) 315/592-7300 Late Night Software 125/555 (UFGATE) 415/695-0759 Leading Edge Auto Info Line 508/836-3967 LegalEase (issues/forms) 509/326-3238 MAC-LINK 514/935-4257 Macalot (support Second Sight for Mac) 412/846-5312 Macinternational (largest MAC BBS) 803/798-3755 Magpie (support) 212/420-0527 MaxiHost Support (small easy BBS) 209/836-2402 McAfee Associates (virus info) 408/988-4004 METRO Online Entertainment 212/831-9280 Micro Foundry, The (software support) 415/598-0398 Micro Message Service (news magazines) 919/779-6674 Micro Tech (OSIRIS support, mail) 314/334-6359 Microlink B (USA Today, news) 303/972-9600 Microrim Technical Support BBS 206/649-9836 Microsystems Software Inc. (support) 508/875-8009 Midwest MIDI 1:147/1007 405/733-3102 Minnesota Spacenet (NASA news) 612/920-5566 MOG-UR'S EMS (CD-ROMS, 2.8 GB Hub Serv)818/366-1238 Movie BBS )reviews for movie & TV) 718/939-5462 N.A.C.D. (Cave Scuba Divina) 912/246-3280 N8EMR Ham (ham/radio) 614/895-2553 NAPLPS Graphics (software) 613/727-5272 NARDAC (Zenith support, federal users) 804/445-1627 NASA Headquarters Info Tech 202/453-9008 NASA Spacelink (flight/space history) 205/895-0028 Nashville Exchange (games, software) 615/383-0727 National Agricultural Library 301/344-8510 National Genealogical (family history) 703/528-2612 NAVWESA (naval weapons engineering) 202/433-6639 Netcom Internet Guest System (lodging) 408/241-9760 Network World Bulletin Board (LAN, WAN)508/620-1178 Neuropsychology Bound 157/3 (support) 216/356-1431 NIST ACTS (computer telephone service) 303/494-4775 NIST Computer Security (virus issues) 301/948-5717 Nixpix (adult graphics images) 303/920-1263 NOAA Space Environment Lab 303/497-5042 NoGate Consulting (PAK archive utility)616/530-3392 Numisnet (coin collecting) 301/498-8205 OASIS (Atlanta BBS) 404/627-2662 Occupational Health/Safety 212/385-2034 Odyssey (adult chat, games, etc.) 818/358-6968 OERI (educational statistics, data) 800/222-4922 Old Colorado City Comm. (political) 719/632-4111 Online Now (new software, CD-ROMS) 807/345-5522 Online With Hayes 404/446-6336 Oracle PC (South Australian TBBS) 6108 260-6222 Oracomm Support 619/346-1608 Osprey's Nest (birdwatching, ecology) 301/989-9036 P.D.S.L.O. (national BBS list) 516/938-6722 PacComm (packet radio equipt. supplier)813/874-3078 PC Ohio (shareware) 216/381-3320 PHYSICS Forum (astronomical sciences) 413/545-1959 Pinecliff 104/28 (shareware) 303/642-7463 PKWare (PKARC and PKZIP Utilities) 414/354-8670 Pleasure Dome (erotic) 804/490-5878 Practical Peripherals (modem support) 818/706-2467 ProComm Support 314/875-0503 Promised Land (WINDOWS, chat & more) 715/387-1339 Public Brand Software (commercial) 317/856-2087 Public Data Network ($2.50/hr access) 503/474-6662 QAQPSTTN (air quality planning) 919/541-5742 QMail Deluxe Support 901/382-5583 Qualitas, Inc. (support) 301/907-8030 Quick BBS Support BBS 363/34 407/896-0494 Random Access Information Services 503/761-8100 Rose Media (Canadian PC board sys.) 416/733-2780 Rusty & Edies (large ML PCBoard) 216/726-0737 Salt Air (PCBOARD BBS software) 801/261-8976 San Diego NeXt User's Group 619/456-2522 Science Resources Studies (fed budget) 202/634-1764 SDN Project 1:141/840 203/634-0370 SEAboard! (ARC, SEADOG, AXE software) 201/473-1991 Seagate Technical Support 408/438-8771 Searchlight (support) 516/689-2566 SemWare Support (QEdit, shareware) 404/641-8968 Short Line 104/36 (varied subjects) 303/733-0773 SIGCAT (CD-ROM/Optical Publishing info)703/648-4168 Sistema Professional Info (Mexico) 525 590-5988 Skeleton Closet (geneology programs) 804/671-8547 Society for Technical Comm. 703/522-3299 Sonshine Express (Christian family) 415/651-2440 Sound Advise (20 line PCBoard) 816/436-4516 Source for Source (Clipper/XBase/etc) 516/968-7824 Spare Parts 1:130/38 (Windows) 817/540-3527 Star-Link Network (75,000 programs) 718/972-6099 State and Local Emergency Management 202/646-2887 Stillwaters (Chicagoland, 500 systems) 708/403-2826 Superdemocracy Foundation (political) 305/370-9376 TAXACOM (botany, FLORA ONLINE news) 716/896-7581 TEAMate Unix Bulletin Board 213/318-5302 Telegodzilla (home of ZModem) 503/621-3746 Telepath (Dr. Dobbs magazine online) 415/364-8315 Telix Support 416/439-8293 That Old Frog's Swamp (Zen Bhuddist) 715/362-3895 The Back Room (largest gay DB) 718/849-1614 The Business BBS 213/477-0408 The General (file library) 619/281-8616 The Ledge PCBoard (Textview Door) 818/896-4015 The Opowd Crowd (sports) 708/885-8865 The Other BBS 1:1/0 (Fiodnet) 717/657-2223 The Professional System (lawyers EDP) 303/740-2223 The Well (popular - hourly charges) 415/332-7190 Trinity 1 (UK distributor Boardwatch) 44 392 410210 Titan (adult, games, GIF images) 904/476-1270 Town Hall (conservative political) 800/648-6964 Transnet (language translation) 217/384-5101 TurboTax Support (income tax info) 619/453-5232 U.S. ROBOTICS - Sit UBU Sit 708/982-5092 US Naval Observatory (enter @TCO) 202/653-1079 USGS Quick Epicenter Determination 800/358-2663 USNO Time of Day for Clocks 202/653-0351 UT Library Online Catalog 512/471-9420 Ventura Professional Forum 408/227-4818 Ward and Randy's CBBS (oldest BBS) 312/545-8086 WeatherBank (forecast for any city) 800/827-2727 Western Digital Technical Support 714/753-1068 Wildcat HQ 210/12 (support) 805/395-0650 Windows Online Info (3.0 programs) 510/736-8343 Windsor Manor 203/688-4973 WordPerfect Customer Support 801/225-4444 WWIV Support BBS 213/208-6689 XTree (support Pro Gold DOS shell) 805/546-9150 XyQuest Tech Support (XyWrite III+) 508/667-5669 Yellow Dream Machine (disability news) 512/451-3222 BCD (Binary Coded Decimal) Storage of numbers in which each decimal digit is converted into binary and is stored in a single character or byte. For example, a 12-digit number would take 12 bytes. See numbers. BCS (1) (The Boston Computer Society) Nonprofit membership organization founded in 1977 by Jonathan Rotenberg. With over 28,000 members, it is the world's largest personal computer association. Services include user and special interest groups, a subscription to BCS publications, access to the Resource Center, public-domain software and shareware. Address: 1 Kendall Square, Cambridge, MA 02139, 617/252-0600. (2) (Binary Compatibility Standard) See ABI. (3) (The British Computer Society) Address: 13 Mansfield St., London, England W1M 0BP. BDOS error See read error and write error. beaconing Continuous signalling of error conditions on a LAN. bead (1) Small programming subroutine. A sequence of beads that are strung together is called a thread. (2) Insulator surrounding the inner wire of a coaxial cable. BEL See bell character. Bell 103 AT&T standard for asynchronous 300 bps full-duplex modems using FSK modulation on dial-up lines. Bell 113 AT&T standard for asynchronous 300 bps full-duplex modems using FSK modulation on dial-up lines. The 113A can originate but not answer calls, while the 113D can answer but not originate. Bell 201 AT&T standard for synchronous 2400 bps full-duplex modems using DPSK modulation. Bell 201B was originally designed for dial-up lines and later for leased lines. Bell 201C was designed for half- duplex operation over dial-up lines. Bell 202 AT&T standard for asynchronous 1800 bps full-duplex modems using DPSK modulation over four-wire leased lines as well as 1200 bps half-duplex operation over dial-up lines. Bell 208 AT&T standard for synchronous 4800 bps modems. Bell 208A is a full-duplex modem using DPSK modulation over four-wire leased lines. Bell 208B was designed for half-duplex operation over dial-up lines. Bell 209 AT&T standard for synchronous 9600 bps full-duplex modems using QAM modulation over four-wire leased lines or half-duplex operation over dial-up lines. Bell 212 AT&T standard for asynchronous 1200 bps full-duplex modems using DPSK modulation on dial-up lines. bell character Control code used to sound an audible bell or tone in order to alert the user (ASCII 7, EBCDIC 2F). Bell compatible Modem that is compatible with modems originally introduced by the Bell Telephone System. Bell Labs Research and development center of the AT&T Company and one of the most renowned scientific laboratories in the world. Bell System AT&T and the Bell Telephone Companies before divestiture. See divestiture and RBOC. benchmark Test of performance of a computer or peripheral device. The best benchmark is the actual set of application programs and data files that the organization will use. Running benchmarks on a single user computer is reasonably effective; however, benchmarking a multiuser system is complicated. Unless the user environment can be duplicated closely, the benchmark may be inaccurate. See Linpack, Dhrystones, Whetstones, Khornerstones and SPECmark. BER (1) (Basic Encoding Rules) One method for encoding information in the OSI environment. For example, it defines how Boolean data is coded. (2) (Bit Error Rate) Average number of bits transmitted in error. Berkeley extensions See BSD UNIX. Bernoulli Box Removable disk system for personal computers from Iomega Corp., Roy, UT. It uses a SCSI interface. Introduced in 1983, it used a 10MB, 8" floppy disk cartridge. In 1987, 20MB 5.25" cartridges were introduced and later 44MB and 90MB. The MultiDisk 150 (1992) accepts 35, 65, 90, 105 and 150MB cartriges. The name comes from 18th century Swiss scientist, Daniel Bernoulli, who demonstrated fluid dynamics principles. Unlike a hard disk in which the read/write head flies over a rigid disk, the Bernoulli floppy is spun at high speed and bends up close to the head. Upon power failure, a hard disk must retract the head to prevent a crash, whereas the Bernoulli floppy naturally bends down. Beta First home VCR format, now defunct. Developed by Sony, it used 1/2" tape cassettes. Beta Hi-fi added CD-quality audio, and SuperBeta improved the image. Today, VHS is the standard 1/2" VCR format. beta test Test of hardware or software that is performed by users under normal operating conditions. See alpha test. betaware Software in beta test that has been provided to a large number of users in advance of the formal release. Bezier In computer graphics, a curve that is generated using a mathematical formula which assures continuity with other Bezier curves. It is mathematically simpler, but more difficult to blend than a b-spline curve. Within CAD and drawing programs, Bezier curves are typically reshaped by moving the handles that appear off of the curve. BFT (Binary File Transmission) Standard for transmitting data between fax boards in less time than conventional modems. It does not allow transfer between fax boards and data modems. BI bus Proprietary high-speed bus used in the VAX series. bi-endian Ability to switch between big endian and little endian ordering. bidirectional Ability to move, transfer or transmit in both directions. bidirectional printer Printer that prints alternate lines from right to left. BIFF (Binary Interchange File Format) Spreadsheet file format that holds data and charts, introduced with Excel Version 2.2. bifurcate To divide into two. Big Blue Slang for IBM coined from the blue covers on most of its earlier mainframes. big endian Order of bytes in a word in which the most significant byte is first. Little endian reverses the order. See bi-endian.  16 bit number: 5A01h (23,041 decimal)  Big endian: 5A01 (Motorola 68xxx)  Little endian: 015A (Intel x86)  bill of materials List of components that make up a system. For example, a bill of materials for a house would include the cement block, lumber, shingles, doors, windows, plumbing, electric, heating and so on. Each subassembly also contains a bill of materials; the heating system is made up of the furnace, ducts, etc. A bill of materials "implosion" links component pieces to a major assembly, while a bill of materials "explosion" breaks apart each assembly or subassembly into its component parts. The first hierarchical databases were developed for automating bills of materials for manufacturing organizations in the early 1960s. billion One thousand times one million. See giga and nanosecond. bin (BINary) Popular directory name for storing executable programs, device drivers, etc. (binary files). binaries Executable programs in machine language. binary Meaning two. The principle behind digital computers. All input to the computer is converted into binary numbers made up of the two digits 0 and 1 (bits). For example, when you press the "A" key on your personal computer, the keyboard generates and transmits the number 01000001 to the computer's memory as a series of pulses. The 1 bits are transmitted as high voltage; the 0 bits are transmitted as low. The bits are stored as charged and uncharged memory cells in the computer. On magnetic disk and tape, the bits are stored as positively and negatively charged spots. Display screens and printers convert the binary numbers into visual characters. The electronic circuits that process these binary numbers are also binary in concept. They are made up of on/off switches (transistors) that are electrically opened and closed. The current flowing through one switch turns on (or off) another switch, and so on. These switches open and close in nanoseconds and picoseconds (billionths and trillionths of a second). A computer's capability to do work is based on its storage capacity (memory and disk) and internal transmission speed. Greater storage capacities are achieved by making the memory cell or magnetic spot smaller. Faster transmission rates are achieved by shortening the time it takes to open and close the switch. In order to increase computer performance, we keep improving binary devices. How Binary Numbers Work Binary numbers are actually simpler than decimal numbers as they use only the digits 0 and 1 instead of 0 through 9. In decimal, when you add 9 and 1, you get 10. But, if you break down the steps you find that by adding 9 and 1, what you get first is a result of 0 and a carry of 1. The carry of 1 is added to the digits in the next position on the left. In the following example, the carry becomes part of the answer since there are no other digits in that position. carry--1  9  + 1  陳陳  10  The following example adds 1 ten times in succession. Note that the binary method has more carries than the decimal method. In binary, 1 and 1 are 0 with a carry of 1.   Binary Decimal Binary Decimal 0 0 101 5 + 1 + 1 + 1 + 1 陳陳 陳陳 陳陳 陳陳 1 1 110 6 + 1 + 1 + 1 + 1 陳陳 陳陳 陳陳 陳陳 10 2 111 7 + 1 + 1 + 1 + 1 陳陳 陳陳 陳陳 陳陳 11 3 1000 8 + 1 + 1 + 1 + 1 陳陳 陳陳 陳陳 陳陳 100 4 1001 9 + 1 + 1 + 1 + 1 陳陳 陳陳 陳陳 陳陳 101 5 1010 10 binary code Coding system made up of binary digits. See BCD, data code and numbers. binary compatible Refers to any data, hardware or software structure (data file, machine code, instruction set, etc.) in binary form that is 100% identical to another. binary field Field that contains binary numbers. It may refer to the storage of binary numbers for calculation purposes, or to a field that is capable of holding any information, including data, text, graphics images, voice and video. See BLOb. binary file (1) Executable program in machine language ready to run. (2) File that contains binary numbers. binary format (1) Numbers stored in pure binary form in contrast with BCD form. See binary numbers. (2) Information stored in a binary coded form, such as data, text, images, voice and video. See binary file, binary field and BLOb. (3) File transfer mode that transmits any type of file without loss of data. binary notation Use of binary numbers to represent values. binary numbers Numbers stored in pure binary form. Within one byte (8 bits), the values 0 to 255 can be held. Two contiguous bytes (16 bits) can hold values from 0 to 65,535. See numbers and binary values. binary search Technique for quickly locating an item in a sequential list. The desired key is compared to the data in the middle of the list. The half that contains the data is then compared in the middle, and so on, either until the key is located or a small enough group is isolated to be sequentially searched. binary synchronous See bisync. binary tree Data structure in which each node contains one parent and no more than two children. binary values The following table shows the maximum number of numeric combinations in a binary structure with all bits set to zero equivalent to one combination. For example, in one bit, which can be 0 or 1, there are two possible values.  Bits Total values 1 2 2 4 3 8 4 16 5 32 6 64 7 128 8 256 9 512 10 1,024 1K 11 2,048 2K 12 4,096 4K 13 8,192 8K 14 16,384 16K 15 32,768 32K 16 65,536 64K 17 131,072 128K 18 262,144 256K 19 524,288 512K 20 1,048,576 1M 21 2,097,152 2M 22 4,194,304 4M 23 8,388,608 8M 24 16,777,216 16M 25 33,554,432 32M 26 67,108,864 64M 27 134,217,728 128M 28 268,435,456 256M 29 536,870,912 512M 30 1,073,741,824 1G 31 2,147,483,648 2G 32 4,294,967,296 4G 33 8,589,934,592 8G 34 17,179,869,184 16G 35 34,359,738,368 32G 36 68,719,476,736 64G 37 137,438,953,472 128G 38 274,877,906,944 256G 39 549,755,813,888 512G 40 1,099,511,627,776 1T bind (1) To assign a machine address to a logical or symbolic reference or address. (2) To assign a type or value to a variable or parameter. See binding time. (3) To link modules together. See linkage editor. binding time (1) In program compilation, the point in time when symbolic references to data are converted into physical machine addresses. (2) In programming languages, when a variable is assigned its type (integer, string, etc.). Traditional compilers and assemblers provide early binding and assign types at compilation. Object- oriented languages provide late binding and assign types at runtime when the variable receives a value from the keyboard or other source. biomechanics Study of the anatomical principles of movement. Biomechanical applications on the computer employ stick modeling to analyze the movement of athletes as well as racing horses. bionic Machine that is patterned after principles found in humans or nature; for example, robots. It also refers to artificial devices implanted into humans replacing or extending normal human functions. BIOS (Basic I/O System) Detailed instructions that activate peripheral devices. See ROM BIOS. bipolar Category of high-speed microelectronic circuit design, which was used to create the first transistor and the first integrated circuit. The most common variety of bipolar chip is TTL (transistor transistor logic). Emitter coupled logic (ECL) and integrated injection logic (I2L) are also part of the bipolar family. Bipolar and MOS are the two major categories of chip design. bipolar transmission Digital transmission technique that alternates between positive and negative signals. The 1s and 0s are determined by varying amplitudes at both polarities while non-data is zero amplitude. BIPS (Billion Instructions Per Second) See MIPS. biquinary code Meaning two-five code. A system for storing decimal digits in a four-bit binary number. birefringence Using a crystal to split light into two frequencies that travel at different speeds and at right angles to each other. It's used to filter out a color in an LCD display. bis Second version. It means twice in Old Latin, or encore in French. BISDN (Broadband IDSN) See ISDN. bison Free Software Foundation's version of yacc. bistable circuit Same as flip-flop. bisync (BInary SYNChronous) Major category of synchronous communications protocols used in mainframe networks. Bisync communications require that both sending and receiving devices are synchronized before transmission of data is started. Contrast with asynchronous transmission. bisynchronous See bisync. bit (BInary digiT) Single digit in a binary number (0 or 1). Within the computer, a bit is physically a transistor or capacitor in a memory cell, a magnetic spot on disk or tape or a high or low voltage pulsing through a circuit. A bit is like a light bulb: on or off. Groups of bits make up storage units in the computer, called characters, bytes, or words, which are manipulated as a group. The most common is the byte, made up of eight bits and equivalent to one alphanumeric character. See space/time. bit cell Boundary in which a single bit is recorded on a tape or disk. bit density Number of bits that can be stored within a given physical area. bit depth Number of on-screen colors (number of bits used to represent a pixel). bit flipping Same as bit manipulation. bit level device Device, such as a disk drive, that inputs and outputs data bits. Contrast with pulse level device. bit manipulation Processing individual bits within a byte. Bit- level manipulation is very low-level programming, often done in graphics and systems programming. bit map See bitmap. bit-oriented protocol Communications protocol that uses individual bits within the byte as control codes, such as IBM's SDLC. Contrast with byte-oriented protocol. bit parallel Transmission of several bits at the same time, each bit travelling over a different wire in the cable. bit pattern Specific layout of binary digits. bit plane Segment of memory used to control an object, such as a color, cursor or sprite. Bit planes may be reserved parts of a common memory or independent memory banks each designed for one purpose. bit rate Transmission speed of binary coded data. Same as data rate. bit serial Transmission of one bit after the other on a single line or wire. bit slice processor Logic chip that is used as an elementary building block for the computer designer. Bit slice processors usually come in 4-bit increments and are strung together to make larger processors (8 bit, 12 bit, etc.). bit specifications (1) Size of the computer's internal word, or registers, which is the amount of data the CPU can compute at the same time. If the clock rates (16MHz, 20MHz, etc.) and basic architecture are equal, a 32-bit computer works twice as fast internally as a 16-bit computer. (2) Size of the computer's data bus, which is the pathway over which data is transferred between memory and the CPU and between memory and the peripheral devices. If the bus clock rates are equal, a 16-bit bus transfers data twice as fast as an 8-bit bus. (3) Size of the address bus, which determines how much memory the CPU can address directly. Each bit doubles the number, for example, 20-bits addresses 1,048,576 bytes; 24-bits addresses 16,772,216 bytes. (4) Number of colors that can be displayed at one time. Unless some of the memory is used for cursor or sprite movement, an 8-bit graphics adapter generates 256 colors; 16-bit, 64K colors; 24-bit, 16.8 million colors. See alpha channel. (5) See binary values. bit stream Transmission of binary signals. bit stuffing Adding bits to a transmitted message in order to round out a fixed frame or to break up a pattern of data bits that could be misconstrued for control codes. bit twiddler Same as hacker. bitblit See bitblt. bitblt (BIT BLock Transfer) In computer graphics, a hardware feature that moves a rectangular block of bits from main memory into display memory. It speeds the display of moving objects (animation, scrolling) on screen. A hardware bitblt provides fastest speed, but bitblts are also implemented in software even in non-graphics systems. For example, text scrolls faster when it is copied as a contiguous block (bitblt) to the next part of the window rather than processing every character on every line. bite See byte. bitmap (1) In computer graphics, an area in memory that represents the video image. For monochrome screens, one bit in the bitmap represents one pixel on screen. For gray scale or color, several bits in the bitmap represent one pixel or group of pixels on screen. (2) Binary representation in which each bit or set of bits corresponds to some object (image, font, etc.) or condition. bitmapped font Set of dot patterns for each letter and digit in a particular typeface (Times Roman, Helvetica, etc.) for a specified type size (10 points, 12 points, etc.). Bitmapped typefaces are either purchased in groups of pre-generated point sizes, or, for a wide supply of fonts, font generators allow the user to create a variety of point sizes. Bitmapped fonts take up disk space for each point size. Contrast with scalable font. See font and font generator. bitmapped graphics Raster graphics method for generating images. Contrast with vector graphics and character graphics. BITNET Popular network of university computers funded by the National Science Foundation and run by the Zero One Corp. BIX (Byte Information eXchange) Online database of computer knowledge from BYTE magazine, designed to help users fix problems and obtain info on hardware and software products. Address: 1030 Mass. Ave., Cambridge, MA 02138, 800/695-4775, 617/491-3393. See online services. Black Apple Early Apple II+ with a black case and external audio controls. Bell and Howell sold them in a training kit. black box (1) Custom-made electronic device, such as a protocol converter or encryption system. Yesterday's black boxes often become today's off- the-shelf products. (2) (Black Box Corp., Pittsburgh, PA) Organization that specializes in communications and LAN products. It offers expert services, custom solutions and hard-to-find products. blank character Space character that takes up one byte in the computer just like a letter or digit. When you press the space bar on a personal computer keyboard, the ASCII character with a numeric value of 32 is created. blank squash Removal of blanks between items of data. For example, in the expression CITY + ", " + STATE, the data is concatenated with a blank squash resulting in AUSTIN, TX rather than AUSTIN TX. blip Mark, line or spot on a medium, such as microfilm, that is optically sensed and used for timing or counting purposes. blit See bitblt. BLOb (Binary Large OBject) Coined by Borland, a database field that holds any digitized information. block (1) Group of disk or tape records that is stored and transferred as a single unit. (2) Group of bits or characters that is transmitted as a unit. (3) Group of text characters that has been marked for moving, copying, saving or other operation. block device Peripheral device that transfers a group of bytes (block, sector, etc.) of data at a time such as a disk. Contrast with character device. block diagram Chart that contains squares and rectangles connected with arrows to depict hardware and software interconnections. For program flow charts, information system flow charts, circuit diagrams and communications networks, more elaborate graphical representations are usually used. block move Ability to mark a contiguous segment of text or data and move it. blocking factor Number of records in a block. blow To write code or data into a PROM chip by blowing the fuses of the 0 bits. The 1 bits are left alone. blow up Same as crash, bomb or abend. BMP (Bit MaP) Windows graphics format that may be device dependent or independent. Device independent BMP files (DIB) are coded for translation to a wide variety of displays and printers. BNC Commonly used connector for coaxial cable. The plug looks like a tiny tin can with the lid off and two short pins sticking out on the upper edge on opposite sides. After insertion, the plug is turned, tightening the pins in the socket. board See printed circuit board and BBS. board level Electronic components that are mounted on a printed circuit board instead of in a cabinet or finished housing. BOC (Bell Operating Company) One of 22 telephone companies that was formerly part of AT&T and now part of one of the seven regional Bell telephone companies. BOCOEX (BOston COmputer EXchange) See computer exchange. body type Typeface and size commonly used for text in paragraph copy. Typically 10 points. BOF (Beginning Of File) Status of a file when it is first opened or when an instruction or command has reset the file pointer. boilerplate Common phrase or expression used over and over. Boilerplate is stored on disk and copied into the document as needed. boldface Characters that are heavier and darker on printed output and brighter than normal on a display screen. boldface attribute Code that turns normal characters into boldface characters on a printer or display screen. boldface font Set of type characters that are darker and heavier than normal type. In a boldface font, all characters have been designed as bold characters. bomb Same as abend and crash. BOMP (Bill Of Materials Processor) One of the first DBMSs used for bill of materials explosion in the early 1960s from IBM. A subsequent version, DBOMP, was used in manufacturing during the 1970s. Boolean data Yes/no or true/false data. Boolean expression Statement using Boolean operators that expresses a condition which is either true or false. Boolean logic The "mathematics of logic," developed by English mathematician George Boole in the mid 19th century. Its rules govern logical functions (true/false). As add, subtract, multiply and divide are the primary operations of arithmetic, AND, OR and NOT are the primary operations of Boolean logic. Boolean operator One of the Boolean logic operators such as AND, OR and NOT. Boolean search Search for specific data. It implies that any condition can be searched for using the Boolean operators AND, OR and NOT. For example, the English language request: "Search for all Spanish and French speaking employees who have MBAs, but don't work in Sales." is expressed in the following dBASE command:  list for degree = "MBA" .and.  (language = "Spanish" .or. language = "French")  .and. .not. department = "Sales"  boot Causing the computer to start executing instructions. Personal computers contain built-in instructions in a ROM chip that are automatically executed on startup. These instructions search for the operating system, load it and pass control to it. Starting up a large computer may require more button pushing and keyboard input. The term comes from "bootstrap," since bootstraps help you get your boots on, booting the computer helps it get its first instructions. See cold boot and warm boot. boot drive Disk drive that contains the operating system. boot failure Inability to locate and/or read the operating system from the designated disk. boot record See boot sector. boot ROM Memory chip that allows a workstation to be booted from the server or other remote station. boot sector Area on disk (usually the first sectors in the first disk partition) reserved for the operating system. On startup, the computer looks in the boot sectors for the operating system, which must be loaded first. boot virus Virus written into the boot sectors of a floppy disk. If the floppy is booted, it infects the system. For example, the Michelangelo virus, which destroys data on March 6th, Michelangelo's birthday, infects a computer if the virus diskette is left in the drive and booted inadvertently when the computer is turned back on. bootable disk Disk that contains the operating system in a form ready to load into the computer. It often refers to a floppy disk that contains the operating system in its boot sectors. If a hard disk personal computer does not find a bootable floppy disk in the primary floppy drive at startup (A: in a PC), it boots from the hard disk. It's a good idea to make a bootable disk for your personal computer in case the hard disk doesn't boot some day. That way, you'll be able to start the computer and access important data. See DOS Sys and DOS Format. bootstrap See boot. Borland (Borland Int'l., Inc., Scotts Valley, CA) Leading PC software company founded in 1983 by Philippe Kahn. Its Turbo Pascal moved Pascal out of the academic halls into a commercial product, and its Turbo C has become an industry standard. Borland C++ and Turbo Pascal for Windows are committed to Windows and object-oriented programming. In 1984, Borland's Sidekick was the first PC desktop accessory program, which popularized TSRs for DOS applications. With Borland's acquisition of Ansa's Paradox in 1987 and Ashton-Tate's dBASE in 1991, it has become the leader in PC database software. Using object- oriented programming as the paradigm for the 1990s, Borland plans to unify Paradox, dBASE, its Quattro Pro spreadsheet and programming languages into an interoperable family of products. Borland C++ ANSI C and C++ compiler from Borland for DOS and Windows applications. It is Turbo C-compatible and its debugger supports Windows programs written in Microsoft C. It includes application frameworks for Windows (ObjectWindows) and DOS (Turbo Vision). Borland C++ for OS/2 is also available. Bourne shell See UNIX. bpi (Bits Per Inch) Used to measure the number of bits stored in a linear inch of a track on a recording surface, such as on a disk or tape. bps (Bits Per Second) Used to measure the speed of data transfer in a communications system. branch (1) Same as GOTO. (2) Connection between two blocks in a flowchart or two nodes in a network. breadboard Thin plastic board full of holes used to hold components (transistors, chips, etc.) that are wired together. It is used to develop electronic prototypes or one-of-a-kind systems. break To temporarily or permanently stop executing, printing or transmitting. break key Key that is pressed to stop the execution of the current program or transmission. breakout box Device inserted into a multiple-line cable for testing purposes that provides an external connecting point to each wire. A small LED may be attached to each line, which glows when a signal is present. BRI See ISDN. bridge (1) To cross from one circuit, channel or element over to another. (2) Computer system that connects two similar LANs together. Some bridges provide conversion between dissimilar LANs, such as Ethernet and Token Ring. Bridges are inserted into a LAN to improve performance by keeping traffic contained within smaller segments. Bridges work at the data link level (OSI layer 2). See transparent bridge, repeater, router, gateway and hub. bridgeware Hardware or software that converts data or translates programs from one format into another. Brief Text editor for PC programming from Borland. It provides automatic indentation and the ability to edit different parts of a source program at the same time. brightness Light level on a display screen. Contrast with contrast. British Telecom Division of the British Post Office that manages telecommunications throughout Great Britain and Northern Ireland. broadband Technique for transmitting large amounts of data, voice and video over long distances. Using high frequency transmission over coaxial cable or optical fibers, broadband transmission requires modems for connecting terminals and computers to the network. Using the same FDM (frequency division multiplexing) technique as cable TV, several streams of data can be transmitted simultaneously. Contrast with baseband. broadcast To disseminate information to several recipients simultaneously. Brooklyn Bridge PC file transfer program from Fifth Generation Systems, Baton Rouge, LA, that transfers data between laptops and desktop computers. brouter (Bridging ROUTER) Communications device that is part bridge and router. Like a bridge, it functions at the data link level (OSI layer 2) and remains independent of higher protocols. Like a router, it manages multiple lines and routes messages. See router, gateway and hub. browse (1) To view and possibly edit a file of data on screen similar to handling text in a word processing document. The user can scroll the data horizontally and vertically. (2) To view and edit the class hierarchy of the objects in an object-oriented programming language. BSC (Binary Synchronous Communications) See bisync. BSD UNIX (Berkeley Software Distribution UNIX) Version of UNIX developed at Univ. of California at Berkeley. Extensions include networking, task switching and larger file names (from 14 to 255 chars.). BTAM (Basic Telecommunications Access Method) IBM communications program that is used in bisynch, non-SNA mainframe networks. Application programs must interface directly with the BTAM access method. BTLZ (British Telecom Lempel Ziv) Data compression algorithm based on the Lempel-Ziv method that can achieve up to 4x the throughput of 2400 and 9600 bps modems. BTOS Burroughs version of CTOS. Btrieve Database management system from Novell that accompanies its NetWare operating systems. bubble Bit in bubble memory or a symbol in a bubble chart. bubble chart Chart that uses bubble-like symbols often used to depict data flow diagrams. Bubble Jet Canon's ink jet printer technology. bubble memory Solid state semiconductor and magnetic storage device suited for rugged applications. It is about as fast as a slow hard disk and holds its content without power. It is conceptually a stationary disk with spinning bits. The unit, only a couple of square inches in size, contains a thin film magnetic recording layer. Globular-shaped bubbles (bits) are electromagnetically generated in circular strings inside this layer. In order to read or write the bubbles, they are rotated past the equivalent of a read/write head. bubble sort Multiple-pass sorting technique that starts by sequencing the first two items, then the second with the third, then the third with the fourth and so on until the end of the set has been reached. The process is repeated until all items are in the correct sequence. bucket Another term for a variable. It's just a place to store something. buckyballs Type of carbon, identified in 1985, that has potential as a superconductor. It is one of a group of "buckminsterfullerenes," named after R. Buckminster Fuller, because of its molecular similarity to his geodesic domes. buffer Reserved segment of memory used to hold data while it is being processed. In a program, buffers are created to hold some amount of data from each of the files that will be read or written. A buffer may also be a small memory bank used for special purposes. buffer flush Transfer of data from memory to disk. buffer pool Area of memory reserved for buffers. bug Persistent error in software or hardware. If the bug is in software, it can be corrected by changing the program. If the bug is in hardware, new circuits have to be designed. The term was coined in the 1940s when a moth was found squashed between the points of an electromechanical relay in the Mark I. Contrast with glitch. A Note from the Author On October 19, 1992, I found my first "real bug." When I fired up my laser printer, it printed blotchy pages. Upon inspection, I found a bug lying belly up in the trough below the corona wire. The printer worked fine after removing it! bug compatible Hardware device that contains the same design flaws as the original. bulk storage Storage that is not used for high-speed execution. May refer to auxiliary memory, tape or disk. Bull HN (Bull HN Information Systems Inc., Billerica, MA) Computer manufacturer that was formerly Honeywell Bull Inc. In 1927, two temperature control companies, founded by Alfred Butz in 1885 and Mark Honeywell in 1906, merged to become the Minneapolis Honeywell Regulator Company. In 1957, Honeywell entered the computer business with Ratheon when it launched the Datamatic 1000, a monstrous, tube-driven machine. Later, it introduced advanced second-generation computers, the Models 800 and 400. In 1963, it introduced its successful 200 series. In 1970, it acquired GE's computer business and its computer division was named Honeywell Information Systems. Through Honeywell's alliance with Bull in Europe and Bull's association with NEC in Japan, products were jointly developed starting in the 1970s. In 1987, Honeywell, Bull and NEC merged to become Honeywell Bull, Inc. In 1989, it became Bull HN to reflect Bull's majority ownership. bulletin board See BBS. bump mapping In computer graphics, a technique for simulating rough textures by creating irregularities in shading. BUNCH (Burroughs, Univac, NCR, Control Data and Honeywell) IBM's competitors after RCA and GE got out of the computer business. bundle To sell hardware and software as a single product or to combine several software packages for sale as a single unit. Contrast with unbundle. bunny suit Protective clothing worn by an individual in a clean room that keeps human bacteria from infecting the chip-making process. The outfit makes people look like oversized rabbits. burn in To test a new electronic system by running it for some length of time. Weak components often fail within the first few hours of use. burst mode High-speed transmission mode in a communications or computer channel. Under certain conditions, the system sends a burst of data at higher speed. For example, a multiplexor channel may suspend transmitting several streams of data and send one high-speed transmission using the entire bandwidth. burster Mechanical device that separates continuous paper forms into cut sheets. A burster can be attached to the end of a collator, which separates multipart forms into single parts. bus Common pathway between hardware devices. A computer bus connects the CPU to its main memory and the memory banks that reside on the control units of the peripheral devices. It is made up of two parts. Addresses are sent over the address bus to signal a memory location, and the data is transferred over the data bus to that location. Widely-used computer buses are ISA, EISA, NuBus, Micro Channel, TURBOchannel, VMEbus, MULTIBUS and STD bus. A network bus is a common cable that connects all devices in the network; for example, Ethernet uses a bus architecture. A signal is broadcast to all nodes at the same time, and the requested station responds.  Computer Bus Local Area Network  敖陳陳陳陳朕 敖陳陳陳陳朕 敖陳陳陳陳  CPU 団陳陳 Main 敖陳 Work-  団 敖 Memory 敖 Station  青陳陳陳陳潰 青陳陳陳陳潰 青陳陳陳陳  敖陳陳陳陳朕 B 敖陳陳陳陳朕 B 敖陳陳陳陳  Disk 団U青 Video U青 Work-  Controller団S敖Controller S敖 Station  青陳陳陳陳潰 青陳陳陳陳潰 青陳陳陳陳  敖陳陳陳陳朕 敖陳陳陳陳朕 敖陳陳陳陳  Parallel 団 青Serial 青 Server  Port or 団陳陳Port or 敖  Printer Communications 青陳陳陳陳  Controller Controller 敖陳陳陳陳  青陳陳陳陳潰 青陳陳陳陳潰 青 Work-  青陳 Station  青陳陳陳陳  bus bridge Device that connects two similar or dissimilar busses together, such as two VMEbuses or a VMEbus and a Futurebus. This is not the same as a communications bridge, which connects networks together. See bridge. bus card Expansion board (card) that plugs into the computer's expansion bus. bus extender (1) Board that pushes a printed circuit board out of the way of surrounding boards for testing purposes. It plugs into an expansion slot, and the expansion board plugs into the bus extender. (2) Device that extends the physical distance of a bus. See repeater. (3) Device that increases the number of expansion slots. It is either an expansion board containing multiple expansion slots, or an expansion board that cables to a separate housing that contains the slots and its own power supply. bus mastering Bus design that allows add-in boards to process independently of the CPU and to be able to access the computer's memory and peripherals on their own. bus mouse Mouse that plugs into an expansion board. It takes up an expansion slot whereas a serial mouse takes up a serial port. The choice depends on how many devices must be connected to each type of socket. business analyst Individual who analyzes the operations of a department or functional unit with the purpose of developing a general systems solution to the problem that may or may not require automation. The business analyst can provide insights into an operation for an information systems analyst. business graphics Numeric data represented in graphic form. While line graphs, bar charts and pie charts are the common forms of business graphics, there are many others. People think in pictures. By transforming numerical data into graphic form, patterns of business activity can be recognized more easily. business machine Any office machine, such as a typewriter or calculator, that is used in clerical and accounting functions. The term has traditionally excluded computers and terminals. Butterfly Switch Parallel processing topology from BBN Advanced Computers Inc., Cambridge, MA, that mimics a crossbar and provides high-speed switching of data between nodes. It can also be used to create a hypercube topology. button Physical button on a device, such as a mouse, or a simulated button on screen that is "pushed" by moving the cursor onto it and clicking the mouse. buy and sell See computer exchange. bypass In communications, to avoid the local telephone company by using satellites and microwave systems. byte Common unit of computer storage (micro to mainframe). It is made up of eight binary digits (bits). A ninth bit may be added as a parity bit for error checking. A byte holds the equivalent of a single character, such as the letter A, a dollar sign or decimal point. For numbers, a byte can hold a single decimal digit (0 to 9), two numeric digits (packed decimal) or a number from 0 to 255 (binary numbers). Byte Specifications The primary specifications of hardware are rated in bytes; for example, a 40-megabyte (40M or 40MB) disk holds 40 million characters of instructions and data. A one-megabyte (1M or 1MB) memory allows one million characters of instructions and data to be stored internally for processing. With database files and word processing documents, the file size is slightly larger than the number of data characters stored in it. Word processing files contain embedded codes for layout settings (margins, tabs, boldface); therefore, a 100,000-byte document implies slightly less than 100,000 characters of text (approx. 30 pages). Database files contain codes that describe the structure of the records, thus, a 100,000-byte database file holds somewhat less than 100,000 characters of data. Unlike data and text, a 100,000-byte graphics file is not indicative of the size of the image contained in it. There are many graphics standards, and the higher the image quality, the more bytes are needed to represent it. A low- resolution graphics file can take as little as 8,000 bytes, while high-resolution files can take 100,000 or more bytes per picture. byte addressable Computer that can address each byte of memory independently of the others. Contrast with word addressable. byte ordering See big endian. byte-oriented protocol Communications protocol that uses control codes made up of full bytes. The bisynchronous protocols used by IBM and other vendors are examples. Contrast with bit-oriented protocol. C High-level programming language developed at Bell Labs that is able to manipulate the computer at a low level like assembly language. During the last half of the 1980s, C has become the language of choice for developing commercial software. C can be compiled into machine languages for almost all computers. For example, UNIX is written in C and runs in a wide variety of micros, minis and mainframes. C is programmed as a series of functions that call each other for processing. Even the body of the program is a function named "main." Functions are very flexible, allowing programmers to choose from the standard library that comes with the compiler, to use third party functions from other C suppliers, or to develop their own. Compared to other high-level programming languages, C appears complicated. Its intricate appearance is due to its extreme flexibility. C was standardized by ANSI (X3J11 committee) and ISO in 1989. The following C example converts fahrenheit to centigrade:  main() {  float fahr;  printf("Enter Fahrenheit ");  scanf("%f", &fahr);  printf("Celsius is %f\n", (fahr-32)*5/9);  }  C shell See UNIX. C++ Object-oriented version of C created by Bjarne Stroustrup. C++ has become popular because it combines traditional C programming with OOP capability. Smalltalk and other original OOP languages did not provide the familiar structures of conventional languages such as C and Pascal. C2 Minimum security level defined by the National Computer Security Center. See NCSC. C: Designation for the primary hard disk in a PC. CA See Computer Associates. cable Flexible metal or glass wire or group of wires. All cables used in electronics are insulated with a material such as plastic or rubber. cable matcher Same as gender changer. cabletext Videotex service that uses coaxial cable. See videotex. cache Pronounced "cash." A reserved section of memory used to improve performance. A disk cache is a reserved section of normal memory or additional memory on the disk controller board. When the disk is read, a large block of data is copied into the cache. If subsequent requests for data can be satisfied in the cache, a slower disk access is not required. If the cache is used for writing, data is queued up in memory and written to the disk in larger blocks. A memory cache is a high-speed memory bank between memory and the CPU. Blocks of instructions and data are copied into the cache and instruction execution and data updating are performed in the higher-speed memory.  栩栩 disk 敖陳陳陳 敖陳陳陳  烝烝烝栩栩烝烝烝 陳 RAM 陳 CPU  烝烝烝栩栩烝烝烝 Cache 青陳陳陳  烝烝 青陳陳陳  Disk cache  敖陳陳陳陳陳 敖陳陳陳陳陳 敖陳陳陳  RAM 陳High-speed 陳 CPU  青陳陳陳陳陳 Memory bank 青陳陳陳  青陳陳陳陳陳  Memory cache  caching controller Disk controller with a built-in cache. See cache. CAD (Computer-Aided Design) Using computers to design products. CAD systems are high-speed workstations or personal computers using CAD software and input devices such as graphic tablets and scanners. CAD output is a printed design or electronic input to CAM systems (see CAD/CAM). CAD software is available for generic design or specialized uses, such as architectural, electrical and mechanical design. CAD software may also be highly specialized for creating products such as printed circuits and integrated circuits. CAD systems are often turnkey systems which are put together by vendors that may develop or integrate software into standard or optimized hardware. Except in a few cases, CAD systems rely extensively on graphics. See graphics, CADD, and CAE. CAD/CAM (Computer-Aided Design/Computer-Aided Manufacturing) Integration of CAD and CAM. Products designed by CAD are direct input into the CAM system. For example, a device is designed and its electronic image is translated into a numerical control programming language, which generates the instructions for the machine that makes it. CADAM Full-featured IBM mainframe CAD application, which includes 3-D capability, solid modeling and numerical control. Originally developed by Lockheed for internal use, it was distributed by IBM starting in the late 1970s. In 1989, IBM purchased the Lockheed subsidiary, CADAM, Inc. CADD (Computer-Aided Design and Drafting) CAD systems with additional features for drafting, such as dimensioning and text entry. CADKEY Integrated 2-D drafting and 3-D design system for PCs from CADKEY, Inc., Manchester, CT. It offers a total design solution with solids creation and built-in DXF and IGES translators. Over 200 manufacturing systems link to CADKEY through its CADL programming language. CAE (1) (Computer-Aided Engineering) Software that analyzes designs which have been created in the computer or that have been created elsewhere and entered into the computer. Different kinds of engineering analyses can be performed, such as structural analysis and electronic circuit analysis. (2) (Common Application Environment) Software development platform that is specified by X/Open. CAI (1) (Computer-Assisted Instruction) Same as CBT. (2) See Computer Associates. Cairo Code name for an object-oriented version of Windows NT to be released after Windows NT is established. CAL (1) (Computer-Assisted Learning) Same as CBT. (2) (Conversational Algebraic Language) Timesharing language from Univ. of California. calculated field Numeric or date field that derives its data from the calculation of other fields. Data is not entered into a calculated field by the user. calculator Machine that provides arithmetic capabilities. It accepts keypad input and displays results on a readout and/or paper tape. Unlike a computer, it cannot handle alphabetic data. call (1) In programming, a statement that references an independent subroutine or program. The call is turned into a branch instruction by the assembler, compiler or interpreter. The routine that is called is responsible for returning to the calling program after it has finished processing. (2) In communications, the action taken by the transmitting station to establish a connection with the receiving station in a dial-up network. call by reference In programming, a call to a subroutine that passes addresses of the parameters used in the subroutine. call by value In programming, a call to a subroutine that passes the actual data of the parameters used in the subroutine. call distributor PBX feature that routes incoming calls to the next available agent or operator. called routine In programming, a program subroutine that performs a task and is accessed by a call or branch instruction in the program. calling program In programming, a program that initiates a call to another program. calling routine In programming, a program subroutine that initiates a call to another program routine. CALS (Computer-Aided Acquisition and Logistics Support) DOD initiative for electronically capturing military documentation and linking related information. CAM (1) (Computer-Aided Manufacturing) Automated manufacturing systems and techniques, including numerical control, process control, robotics and materials requirements planning (MRP). See CAD/CAM. (2) (Common Access Method) ANSI standard for SCSI host adapters that supports simultaneous operations on multiple SCSI devices (multitasking I/O). This standard, traditionally unsupported in the PC world, is gradually being implemented in the PC's ROM BIOS under interrupt 4F. See SCSI. (3) (Content Addressable Memory) Same as associative storage. candela Unit of measurement of the intensity of light. An ordinary wax candle generates one candela. See lumen. canned program Software package that provides a fixed solution to a problem. Canned business applications should be analyzed carefully as they usually cannot be changed much, if at all. canned routine Program subroutine that performs a specific processing task. canonical synthesis Process of designing a model of a database without redundant data items. A canonical model, or schema, is independent of the hardware and software that will process the data. capacitor Electronic component that holds a charge. It comes in varying sizes for use in power supplies to the tiny cells in dynamic RAM chips. capstan On magnetic tape drives, a motorized cylinder that traps the tape against a free-wheeling roller and moves it at a regulated speed. CAR (Computer-Assisted Retrieval) Systems that use the computer to keep track of text documents or records stored on paper or on microform. The computer is used to derive the location of a requested item, which must be manually retrieved from a shelf, bin, or microform. card See printed circuit board, magnetic stripe, punched card and HyperCard. card cage Cabinet or metal frame that holds printed circuit cards. card column Vertical column that is used to represent a single character of data by its pattern of punched holes. The common IBM card contains 80 card columns. card image Representation of punched cards in which each hole in the card is represented by a bit on tape or disk. card punch (1) Early peripheral device that punches holes into cards at 100 to 300 cards per minute. (2) Same as keypunch machine. card reader (1) Peripheral device that reads magnetic stripes on the back of a credit card. (2) Early peripheral device that reads punched cards at 500 to 2,000 cards/minute. The code is detected by light patterns created by the holes in the card. cardinal number Number that states how much or how many. In "record 43 has 7 fields," the 7 is cardinal. Contrast with ordinal number. caret Up-arrow (^) symbol used to represent a decimal point or the control key. For example, ^Y means Ctrl-Y. It is the shift-6 key on the keyboard. carpal tunnel syndrome Compression of the main nerve to the hand due to scarring or swelling of the surrounding soft tissue in the wrist (area formed by carpal bones on top and muscle tendons below). Caused by trauma, arthritis and improper positioning of the wrist, it can result in severe damage to the hands. See RSI and Wrist Pro. carriage Printer or typewriter mechanism that holds the platen and controls paper feeding and movement. carriage return See return key. carrier Alternating current that vibrates at a fixed frequency, used to establish a boundary, or envelope, in which a signal is transmitted. Carriers are commonly used in radio transmission (AM, FM, TV, microwave, satellite, etc.) in order to differentiate transmitting stations. For example, an FM station's channel number is actually its carrier frequency. The FM station merges (modulates) its audio broadcast (data signal) onto its carrier and transmits the combined signal over the airwaves. At the receiving end, the FM tuner latches onto the carrier frequency, filters out the audio signal, amplifies it and sends it to the speaker. Carriers can be used to transmit several signals simultaneously. For example, multiple voice, data and/or video signals can travel over the same line with each residing in its own carrier vibrating at a different frequency. carrier based Transmission system that generates a fixed frequency (carrier) to contain the data being transmitted. carrier frequency Unique frequency used to "carry" data within its boundaries. It is measured in cycles per second, or Hertz. See FDM. Carterfone decision FCC decree (1968) that permitted users to connect their own telephone equipment to the public telephone system. cartridge Self-contained, removable storage module that contains disks, magnetic tape or memory chips. Cartridges are inserted into slots in the drive, printer or computer. See font cartridge. CAS (Communications Application Specification) Intel fax/modem protocol that allows personal computers to exchange data with fax machines. Introduced in 1988, Intel provides both the boards and the chips. cascade Connected series of chips or other devices. CASE (Computer Aided Software Engineering or Computer Aided Systems Engineering) Software that is used in any and all phases of developing an information system, including analysis, design and programming. For example, data dictionaries and diagramming tools aid in the analysis and design phases, while application generators speed up the programming phase. CASE tools provide automated methods for designing and documenting traditional structured programming techniques. The ultimate goal of CASE is to provide a language for describing the overall system that is sufficient to generate all the necessary programs. case-based reasoning AI problem solving technique that catalogs experience into "cases" and matches the current problem to the experience. Such systems are easier to maintain than rule-based expert systems, because changes require adding new cases without the complexity of adding new rules. It is used in many areas including pattern recognition, diagnosis, troubleshooting and planning. case sensitive Distinguishing lower case from upper case. In a case sensitive language, "abc" is considered different data than "ABC." case statement In programming, a variation of the if-then-else statement that is used when several ifs are required in a row. The following C example tests the variable KEY1 and performs functions based on the results.  switch (key1) {  case '+': add(); break;  case '-': subtract(); break;  case '*': multiply(); break;  case '/': divide(); break;  }  cash memory See cache. cassette Removable storage module that contains a supply reel of magnetic tape and a takeup reel. Data cassettes look like audio cassettes, but are made to higher tolerances. casting In programming, the conversion of one data type into another. cat (conCATenate) UNIX command that displays the contents of a file. catalog Directory of disk files or files used in an application. Also any map, list or directory of storage space used by the computer. cathode In electronics, a device that emits electrons, which flow from the negatively charged cathode to the positively charged anode. cathode ray tube See CRT. CATV (Community Antenna TV) Original name for cable TV, which used a single antenna at the highest location in the community. Now refers to cable TV. CAU (Controlled Access Unit) Intelligent hub from IBM for Token Ring networks. Failed nodes are identified by the hub and reported via IBM's LAN Network Manager software. CAV (Constant Angular Velocity) Disk technique that spins the disk at a constant speed. The number of bits in each track is the same, but their density varies because the inner tracks have smaller circumferences than the outer tracks. Contrast with CLV. CB (Citizen's Band) Frequency band for public radio transmission in the 27 MHz range. CB simulator See teleconferencing (3). CBEMA (Computer and Business Equipment Manufacturers Assn.) Membership organization founded in 1916 composed of over 25 manufacturers and suppliers. It is concerned with the development of standards for data processing and business equipment in the U.S. and abroad. Address: 311 First St., N.W., Washington, DC 20001, 202/737-8888. CBR (1) (Computer-Based Reference) Reference materials accessible by computer in order to help people do their jobs quicker. For example, this Glossary on disk! (2) See case-based reasoning. CBT (Computer-Based Training) Using the computer for training and instruction. CBT programs are called courseware and provide interactive training sessions for all disciplines. It uses graphics extensively, as well as CD ROM and videodisc. CBT courseware is developed with authoring languages, such as Adroit, PILOT and Demo II, which allow for the creation of interactive sessions. CBX (Computerized Branch eXchange) Same as PBX. cc:Mail VIM-compliant e-mail system from Lotus. Lotus acquired cc:Mail, a Mountain View, CA, software developer. CCA (1) (Common Cryptographic Architecture) IBM encryption software for MVS and DOS applications. (2) (Compatible Communications Architecture) Network Equipment Technology protocol for transmitting asynchronous data over X.25 networks. (3) (Communications Control Architecture) U.S. Navy network that includes an ISDN backbone called BITS (Base Info. Transfer System). CCD (Charge Coupled Device) Electronic memory made of a special type of MOS transistor that can store patterns of charges in a sequential fashion. CCDs are used in TV and scanning devices since they can be charged by light as well as by electricity. CCFL (Cold Cathode Flurorescent Lamp) Same as CCFT. CCFT (Cold Cathode Fluorescent Tube) Type of light source for a backlit screen. It weighs more and uses more power than other backlights. CCIA (Computer and Communications Industry Assn.) Membership organization composed of over 60 hardware and software vendors, service bureaus, leasing and repair companies. It represents their interests in domestic and foreign trade, and, working with the NIST, keeps members advised of regulatory policy. Address: 666 11th St., N.W., Washington, DC 20001, 202/783-0070. CCIS (Common Channel Interoffice Signaling) Telephone communications technique that transmits voice and control signals over separate channels. Control signals are transmitted over a packet-switched digital network, providing faster connects and disconnects and allowing data, such as calling number, to be included. See CCS (2). CCITT (Consultative Committee for International Telephony and Telegraphy) International organization for communications standards. It is one of four organs of the International Telecommunications Union, founded in 1865, headquartered in Geneva and comprised of over 150 member countries. CCP (Certificate in Computer Programming) Award for successful completion of an examination in computer programming offered by ICCP. CCS (1) (Common Communications Support) SAA specifications for communications, which includes data streams (DCA, 3270), application services (DIA, DDM), session services (LU 6.2) and data links (X.25, Token Ring). (2) (Common Channel Signaling) Integral part of ISDN known as "Signaling System 7," which advances the CCIS method for transmitting control signals. It allows call forwarding, call waiting, etc., to be provided anywhere in the network. (3) (Common Command Set) De facto instruction set between a SCSI-1 adapter and a hard disk. (4) (Continuous Composite Servo) Magneto-optic format that places the signal track between two alignment tracks. (5) (100 Call Seconds) Unit of measurement equal to 100 seconds of conversation. One hour = 36 CCS. CD (Compact Disc) Audio disc that contains up to 72 minutes of hi-fi stereo sound. The disc is 4.75" in diameter, recorded on one side, and individual selections can be played back in any sequence. Unlike phonograph records in which the platter contains "carved sound waves," CDs are recorded in digital form as microscopic pits (binary code) covered by a clear, protective plastic layer. Instead of a needle vibrating in the groove, a laser shines onto the pits and the reflections are decoded. Sound is converted into digital code by sampling the sound waves 44,056 times per second and converting each sample into a 16-bit number. It requires about 1.5 million bits of storage for each second of stereo hi-fi sound. Digital sound is so clear because the numbers are turned into sound electronically. There's no tape hiss or needle pops and clicks. In addition, the CD can handle a wider range of volume (dynamic range), providing more realism. A soft whisper can be interrupted by a loud cannon blast. If a phonograph were pushed that far, the needle would jump out of the groove. Other forms of CDs (CD ROM, CD ROM XA, CD-I and DVI) all stem from the audio CD. Introduced in the U.S. in 1983, sales of CDs and CD players exceeded sales of LPs and turntables in 1986. CD audio Same as CD and DAD. CD caddy Plastic container that holds a CD ROM disc. The caddy is inserted into the disc drive. CD-I (Compact Disc-Interactive) Compact disc format developed by Philips and Sony that holds data, audio, still video and animated graphics. It provides up to 144 minutes of CD-quality stereo, 9.5 hours of AM-radio-quality stereo or 19 hours of monophonic audio. CD-I includes an operating system standard as well as proprietary hardware methods for compressing the data further in order to display video images. CD-I discs require a CD-I player and will not play in a CD ROM player. See CD, CD ROM, DVI. CD ROM (Compact Disc Read Only Memory) Compact disc format used to hold text, graphics and hi-fi stereo sound. It's like a music CD, but uses a different track format for data. The music CD player cannot play CD ROMs, but CD ROM players usually play music CDs and have output jacks for a headphone or amplified speakers. A CD ROM player connects to a controller card, which is plugged into one of the computer's expansion slots. CD ROMs hold in excess of 600MB of data, which is equivalent to about 250,000 pages of text or 20,000 medium-resolution images. Audio and data reside on separate tracks and cannot be heard and viewed together. See CD ROM XA, CD-I and DVI. CD ROM Extensions Software required to use a CD ROM player on a PC running DOS. It usually comes with the player and includes a driver specialized for the player as well as Microsoft's MSCDEX.EXE driver. CD ROM XA (CD ROM eXtended Architecture) CD ROM enhancement introduced in 1988 by Philips, Sony and Microsoft that lets text and pictures be narrated by allowing concurrent audio and video. It provides up to 9.5 hours of AM-quality stereo or 19 hours of monophonic audio. It also functions as a bridge between CD ROM and CD-I, since CD ROM XA discs will play on a CD-I player. CD ROM XA uses a standard CD ROM player, but requires a CD ROM XA controller card in the computer. See CD-I and DVI. CD+Graphics CD format that adds video. You can listen to the opera and read the text on screen. CDA (Compound Document Architecture) Compound document format from Digital that creates hot links between documents. CDC See Control Data. CDDI (Copper Distributed Data Interface) Version of FDDI that uses twisted pair rather than optical fiber. cdev (Control Panel DEVice) Customizable settings in the Macintosh Control Panel that pertain to a particular program or device. Cdevs for the mouse, keyboard and startup disk, among others, come with the Mac. Others are provided with software packages and utilities. CDIF (CASE Data Interchange Format) EIA standard for exchanging data between CASE tools. See PCTE. CDIP (Sidebrazed Ceramic DIP) High-qualty ceramic DIP that typically uses gold-plated leads attached by brazing. CDMA (Code Division Multiple Access) Spread spectrum technique that converts analog signals into digital for transmission over the cellular network. It provides 10 to 20 times the capacity of the analog network. Qualcomm, Inc., San Diego, CA, has several patents on products using its CDMA implementation. CDP (Certificate in Data Processing) Award for the successful completion of an examination in hardware, software, systems analysis, programming, management and accounting, offered by ICCP. CDPD (Cellular Digital Packet Data) Transmission of digital data over the cellular network. Based on IBM's CelluPlan II, it moves data over unused voice channels at 19.2Kbps. CDTV (Commodore Dynamic Total Vision) CD system from Commodore that combines audio, graphics and text. Introduced in 1991, it is an interactive multimedia system for the home. The player connects to a TV and also plays music CDs, including CD+Graphics and CD+MIDI. CEbus (Consumer Electronics bus) EIA standard for a control network. Ceefax Teletext service of the British Broadcasting Corporation. CEG (Continous Edge Graphics) VGA RAMDAC chip from Edsun Labs that adds anti-aliasing on the fly. It can also calculate intermediate shades, thus providing thousands of colors on an 8-bit board that normally generates only 256 colors. cell (1) Elementary unit of storage for data (bit) or power (battery). (2) In a spreadsheet, the intersection of a row and column. cell relay Transmission technology that uses small fixed- length packets (cells) that can be switched at high speed. Good for multimedia transmission. See ATM. centering cone Short plastic or metal cone used to align a 5.25" floppy disk to the drive spindle. It is inserted into the diskette's center hole when the drive door is closed. centimeter Unit of measurement that is 1/100th of a meter or approximately 4/10ths of an inch (0.39 inch). central office Telephone switching facility that interconnects subscribers' telephone lines to each other and to intra and intercity trunk lines. central processing unit See CPU. central processor Same as CPU. centralized processing Processing performed in one or more computers in a single location. All terminals in the organization are connected to the central computers. Contrast with distributed processing and decentralized processing. CENTREX PBX services provided by a local telephone company. Switching is done in the telephone company's central office. Some services do the switching at the customer's site, but control it in the central office. Centronics Standard 36-pin parallel interface for connecting printers and other devices to a computer. It defines the plug, socket and signals used and transfers data asynchronously up to 200 Kbytes/sec. The plug (1.5" wide, 1/8" thick) has 18 contacts each on the top and bottom. The socket contains one opening with matching contacts. This de facto standard was developed by Centronics Corp., maker of the first successful dot matrix printers. The printer was introduced in 1970, and the company was bought by Genicom Corp. in 1987. See printer cable. CEO (Comprehensive Electronic Office) Office software from Data General introduced in 1981. It includes word processing, e-mail, spreadsheets, business graphics and desktop accessories. CERDIP (CERamic DIP) Type of DIP that uses two ceramic layers epoxied together. CGA (Color/Graphics Adapter) IBM video display standard that provides low-resolution text and graphics. It was the first graphics standard for the IBM PC and has been superseded by EGA and VGA. CGA requires a digital RGB Color Display monitor. See PC display modes. CGI (Computer Graphics Interface) Device independent graphics language for display screens, printers and plotters that stemmed from GKS. CGM (Computer Graphics Metafile) Standard format for interchanging graphics images. CGM stores images primarily in vector graphics, but also provides a raster format. Earlier GDM and VDM formats have been merged into the CGM standard. chad Piece of paper that is punched out on a punched card, paper tape or on the borders of continuous forms. A chadded form is when the holes are cut completely through. A chadless form is when the chads are still attached to one edge of the hole. chain printer Line printer that uses character typefaces linked together in a chain as its printing mechanism. The chain spins horizontally around a set of hammers. When the desired character is in front of the selected print position, the corresponding hammer hits the paper into the ribbon and onto the character in the chain. chained list Group of items in which each item contains the location of the next item in sequence. chaining Linking items or records to form a chain. Each link in the chain points to the next item. change file Transaction file used to update a master file. channel (1) High-speed metal or optical fiber pathway between the computer and the control units of the peripheral devices. Channels imply independent transmission paths in which multiple channels can transfer data concurrently with each other and with other processing. In a personal computer, the bus serves as a common, shared channel. (2) In communications, any pathway between two computers or terminals. It may refer to the physical medium, such as coaxial cable, or to a specific carrier frequency (subchannel) within a larger channel or wireless medium. channel bank Multiplexor that merges several low-speed voice or data lines into one high-speed (typically T1) line and vice versa. channel program Instructions executed by a peripheral channel. The channel executes the channel program independently of the CPU, allowing concurrent operations to take place in the computer. chaos Science that deals with the underlying order of the seemingly random nature of the universe. See fractals. character Single alphabetic letter, numeric digit, or special symbol such as a decimal point or comma. A character is equivalent to a byte; for example, 50,000 characters take up 50,000 bytes. character based Same as text based. character cell Matrix of dots used to form a single character on a display screen or printer. For example, an 8x16 cell is made up of 16 rows each containing eight dots. Character cells are displayed and printed contiguously; therefore the design of each letter, digit or symbol within the cell must include surrounding blank space. character code Same as data code. character data Alphanumeric data or text. Contrast with numeric data. character device Peripheral device that transfers data one byte at a time at a time, such as a parallel or serial port. Contrast with block device. character field Data field that holds alphanumeric characters. Contrast with numeric field. character generator (1) Circuitry that converts data characters into dot patterns for a display screen. (2) Device that creates text characters that are superimposed onto video frames. character graphics Set of special symbols strung together like letters of the alphabet to create elementary graphics and forms, as in the following example:  栩  嬪様様用様様様冤様様様 栩 栩  栩 栩 栩  Character Graphics  character mode Same as text mode. character-oriented protocol See byte-oriented protocol. character pitch Measurement of the number of characters per inch. See cpi. character printer Printer that prints one character at a time, such as a daisy wheel or dot matrix printer. See printer. character recognition Ability of a machine to recognize printed text. See OCR and MICR. character set (1) Group of unique symbols and codes. For example, the ASCII character set contains 128 characters numbered 0 to 127. The English character set is 26 symbols (A-Z). (2) See symbol set. character string Group of alphanumeric characters. Contrast with numeric data. character terminal Display screen without graphics capability. characteristic In logarithms and floating point, the number that indicates where the decimal point is placed. CHARGECARD Hardware memory manager for 286 PCs from ALL Computers Inc., Toronto, that turns extended memory into EMS and uses unused high memory (640-1024K) for drivers and TSRs. The 286 chip is removed and plugged into the CHARGECARD, which is plugged back into the socket. chat mode Communications option that lets users type messages back and forth to each other. Each keystroke is transmitted as it is pressed. Cheapernet See Ethernet. check bits Calculated number used for error checking. The number is derived by some formula from the binary value of one or more bytes of data. See parity checking, checksum and CRC. check box Small box that displays an X or checkmark when the associated option is selected. check digit Numeric digit used to ensure that account numbers are correctly entered into the computer. Using a formula, a check digit is calculated for each new account number, which then becomes part of the number, often the last digit. When an account number is entered, the data entry program recalculates the check digit and compares it to the check digit entered. If the digits are not equal, the account number is considered invalid. check sum See checksum. checkpoint/restart Method of recovering from a system failure. A checkpoint is a copy of the computer's memory that is periodically saved on disk along with the current register settings (last instruction executed, etc.). In the event of any failure, the last checkpoint serves as a recovery point. When the problem has been fixed, the restart program copies the last checkpoint into memory, resets all the hardware registers and starts the computer from that point. Any transactions in memory after the last checkpoint was taken until the failure occurred will be lost. checksum Value used to ensure data is transmitted without error. It is created by adding the binary value of each alphanumeric character in a block of data and sending it with the data. At the receiving end, a new checksum is computed and matched against the transmitted checksum. A non-match indicates an error. Just as a check digit tests the accuracy of a single number, a checksum tests a block of data. Checksums detect single bit errors and some multiple bit errors, but are not as effective as the CRC method. Chicago Code name for a future 32-bit version (386 and up) of Windows that runs under DOS. May be released as Windows 4.0 and DOS 7. chicklet keyboard Keyboard with small, square keys not suitable for touch typing. child In database management, the data that is dependent on its parent. See parent-child. child program Secondary or subprogram called for and loaded into memory by the main program. See parent program. chip Integrated circuit. Chips are squares or rectangles that measure approximately from 1/16th to 5/8th of an inch on a side. They are about 1/30th of an inch thick, although only the top 1/1000th of an inch holds the actual circuits. Chips contain from a few dozen to several million electronic components (transistors, resistors, etc.). The terms chip, integrated circuit and microelectronic are synonymous. TYPES OF CHIPS BY FUNCTION Logic Chip A single chip can perform some or all of the functions of a processor. A microprocessor is an entire processor on a single chip. Desktop and portable computers use one or more microprocessors while larger computers may employ several types of microprocessors as well as hundreds or thousands of specialized logic chips. Memory Chip Random access memory (RAM) chips contain from a couple of hundred thousand to several million storage cells (bits). They are the computer's working storage and require constant power to keep their bits charged. Firmware chips, such as ROMs, PROMs, EPROMs, and EEPROMs are permanent memory chips that hold their content without power. Computer on a Chip A single chip can contain the processor, RAM, ROM, I/O control unit, and a timing clock. It is used in myriads of consumer and industrial products. Analog/Digital Converter A single chip can perform the conversion between analog and digital signals, for example, a codec in a telephone. Special Purpose Chip Chips used in low-cost consumer items (watches, calculators, etc.) as well as higher-cost products (video games, automobile control, etc.) may be designed from scratch to obtain economical and effective performance. Today's ASIC chips can be quickly created for any special purpose. Logic Array and Gate Array These chips contain logic gates which have not been tied together. A final set of steps applies the top metal layer onto the chip stringing the logic gates together into the pattern required by the customer. This method eliminates much of the design and fabrication time for producing a chip. Bit Slice Processor Bit slice chips contain elementary electronic circuits that serve as building blocks for the computer architect. They are used to custom-build a processor for specialized purposes. HOW THE CHIP CAME ABOUT Revolution In late 1947, the semiconductor industry was born at AT&T's Bell Labs with the invention of the transistor by John Bardeen, Walter Brattain and William Shockley. The transistor, fabricated from solid materials that could change their electrical conductivity, would eventually replace all the bulky, hot, glass vacuum tubes used as electronic amplifiers in radio and TV and as on/off switches in computers. By the late 1950s, the giant first- generation computers were giving way to smaller, faster and more reliable transistorized machines. Evolution The original transistors were discrete components; each one was soldered onto a circuit board to connect to other individual transistors, resistors and diodes. Since hundreds of transistors were made on one round silicon wafer and cut apart only to be reconnected again, the idea of building them in the required pattern to begin with was obvious. In the late 1950s, Jack Kilby of TI and Robert Noyce of Fairchild Semiconductor created the integrated circuit, a set of interconnected transistors and resistors on a single chip. Since then, the number of transistors that have been put onto a single chip has increased exponentially, from a handful in the early 1960s to millions by the late 1980s. Today, a million transistors take up no more space than the first transistor. A byproduct of miniaturization is speed. The shorter the distance a pulse travels, the faster it gets there. The smaller the components making up the transistor, the faster the transistor switches. Switch times of transistors are measured in billionths and trillionths of a second. In fact, a Josephson junction transistor has been able to switch in 50 quadrillionths of a second. Logic and Memory In first- and second-generation computers, internal main memory was made of such materials as tubes filled with liquid mercury, magnetic drums and magnetic cores. As integrated circuits began to flourish in the 1960s, design breakthroughs allowed memories to also be made of semiconductor materials. Thus, logic circuits, the "brains" of the computer, and memory circuits, its internal workspace, were moving along the same miniaturization path. By the end of the 1970s, it was possible to put a processor, working memory (RAM), permanent memory (ROM), a control unit for handling input and output and a timing clock on the same chip. Within 25 years, the transistor on a chip grew into the computer on a chip. When the awesome UNIVAC I, which you could literally walk into, was introduced in 1951, who would have believed that the equivalent electronics would later be built into a child's stuffed bear. More Evolution Just as integrated circuits eliminated cutting apart the transistors only to be reconnected again, eventually wafer scale integration will eliminate cutting apart whole chips only to be reconnected again. In time, instead of adding more circuits across the surface, the circuits will be built in overlapping layers. Within the next 10 to 15 years, it is conceivable that the electronics in today's multi-million-dollar supercomputer can be built within a cube one inch square! THE MAKING OF A CHIP Computer circuits are pathways carrying electrical pulses from one point to another. The pulses flow through on/off switches, called transistors, which open or close when electrically activated. The current flowing through one switch effects the opening or closing of another and so on. Small clusters of transistors form logic gates, which are the building blocks behind all this magic, and a specific combination of logic gates make up a circuit. From Logic to Plumbing Today, the majority of circuits being used have already been designed and reside in circuit libraries in a computer. A computer designer merely has to pick and choose ready-made modules (standard cells) from a menu. But they all had to be invented at one point, and new circuits still have to go through an elaborate process to convert logical patterns on paper into an equivalent maze of plumbing on the chip. Computers help make computers. The logical design is entered into the computer and converted into transistors, diodes and resistors. Then the combination of electronic components is turned into a plumber's nightmare that is displayed for human inspection. After corrections have been made, the completed circuits are transferred to specialized machinery that create lithographic plates made out of glass, called photomasks. The photomasks are the actual size of the wafer and contain as many copies of the design of the chip as will fit on the wafer. The transistors are built by creating subterranean layers in the silicon, and a different photomask is created to isolate each layer to be worked on. With each layer, the same part of every transistor on every chip is constructed at the same time. Chips Are Just Rocks The base material of a chip is usually silicon, although materials such as sapphire and gallium arsenide are also used. Silicon is found in quartz rocks and is purified in a molten state. It is then chemically combined (doped) with other materials to alter its electrical properties. The result is a silicon crystal ingot from three to five inches in diameter that is either positively (p-type) or negatively charged (n-type). Wafers, about 1/30th of an inch thick, are cut from this "crystal salami." Building the Layers Circuit building starts out by adhering a layer of silicon dioxide insulation on the wafer's surface. The insulation is coated with film and exposed to light through the first photomask, hardening the film and insulation below it. The unhardened areas are etched away exposing the silicon base below. By shooting a gas under heat and pressure into the exposed silicon (diffusion), a sublayer with different electrical properties is created beneath the surface. Through multiple stages of masking, etching, and diffusion, the sublayers on the chip are created. The final stage lays the top metal layer (usually aluminum), which interconnects the transistors to each other and to the outside world. Each chip is tested on the wafer, and bad chips are marked for elimination. The chips are sliced out of the wafer, and the good ones are placed into packages (DIPs, SIMMs, SIPs, etc.). The chip is connected to the package with tiny wires, then sealed and tested as a complete unit. Chip making is extremely precise. Operations are performed in a "clean room," since air particles can mix with the microscopic mixtures and easily render a chip worthless. Depending on the design complexity, more chips can fail than succeed. The Future In order to miniaturize elements of a transistor even further, the photomasks have to be made with x-rays or other beams which are narrower than light. Eventually, circuit patterns will be etched directly onto the chip, eliminating the entire photographic masking process. During the 1990s, multi-million-transistor chips will be commonplace. However, when wafer scale integration becomes a reality, one wafer could hold 100 megabytes of memory along with a quantum reduction in cost. If superconductor transistors take hold, there will be a gigantic leap in performance. Should both technologies arise at the same time, hold on to your hats! chip card See smart card and memory card. chip carrier (1) Package that a chip is mounted in. (2) Chip package with connectors on all sides. See leaded chip carrier and leadless chip carrier. chip set Group of chips designed to work together to perform a function. Chkdsk See DOS Chkdsk. CHMOS (High-density CMOS) Chip with a high density of CMOS transistors. Chooser Macintosh desk accessory that allows the user to select a printer, file server or network device, such as a network modem. CICS (Customer Information Control System) TP monitor from IBM that provides transaction processing for IBM mainframes. It controls the interaction between applications and users and lets programmers develop screen displays without detailed knowledge of the terminals used. It provides terminal routing, password security, transaction logging for error recovery and activity journals for performance analysis. CICS commands are written into assembly language, COBOL, PL/I and RPG programs. It implements SNA layers 4, 5 and 6. CID (Configuration, Installation and Distribution) IBM software for controlling software distribution throughout a network from a central source. CIF (Common Intermediate Format) Video format that transmits 36.45 Mbits/sec at 30 frames/sec. See QCIF and H.261. CIM (1) (Computer-Integrated Manufacturing) Integrating office/accounting functions with automated factory systems. Point of sale, billing, machine tool scheduling and supply ordering are part of CIM. (2) (CompuServe Information Manager) See CompuServe. cine-oriented Film-image orientation like that of movie film, which runs parallel to the outer edge of the medium. Contrast with comic-strip oriented. CIO (Chief Information Officer) Executive officer in charge of all information processing in an organization. ciphertext Data that has been coded (enciphered, encrypted, encoded) for security purposes. CIR (Committed Information Rate) In a frame relay network, the minimum speed maintained between nodes. circuit (1) Set of electronic components that perform a particular function in an electronic system. (2) Same as communications channel. circuit analyzer (1) Device that tests the validity of an electronic circuit. (2) In communications, same as data line monitor. circuit board Same as printed circuit board. circuit breaker Protective device that opens a circuit upon sensing a current overload. Unlike a fuse, it can be reset. circuit card Same as printed circuit board. circuit cellular Transmission of data over the cellular network using a voice channel and modem similar to using land-based modems. Contrast with packet cellular. See wireless. circuit switching Temporary connection of two or more communications channels. Users have full use of the circuit until the connection is terminated. Contrast with message switching, which stores messages and forwards them later, and contrast with packet switching, which breaks up a message into packets and routes each packet through the most expedient path at that moment. CIS (CompuServe Information Service) See CompuServe. CISC (Complex Instruction Set Computer) Pronounced "sisk." Traditional computer architecture that uses microcode to execute very comprehensive instructions. Instructions may be variable in length and use all addressing modes, requiring complex circuitry to decode them. Contrast with RISC. CL/1 (Connectivity Language/1) Database language from Apple that lets a Macintosh access an SQL-based database in another computer. CL/1 applications communicate with the CL/1 client program in the Mac, and the client program communicates with the CL/1 server program in the host computer. cladding Plastic or glass sheath that is fused to and surrounds the core of an optical fiber. It keeps the light waves inside the core and adds strength to it. The cladding is covered with a protective outer jacket. clamping ring The part of a 5.25" floppy disk drive that presses the disk onto the spindle. It is usually part of the centering cone. Clarion PC application development programs from Clarion Software Corp., Pompano Beach, FL. Professional Developer includes a Pascal-like programming language, DBMS and prototyping generator. Personal Developer is for non-programmers. Claris (Claris Corp., Santa Clara, CA) Software subsidiary of Apple that was separated from the corporation (although mostly owned by it) in 1988 and then bought back in 1990. Claris CAD Full-featured 2-D CAD program for the Macintosh from Claris Corp. that is noted for its ease of use. It provides an easy-to-learn path into CAD, while offering most features found in CAD programs. class In object-oriented programming, a user-defined data type that defines a collection of objects that share the same characteristics. A class member (object) is an "instance" of the class. Concrete classes are designed to be "instantiated." Abstract classes are designed to pass on characteristics through inheritance. Class A, B See FCC Class. class library Object-oriented programming classes suplied by third parties; for example, a GUI library. Classic See Macintosh. CLCC (Ceramic LCC) See LCC. clean room Room in which the air is highly filtered in order to keep out impurities. clear memory To reset all RAM and hardware registers to a zero or blank condition. Rebooting the computer may or may not clear memory, but turning the computer off and on again guarantees that memory is cleared. click To select an object by pressing the mouse button when the cursor is pointing to the required menu option or icon. client (1) Workstation or personal computer in a client/server environment. See client/server. (2) One end of the spectrum in a request/supply relationship between programs. See X Window and OLE. client application Application running in a network workstation. See also OLE. client/server Architecture in which the client (personal computer or workstation) is the requesting machine and the server is the supplying machine (LAN file server, mini or mainframe). The client provides the user interface and performs some or most of the application processing. The server maintains the databases and processes requests from the client to extract data from or update the database. The server also controls the application's integrity and security. Contrast with centralized processing, in which dumb (non-processing) terminals are connected to a mini or mainframe. Client/server implies software that is designed for multiple users. For example, if two users are attempting to update the same database record at the same time, the update must be reflected instantly on the other user's screen. Simply downloading files from the server to the client is not true client/server architecture. client/server protocol Communications protocol that provides a structure for requests between client and server in a network. It refers to OSI layer 7. clip art Set of canned images used to illustrate word processing and desktop publishing documents. clipboard Reserved memory used to hold data that has been copied from one application in order to be inserted into another. Clipper (1) Application development system from Computer Associates. Originally a dBASE compiler, it has become a complete stand-alone development environment with many unique features. Clipper was developed by Nantucket Corp., which was acquired by CA in 1992. (2) Family of 32-bit RISC microprocessors from Intergraph Corp., Huntsville, AL. clipping Cutting off outer edges or boundaries of a word, signal or image. See scissoring. clipping level Disk's ability to maintain its magnetic properties and hold its content. A high-quality level range is 65-70%; low quality is below 55%. clock Internal timing device. The different varieties of clocks are: CPU Clock Uses a quartz crystal to generate a uniform electrical frequency from which digital pulses are created and used. See clock speed. Realtime Clock Time-of-day clock that keeps track of hours, minutes and seconds and makes this data available to the programs. Timesharing Clock A timer set to interrupt the CPU at regular intervals in order to provide equal time to all the users of the computer. Communications Clock In a synchronous communications device, the clock maintains the uniform transmission of data between the sending and receiving terminals and computers. clock/calendar Internal time clock and month/year calendar that is kept active with a battery. Its output allows software to remind users of appointments, to determine the age of a transaction and to activate tasks at specified times. clock doubling Doubling the internal processing speed of a CPU while maintaining the original clock speed for I/O (transfers in/out of the chip). Intel popularized the technique with its Speed Doubler chips. See 486 and clock tripling. clock pulse Signal used to synchronize the operations of an electronic system. Clock pulses are continuous, precisely spaced changes in voltage. See clock speed. clock speed Internal heartbeat of a computer. The clock circuit uses fixed vibrations generated from a quartz crystal to deliver a steady stream of pulses to the CPU. A faster clock will speed up internal processing provided the computer's circuits can handle the increased speed. For example, the same processor running at 20MHz is twice as fast internally as one running at 10MHz. clock tripling Tripling the internal processing speed of a CPU while maintaining the original clock speed for I/O. clone Device that works like the original, but does not necessarily look like it. It implies 100% functional compatibility. closed With regard to a switch, closed is "on." Open is "off." closed architecture System whose technical specifications are not made public. Contrast with open architecture. closed shop Environment in which only data processing staff is allowed access to the computer. Contrast with open shop. closed system System in which specficiations are kept proprietary to prevent third-party hardware or software from being used. Contrast with open system. cluster Some number of disk sectors (typically two to 16) treated as a unit. The entire disk is divided into clusters, each one a minimum unit of storage. Thus, a 30-byte file may use up 2,048 bytes on disk if the disk cluster is four 512-byte sectors. See lost cluster. cluster controller Control unit that manages several peripheral devices, such as terminals or disk drives.   敖陳terminal  敖陳terminal  敖陳陳陳朕 敖陳陳陳珍津陳terminal  Computer Cluster 団陳terminal  or FEP 団陳Controller団陳陳陳terminal  青陳陳陳潰 青陳陳陳陳潰 CLUT (Color Look Up Table) Hardware or software table that contains color mixing information (intensity of red, green and blue) for each color in a palette or series of palettes. CLV (Constant Linear Velocity) Disk technique that spins a disk at different speeds. By varying the speed depending on which track is being accessed, the physical density of bits in each track can be the same, thus allowing the outer tracks to hold more data than the inner tracks. CLV mechanisms are used in CD ROM players in order to store larger amounts of data. Contrast with CAV. See ZBR. CMI (Computer-Managed Instruction) Using computers to organize and manage an instructional program for students. It helps create test materials, tracks the results and monitors student progress. CMIP (Common Management Information Protocol) Pronounced "C-mip." OSI protocol that defines the format for network monitoring and control information. CMIS (Common Management Information Services) Pronounced "C-miss." OSI standard that defines the functions for network monitoring and control. CMOS (Complementary MOS) Pronounced "C moss." Type of integrated circuit widely used for processors and memories. It uses PMOS and NMOS transistors in a complementary fashion that results in less power to operate. CMOS RAM (1) Memory made of CMOS chips. Due to their low power requirement, they are increasingly being used for main memory in portable computers. (2) Small, battery-backed memory bank in a personal computer that is used to hold time, date and system information such as drive types. CMOT (CMIP Over TCP/IP) Abbreviated version of the CMIP protocol for TCP/IP networks. CMS (1) (Conversational Monitor System) Software that provides interactive communications for IBM's VM operating system. It allows a user or programmer to launch an application from a terminal and interactively work with it. The CMS counterpart in MVS is called TSO. Contrast with RSCS, which provides batch communications for VM. (2) (Call Management System) AT&T call accounting package for its PBXs. CMYK (Cyan Magenta Yellow blacK) Color model used for printing. In theory, cyan, magenta and yellow (CMY) can print all colors, but inks are not pure and black comes out muddy. Black ink is required for quality printing. See colors and RGB. CNC (Computerized Numerical Control) See numerical control. CNE See NetWare. CNI See NetWare. CO (Central Office) Local telephone company switching station that covers a geographic area such as a town or part of a city. co-resident Program or module that resides in memory along with other programs. coaxial cable High-capacity cable used in communications and video, commonly called co-ax. It contains an insulated solid or stranded wire surrounded by a solid or braided metallic shield, wrapped in a plastic cover. Fire-safe teflon coating is optional. Although similar in appearance, there are several types of coaxial cable, each designed with a different width and impedance for a particular purpose (TV, baseband, broadband). Coax provides a higher bandwidth than twisted wire pair. COBOL (COmmon Business Oriented Language) High-level business programming language that has been the primary business application language on mainframes and minis. It is a compiled language and was one of the first high-level languages developed. Formally adopted in 1960, it stemmed from a language called Flowmatic in the mid 1950s. COBOL requires more writing than other languages, but winds up more readable as a result. For example, multiply hourly-rate by hours-worked giving gross-pay is self-explanatory. COBOL is structured into the following divisions: Division name Contains IDENTIFICATION Program identification. ENVIRONMENT Types of computers used. DATA Buffers, constants and work areas. PROCEDURE The processing (program logic). The following COBOL example converts a Fahrenheit number to Celsius. To keep the example simple, it performs the operation on the operator's terminal rather than a user terminal.  IDENTIFICATION DIVISION.  PROGRAM-ID. EXAMPLE.  ENVIRONMENT DIVISION.  CONFIGURATION SECTION.  SOURCE-COMPUTER. IBM-370.  OBJECT-COMPUTER. IBM-370.  DATA DIVISION.  WORKING-STORAGE SECTION.  77 FAHR PICTURE 999.  77 CENT PICTURE 999.  PROCEDURE DIVISION.  DISPLAY 'Enter Fahrenheit ' UPON CONSOLE.  ACCEPT FAHR FROM CONSOLE.  COMPUTE CENT = (FAHR- 32) * 5 / 9.  DISPLAY 'Celsius is ' CENT UPON CONSOLE.  GOBACK.  IBM COBOLs In 1994, IBM will drop support of OS/VS COBOL, which conforms to ANSI 68 and ANSI 74 standards and limits a program's address space to 16 bits. IBM's VS COBOL II (1984) and COBOL/370 (1991) conform to ANSI 85 standards and provide 31-bit addressing, which allows programs to run "above the line." COBOL/370 is more compliant with AD/Cycle, has more string, math and date functions, including four-digit years, allows development through a PC window and provides enhanced runtime facilities. CODASYL (COnference on DAta SYstems Languages) Organization devoted to the development of computer languages. Founded in 1959, it is made up of individuals and institutions that contribute their own time and effort. COBOL is a product of CODASYL. For information, contact Jan Prokop, 29 Hartwell Avenue, Lexington, MA 02173, 617/863-5100. code (1) Set of machine symbols that represents data or instructions. See data code and machine language. (2) Any representation of one set of data for another. For example, a parts code is an abbreviated name of a product, product type or category. A discount code is a percentage. (3) To write a program. See source code and line of code. (4) To encode for security purposes. See encryption. code generator See application generator and macro recorder. code page In DOS 3.3 and higher, a table that sets up the keyboard and display characters for various foreign languages. codec (COder-DECoder) Electronic circuit that converts voice or video into digital code (and vice versa) using techniques such as pulse code modulation and delta modulation. A codec is an A/D and D/A converter. coder (1) Junior, or trainee, programmer who writes simple programs or writes the code for a larger program that has been designed by someone else. (2) Person who assigns special codes to data. CodeView Microsoft debugger for programs written with Microsoft C and CodeView-compatible compilers. Like other modern debuggers, it links source and object program letting the programmer step through the source code as the program is executed. COFF (Common Object File Format) UNIX System V machine language format. COGO (COordinate GeOmetry) Programming language used for solving civil engineering problems. Coherent Version of UNIX for 386s and up from Mark Williams Co., Northbrook, IL, that supports a variety of office applications off the shelf. It includes a C compiler, over 200 utilities and the Bourne and Korn shells. It uses minimal system resources. cold boot Starting the computer by turning power on. Turning power off and then back on again clears memory and many internal settings. Some program failures will lock up the computer and require a cold boot to use the computer again. In other cases, only a warm boot is required. See warm boot and boot. cold start Same as cold boot. collating sequence Sequence, or order, of the character set built into a computer. See ASCII chart and EBCDIC chart. collator (1) Punched card machine that merges two decks of cards into one or more stacks. (2) Utility program that merges records from two or more files into one file. collector Output side of a bipolar transistor. Same as drain in a MOS transistor. collision detection See CSMA/CD. color bits Number of bits associated with each pixel that represent its color. For 16 colors, four bits are used; for 256 colors, eight bits. color cycling In computer graphics, a technique that simulates animation by continuously changing colors rather than moving the objects. Also called color lookup table animation. color graphics Ability to display graphic images in colors. color keying Technique for superimposing a video image onto another. For example, to float a car on the ocean, the car image is placed onto a blue background. The car and ocean images are scanned together. The ocean is made to appear in the resulting image wherever background (blue) exists in the car image. The ocean is cancelled wherever the car appears (no background). color map See CLUT. color monitor See monitor. color printer Printer that prints in color using dot matrix, electrophotographic, Cycolor, electrostatic, ink jet or thermal-transfer techniques. See printer. color separation Separating a picture by colors in order to make negatives and plates for color printing. Full color requires four separations: cyan, magenta, yellow and black (CMYK). colors Perception of the different wavelengths of light. It is possible to create almost all visible colors using two systems of primary colors. Transmitted colors use red, green and blue (RGB), and reflected colors use cyan (light blue), magenta (purplish- red), yellow and black (CMYK). Color displays use RGB (colors are added to create white) and color printing uses CMYK (colors are subtracted to create white). column Vertical set of data or components. Contrast with row. column move Relocating a rectangular block of characters within a text document or a column in a spreadsheet. COM (Computer Output Microfilm) Creating microfilm or microfiche from computer output. A COM machine can be online or stand-alone (transfer via tape/disk). It receives print-image output from the computer and creates a film image of each page. Additional graphics (lines, logos, etc.) may be added. COM file (1) (COMmand file) Executable DOS or OS/2 program that takes up less than 64K and fits within one segment. It is an exact replica of how it looks in memory. See EXE file. (2) VMS file containing commands to be excecuted. COM port Serial communications port on a PC. See COM1 and serial port. COM1 Logical name assigned to serial port #1 in DOS and OS/2. COM ports are usually connected to a modem or mouse and sometimes to a printer. DOS versions up to 3.2 support COM1 and COM2. Version 3.3 supports up to COM4, and OS/2 supports eight COM ports. Contrast with LPT1. COMDEX (COMputer Dealers EXposition) Trade show intended for PC manufacturers, developers, dealers and distributors. Sponsored by The Interface Group, Needham, MA, 617/449-6600, COMDEX/Fall is the largest U.S. computer show. In 1979, less than 4,000 attended COMDEX/Fall with 157 exhibitors. In 1992, 2,000 exhibitors drew 145,000 attendees. COMDEX Events COMDEX/Spring, Atlanta May 24-27, 1993 May 23-26, 1994 May 22-25, 1995 COMDEX/Fall, Las Vegas Nov. 15-19, 1993 Nov. 14-18, 1994 Nov. 13-17, 1995 COMDEX/Canada, Toronto July 13-15, 1993 June 14-16, 1994 June 13-15, 1995 COMDEX/South America, Sao Paulo Aug. 23-27, 1993 Aug. 1994 Sept. 1995 comic-strip oriented Film-image orientation like a comic strip, which runs perpendicular to the outer edge of the film. Contrast with cine-oriented. comm port May refer to any serial communications port or specifically to the serial ports on a PC. See COM1. comma delimited Record layout that separates data fields with a comma and usually surrounds character data with quotes, for example: "Pat Smith","5 Main St.","New Hope","PA","18950" "K. Jones","34 E. 88 Ave.","Syosset","NY","10024"  command Instruction for the computer. See command-driven, menu-driven and function. command-driven Program that accepts commands as typed-in phrases. It is usually harder to learn, but may offer more flexibility than a menu-driven program. Once learned, command-driven programs may be faster to use, because the user can state a request succinctly. Contrast with menu-driven. command interpreter Same as command processor. Command key On Apple keyboards, a key with the outline of an Apple, a propeller, or both. It is pressed along with another key to command the computer. command language Special-purpose language that accepts a limited number of commands, such as a query language, job control language (JCL) or command processor. Contrast with programming language, which is a general purpose language. command line In a command-driven system, the area on screen that accepts typed-in commands. command mode Operating mode that causes the computer or modem to accept commands for execution. command processor System program that accepts a limited number of user commands and converts them into the machine commands required by the operating system or some other control program or application. command queuing Ability to store multiple commands and execute them one at a time. command set Same as instruction set. command shell Same as command processor. COMMAND.COM Command processor for DOS and OS/2 in Real Mode. See DOS COMMAND.COM. comment Descriptive statement in a source language program that is used for documentation. comment out To disable lines of code in a program by surrounding them with comment-start and comment- stop characters. commercial software Software that is designed and developed for sale to the general public. Commodore (Commodore Business Machines, Inc., West Chester, PA) In 1977, Commodore introduced the PET computer and launched the personal computer industry along with Apple and Radio Shack. In 1982, it introduced the Commodore 64 (64K RAM) and later the Commodore 128. These were popular home computers, and over 10 million have been sold. In 1985, the successful Amiga series was introduced, which features advanced capabilities at affordable prices. Also offered are a complete line of IBM-compatible PCs. common carrier Government-regulated organization that provides telecommunications services for public use, such as AT&T, the telephone companies, ITT, MCI and Western Union. communications Electronic transfer of information from one location to another. Data communications refers to digital transmission, and telecommunications refers to analog and digital transmission, including voice and video. The Protocol The way communications systems "talk to" each other is defined in a set of standards called protocols. Protocols work in a hierarchy starting at the top with the user's program and ending at the bottom with the plugs, sockets and electrical signals. See communications protocol and OSI. Personal Computer Communications Personal computer communications takes several forms. (1) Data can be transferred between two distant personal computers by using modems, a telephone line and a communications program in each computer. (2) Data can be transferred between two local computers by cabling them together with a null modem cable and a communications program in each computer. (3) Personal computers can act like a remote terminal to a mini or mainframe. For example, DCA's IRMAboard plugs into a personal computer and turns it into an IBM mainframe terminal. (4) Personal computers can be part of a local area network (LAN), in which databases and printers can be shared among users. If the LAN interconnects with a mini or mainframe networks, then personal computers can communicate with larger computers. Minicomputer Communications Minicomputer communications systems control as many as several hundred terminals connected to a single computer system. They support a variety of low- speed dial-up terminals and high-speed local terminals. With larger minicomputers, the communications processing is handled in separate machines, called communications controllers. Minicomputers are designed with communications in mind. The communications programs and operating systems are often integrated and provide simpler operation than mainframes. Minicomputers can connect to a mainframe by emulating a mainframe terminal, in which case, the mainframe thinks it's talking to another user terminal. Minicomputers can connect directly to some LANs, or to all LANs via a gateway, which converts the protocols. Mainframe Communications Mainframe systems can control several thousand remote terminals. They support a variety of low- speed dial-up terminals and high-speed local terminals. Large mainframes use separate machines, called communications controllers or front end processors, to handle the communications processing. These machines take the data from the mainframes and package it for transmission over the network. They also strip the communications codes from the incoming messages and send pure data to the mainframes for processing. Mainframes set the standards for communications. It's usually up to the mini and micro vendors to provide compatibility with the mainframe systems. Analog vs Digital Communications The most common form of long-distance communications has been the telephone system, which, up until a few years ago, transmitted only voice frequencies. This technique, known as analog communications, has been error prone, because the electronic frequencies get mixed together with unwanted signals (noise) that are nearby. In analog telephone networks, amplifiers are placed in the line every few miles to boost the signal, but they cannot distinguish between signal and noise. Thus, the noise is amplified along with the signal. By the time the receiving person or machine gets the signal, it may be impossible to decipher it. In a digital network, only two (binary) distinct frequencies or voltages are transmitted. Instead of amplifiers, repeaters are used, which analyze the incoming signal and regenerate a new outgoing signal. Any noise on the line is filtered out at the next repeater. When data is made up of only two signals (0 and 1), it can be more easily distinguished from the garble. Digital is simple! Communications Act Establishment of the Federal Communications Commission (FCC) in 1934, the regulatory body for interstate and foreign telecommunications. Its mission is to provide high-quality services at reasonable cost to everyone in the U.S. on a nondiscriminatory basis. communications channel Also called a circuit or line, it is a pathway over which data is transferred between remote devices. It may refer to the entire physical medium, such as a telephone line, optical fiber, coaxial cable or twisted wire pair, or, it may refer to one of several carrier frequencies transmitted simultaneously within the line as in broadband transmission (see broadband). communications controller Peripheral control unit that connects several communications lines to a computer and performs the actual transmitting and receiving as well as various message coding and decoding activities. Communications controllers are typically nonprogrammable units designed for specific protocols and communications tasks. Contrast with front end processor, which can be programmed for a variety of protocols and network conditions. communications network (1) Communications channels that interconnect terminals and computers. (2) Communications channels, all hardware that supports the interconnections and all software that manages the transmission. communications parameters Basic settings for modem transmission, which include bit rate (300, 1200, 2400, etc.), parity (none, even, odd), number of data bits (7 or 8) and number of stop bits (typically 1). See N-8-1. communications program Software that manages the transmission of data between computers and terminals. In personal computers, it manages transmission to and from the computer's serial port. It includes several communications protocols and can usually emulate dumb terminals for hookup to minis and mainframes. In a file server, the communications program is called the network operating system (NetWare, LANtastic). In mini and mainframe networks, the programs that support communications are called access methods, network control programs and TP monitors. See front end processor. communications protocol Hardware or software standards that govern transmission between two stations. On personal computers, communications programs offer a variety of protocols (Kermit, Xmodem, Zmodem, etc.) to transfer files via modem. On LANs, protocols are embodied in Ethernet, Token Ring and other access methods. In mainframe networks, there are multiple levels of protocols, and protocols within protocols. It's a complicated business managing enterprise-wide networks. The following conceptual exchange is at the data link level (Zmodem, Ethernet, etc.), which ensures that a block of data is transferred between two nodes without error. The Data Link Protocol Are you there? Yes, I am. Are you ready to receive? Yes, I am. Here comes the message--bla, bla, bla-- did you get it? Yes, I did. Here comes the next part--bla, bla, bla-- did you get it? No, I didn't. Here it comes again-- bla, bla, bla-- did you get it? Yes, I did. There is no more. Goodbye. Goodbye. communications satellite Radio relay station in orbit 22,300 miles above the equator. It travels at the same rate of speed as the earth (geosynchronous), so that it appears stationary. It contains many communications channels that receive analog and digital signals from earth stations. All signals are transmitted within a carrier frequency. The signals are amplified and transmitted back to earth, covering either a small geographical area (spot beam) or almost a third of the earth's surface. In the latter case, private data is often encrypted. communications server Computer in a network that manages access to external networks. It may manage a pool of modems and/or provide gateways to dissimilar networks. compact disc See CD. COMPACT II High-level numerical control programming language used to generate instructions for numerical control (machine tool) devices. compandor (COMpressor/exPANDOR) Device that improves the signal for AM radio transmission. On outgoing transmission, it raises the amplitude of weak signals and lowers the amplitude of strong signals. On incoming transmission, it restores the signal to its original form. Compaq (Compaq Computer Corp., Houston, TX) PC manufacturer founded in 1982 by Rod Canion, Bill Murto and Jim Harris. In 1983, it shipped 53,000 PC-compatible COMPAQ Portables, which resulted in $111 million in revenues and an American business record. The Portable's success was due to its rugged construction, ability to run all PC software and its semi-portability (it weighed 30 pounds!). In 1984, it introduced its DESKPRO desktop computers and achieved a computer-industry sales record in its second year. In 1986, it was the first to offer a 386-based machine. Compaq is an industry leader known for its rugged and reliable computers. comparator Device that compares two quantities and determines their equality. compare Fundamental computer capability. By comparing one set of data with another, the computer can locate, analyze, select, reorder and make decisions. After comparing, the computer can indicate whether the data were equal or which set was numerically greater or less than the other. See ASCII chart and "The 3 C's" in computer. compatibility See standards & compatibility. compatibility mode Feature of a computer or operating system that allows it to run programs written for a different system. Programs often run slower in compatiblity mode. compilation Compiling a program. See compiler. compile time Time it takes to translate a program from source language into machine language. Link editing time may also be included in compile time. compiler (1) Software that translates a high-level programming language (COBOL, C, etc.) into machine language. A compiler usually generates assembly language first and then translates the assembly language into machine language. The following example compiles program statements into machine language: Source code Assembly Language Machine language IF COUNT=10 Compare A to B Compare 3477 2883 GOTO DONE If equal go to C If = go to 23883 ELSE Go to D Go to 23343 GOTO AGAIN ENDIF  Actual machine code 10010101001010001010100 10101010010101001001010 10100101010001010010010 (2) Software that converts a high-level language into a lower-level representation. For example, a help compiler converts a text document embedded with appropriate commands into an online help system. A dictionary compiler converts terms and definitions into a dictionary lookup system. compiler language See high-level language and compiler. complement Number derived by subtracting a number from a base number. For example, the tens complement of 8 is 2. In set theory, complement refers to all the objects in one set that are not in another set. Complements are used in digital circuits, because it's faster to subtract by adding complements than by performing true subtraction. The binary complement of a number is created by reversing all bits and adding 1. The carry from the high-order position is eliminated. The following example subtracts 5 from 8.  Decimal Binary Subtraction by  Subtraction Equivalent Adding the complement 8 1000 1000 -5 -0101 +1011 陳 陳陳 陳陳 3 0011 0011 component One element of a larger system. A hardware component can be a device as small as a transistor or as large as a disk drive as long as it is part of a larger system. Software components are routines or modules within a larger system. composite video Video-only (no audio) part of a TV signal. Used on early personal computers for TV hookup, it mixes red, green, blue and sync signals like a standard TV and is not as crisp as separate red, green and blue cables (RGB). compound document Text file that contains both text and graphics. Eventually, it will routinely hold voice annotations and video clips. See OLE. compress To compact data to save space. See data compression. compression See data compression. compression ratio Measurement of compressed data. For example, a file compressed into 1/4th of its original size can be expressed as 4:1, 25%, 75% or 2 bits per byte. compressor (1) Device that diminishes the range between the strongest and weakest transmission signals. See compandor. (2) Routine or program that compresses data. See data compression. Compsurf Netware utility that performs a high-level hard disk format. NetWare servers require their own proprietary format. CompuServe Online information service that provides conferencing, news, sports, weather, e-mail and access to a large variety of databases. CompuServe Information Manager (CIM) software for the personal computer makes it easier to navigate through the system. See online services. compute To perform mathematical operations or general computer processing. See computer (The 3 C's). compute bound Same as process bound. computer General-purpose machine that processes data according to a set of instructions that are stored internally either temporarily or permanently. The computer and all equipment attached to it are called hardware. The instructions that tell it what to do are called software. A set of instructions that perform a particular task is called a program, or software program. WHAT A COMPUTER DOES The instructions in the program direct the computer to input, process and output as follows: Input/Output The computer can selectively retrieve data into its main memory (RAM) from any peripheral device (terminal, disk, tape, etc.) connected to it. After processing the data internally, the computer can send a copy of the results from its memory out to any peripheral device. The more memory it has, the more programs and data it can work with at the same time. Storage By outputting data onto a magnetic disk or tape, the computer is able to store data permanently and retrieve it when required. A system's size is based on how much disk storage it has. The more disk, the more data is immediately available. PROCESSING (The 3 C's*) Once the data is in the computer's memory, the computer can process it by calculating, comparing and copying it. Calculate The computer can perform any mathematical operation on data by adding, subtracting, multiplying and dividing one set with another. Compare The computer can analyze and evaluate data by matching it with sets of known data that are included in the program or called in from storage. Copy The computer can move data around to create any kind of report or listing in any order. By calculating, comparing and copying, the computer accomplishes all forms of data processing. For example, records are sorted into a new order by comparing two records at a time and copying the record with the lower value in front of the one with the higher value. The computer finds one customer out of thousands by comparing the requested account number to each record in the file. The dBASE query statement: SUM SALARY FOR TITLE = "NURSE" causes the computer to compare the title field in each record for NURSE and then add (calculate) the salary field for each match. In word processing, inserting and deleting text is accomplished by copying characters from one place to another. Remember The 3 C's* If you wonder whether the computer can solve a problem, identify your data on paper. If it can be calculated, compared and copied on paper, it can be processed in the computer. *(The 3 C's is a registered service mark of The Computer Language Company Inc.) THE STORED PROGRAM CONCEPT The computer's ability to call in instructions and follow them is known as the stored program concept. Instructions are copied into memory from a disk, tape or other source before any data can be processed. The computer is directed to start with the first instruction in the program. It copies the instruction from memory into its control unit circuit and matches it against its built-in set of instructions. If the instruction is valid, the processor carries it out. If not, the computer comes to an abnormal end (abend, crash). The computer executes instructions sequentially until it finds a GOTO instruction that tells it to go to a different place in the program. It can execute millions of instructions per second tracing the logic of the program over and over again on each new set of data it brings in. As computers get faster, operations can be made to overlap. While one program is waiting for input from one user, the operating system (master control program) directs the computer to process data in another program. Large computers are designed to allow inputs and outputs to occur simultaneously with processing. While one user's data is being processed, data from the next user can be retrieved into the computer. It can take hundreds of thousands of discrete machine steps to perform very routine tasks. Your computer could easily execute a million instructions to put a requested record on screen for you. GENERATIONS OF COMPUTERS First-generation computers, starting with the UNIVAC I in 1951, used vacuum tubes, and their memories were made of thin tubes of liquid mercury and magnetic drums. Second-generation systems in the late 1950s replaced tubes with transistors and used magnetic cores for memories (IBM 1401, Honeywell 800). Size was reduced and reliability was significantly improved. Third-generation computers, beginning in the mid 1960s, used the first integrated circuits (IBM 360, CDC 6400) and the first operating systems and DBMSs. Online systems were widely developed, although most processing was still batch oriented using punched cards and magnetic tapes. Starting in the mid 1970s, the fourth generation brought us computers made entirely of chips. It spawned the microprocessor and personal computer. It introduced distributed processing and office automation. Query languages, report writers and spreadsheets put large numbers of people in touch with the computer for the first time. The fifth generation ought to become more visible by the mid 1990s with voice recognition, natural and foreign language translation, fiber optics, optical disks and technologies still in the research labs. By the 21st century, a computer should be able to converse somewhat intelligently with us. COMPUTERS COME IN MANY SIZES Computers are as small as a chip or as large as a truck. The difference is in the amount of work they do within the same time frame. Its power is based on many factors, including word size and the speed of its CPU, memory and peripherals. Following is a rough guide to system cost: Computer system type Approximate price (Bits show word size) In 1993 $US Computer on a chip (chip only) (4, 8, 16-bit) $2 - 75 Microprocessor (chip only) (4, 8, 16, 32, 64-bit) $5 - 500 Personal computer (8, 16, 32, 64-bit) $500 - 15,000 Minicomputer (16, 32, 64-bit) $15,000 - 250,000 Supermini (32, 64-bit) $200,000 - 750,000 Mini-supercomputer (64-bit) $100,000 - 750,000 Mainframe (32, 64-bit) $150,000 - 3,000,000 Supercomputer (64-bit) $1,000,000 - 20,000,000 computer architecture Design of a computer system. It sets the standard for all devices that connect to it and all the software that runs on it. It is based on the type of programs that will run (business, scientific) and the number of them run concurrently. It specifies how much memory is needed and how it is managed (memory protection, virtual memory, virtual machine). It specifies register size and bus width (16-, 32-, 64-bit) and how concurrency is handled (channels, bus mastering, parallel processing). Its native language instruction set stipulates what functions the computer performs and how instructions are written to activate them. This determines how programs will communicate with it forever after. The trend toward large, complicated instruction sets has been reversed with RISC computers, which use simpler instructions. The result is a leaner, faster computer, but requires that the compilers generate more code for complex functions that used to be handled in hardware. Fault tolerant operation influences every aspect of computer architecture, and computers designed for single purposes, such as array processors and database machines, require special designs. Computer Associates (Computer Associates Int'l., Inc., Islindia, NY) World's largest diversified software vendor offering over 350 applications from micro to mainframe. Founded in 1976 by Charles Wang and three associates, its first product was CA-SORT, an IBM mainframe utility. In personal computers, it was originally known for SuperCalc, one of the first spreadsheets. With 1991 revenues exceeding 1.6 billion, CA is concentrating heavily in the Windows market. computer center Same as datacenter. computer designer Person who designs the electronic structure of a computer. computer exchange Commodity exchange through which the public can buy and sell used computers. After a match, the buyer sends a check to the exchange and the seller sends the equipment to the buyer. If the buyer accepts it, the money is sent to the seller less commission. Boston Computer Exchange (BoCoEx) 617/542-4414 FAX 617/542-8849 National Computer Exchange (NaComEx) 212/614-0700 FAX 212/777-1290 The Newman Group 313/426-3200 FAX 313/426-0777 computer graphics See graphics. computer language Programming language, machine language or the language of the computer industry. Computer Library Ziff Communications Company division that provides information services. See Computer Select. computer literacy Understanding computers and related systems. It includes a working vocabulary of computer and information system components, the fundamental principles of computer processing and a perspective for how non-technical people interact with technical people. It does not deal with how the computer works (digital circuits), but does imply knowledge of how the computer does its work (calculate, compare and copy). It requires a conceptual understanding of systems analysis & design, application programming, systems programming and datacenter operations. To be a computer literate manager, you must be able to define information requirements effectively and have an understanding of decision support tools, such as query languages, report writers, spreadsheets and financial planning systems. To be truly computer literate, you must understand "standards & compatibility" in this Glossary. If you can't sleep at night, it's a guaranteed cure for insomnia! computer on a chip Single chip that contains the processor, RAM, ROM, clock and I/O control unit. It is used for myriads of applications from automobiles to toys. computer power Effective performance of a computer. It can be expressed in MIPS (millions of instructions per second), clock speed (10Mhz, 16Mhz) and in word or bus size, (16-bit, 32-bit). However, as with automobile horsepower, valves and cylinders, such specifications are only guidelines. Real power is whether it gets your job done quickly. A software package is "powerful" if it has a large number of features. Computer Press Assn. See CPA. Remember... use the acronym first! computer readable Same as machine readable. computer science Field of computer hardware and software. It includes systems analysis & design, application and system software design and programming and datacenter operations. For young students, the emphasis in typically on learning a programming language or running a personal computer with little attention to information science, the study of information and its uses. If students were introduced to data administration, DBMS concepts and transaction and master files, they would have a better grasp of an organization's typical information requirements. Computer Security Act First step in improving the security and privacy of information contained in federal computer systems. Signed 1/8/88 by President Reagan, the Act: Establishes a central authority for developing guidelines for protecting unclassified, but sensitive information stored in government computers. Requires each agency to formulate a computer security plan, tailored to its own circumstances and based on the guidelines. Mandates that each agency provide training for its computer employees on the threats and vulnerabilities of its computer systems. Ensures that the National Security Agency and other defense-related government agencies not control computer security standards in civilian agencies of government. Computer Select CD ROM service from Computer Library that provides articles and abstracts from over 140 computer- related periodicals. It includes over 67,000 hardware, software and communications products and 11,000 manufacturer's profiles. Subscribers receive a CD ROM every month with articles from the preceding 12 months. computer services Data processing (timesharing, batch processing), software development and consulting services. See service bureau. computer system Complete computer made up of the CPU, memory and related electronics (main cabinet), all the peripheral devices connected to it and its operating system. Computer systems fall into ranges called microcomputers (personal computers), minicomputers and mainframes, roughly small, medium and large. Computer systems are sized for the total user workload based on (1) number of terminals required, (2) type of work performed (interactive processing, batch processing, CAD, engineering, scientific), and (3) amount of online data required. Following are the components of a computer system and their significance:  Component Significance Machine language Compatibility with future hardware/software Operating system Performance and future hardware/software compatibility Clock speed Performance (MIPS rate) Number of Number of concurrent users terminals Memory capacity Performance Disk capacity Amount of available information Communications Access to inhouse and external information Programming Compatibility with future languages hardware Fail-safe design Reliability COMSAT (COMmunications SATellite Corp.) Private communications satellite company created by Congress in 1962 that provides communications capacity to carriers such as AT&T and MCI. In 1965, it launched Early Bird, the first commercial satellite to transmit signals from a geosynchronous orbit. See INTELSAT and INMARSAT. Comspec See DOS Comspec. CON (CONsole) DOS name for the keyboard and screen. See DOS device names and DOS Copy con. concatenate To link structures together. Concatenating files appends one file to another. In speech synthesis, units of speech called phonemes (k, sh, ch, etc.) are concatenated to produce meaningful sounds. concentrator Device that joins several communications channels together. It is similar to a multiplexor except that it does not spread the signals back out again on the other end. The receiving computer performs that function. conceptual view See view. concurrency control In a DBMS, managing simultaneous access to a database. It prevents two users from editing the same record at the same time and is also concerned with serializing transactions for backup and recovery. Concurrent DOS Early multiuser DOS-compatible operating system from Digital Research. See Multiuser DOS. concurrent operation See multitasking, multiprocessing and parallel processing. concurrent processing See multiprocessing. conditional branch In programming, an instruction that directs the computer to another part of the program based on the results of a compare. In the following (simulated) assembly language example, the second line is the conditional branch.  COMPARE FIELDA with FIELDB  GOTO MATCHROUTINE if EQUAL.  High-level language statements, such as IF THEN ELSE and CASE, are used to express the compare and conditional branch. conditioning Extra cost options in a private telephone line that improve performance by reducing distortion and amplifying weak signals. conductor Material that can carry electrical current. Contrast with insulator. CONFIG.SYS DOS and OS/2 configuration file. It resides in the root directory and is used to load drivers and change settings at startup. See DOS CONFIG.SYS. configuration Makeup of a system. To "configure" is to choose options in order to create a custom system. "Configurability" is a system's ability to be changed or customized. configuration file File that contains information about a specific user, program, computer or file. configuration management System for gathering current configuration information from all nodes in a LAN. See version control. configure See configuration. connect time Amount of time a user at a terminal is logged on to a computer system. See online services and service bureau. Connection Machine Family of parallel processing computers from Thinking Machines Corp., Cambridge, MA, that contain from 4K to 64K processors. They can be set up as hypercubes or other topologies and require another computer as a front end. Used for such applications as signal processing, simulation and database retrieval. connection-oriented In communications, requiring a direct connection or established session between two nodes for transmission. Contrast with connectionless. connectionless In communications, the inclusion of source and destination addresses within each packet so that a direct connection or established session between nodes is not required. Contrast with connection- oriented. connectivity May refer to communications in general or to hardware that links networks together, such as bridges, routers and gateways. connector (1) Any plug, socket or wire that links two devices together. (2) In database management, a link or pointer between two data structures. (3) In flowcharting, a symbol used to break a sequence and resume the sequence elsewhere. It is often a small circle with a number in it. console (1) Main operator's terminal on a large computer. (2) Any display terminal. constant In programming, a fixed value in a program. Minimum and maximum amounts, dates, prices, headlines and error messages are examples. constant ratio code Code that always contains the same ratio of 0s to 1s. consultant Independent specialist that may act as an advisor or perform detailed systems analysis and design. They often help users create functional specifications from which hardware or software vendors can respond. contact Metal strip in a switch or socket that touches a corresponding strip in order to make a connection for current to pass. Contacts may be made of precious metals to avoid corrosion. contention Condition that arises when two devices attempt to use a single resource at the same time. See CSMA/CD. contention resolution Deciding which device gains access to a resource first when more than one wants it at the same time. context sensitive help Help screens that provide specific information about the condition or mode the program is in at the time help is sought. context switching Switching between active applications. It often refers to a user jumping back and forth between several programs in contrast with repeated task switching performed by the operating system. However, the terms context switching and task switching are used synonymously. contextual search To search for records or documents based upon the text contained in any part of the file as opposed to searching on a pre-defined key field. contiguous Adjacent or touching. Contrast with fragmentation. continuity check Test of a line, channel or circuit to determine if the pathway exists from beginning to end and can transmit signals. continuous carrier In communications, a carrier frequency that is transmitted even when data is not being sent over the line. continuous forms Roll of paper forms with perforations for separation into individual sheets after printing. See pin feed and burster. contrast Difference between the lightest and darkest areas on a display screen. Contrast with brightness. control ball Same as trackball. control block Segment of disk or memory that contains a group of codes used for identification and control purposes. control break (1) Change of category used to trigger a subtotal. For example, if data is subtotalled by state, a control break occurs when NJ changes to NM. (2) See Ctrl-Break. control character See control code. control code One or more characters used as a command to control a device. The first 32 characters in the ASCII character set are control codes for communications and printers. There are countless codes used to control electronic devices. See escape character. Control Data (Control Data Systems, Inc., Minneapolis, MN) One of the first computer companies. Founded in 1957, Bill Norris was its first president and guiding force. Its first computer, the 1604, was introduced in 1957 and delivered to the U.S. Navy Bureau of Ships. Since then, it has been heavily involved with governmental agencies. Control Data offers a product line from workstation to supercomputer and has specialized in large mainframes used in scientific environments and large service bureaus. In 1992, it split into two independent companies. Control Data Systems, Inc. makes computers, and Ceridian Corp. handles military products and provides a variety of services. control field Same as key field. control key Abbreviated "ctrl" or "ctl." Key that is pressed with a letter or digit key to command the computer; for example, holding down control and pressing U, turns on underline in some word processors. The caret (shift-6) symbol represents the control key: ^Y means control-Y. control network Network of sensors and actuators used for home automation and industrial control. Control Panel Routine that changes the computer's environment settings, such as keyboard and mouse sensitivity, sounds, colors and communications and printer access. It is a desk accessory in the Macintosh and a utility program in Windows. control parallel Same as MIMD. control program Software that controls the operation of and has highest priority in a computer. Operating systems, network operating systems and network control programs are examples. Contrast with application program. control total Same as hash total. control unit (1) Within the processor, the circuitry that locates, analyzes and executes each instruction in the program. (2) Within the computer, a control unit, or controller, is hardware that performs the physical data transfers between memory and a peripheral device, such as a disk or screen, or a network. Personal computer control units are contained on a single plug-in expansion board, called a controller or adapter (disk controller, display adapter, network adapter). In large computers, they may be contained on one or more boards or in a stand-alone cabinet. In single chip computers, a built-in control unit accepts keyboard input and provides serial output to a display. control variable In programming, a variable that keeps track of the number of iterations of a process. Its value is incremented or decremented with each iteration, and it is compared to a constant or other variable to test the end of the process or loop. controller See control unit (2). conventional memory In a PC, the first 640K of memory. The next 384K is called the UMA (upper memory area). The term also often refers to the entire first megabyte (1024K) of RAM, which is the memory that DOS can directly manage without the use of additional memory managers. See DOS memory manager. conventional programming Using a procedural language. convergence Intersection of red, green and blue electron beams on one CRT pixel. Poor convergence decreases resolution and muddies white pixels. conversational Interactive dialogue between the user and the computer. conversion (1) Data conversion is changing data from one file or database format to another. It may also require code conversion between ASCII and EBCDIC. (2) Media conversion is changing storage media such as from tape to disk. (3) Program conversion is changing the programming source language from one dialect to another, or changing application programs to link to a new operating system or DBMS. (4) Computer system conversion is changing the computer model and peripheral devices. (5) Information system conversion requires data conversion and either program conversion or the installation of newly purchased or created application programs. converter (1) Device that changes one set of codes, modes, sequences or frequencies to a different set. See A/D converter. (2) Device that changes current from 60Hz to 50Hz, and vice versa. cooperative processing Sharing a job among two or more computers such as a mainframe and a personal computer. It implies splitting the workload for the most efficiency. coordinate Belonging to a system of indexing by two or more terms. For example, points on a plane, cells in a spreadsheet and bits in dynamic RAM chips are identified by a pair of coordinates. Points in space are identified by sets of three coordinates. coprocessor Secondary processor used to speed up operations by handling some of the workload of the main CPU. See math coprocessor. copy To make a duplicate of the original. In digital electronics, all copies are identical. The text in this Glossary takes up about 1.7 megabytes. During the course of writing and updating it, the text has been copied hundreds of times, causing billions of bits to be transmitted between disk and memory. Just to show that things aren't entirely perfect, a character does get garbled every once in a while. We'll have to settle for 99.9999% instead of 100%! See DOS Copy. copy buster Program that bypasses the copy protection scheme in a software program and allows normal, unprotected copies to be made. copy protection Resistance to unauthorized copying of software. Copy protection was never an issue with mainframes and minicomputers, since vendor support has always been vital in those environments. In the early days of floppy-based personal computers, many copy protection methods were used. However, with each scheme introduced, a copy buster program was developed to get around it. When hard disks became the norm, copy protection was abolished. In order to manage a hard disk, files must be easily copied. This is a constant dilemma for software vendors. Every user has the manufacturing facilities to produce a perfect copy of the original! Anyone figuring out a way to prevent unauthorized copies without interfering with routine computer management will become a billionaire overnight! core Round magnetic doughnut that represents one bit in a core storage system. A computer's main memory used to be referred to as core. core storage Non-volatile memory that holds magnetic charges in ferrite cores about 1/16th" diameter. The direction of the flux determines the 0 or 1. Developed in the late 1940s by Jay W. Forrester and Dr. An Wang, it was used extensively in the 1950s and 1960s. Since it holds its content without power, it is still used in specialized applications in the military and in space vehicles. Core System First proposed standard for computer graphics, developed by the Graphics Standards Planning Committee of SIGGRAPH and used in the late 1970s and early 1980s. Its objectives were portability of programs between computers and the separation of modeling graphics from viewing graphics. Almost all features of the Core System were incorporated into the ANSI-endorsed GKS standard. Corel Draw Popular windows-based illustration program for 286s and up from Corel Systems Corp., Ottawa, Ontario. Introduced in 1989, it includes over 100 fonts and is known for its speed and ease of use. It generates its own CDR vector graphics files, but can import other graphics formats. CorelRAID Software from Corel Systems Corp., Ottawa, Ontario, that creates RAID arrays on a Novel 3.11 server using an ASPI-compatible SCSI host adapter and three or more SCSI disks. CorelSCSI SCSI driver from Corel Systems Corp., Ottawa, Ontario, that supports a wide variety of SCSI devices, including removable media, juke boxes, digital cameras and WORM drives and translates them into the ASPI standard. See PowerSCSI!. corona wire Charged wire in a laser printer that draws the toner off the drum onto the paper. It must be cleaned when the toner cartridge is replaced. corrupted file Data or program file that has been altered in some manner causing the bits to be rearranged and rendering it unreadable. corruption Altering of data or programs due to viruses, hardware or software failure or power failure. See data recovery. COS (Corporation for Open Systems Int'l.) Not for profit R&D consortium founded in 1986, dedicated to assuring acceptance of a worldwide open network architecture. It is made up of manufacturers and user organizations that provide development, service, and support of systems that conform to international standards, including OSI and ISDN. Address: 1750 Old Meadow Road, Suite 400, McLean, VA 22102, 703/883-2700. cost/benefits analysis Study that projects the costs and benefits of a new information system. Costs include people and machine resources for development as well as running the system. Tangible benefits are derived by estimating the cost savings of both human and machine resources to run the new system versus the old one. Intangible benefits, such as improved customer service and employee relations, may ultimately provide the largest payback, but are harder to quantify. counter (1) In programming, a variable that is used to keep track of anything that must be counted. The programming language determines the number of counters (variables) that are available to a programmer. (2) In electronics, a circuit that counts pulses and generates an output at a specified time. Courier Monospaced typeface originating from the typewriter. courseware Educational software. See CBT. covert channel Transfer of information that violates a computer's built-in security systems. A covert storage channel refers to depositing information in a memory or storage location that can be accessed by different security clearances. A covert timing channel is the manipulation of a system resource in such a way that it can be detected by another process. CP (1) (Copy Protected) See copy protection. (2) (Central Processor) See processor and CPU. (3) See control program. CP/M (Control Program for Microprocessors) Single user operating system for the 8080 and Z80 microprocessors from Digital Research. Created by Gary Kildall, CP/M had its heyday in the early 1980s. CP/M was an unsophisticated program that didn't instill confidence in users, yet it was a major contributor to the personal computer revolution. Because the industry never standardized on a CP/M disk or video format, software publishers had to support dozens of screen displays and floppy disk formats. This chaos helped IBM set the standard with its PC. Although IBM asked Kildall to provide the operating system for its new PC, he didn't agree to certain demands. IBM went to Microsoft, which purchased an operating system from another company and turned it into DOS. DOS was modeled after CP/M. CPA (Computer Press Assn.) Organization founded in 1983 that promotes excellence in computer journalism. Comprised of approximately 300 members (1992), its annual awards honor outstanding journalism in print, broadcast and electronic media. Address is 529 18th Ave., San Francisco, CA 94121, 415/750-9281. CPE (Customer Premises Equipment) Communications equipment that resides on the customer's premises. CPF (Control Program Facility) IBM System/38 operating system that includes an integrated relational DBMS. CPGA (Ceramic PGA) See PGA. cpi (1) (Characters Per Inch) Measures the density of characters per inch on tape or paper. A printer's CPI button switches character pitch. (2) (Counts Per Inch) Measures the resolution of a mouse/trackball as flywheel notches per inch (horizontal and vertical flywheels rotate as the ball is moved). Notches are converted to cursor movement. (3) (CPI) (Common Programming Interface) See SAA and CPI-C. CPI-C (Common Programming Interface for Communications) General-purpose communications interface under IBM's SAA. Using APPC verbs as its foundation, it provides a common programming interface across IBM platforms. See APPC. CPM (Critical Path Method) Project management planning and control technique implemented on computers. The critical path is the series of activities and tasks in the project that have no built-in slack time. Any task in the critical path that takes longer than expected will lengthen the total time of the project. cps (Characters Per Second) Measures the speed of a serial printer or the speed of a data transfer between hardware devices or over a communications channel. CPS is equivalent to bytes per second. CPU (Central Processing Unit) Computing part of the computer. Also called the processor, it is made up of the control unit and ALU. A personal computer CPU is a single microprocessor chip. A minicomputer CPU is contained on one or more printed circuit boards. A mainframe CPU is made up of several boards. The CPU, clock and main memory make up a computer. A complete computer system requires the addition of control units, input, output and storage devices and an operating system. CPU bound Same as process bound. CPU chip Same as microprocessor. CPU time Amount of time it takes for the CPU to execute a set of instructions and explicitly excludes the waiting time for input and output. CR (Carriage Return) Return key or the actual code that is generated when the key is pressed (decimal 13, hex 0D). See return key. CR/LF (Carriage Return/Line Feed) End of line characters used in standard PC text files (ASCII 13 10). In the Mac, only the CR is used; in UNIX, the LF. CRAM (Card RAM) Magnetic card mass storage device made by NCR in the 1960s. In order to read or write data, a card was pulled out of the cartridge and wrapped around a rotating drum. crash See abend and head crash. Cray (Cray Research, Inc., Eagan, MN) Supercomputer manufacturer founded in 1972 by Seymour Cray, a leading designer of large-scale computers at Control Data. In 1976, it shipped its first computer to Los Alamos National Lab. The CRAY-1 was a 75MHz, 64-bit machine with a peak speed of 160 megaflops, making it the world's fastest vector processor. Large-scale Cray computers are multi-million- dollar machines that use multiple processors, liquid-cooled circuits, have gigabytes of main memory and calculate well into the gigaflop range. In 1989, Cray left Cray Research and founded Cray Computer Corp. CRC (Cyclical Redundancy Checking) Error checking technique used to ensure the accuracy of transmitting digital data. The transmitted messages are divided into predetermined lengths which, used as dividends, are divided by a fixed divisor. The remainder of the calculation is appended onto and sent with the message. At the receiving end, the computer recalculates the remainder. If it does not match the transmitted remainder, an error is detected. Cricket Presents Desktop presentation program for the Macintosh from Computer Associates. It provides the ability to create output for overheads, handouts, speaker notes and film recorders. crippleware Demonstration software with built-in limitations; for example, a database package that lets only 50 records be entered. Cristina Foundation See NCF. criteria range Conditions for selecting records; for example, "Illinois customers with balances over $10,000." crop marks Printed lines on paper used to cut the form into its intended size. cross assembler Assembler that generates machine language for a foreign computer. It is used to develop programs for computers on a chip or microprocessors used in specialized applications, which are either too small or are incapable of handling the development software. cross compiler Compiler that generates machine language for a foreign computer. See cross assembler. cross tabulate To analyze and summarize data. For example, cross tabulation is used to summarize the details in a database file into totals in a spreadsheet. crossfoot Numerical error checking technique that compares the sum of the columns with the sum of the rows. crosshatch Criss-crossed pattern used to fill in sections of a drawing to distinguish them from each other. crossover cable Same as null modem cable. crosstalk (1) In communications, interference from an adjacent channel. (2) (Crosstalk) Family of PC communications programs from DCA, Inc., Alpharetta, GA. Crosstalk products were originally developed by Microstuf, Inc. (later merged with DCA). Crosstalk XVI (1983) is the PC version of the original Crosstalk developed for CP/M computers. It included a script language. Crosstalk Mk.4 (1987) supports a variety of protocols and terminals, allows concurrent sessions and provides user-definable menus and a revised language called CASL (Crosstalk Application Script Language). Crosstalk for Windows (1989) provides additional commands. CRT (Cathode Ray Tube) Vacuum tube used as a display screen in a video terminal or TV. The term often refers to the entire terminal. crunch (1) To process data. See number crunching. (2) To compress data. See data compression. cryogenics Using materials that operate at very cold temperatures. See superconductor. cryptography Conversion of data into a secret code for security purposes. Same as encryption. crystal Solid material containing a uniform arrangement of molecules. See quartz crystal. crystalline Solid state of a crystal. Contrast with nematic. CSA (1) (Canadian Standards Assn.) Canadian counterpart of U.S. Underwriters Laboratory. (2) (Client Server Architecture) See client/server. (3) (CallPath Services Architecture) IBM standard that integrates applications with the telephone system, designed for use with AT&T, Northern Telecom and other PBX vendors. CSIC (Customer Specific Integrated Circuit) Pronounced "C-sick." Custom-developed chips from Motorola. CSMA/CD (Carrier Sense Multiple Access/Collision Detection) Baseband communications access method. When a device wants to gain access to the network, it checks to see if the network is free. If it is not, it waits a random amount of time before retrying. If the network is free and two devices attempt access at exactly the same time, they both back off to avoid a collision and each wait a random amount of time before retrying. CSP (1) (Cross System Product) IBM application generator that runs in all SAA environments. CSP/AD (CSP/Application Development) programs provide the interactive development environment and generate a pseudo code that is interpreted by CSP/AE (CSP/Application Execution) software in the running computer. For AS/400 applications, CSP/AD generates compiled code. For the PS/2, EZ-PREP and EZ-RUN are the CSP/AD and CSP/AE counterparts. (2) (Certified Systems Professional) Award for successful completion of an ICCP examination in systems development. CSU See DSU/CSU. CSV (Comma Separated Value) Same as comma delimited. CTI (Computer Telephone Integration) Joining data and voice systems to enhance telephone services. For example, automatic number identification (ANI) allows a caller's records to be retrieved from the database while the call is routed to the appropriate party. Automatic telephone dialing from an address list is an outbound example. Ctl See control key. CTO (Chief Technical Officer) Executive responsible for the technical direction of an organization. CTOS Operating system that runs on the Intel-based Unisys B-series, originally developed by Convergent Technologies (now part of Unisys). Designed for network use, its message-based approach allows program requests to be directed to any station in the network. Ctrl See control key. Ctrl-Alt-Del In a PC, holding down the CTRL and ALT keys and pressing the DEL key reboots the system. Ctrl-Break In a PC, holding down the CTRL key and pressing the BREAK key cancels the running program or batch file. Same as Ctrl-C. See DOS Break. Ctrl-C In a PC, holding down the CTRL key and pressing the C key cancels the running program or batch file. Same as Ctrl-Break. See DOS Break. Ctrl-S In a PC, holding down the CTRL key and pressing the S key pauses and continues the running program. CTS (1) (Clear To Send) RS-232 signal sent from the receiving station to the transmitting station that indicates it is ready to accept data. Contrast with RTS. (2) See carpal tunnel syndrome. CUA (Common User Access) SAA specifications for user interfaces, which includes OS/2 PM and character- based formats of 3270 terminals. It is intended to provide a consistent look and feel across platforms and between applications. CUI (Character-based User Interface) User interface that uses the character, or text, mode of the computer and typically refers to typing in commands. Contrast with GUI. Curie point Temperature (150 C) at which certain elements are susceptible to magnetism. See magneto-optic. current (1) Present activities or the latest version or model. (2) Flow of electrons within a wire or circuit, measured in amps. (3) (Current) Windows PIM from IBM that includes a calendar, address book, phone dialer, outliner, word processor and Gantt charts for keeping track of projects. current directory Disk directory the system is presently working in. Unless otherwise specified, commands that deal with disk files imply the current directory. current loop Serial transmission method originating with teletype machines that transmits 20 milliAmperes of current for a 1 bit and no current for a 0 bit. Today's circuit boards can't handle 20mA current and use optical isolators at the receiving end to detect lower current. Contrast with RS-232. cursor (1) Movable symbol on screen that is the contact point between the user and the data. In text systems, it is a blinking rectangle or underline. On graphic systems, it is also called a pointer, and it usually changes shape (arrow, square, paintbrush, etc.) when it moves into a different part of the screen. (2) Pen-like or puck-like device used with a digitizer tablet. As the tablet cursor is moved across the tablet, the screen cursor moves correspondingly. See digitizer tablet. cursor keys Keys that move the cursor on screen, which include the up, down, left and right arrow, home, end, PgUp and PgDn keys. In addition to cursor keys, a mouse or tablet cursor also moves the cursor. customized software Software designed for an individual customer. cut & paste To move a block of text from one part of a document to another or from one file to another. CUT mode (Control Unit Terminal mode) Mode that allows a 3270 terminal to have a single session with the mainframe. Micro to mainframe software emulates this mode to communicate with the mainframe. Contrast with DFT mode. CVF (Compressed Volume File) See DOS DoubleSpace. CYBER Trade name for Control Data computers that includes models from high-speed workstations to supercomputers. cybernetics Comparative study of human and machine processes in order to understand their similarities and differences. It often refers to machines that imitate human behavior. See AI and robot. cyberpunk Relating to futuristic delinquency: hackers breaking into computer banks, survival based on high-tech wits. Stems from science fiction novels such as "Neuromancer" and "Shockwave Rider." cyberspace Term coined by William Gibson in his novel "Neuromancer," to refer to a futuristic computer network that people use by plugging their brains into it! See virtual reality. cycle (1) Single event that is repeated. For example, in a carrier frequency, one cycle is one complete wave. (2) Set of events that is repeated. For example, in a polling system, all of the attached terminals are tested in one cycle. See machine cycle and memory cycle. cycle stealing CPU design technique that periodically "grabs" machine cycles from the main processor usually by some peripheral control unit, such as a DMA (direct memory access) device. In this way, processing and peripheral operations can be performed concurrently or with some degree of overlap. cycle time Time interval between the start of one cycle and the start of the next cycle. cycles per second Number of times an event or set of events is repeated in a second. See Hertz. Cycolor Printing process from Mead Imaging that prints full tonal images like photographs. It uses a special film coated with light-sensitive microcapsules, called cyliths, that contain leuco dyes. The film is exposed to the color image that is being printed, resulting in a latent image of hard and soft cyliths. The latent image donor film is transferred onto a special Cycolor paper by being squeezed together through pressure rollers, thus releasing the dyes from the film onto the paper. The paper is then briefly heated, and the result is a full-color image that resembles a photograph. cylinder Aggregate of all tracks that reside in the same location on every disk surface. On multiple- platter disks, the cylinder is the sum total of every track with the same track number on every surface. On a floppy disk, a cylinder comprises the top and corresponding bottom track. When storing data, the operating system fills an entire cylinder before moving to the next one. The access arm remains stationary until all the tracks in the cylinder have been read or written. cylinder skew Offset distance from the start of the last track of the previous cylinder so that the head has time to seek from cylinder to cylinder and be at the start of the first track of the new cylinder. See head skew. D/A converter (Digital to Analog Converter) Device that converts digital pulses into analog signals. See A/D converter. D/CAS (Working Group for Data/CASsette Drive Compatibility) Organization standardizing audio technology for tape backup. With high-density recording, an upgraded version of the common audio tape cassette holds 600MB of data. D/DAT See DATA/DAT. D-RAM See dynamic RAM. D&B Software (Dun & Bradstreet Software, Atlanta; The Dun & Bradstreet Corp.) Software and consulting organization formed in 1990 as a merger of Management Science America (MSA) and McCormack & Dodge. It is one of the largest software companies in the world. MSA was originally founded in 1963 to provide textile consulting services. Under the leadership of John Imlay, who rejoined the company in 1970 as Chairman and CEO, MSA grew rapidly in business applications software and was the first to enter the international marketplace in 1979. McCormack & Dodge began as a packaged financial software firm in 1969 and later introduced the first integrated environment for mainframe business applications. In 1983, it was acquired by The Dun & Bradstreet Corp. Imlay directed the merger and has headed the new company in the development of client-server versions of its mainframe software. D4 Framing format for T1 transmission that places 12 T1 frames into a superframe. See ESF. DA See desk accessory and data administrator. DAC See D/A converter. DAD (1) (Database Action Diagram) Documentation that describes the processing performed on data in a database. (2) (Digital Audio Disc) Same as CD. daemon Pronounced "demon." Program that waits in the background ready to perform some action when a certain event occurs. From Greek mythology meaning "guardian spirit." Same as agent. daisy chain Connected in series, one after the other. Transmitted signals go to the first device, then to the second and so on.  敖陳陳朕敖陳陳朕敖陳陳朕  栩栩 栩栩栩 栩栩栩 栩栩  Daisy chain  daisy wheel Print mechanism that uses a plastic or metal hub with spokes like an old-fashioned wagon wheel minus the outer rim. At the end of each spoke is the carved image of a type character. When the required character spins around to the print hammer, the image is banged into a ribbon and onto paper. The mechanism is then moved to the next location. Daisy wheel printers print typewriter-like quality from 10 to 75 cps and have been superseded by dot matrix and laser printers. DAL (Data Access Language) Database interface from Apple that allows the Mac to access DAL-supported databases on Macs or non-Apple computers. It is a superset of SQL. Database vendors license the specs and translate DAL calls to their database engines. damping Technique for stabilizing an electronic or mechanical device by eliminating unwanted or excessive oscillations. Darlington circuit Amplification circuit that uses two transistors coupled together. DARPA (Defense Advanced Research Projects Agency) See ARPANET. DASD (Direct Access Storage Device) Pronounced "dazdee." Peripheral device that is directly addressable, such as a disk or drum. DAT (1) (Digital Audio Tape) CD-quality, digital recording technology for magnetic tape. A 4mm, helical-scan DAT drive holds several gigabytes with extended-length tapes when adapted for data storage use. See tape backup. (2) (Dynamic Address Translator) Hardware circuit that converts a virtual memory address into a real address. data (1) Technically, raw facts and figures, such as orders and payments, which are processed into information, such as balance due and quantity on hand. However, in common usage, the terms data and information are used synonymously. The amount of data versus information kept in the computer is a tradeoff. Data can be processed into different forms of information, but it takes time to sort and sum transactions. Up-to-date information can provide instant answers. A common misconception is that software is also data. Software is executed, or run, by the computer. Data is "processed." Software is "run." (2) Any form of information whether in paper or electronic form. In electronic form, data refers to files and databases, text documents, images and digitally-encoded voice and video. (3) Plural form of datum. data abstraction In object-oriented programming, creating user- defined data types that contain their own data and processing. These data structures, or objects, are unaware of each other's physical details and know only what services each other performs. This is the basis for polymorphism and information hiding. data acquisition (1) Automatic collection of data from sensors and readers in a factory, laboratory, medical or scientific environment. (2) Gathering of source data for data entry into the computer. data administration Analysis, classification and maintenance of an organization's data and data relationships. It includes the development of data models and data dictionaries, which, combined with transaction volume, are the raw materials for database design. Database administration often falls within the jurisdiction of data administration; however, data administration functions provide the overall management of data as an organizational resource. Database administration is the technical design and management of the database. Data Is Complex The flow of data/information within a company is complex since the same data is viewed differently as it moves from one department to the other. For example: When a customer places an order, the order becomes a commission for sales, a statistic for marketing, an order to keep track of in order processing, an effect on cash flow for financial officers, picking schedules for the warehouse, and production scheduling for manufacturing. Users have different requirements for interrogating and updating data. Operations people need detail, management needs summaries. Database design must take this into consideration. data administrator Person who coordinates activities within the data administration department. Contrast with database administrator. data bank Any electronic depository of data. data base Data base is one word (database) in this Glossary. data bus Internal pathway across which data is transferred to and from the processor. The expansion slots in personal computers are connected to the data bus. data carrier (1) Any medium such as a disk or tape that can hold machine readable data. (2) Carrier frequency into which data is modulated for transmission in a network. data cartridge Removable magnetic tape module driven by a wheel inside the drive that presses against a passive roller in the cartridge. A tension belt is attached to the roller that presses against the supply and takeup reel. See QIC. data cassette Audio cassette made to higher tolerances for data storage. Data Cell IBM mass storage device (1960s) that used tape strips selected out of a cartridge and wrapped around a rotating drum for reading. See RACE and CRAM. data code (1) Digital coding system for data in a computer. See ASCII and EBCDIC. (2) Coding system used to abbreviate data; for example, codes for regions, classes, products and status. data collection Acquiring source documents for the data entry department. It comes under the jurisdiction of the data control or data entry department. See data acquisition. data communications Same as communications. data compression Encoding data to take up less storage space. For example, short names in fixed length fields waste a lot of space. A simple method called run length encoding converts the spaces into a code that indicates how many blanks follow. There are two major methods used for data compression: statistical and dictionary, and two widely-used examples of each: Huffman coding and LZW (Lempel-Ziv-Welch). Text files can be compressed the most; for example, the text you're reading can be compressed from 50 to 70% depending on method used. Dense machine language files compress about a third to a half. Some graphics files leave little room for compaction, others compress well. data control department Function responsible for collecting data for input into a computer's batch processing operations as well as the dissemination of the finished reports. The data entry department may be under the jursidiction of the data control department or vice versa. DATA/DAT (DATA/Digital Audio Tape) DAT format for data backup that can be divided into as many as 254 partitions allowing for updating in place. See tape backup. data declaration Same as data definition (1). data definition (1) In a source language program, the definitions of data structures (variables, arrays, fields, records, etc.). (2) Description of the record layout in a file system or DBMS. data dictionary Database about data and databases. It holds the name, type, range of values, source, and authorization for access for each data element in the organization's files and databases. It also indicates which application programs use that data so that when a change in a data structure is contemplated, a list of affected programs can be generated. The data dictionary may be a stand-alone system or an integral part of, and used to control, the DBMS. Data integrity and accuracy is better ensured in the latter case. data dipper Software in a personal computer that queries a mainframe database. data division The part of a COBOL program that defines the data files and record layouts. data element Fundamental data structure in a data processing system. Any unit of data defined for processing is a data element; for example, ACCOUNT NUMBER, NAME, ADDRESS and CITY. A data element is defined by size (in characters) and type (alphanumeric, numeric only, true/false, date, etc.). A specific set of values or range of values may also be part of the definition. Technically, a data element is a logical definition of data, whereas a field is the physical unit of storage in a record. For example, the data element ACCOUNT NUMBER, which exists only once, is stored in the ACCOUNT NUMBER field in the customer record and in the ACCOUNT NUMBER field in the order records. Data element, data item, field and variable all describe the same unit of data and are used interchangeably. data encryption See encryption and DES. data entry Entering data into the computer, which includes keyboard entry, scanning and voice recognition. When transactions are entered after the fact (batch data entry), they are just stacks of source documents to the keyboard operator. Deciphering poor handwriting from a source document is a judgment call that is often error prone. In online data entry operations, in which the operator takes information in person or by phone, there's interaction and involvement with the transaction and less chance for error. data entry department The part of the datacenter where the data entry terminals and operators are located. data entry operator Person who enters data into the computer via keyboard or other reading or scanning device. data entry program Application program that accepts data from the keyboard or other input device and stores it in the computer. It may be part of an application that also provides updating, querying and reporting. The data entry program establishes the data in the database and should test for all possible input errors. See validity checking, table lookup, check digit and intelligent database. data file Collection of data records. Contrast with word processing file and graphics file. data flow (1) In computers, the path of data from source document to data entry to processing to final reports. Data changes format and sequence (within a file) as it moves from program to program. (2) In communications, the path taken by a message from origination to destination and includes all nodes through which the data travels. data flow diagram Description of data and the manual and machine processing performed on the data. data fork The part of a Macintosh file that contains data. For example, in a HyperCard stack, text, graphics and HyperTalk scripts reside in the data fork, while fonts, sounds, control information and external functions reside in the resource fork. data format Same as file format. Data General (Data General Corp., Westboro, MA) Computer manufacturer founded in 1968 by Edson de Castro. In 1969, it introduced the Nova, the first 16-bit mini with four accumulators, a leading technology at the time. During its early years, the company was successful in the scientific, academic and OEM markets. With its Comprehensive Electronic Office (CEO) software in the early 1980s, it gained entry into the commercial marketplace. Computer offerings include the 32-bit ECLIPSE family and UNIX-based systems using Motorola 88000 CPUs. data glove Glove used to report the position of a user's hand and fingers to a computer. See virtual reality. data independence DBMS technique that separates data from the processing and allows the database to be structurally changed without affecting most existing programs. Programs access data in a DBMS by field and are concerned with only the data fields they use, not the format of the complete record. Thus, when the record layout is updated (fields added, deleted or changed in size), the only programs that must be changed are those that use those new fields. data integrity Process of preventing accidental erasure or adulteration in a database. data item Unit of data stored in a field. See field. data library Section of the datacenter that houses offline disks and tapes. Data library personnel are responsible for cataloging and maintaining the media. data line Individual circuit, or line, that carries data within a computer or communications channel. data line monitor In communications, a test instrument that analyzes the signals and timing of a communications line. It either visually displays the patterns or stores the activity for further analysis. data link In communications, the physical interconnection between two points (OSI layers 1 and 2). It may also refer to the modems, protocols and all required hardware and software to perform the transmission. data link escape Communications control character which indicates that the following character is not data, but a control code. data link protocol In communications, the transmission of a unit of data from one node to another (OSI layer 2). It is responsible for ensuring that the bits received are the same as the bits sent. Following are the major categories: Asynchronous Transmission Originating from mechanical teletype machines, asynchronous transmission treats each character as a unit with start and stop bits appended to it. It is the common form of transmission between the serial port of a personal computer or terminal and a modem. ASCII, or teletype, protocols provide little or no error checking. Xmodem, Ymodem and Kermit are typical error checking protocols. Synchronous Transmission Developed for mainframe networks using higher speeds than teletype terminals, synchronous transmission sends contiguous blocks of data, with both sending and receiving stations synchronized to each other. Synchronous protocols include error checking. Examples are IBM's SDLC, Digital's DDCMP, and the international HDLC. LANs Developed for medium to high transmission speeds between stations, LANs typically use collision detection (CSMA/CD) or token passing methods for transmitting data between nodes. Examples are IBM's Token Ring, Datapoint's ARCNET, Xerox's Ethernet and AT&T's Starlan. The IEEE 802 specification for LANs breaks the data link layer into two sublayers: the LLC (Logical Link Control) and MAC (Media Access Control). The LLC provides a common interface point to the MAC layers, which specify the access method used. The following compares the data link layer in LANs to IBM's SNA and ISO's OSI model. Path Control Network 陳陳 団陳陳陳陳 団陳陳陳陳 敖陳陳陳陳陳陳陳朕 Data LLC Link SDLC HDLC 団陳陳陳陳陳陳陳調 Layer MAC (CSMA/CD, 陳陳 団陳陳陳陳 団陳陳陳陳 団陳朕 Token Bus, Token Ring 青陳陳陳陳陳 Physical Physical Physical 青陳陳陳陳 青陳陳陳陳 青陳陳陳陳陳陳陳潰  SNA OSI IEEE 802  data management Refers to several levels of managing data. From bottom to top, they are: (1) The part of the operating system that manages the physical storage and retrieval of data on a disk or other device. See access method. (2) Software that allows for the creation, storage, retrieval and manipulation of files interactively at a terminal or personal computer. See file manager and DBMS. (3) Function that manages data as an organizational resource. See data administration. (4) Management of all data/information in an organization. It includes data administration, the standards for defining data and the way in which people perceive and use it. data management system See DBMS. data manipulation Processing data. data manipulation language Language that requests data from a DBMS. It is coded within the application program such as COBOL or C. data model Description of the principles of organization of a database. data modeling Identification of the design principles for a data model. data module Sealed, removable storage module containing magnetic disks and their associated access arms and read/write heads. data name Name assigned to a field or variable. data network Communications network that transmits data. See communications. data parallel Same as SIMD. data processing Capturing, storing, updating and retrieving data and information. It may refer to the industry or to data processing tasks in contrast with other operations, such as word processing. data processor (1) Person who works in data processing. (2) Computer that is processing data, in contrast with a computer performing another task, such as controlling a network. data projector Video machine that projects output from a computer onto a remote screen. It is bulkier than a flat LCD panel, but is faster for displaying high-speed animation. Data Propagator IBM query language that maintains consistency between DB2 and IMS/ESA DB databases. When data is changed in the IMS database, it is automatically changed in the DB2 database. data rate (1) Data transfer speed within the computer or between a peripheral and computer. (2) Data transmission speed in a network. data recovery Restoring data that has been physically damaged or corrupted on a disk or tape. Disks and tapes can become corrupted due to viruses, bad software, hardware failure as well as from power failures that occur while the magnetic media is being written. See DOS data recovery. data representation How data types are structured; for example, how signs are represented in numerical values or how strings are formatted (enclosed in quotes, terminated with a null, etc.). data resource management Same as data administration. data set (1) Data file or collection of interrelated data. (2) AT&T name for modem. data signal Physical data as it travels over a line or channel (pulses or vibrations of electricity or light). data sink Device or part of the computer that receives data. data source Device or part of the computer in which data is originated. data stream Continuous flow of data from one place to another. data striping See disk striping. data structure Physical layout of data. Data fields, memo fields, fixed length fields, variable length fields, records, word processing documents, spreadsheets, data files, database files and indexes are all examples of data structures. data switch Switch box that routes one line to another; for example, to connect two computers to one printer. Manual switches have dials or buttons. Automatic switches test for signals and provide first-come, first-served switching. data system Same as information system. data tablet Same as digitizer tablet. data transfer Movement of data within the computer system. Typically, data is said to be transferred within the computer, but it is "transmitted" over a communications network. A transfer is actually a copy function since the data is not automatically erased at the source. data transfer rate Same as data rate. data transmission Sending data over a communications network. data transparency Ability to easily access and work with data no matter where it is located or what application created it. data type Category of data. Typical data types are numeric, alphanumeric (character), dates and logical (true/false). Programming languages allow for the creation of different data types. When data is assigned a type, it cannot be treated like another type. For example, alphanumeric data cannot be calculated, and digits within numeric data cannot be isolated. Date types can only contain valid dates. database (1) Set of interrelated files that is created and managed by a DBMS. (2) Any electronically-stored collection of data. Database 2 See DB2. database administrator Person responsible for the physical design and management of the database and for the evaluation, selection and implementation of the DBMS. In small organizations, the database administrator and data administrator are one in the same; however, when the two responsibilities are managed separately, the database administrator's function is more technical. database analyst See data administrator and database administrator. database designer See data administrator and database administrator. database driver Software routine that accesses a database. It allows an application or compiler to access a particular database format. database engine Same as database manager. database machine Specially-designed computer for database access that is coupled to the main computer via high-speed channel. It uses multiple processors to perform fast disk searches. Contrast with database server, which is used in a LAN. The database machine is tightly coupled to the main CPU; the database server is loosely coupled in the network. database management system See DBMS. database manager (1) With personal computers, software that allows a user to manage multiple data files (same as DBMS). Contrast with file manager, which works with one file at a time. (2) Software that provides database management capability for traditional programming languages, such as COBOL, BASIC and C, but without the interactive capabilities. (3) The part of the DBMS that stores and retrieves the data. database publishing Using desktop publishing to produce reports of database contents. database server Computer in a LAN dedicated to database storage and retrieval. Contrast with file server, which stores many kinds of files and programs for shared use. datacenter Department that houses the computer systems and related equipment, including the data library. Data entry and systems programming may also come under its jurisdiction. A control section is usually provided that accepts work from and releases output to user departments. datacom (DATA COMmunications) See communications. DataEase Relational DBMS for PCs from DataEase Int'l., Inc., Trumbull, CT. It provides a menu-driven interface for developing applications without programming and is noted for its ease of use. datagram TCP/IP message unit that contains internet source and destination addresses and data. DataPhone AT&T trade name for equipment and services. See DDS. date math Calculations made upon dates. For example, March 30 + 5 yields April 4. datum Singular form of data; for example, one datum. It is rarely used, and data, its plural form, is commonly used for both singular and plural. daughter board Small printed circuit board that is attached to or plugs into a removable printed circuit board. dazdee See DASD. DB See database and decibel. DB-9, DB-15, DB-25.. (DB-9, DB-15, DB-25, DB-37, DB-50) Category of plugs and sockets with 9, 15, 25, 37 and 50 pins respectively, used to hook up communications and computer devices. The DB refers to the physical structure of the connector, not the purpose of each line. DB-9 and DB-25 connectors are commonly used for RS-232 interfaces. The DB-25 is also used on the computer end of the parallel printer cable for PCs (the printer end is a Centronics 36-pin connector). A high-density DB-15 connector is used for the VGA port on a PC, which has 15 pins in the same shell as the DB-9 connector. DB/DC (DataBase/Data Communications) Refers to software that performs database and data communications functions. DB2 (DataBase 2) Relational DBMS from IBM that runs on large mainframes. It is a full-featured DBMS that has become IBM's major database product. It uses the SQL language interface. DBA See database administrator. dBASE Relational DBMS for PCs from Borland. It was the first comprehensive DBMS for personal computers. Originally named Vulcan, dBASE was created by Wayne Ratliff to manage a company football pool. It was modeled after JPLDIS, the DBMS at Jet Propulsion Labs in Los Angeles. Renamed dBASE II when Hal Lashlee and George Tate formed Ashton-Tate to market it (Ashton-Tate was acquired by Borland in 1991), dBASE became a huge success within a couple of years. It is the most widely used PC database system, and its file formats have become de facto standards. dBASE provides a Pascal-like, interpreted programming language and fourth-generation commands for interactive use. The following programming language example converts Fahrenheit to Celsius:  INPUT "Enter Fahrenheit " TO FAHR  ? "Celsius is ", (FAHR - 32) * 5 / 9  The following fourth-generation language example opens the product file and displays green items:  use products  list for color ='GREEN'  dBASE II Introduced in 1981, it was the original command- driven dBASE for CP/M machines and later for PCs. dBASE II data formats and programs must be converted to run under dBASE III. dBASE III & III PLUS Introduced in 1984, dBASE III was a major upgrade of dBASE II for PCs only. It handles larger databases, has more programming commands and includes a memo field and menus. In 1986, dBASE III PLUS introduced redesigned menus and added new features including the ability to store queries and relational views. dBASE IV Introduced in 1988, it is a major upgrade of dBASE III PLUS with redesigned menus and report and forms generation screens. It adds a QBE method for asking questions as well as an SQL language interface. Many new programming commands and features are added, including arrays and windows. Versions of dBASE IV are also available for UNIX on 386s, Sun workstations and VAXs under VMS, and a runtime version is available for the Macintosh. dBASE compiler Software that converts dBASE source language into machine language. The resulting programs execute on their own like COBOL or C programs and do not run under dBASE. See Clipper, Force and Quicksilver. dBASE Mac Macintosh DBMS from Ashton-Tate that never caught on because it was incompatible with dBASE. DBF file dBASE data file extension. dBASE II and dBASE III files both use DBF, but are not compatible. DBMS (DataBase Management System) Software that controls the organization, storage, retrieval, security and integrity of data in a database. It accepts requests from the application and instructs the operating system to transfer the appropriate data. DBMSs may work with traditional programming languages (COBOL, C, etc.) or they may include their own programming language for application development. DBMSs let information systems be changed more easily as the organization's requirements change. New categories of data can be added to the database without disruption to the existing system. MAJOR FEATURES OF A DBMS Data Security The DBMS can prevent unauthorized users from viewing or updating the database. Using passwords, users are allowed access to the entire database or subsets of it called subschemas. For example, in an employee database, some users may be able to view salaries while others may view only work history and medical data. Data Integrity The DBMS can ensure that no more than one user can update the same record at the same time. It can keep duplicate records out of the database; for example, no two customers with the same customer number can be entered. Interactive Query Most DBMSs provide query languages and report writers that let users interactively interrogate the database and analyze its data. This important feature gives users access to all management information as needed. Interactive Data Entry and Updating Many DBMSs provide a way to interactively enter and edit data, allowing you to manage your own files and databases. However, interactive operation does not leave an audit trail and does not provide the controls necessary in a large organization. These controls must be programmed into the data entry and update programs of the application. This is a common misconception about personal computer DBMSs. Complex business systems can be developed in dBASE and Paradox, etc., but not without programming. This is not the same as creating lists of data for your own record keeping. Data Independence With DBMSs, the details of the data structure are not stated in each application program. The program asks the DBMS for data by field name; for example, a coded equivalent of "give me customer name and balance due" would be sent to the DBMS. Without a DBMS, the programmer must reserve space for the full structure of the record in the program. Any change in data structure requires changing all application programs. DATABASE DESIGN A business information system is made up of subjects (customers, employees, vendors, etc.) and activities (orders, payments, purchases, etc.). Database design is the process of organizing this data into related record types. The DBMS that is chosen is the one that can support the organization's data structure while efficiently processing the transaction volume. Organizations may use one kind of DBMS for daily transaction processing and then move the detail to another DBMS better suited for random inquiries and analysis. Overall systems design decisions are performed by data administrators and systems analysts. Detailed database design is performed by database administrators. HIERARCHICAL, NETWORK AND RELATIONAL DATABASES Information systems are made up of related files: customers and orders, vendors and purchases, etc. A key DBMS feature is its ability to manage these relationships. Hierarchical databases link records like an organization chart. A record type can be owned by only one owner. In the following example, orders are owned by only one customer. Hierarchical structures were widely used with early mainframe systems; however, they are often restrictive in linking real-world structures.  敖陳陳陳陳陳陳朕  Customer  青陳陳陳陳陳堕潰   敖祖陳陳陳陳陳  Order  青陳陳陳陳陳陳  In network databases, a record type can have multiple owners. In the example below, orders are owned by both customers and products, reflecting their natural relationship in business.  敖陳陳陳陳陳陳朕 敖陳陳陳陳陳陳  Customer Product  青陳陳陳陳陳堕潰 青賃陳陳陳陳陳   敖祖陳陳陳陳祖  Order  青陳陳陳陳陳陳  Relational databases do not link records together physically, but the design of the records must provide a common field, such as account number, to allow for matching. Often, the fields used for matching are indexed in order to speed up the process. In the following example, customers, orders and products are linked by comparing data fields and/or indexes when information from more than one record type is needed. This method is more flexible for ad hoc inquiries. Many hierarchical and network DBMSs also provide this capability. 敖陳陳陳陳陳朕 敖陳陳陳陳陳陳 敖陳陳陳陳陳陳  Customer Order Product 青陳陳陳陳陳潰 青陳陳陳陳陳陳 青陳陳陳陳陳陳  INTELLIGENT DATABASES All DBMSs provide some data validation; for example, they can reject invalid dates or alphabetic data entered into money fields. But most validation is left up to the application programs. Intelligent databases provide more validation; for example, table lookups can reject bad spelling or coding of items. Common algorithms can also be used such as one that computes sales tax for an order based on zip code. When validation is left up to each application program, one program could allow an item to be entered while another program rejects it. Data integrity is better served when data validation is done in only one place. Mainframe DBMSs are increasingly becoming intelligent. Eventually all DBMS will follow suit. FUTURE DATABASES The world of information is made up of data, text, pictures and voice. Many DBMSs manage text as well as data, but very few manage both with equal proficiency. Throughout the 1990s, DBMSs will begin to integrate all forms of information. Eventually, it will be common for a database to handle data, text, graphics, voice and video with the same ease as today's systems handle data. When this happens, the office of the future will have finally arrived! 浜陽 to/from terminals 様様様様様様(RAM)様様様 菜吊陳陳陳朕 敖陳陳陳陳陳陳陳陳陳陳陳陳陳朕 些 Comm. TP Monitor (Multiuser) 些 Access 青楪陳陳陳楪陳陳陳陳陳陳楪陳潰 些 Methods 敖陳陳瀋陳陳 敖陳陳瀋陳陳朕 挫陳陳陳陳調 Application Application 些 in COBOL or in DBMS's 些 other lang. own language 些 青陳陳陳陳嬬 青陳陳楪陳陳潰 些 OS ......................... ....... 些 .敖陳瀋陳陳陳陳朕 敖陳陳瀋陳陳 . 些 .Interactive: Interpreter . 些 .enter, edit, 青陳陳楪陳陳 . 些 .query, reports . 挫陳陳陳陳調.青陳陳楪陳陳陳潰 . 些 Disk . 敖陳瀋陳陳陳陳吊陳陳陳陳瀋陳陳朕. 些 Access Database manager . 些 Methods . 青陳陳陳陳陳陳陳陳陳陳陳陳陳陳潰. 裟嬬陳陳陳潰...............DBMS ................ 藩陽 to/from disk 様様様様様様様様様様様様様様夕  DBMS  DBOMP (DataBase Organization and Maintenance Processor) Early DBMS that was derived from BOMP. DBS (Direct Broadcast Satellite) One-way broadcast service direct from a satellite to a user's dish (antenna). They are used to deliver private information and TV services. dBXL dBASE III PLUS-compatible DBMS from WordTech Systems, Inc., Orinda, CA, that features a menu- driven option for interactive use. See Arago. DC (1) (Direct Current) Electrical current that travels in one direction and used within the computer's electronic circuits. Contrast with AC. (2) (Data Communications) See DB/DC. DCA (1) (Document Content Architecture) IBM file formats for text documents. DCA/RFT (Revisable- Form Text) is the primary format and can be edited. DCA/FFT (Final-Form Text) has been formatted for a particular output device and cannot be changed. For example, page numbers, headers and footers are placed on every page. (2) (Distributed Communications Architecture) Network architecture from Unisys. (3) (Digital Communications Associates, Inc., Alpharetta, GA) Communications products manufacturer. See IRMAboard. DCC (Digital Compact Cassette) Digital tape format that uses a variation of the common audio cassette. Also plays analog audio cassettes. DCE (1) (Data Communications Equipment or Data Circuit- terminating Equipment) Device that establishes, maintains and terminates a session on a network. It may also convert signals for transmission. It is typically the modem. Contrast with DTE. (2) (Distributed Computing Environment) See OSF. DCS (1) (Distributed Communications System) Telephone system that puts small switches close to subscribers making local loops shorter and maximizing long lines to the central office. (2) (Distributed Control System) Process control system that uses disbursed computers throughout the manufacturing line for control. (3) (Digital Cross-connect System) High-speed data channel switch that accepts separate instructions for switching independently of the data travelling through it. (4) (Document Control Software) Menu-driven query system from Workgroup Technologies for Oracle databases on PCs and Sun stations. (5) (Desktop Color Separation) Quark format for defining color separated output from a personal computer. DCT See discrete cosine transform. DD (Double Density) Designation for low-density diskettes, typically the 5.25" 360K and 3.5" 720K floppies. See double density. Contrast with HD. DDBMS (Distributed Database Management System) See distributed database. DDCMP (Digital Data Communications Message Protocol) Digital's proprietary, synchronous data link protocol used in DECnet. DDE (Dynamic Data Exchange) Message protocol in Windows that allows application programs to request and exchange data automatically. A program in one window can query a program in another window. DDL (1) (Data Description Language) Language used to define data and their relationships to other data. It is used to create files, databases and data dictionaries. (2) (Document Description Language) Printer control language from Imagen that runs on the HP LaserJet series. (3) (Direct Data Link) Ability of a supplier to directly interrogate a customer's inventory database in order to manage scheduling and shipping more efficiently. Pioneered by Ford Motor Co. in 1988, Ford lets suppliers check stock levels in assembly plants throughout North America. DDM (Distributed Data Management) Software in an IBM SNA environment that allows users to access data in remote data files within the network. DDM works with IBM's LU 6.2 session to provide peer-to-peer communications and file sharing. DDP (Distributed Data Processing) See distributed processing. DDS (1) (Dataphone Digital Service) AT&T private line digital service with data rates from 2400 bps to 56Kbps. Private analog lines can be connected to DDS lines. (2) (Digital Data Service) Private line digital services from non-AT&T carriers. (3) (Digital Data Storage) DAT format for data backup. It is a sequential recording method; data must be appended at the end of previous data. See tape backup. de facto standard Widely-used format or language not endorsed by a standards organization. de jure standard Format or language endorsed by a standards organization. deadlock See deadly embrace. deadly embrace Stalemate that occurs when two elements in a process are each waiting for the other to respond. For example, in a network, if one user is working on file A and needs file B to continue, but another user is working on file B and needs file A to continue, each one waits for the other. Both are temporarily locked out. The software must be able to deal with this. deallocate To release a computer resource that is currently assigned to a program or user, such as memory or a peripheral device. deblock To separate records from a block. debug To correct a problem in hardware or software. Debugging software is finding the errors in the program logic. Debugging hardware is finding the errors in circuit design. debugger Software that helps a programmer debug a program by stopping at certain breakpoints and displaying various programming elements. The programmer can step through source code statements one at a time while the corresponding machine instructions are being executed. DEC (Digital Equipment Corp.) Trade name for products (DECmate, DECnet, etc.). Many refer to the company as DEC. decay Reduction of strength of a signal or charge. decentralized processing Computer systems in different locations. Although data may be transmitted between the computers periodically, it implies limited daily communications. Contrast with distributed processing and centralized processing. decibel (dB) Unit that measures loudness or strength of a signal. dBs are a relative measurement derived from an initial reference level and a final observed level. A whisper is about 10 dB, a noisy factory 90 dB, loud thunder 110 dB. 120 dB is painful. decimal Meaning 10. Universal numbering system that uses 10 digits. Computers use binary numbers because it is easier to design electronic systems that can maintain two states rather than 10. decision box Diamond-shaped symbol that is used to document a decision point in a flowchart. The decision is written in the decision box, and the results of the decision branch off from the points in the box. decision instruction In programming, an instruction that compares one set of data with another and branches to a different part of the program depending on the results. decision making Making choices. The proper balance of human and machine decision making is an important part of a system's design. It is easy to think of automating tasks traditionally performed by people, but it is not that easy to analyze how decisions are made by an experienced, intuitive worker. If an improper analysis of human decision making is made, the wrong decision making may be placed into the machine, which can get buried in documentation that is rarely reviewed. This will become an important issue as AI applications proliferate. From a programming point of view, decision making is performed two ways: algorithmic, a precise set of rules and conditions that never change, or heuristic, a set of rules that may change over time (self-modify) as conditions occur. Heuristic techniques are employed in AI systems. decision support system See DSS and EIS. decision table List of decisions and their criteria. Designed as a matrix, it lists criteria (inputs) and the results (outputs) of all possible combinations of the criteria. It can be placed into a program to direct its processing. By changing the decision table, the program is changed accordingly. decision tree Graphical representation of all alternatives in a decision making process. deck (1) The part of a magnetic tape unit that holds and moves the tape reels. (2) Set of punched cards. (3) See DEC. declaration In programming, an instruction or statement that defines data (fields, variables, arrays, etc.) and resources, but does not create executable code. DECmate Family of computer systems from Digital specialized for word processing. Introduced in 1981, DECmates use the PDP-8 architecture. DECmcc (DEC Managment Control Center) Digital's network management software for DECnet and TCP/IP. DECmcc Management Stations for VMS and ULTRIX support X Window and provide color-coded alarms. DECnet Digital's communications network, which supports Ethernet-style LANs and baseband and broadband WANs over private and public lines. It interconnects PDPs, VAXs, PCs, Macs and workstations. In DECnet philosophy, a node must be an intelligent machine and not simply a terminal as in other systems. See DNA. DECnet/DOS allows DOS machines to function as end nodes in DECnet networks, and DECnet/OSI is the implementation of DECnet Phase V that supports OSI and provides compatibility with DECnet Phase IV and TCP/IP. decoder Hardware device or software program that converts a coded signal back into its original form. decollator Device that separates multiple-part paper forms while removing the carbon paper. decompiler Program that converts machine language back into a high-level source language. The resulting code may be very difficult to maintain as variables and routines are named generically: A0001, A0002, etc. decompress To restore compressed data back to its original size. decrement To subtract a number from another number. Decrementing a counter means to subtract 1 or some other number from its current value. DECstation (1) Series of RISC-based single-user workstations from Digital, introduced in 1989, that run under ULTRIX. (2) PC series from Digital introduced in 1989. (3) Small computer system from Digital, introduced in 1978, used primarily for word processing (DECstation 78). DECsystem (1) Series of RISC-based, 32-bit computers from Digital that run under ULTRIX. Introduced in 1989, the 5400 model is a Q-bus system; the 5800 model uses the XMI bus. (2) Series of mainframes from Digital that were introduced from 1974 through 1980 and were the successor to the 36-bit PDP-10 computers. DECtalk Voice synthesizing system from Digital that accepts serial ASCII text and converts it into audible speech. It is used in Touch-tone telephone response systems as well as for voice-output for visually handicapped users. DECwindows Digital's windowing architecture, based on X Window, Version 11. It is compatible with X Window while adding a variety of enhancements. dedicated channel Computer channel or communications line that is used for one purpose. dedicated service Service that is not shared by other users or organizations. default Current setting or action taken by hardware or software if the user has not specified otherwise. default directory Same as current directory. default drive Disk drive used if no other drive is specified. default font Typeface and type size used if none other is specified. defragment To reorganize the disk by putting files into contiguous order. Because the operating system stores new data in whatever free space is available, data files become spread out across the disk if they are updated often. This causes extra read/write head movement to read them back. Periodically, the hard disk should be defragmented to put files back into order. See DOS Defrag. degausser Device that removes unwanted magnetism from a monitor or the read/write head in a disk or tape drive. DEL key (DELete key) Keyboard key used to delete the character under the screen cursor or some other block of data. It is often used in combination with the shift, control and alt keys to delete various text segments. delay line Communications or electronic circuit that has a built-in delay. Acoustic delay lines were used to create the earliest computer memories. For example, the UNIVAC I used tubes of liquid mercury that would slow down the digital pulses long enough (a fraction of a second) to serve as storage. delete To remove an item of data from a file or to remove a file from the disk. See undelete. delimiter Character or combination of characters used to separate one item or set of data from another. For example, in comma delimited records, a comma is used to separate each field of data. Dell (Dell Computer Corp., Austin, TX) PC manufacturer founded in 1984 by Michael Dell. Originally selling PCs under the "PCs Limited" brand, Dell was the first to legitimize mail-order PCs by providing quality telephone support. Dell made the Fortune 500 in 1991, and its fiscal 1993 revenues may exceed one billion. delta modulation Technique that is used to sample voice waves and convert them into digital code. Delta modulation typically samples the wave 32,000 times per second, but generates only one bit per sample. See PCM. DEMA (Assn. for Input Technology and Management) Organization devoted to the advancement of managers in data entry technologies. Founded in 1976 as the Data Entry Management Assn., it sponsors educational courses and conferences. Address: 101 Merritt 7, Norwalk, CT 06851, 203/846-3777. demand paging Copying a program page from disk into memory when required by the program. demand processing Same as transaction processing. Demo II Demonstration, authoring and prototyping program for PCs from Intersolv, Rockville, MD. It is used to create courseware and slide shows and simulate interactive user interfaces for prototyping. Originally "Dan Bricklin's Demo Program," written by the author of VisiCalc. demodulate To filter out the data signal from the carrier. See modulate. demon See daemon. demoware Demonstration software that shows some or all of the features of a commercial product. See crippleware. demultiplex To reconvert a transmission that contains several intermixed signals back into its original separate signals. density See packing density and bit density. departmental computing Processing a department's data with its own computer system. See distributed processing. dependent segment In database management, data that depends on data in a higher level for its full meaning. dequeue Pronounced "d-q." To remove items from a queue in order to process or transmit them. DES (Data Encryption Standard) NIST-standard encryption technique that scrambles data into an unbreakable code for public transmission. It uses a binary number as an encryption key with 72 quadrillion possible combinations. The key, randomly chosen for each session, is used to create the encryption pattern for transmission. See RSA. descenders The parts of the lower case characters g, j, p, q and y that fall below the line. Sometimes these characters are displayed and printed with shortened descenders in order to fit into a smaller character cell, making them difficult to read. descending sort Arranging data from high to low sequence (Z to A, 9 to 0). descriptor (1) Word or phrase that identifies a document in an indexed information retrieval system. (2) Category name used to identify data. deserialize To convert a serial stream of bits into parallel streams of bits. Designer Popular, full-featured Windows drawing program from Micrografx, Inc., Richardson, TX. It was the first PC program to provide almost all the design tools found in Macintosh drawing programs. It creates its own DRW file format and supports PIC files compatible with other Micrografx products. desk accessory In the Macintosh, a program that is always available from the Apple menu no matter what application is running. With System 7, all applications can be turned into desk accessories. desk checking Manually testing the logic of a program. DeskJet Family of popular desktop ink-jet printers for PCs from HP. Color models are also available. DESKPRO Compaq trade name for its PCs. desktop (1) On-screen representation of a desktop. See Macintosh user interface and Windows. (2) Buzzword attached to applications traditionally performed on more expensive machines that are now on a personal computer (desktop publishing, desktop mapping, etc.). desktop accessory Software that simulates an object normally found on an office desktop, such as a calculator, notepad and appointment calendar. It is typically RAM resident. See TSR. desktop application See desktop accessory. desktop computer Same as personal computer or microcomputer. desktop manager The part of a GUI that displays the desktop and icons, allows programs to be launched from the icon and files to be visually dragged & dropped (copied, deleted, etc.). The desktop manager combined with the window manager make up the GUI. The desktop manager is included with the Mac and Windows. In OSF/Motif and Open Look, products such as IXI's X.desktop and Visix Software's Looking Glass add this capability. desktop mapping Using a desktop computer to perform digital mapping functions. desktop media Integration of desktop presentations, desktop publishing and multimedia (coined by Apple). desktop organizer See desktop accessory. desktop presentations Creation of presentation materials on a personal computer, which includes charts, graphs and other graphics-oriented information. It implies a wide variety of special effects for both text and graphics that will produce output for use as handouts, overheads and slides as well as sequences that can be viewed on screen. Advanced systems generate animation and control multimedia devices. desktop publishing Abbreviated "DTP." Using a personal computer to produce high-quality printed output or camera-ready output for commercial printing. It requires a desktop publishing program, high-speed personal computer, large monitor and a laser printer. DTP packages provide the ultimate in page layout capabilities, including magazine style columns, rules and borders, page, chapter and caption numbering as well as precise typographic aligment. A key feature is its ability to manage text and graphics on screen WYSIWYG style. The program can flow text around graphic objects in a variety of ways. Text and graphics may be created in the DTP program, but few of them have full-featured text and graphics capability. Usually, the work is created in word processing, CAD, drawing and paint programs and then imported into the publishing system. A laser printer may be used for final text output, but it cannot print line art and shaded drawings respectably unless its resolution is 1000 dpi or greater. Imagesetters, at resolutions of 1270 and 2540 dpi, can accept file formats from popular DTP packages and generate high-quality camera ready material. Since DTP has dramatically brought down the cost of high-end page makeup, it is often thought of as "the" way to produce inhouse newsletters and brochures. However, creating quality material takes experience. Desktop publishing is no substitute for a graphics designer who knows which fonts to use and how to lay out the page artistically. DeskWriter Family of popular desktop ink-jet printers for the Macintosh from HP. Color models are also available. DESQview Popular multitasking, windows environment for DOS from Quarterdeck Office Systems, Santa Monica, CA. It runs multiple DOS text and graphics programs in resizable windows. Calendar, notepad, calculator and communications utilities are also available. DESQview 386 for 386s and up includes the widely-used QEMM-386 expanded memory manager and utilizes the virtual machine capability of the 386. DESQview/X Version of DESQview that runs DOS, Windows and X Window applications locally or remotely on other DESQview/X PCs or X workstations. QEMM-386 and Adobe Type Manager are included. There are several ways DESQview/X can be implemented. It adds X Windows to a PC network, allowing each DOS machine to run multiple applications on different PCs in the network. As an integration product, it allows DOS and Windows apps to run in an X Window network under UNIX or any other X-based environment. In a stand-alone DOS machine, it adds a graphical and customizable interface to DESQview. Optional DESQview/X Motif and X11 toolkits allow Motif and X applications to be recompiled to a DOS machine. destructive memory Memory that loses its content when it is read, requiring that the circuitry regenerate the bits after the read operation. detail file Same as transaction file. developer's toolkit Set of software routines used in programming to link an application program to a particular operating environment (GUI, OS, DBMS, etc.). development cycle See system development cycle. development system (1) Programming language and related components. It includes the compiler, text editor, debugger, function library and any other supporting programs that enable a programmer to write a program. (2) Computer and related software for developing applications. development tool Any hardware or software that assists in the creation of electronic machines or software programs. See developer's toolkit. device (1) Electronic or electromechanical machine or component from a transistor to a disk drive. Device always refers to hardware. (2) In semiconductor design, it is an active component, such as a transistor or diode, in contrast to a passive component, such as a resistor or capacitor. device adapter Same as interface adapter. device address See address. device control character Communications code that activates a function on a terminal. See ASCII chart (17-20). device dependent Refers to programs that address specific hardware features and work with only one type of peripheral device. Contrast with device independent. See machine dependent. device driver See driver. device independent Refers to programs that work with a variety of peripheral devices. The hardware-specific instructions are in some other program (OS, DBMS, etc.). Contrast with device dependent. See machine independent. device level (1) In circuit design, refers to working with individual transistors rather than complete circuits. (2) Refers to communicating directly with the hardware at a machine language level. device name Name assigned to a hardware device that represents its physical address. For example, LPT1 is a DOS device name for the parallel port. DFT mode (Distributed Function Terminal mode) Mode that allows a 3270 terminal to have five concurrent sessions with the mainframe. Contrast with CUT mode. DG See Data General. DGIS (Direct Graphics Interface Standard) Graphics interface for PC video display boards from Graphic Software Systems, Beaverton, OR. It is primarily used with TI's 340x0 graphics chip and custom drivers are licensed to video board manufacturers. Dhrystones Benchmark program that tests a general mix of instructions. The results in Dhrystones per second are the number of times the program can be executed in one second. See Whetstones. DIA (Document Interchange Architecture) IBM SNA format used to exchange documents from dissimilar machines within an LU 6.2 session. It acts as an envelope to hold the document and does not set any standards for the content of the document, such as layout settings or graphics standards. Diablo emulation Printer that accepts the same commands as the Diablo printer. diacritical Small mark added to a letter that changes its pronunciation, such as the French cedilla (). diagnostic board Expansion board with built-in diagnostic tests that reports results via its own readout. Boards for PCs, such as Landmark's KickStart and UNICORE's POSTcard, have their own POST system and can test a malfunctioning computer that doesn't boot. diagnostic tracks Spare tracks on a disk used by the drive or controller for testing purposes. diagnostics (1) Software routines that test hardware components (memory, keyboard, disks, etc.). In personal computers, they are often stored in ROM and activated on startup. (2) Error messages in a programmer's source code that refer to statements or syntax that the compiler or assembler cannot understand. dial-up line Two-wire line as found in the dial-up network. Contrast with leased line. dial-up network Switched telephone network regulated by government and administered by common carriers. dial-up services See online services. DIALOG Online information service that contains the world's largest collection of databases. Address: 3460 Hillview Ave., Palo Alto CA 94304, 415/858- 2700. See online services. dialog box Small, on-screen window displayed in response to some request. It provides the options currently available to the user. diazo film Film used to make microfilm or microfiche copies. It is exposed to the original film under ultraviolet light and is developed into identical copies. Copy color is typically blue, blue-black or purple. DIB (Device Independent Bit map) See BMP. dibit Any one of four patterns from two consecutive bits: 00, 01, 10 and 11. Using phase modulation, a dibit can be modulated onto a carrier as a different shift in the phase of the wave. DIBOL (DIgital coBOL) Version of COBOL from Digital that runs on the PDP and VAX series. dice See die. dictionary method See LZW. die Formal term for the square of silicon containing an integrated circuit. The popular term is chip. dielectric Insulator (glass, rubber, plastic, etc.). Dielectric materials can be made to hold an electrostatic charge, but current cannot flow through them. DIF (1) (Data Interchange Format) Standard file format for spreadsheet and other data structured in row and column form. Originally developed for VisiCalc, DIF is now under Lotus' jurisdiction. (2) (Display Information Facility) IBM System/38 program that lets users build custom programs for online access to data. (3) (Document Interchange Format) File standard developed by the U.S. Navy in 1982. (4) (Dual In-line Flatpack) Type of surface mount DIP with pins extending horizontally outward. Difference Engine Early calculator designed by Charles Babbage (1820s) and subsidized by the British government. It used rods and wheels, which was tried before by other designers. Never completed, Babbage turned his attention to the Analytical Engine. Differential Analyzer Analog computational device built to solve differential equations by Vannevar Bush (MIT, 1930s). Less than a dozen were built, but they were effective in calculating ballistics tables in World War II. The machine took up an entire room and was programmed by changing camshaft-like gears with screwdriver and wrench. differential backup See backup types. differential configuration Use of wire pairs for each electrical signal for high immunity to noise and crosstalk. Contrast with single-ended configuration. diffusion Semiconductor manufacturing process that infuses tiny quantities of impurities into a base material, such as silicon, to change its electrical characteristics. digit Single character in a numbering system. In decimal, digits are 0 through 9. In binary, digits are 0 and 1. digital (1) Traditionally, the use of numbers and comes from digit, or finger. Today, digital is synonymous with computer. (2) Digital. See Digital Equipment. digital camera Video camera that records its images in digital form. Unlike traditional analog cameras that convert light intensities into infinitely variable signals, digital cameras convert light intensities into discrete numbers. It breaks down the picture image into a fixed number of pixels (dots), tests each pixel for light intensity and converts the intensity into a number. In a color digital camera, three numbers are created, representing the amount of red, green and blue in each pixel. digital channel Communications path that handles only digital signals. All voice and video signals have to be converted from analog to digital in order to be carried over a digital channel. Contrast with analog channel. digital circuit Electronic circuit that accepts and processes binary data (on/off) according to the rules of Boolean logic. Digital Plumbing! A digital circuit can be conceptualized as a mass of plumbing: the circuit paths are the pipes, the transistors are the valves, and the electricity is the water. Imagine opening a valve, and the water that passes through it and down a pipe will eventually reach a second valve, causing it to turn on, allowing water in another pipe to flow through the second valve, which will reach another valve, and so on. A resistor can be viewed as a large pipe that narrows into a pipe with a smaller diameter, a capacitor as a storage tank, and a diode as a one- way valve, allowing water to flow in only one direction. digital computer Computer that accepts and processes data that has been converted into binary numbers. All common computers are digital. Contrast with analog computer. Digital Darkroom Macintosh graphics editing program from Silicon Beach Software, Inc., for enhancing black & white photographs. Version 2.0 supports color overlays for colorizing gray scale images. digital data Data in digital form. All data in the computer is in digital form. Digital Equipment (Digital Equipment Corp., Maynard, MA) Major computer manufacturer, commonly known as DEC or Digital. Founded in 1957 by Kenneth Olsen, who headed the company until he retired in 1992, Digital pioneered the minicomputer industry with its PDP series. Its early success came from the scientific, process control and academic communities; however, after the VAX was announced in 1977, Digital gained a strong foothold in commercial data processing. The VAX evolved into a complete line from desktop to mainframe, using the same VMS operating system in all models and causing Digital to achieve substantial growth in the 1980s. Over the years, Digital has been widely recognized for its high-quality systems. Its strategy for the 1990s and beyond is its powerful, RISC-based Alpha architecture introduced in 1992, which will evolve into a complete family of systems. digital mapping Digitizing geographic information for a geographic information system (GIS). digital monitor Video monitor that accepts a digital signal from the computer and converts it into analog signals to illuminate the screen. Common examples are MDA, CGA and EGA monitors. Contrast with analog monitor. digital PABX See digital PBX. Digital Paper Non-erasable storage material from ICI Electronics used for tape and disk archival storage. It uses a polyester film coated with a reflective layer on top of which is adhered a dye polymer layer that is sensitive to infrared light. A laser burns pits into the film as close as half a micron apart. Capacities are about one Gbyte on a 5.25" disk and 600 GBytes on a 2,400 foot tape reel. digital PBX (digital Private Branch Exchange) Modern PBX that uses digital methods for switching in contrast to older PBXs that use analog methods. digital radio Microwave transmission of digital data via line of sight transmitters. digital recording See magnetic recording. Digital Research (Digital Research, Inc., Monterey, CA) Software company founded in 1976 by Gary Kildall that spearheaded the microcomputer revolution with its CP/M operating system. DRI's products include the GEM windows environment, FlexOS realtime operating system and DR DOS, a DOS-compatible operating system with advanced features. In 1991, it was acquired by Novell, Inc., Provo, UT, makers of the widely-used NetWare operating systems. digital signal processing Category of techniques that analyze signals from a wide range of sources, such as voice, weather satellites, earthquake monitors and nuclear tests. It converts the signals into digital data and analyzes it using various algorithms such as Fast Fourier Transform. Once a signal has been reduced to numbers, its components can be isolated and analyzed more readily than in analog form. It is used in such fields as biomedicine, sonar, radar, seismology, speech and data communictions. digital signature Coded message that can be verified by the receiver as being sent by an authentic sender. See RSA and DSS (2). digitize To convert an image or signal into digital code by scanning, tracing on a graphics tablet or using an analog to digital conversion device. 3-D objects can be digitized by a device with a mechanical arm that is moved onto all the corners. digitizer tablet Graphics drawing tablet used for sketching new images or tracing old ones and for selecting from menus. The user makes contact with the tablet with a pen-like or puck-like device called a cursor (mistakenly called a mouse), which is connected to the tablet by a wire. For sketching, the user draws with the tablet cursor and the screen cursor "draws" a corresponding image. When tracing an image on the tablet, a series of x-y coordinates (vector graphics) are created, either as a continuous stream of coordinates, or as end points. Menu selection is accomplished by a tablet overlay or by a screen display. The tablet cursor selects an item by making contact with it on the overlay, or by controlling the screen cursor. See mouse. dimension One axis in an array. In programming, a dimension statement defines the array and sets up the number of elements within the dimensions. dimensioning In CAD programs, the management and display of the measurements of an object. There are various standards that determine such things as tolerances, sizes of arrowheads and orientation on the paper. DIN connector (Deutsches Institut fr Normung - German Standards Institute) Plug and socket used to connect a variety of devices; for example, the PC keyboard uses a five-pin DIN. DIN plugs look like an open metal can about a half inch in diameter with pins inside in a circular pattern. dingbats Group of typesetting and desktop publishing symbols from International Typeface Corp. that include arrows, pointing hands, stars and circled numbers. They are formally called ITC Zapf Dingbats. diode Electronic component that acts primarily as a one- way valve. As a discrete component or built into a chip, it is used in a variety of functions. It is a key element in changing AC into DC. They are used as temperature and light sensors and light emitters (LEDs). In communications, they filter out analog and digital signals from carriers and modulate signals onto carriers. In digital logic, they're used as one-way valves and as switches similar to transistors. DIP (Dual In-line Package) Common rectangular chip housing with leads (pins) on both long sides. Tiny wires bond the chip to metal leads that wind their way down into spider-like feet that are inserted into a socket or are soldered onto the board. DIP switch (Dual In-line Package switch) Set of tiny toggle switches built into a DIP, which is mounted directly on a circuit board. The tip of a pen or pencil is required to flip the switch on or off. Remember! Open is "off." Closed is "on." Dir (DIRectory) CP/M, DOS and OS/2 command that lists the file names on the disk. See DOS Dir. direct access Ability to go directly to a specific storage location without having to go through what's in front of it. Memories (RAMs, ROMs, PROMs, etc.) and disks are the major direct access devices. direct access method Technique for finding data on a disk by deriving its storage address from an identifying key in the record, such as account number. Using a formula, the account number is converted into a sector address. This is faster than comparing entries in an index, but it only works well when keys are numerically close: 100, 101, 102. direct-connect modem Modem that connects to a telephone line without the use of an acoustic coupler. directory Simulated file drawer on disk. Programs and data for each application are typically kept in a separate directory (spreadsheets, word processing, etc.). Directories create the illusion of compartments, but are actually indexes to the files which may be scattered all over the disk. directory management Maintenance and control of directories on a hard disk. Usually refers to menuing software that is easier to use than entering commands. directory tree Graphic representation of a hierarchical directory as in the following example. See DOS Tree.  DATABASE  BUDGETS  CLIENTS   STORIES  SHORT  NOVELS  dirty power Non-uniform AC power (voltage fluctuations, noise and spikes), which comes from the electric utility or from electronic equipment in the office. disable To turn off a function. Disabled means turned off, not broken. Contrast with enable. disc Alternate spelling for disk. Compact discs and videodiscs are spelled with the "c." Most computer disks are spelled with a "k." discrete Component or device that is separate and distinct and treated as a singular unit. discrete component Elementary electronic device constructed as a single unit. Before integrated circuits (chips), all transistors, resistors and diodes were discrete. They are widely used in high-power applications and are still used on circuit boards intermingled with the chips. discrete cosine transform Algorithm, similar to Fast Fourier Transform, that converts data (pixels, waveforms, etc.) into sets of frequencies. The first frequencies in the set are the most meaningful; the latter, the least. For compression, latter frequencies are stripped away based on allowable resolution loss. discretionary hyphen User-designated place in a word for hyphenation. If the word goes over the margin, it will split in that location. dish Saucer-shaped antenna that receives, or transmits and receives, signals from a satellite. disk Direct access storage device. See floppy disk, hard disk, magnetic disk, optical disk and videodisc. disk array Two or more disk drives combined in a single unit for increased capacity, speed and/or fault tolerant operation. See RAID. disk based (1) Computer system that uses disks as its storage medium. (2) Application that retrieves data from the disk as required. Contrast with memory based. disk cache See cache. disk cartridge Removable disk module that contains a single hard disk platter or a floppy disk. disk controller Circuit that controls transmission to and from the disk drive. In a personal computer, it is an expansion board that plugs into an expansion slot in the bus. See hard disk. disk crash See head crash. disk drive Peripheral storage device that holds, spins, reads and writes magnetic or optical disks. It may be a receptacle for disk cartridges, disk packs or floppy disks, or it may contain non-removable disk platters like most personal computer hard disks. disk dump Printout of disk contents without report formatting. disk duplicator Device that formats and makes identical copies of floppy disks for software distribution. Simple units contain two floppy disks and require manual loading, elaborate units have automatic loading and may also attach the labels. disk emulator Solid state replication of a disk drive. disk file Set of instructions or data that is recorded, cataloged and treated as a single unit on a disk. Source language programs, machine language programs, spreadsheets, data files, text documents, graphics files and batch files are examples. disk format Storage layout of a disk as determined by its physical medium and as initialized by a format program. For example, a 5.25" 360KB floppy vs a 3.5" 1.44MB floppy or a DOS disk vs a Mac disk. See low-level format, high-level format, DOS format and file format. disk management Maintenance and control of a hard disk. Refers to a variety of utilities that provide format, copy, diagnostic, directory management and defragmenting functions. disk memory Same as disk storage. In this book, disks and tapes are called storage devices, not memory devices. disk mirroring Recording of redundant data for fault tolerant operation. Data is written on two partitions of the same disk, on two separate disks within the same system or on two separate computer systems. disk operating system See DOS. disk optimizer Utility program that defragments a hard disk. See defragment. disk pack Removable hard disk module used in minis and mainframes that contains two or more platters housed in a dust-free container. For mounting, the bottom of the container is removed. After insertion, the top is removed. disk partition Subdivision of a hard disk. The maximum size of a disk partition depends on the operating system used. See DOS Fdisk. disk striping Spreading data over multiple disk drives to improve performance. Data is interleaved by bytes or by sectors across the drives. For example, with four drives and a controller designed to overlap reads and writes, four sectors could be read in the same time it normally takes to read one. Disk striping does not inherently provide fault tolerance or error checking. It is used in conjunction with various other methods. See RAID. Diskcopy DOS and OS/2 utility used to copy entire floppy disks track by track. See DOS Diskcopy. diskette Same as floppy disk. diskless workstation Workstation without a disk. Programs and data are retrieved from the network server. DISOSS (DIStributed Office Support System) IBM mainframe centralized document distribution and filing application that runs under MVS. Its counterpart under VM is PROFS. It allows for e-mail and the exchange of documents between a variety of IBM office devices, including word processors and PCs. dispatcher Same as scheduler. dispersed intelligence Same as distributed intelligence. displacement Same as offset. See base/displacement. display (1) To show text and graphics on a video or flat panel screen. (2) Screen or monitor. display adapter Same as video display board. display attribute See attribute. display board Same as video display board. display card Same as video display board. display cycle In computer graphics, the series of operations required to display an image. display device See display screen and video display board. display element (1) In graphics, a basic graphic arts component, such as background, foreground, text or graphics image. (2) In computer graphics, any component of an image. display entity In computer graphics, a collection of display elements that can be manipulated as a unit. display font Same as screen font. display frame In computer graphics, a single frame in a series of animation frames. display list In computer graphics, a collection of vectors that make up an image stored in vector graphics format. display list processor In computer graphics, an engine that generates graphic geometry (draws lines, circles, etc.) directly from the display list and independently of the CPU. Display PostScript Screen counterpart of the PostScript printer language that translates elementary commands in an application to graphics and text elements on screen. It is designed for inclusion in an operating system to provide a standard, device- independent display language. display screen Surface area upon which text and graphics are temporarily made to appear for human viewing. It is typically a CRT or flat panel technology. display terminal See video terminal. DisplayWrite Full-featured IBM word processing program for PCs that stems from the typewriter-oriented DisplayWriter word processing system first introduced in 1980. See XyWrite III Plus. dissassembler Software that converts machine language back into assembly language. The resulting code is difficult to maintain as variables and routines are named generically (A001, A002, etc.). distributed computing Same as distributed processing. See parallel computing. distributed data processing See distributed processing. distributed database Database physically stored in two or more computer systems. Although geographically dispersed, a distributed database system manages and controls the entire database as a single collection of data. If redundant data is stored in separate databases due to performance requirements, updates to one set of data will automatically update the additional sets in a timely manner. distributed file system Software that keeps track of files stored across multiple networks. It converts file names into physical locations. distributed function Distribution of processing functions throughout the organization. distributed intelligence Placing processing capability in terminals and other peripheral devices. Intelligent terminals handle screen layouts, data entry validation and other pre-processing steps. Intelligence placed into disk drives and other peripherals relieves the central computer from routine tasks. distributed logic See distributed intelligence. distributed processing System of computers connected together by a communications network. The term is loosely used to refer to any computers with communications between them. However, in true distributed processing, each computer system is chosen to handle its local workload, and the network has been designed to support the system as a whole. Contrast with centralized processing and decentralized processing. dithering In computer graphics, the creation of additional colors and shades from an existing palette. In monochrome displays, shades of grays are created by varying the density and patterns of the dots. In color displays, colors and patterns are created by mixing and varying the dots of existing colors. Dithering is used to create a wide variety of patterns for use as backgrounds, fills and shading, as well as for creating halftones for printing. It is also used in anti-aliasing. divestiture Breakup of AT&T. By federal court order, AT&T divested itself on 1/1/84 of its 23 operating companies. Bell Labs was renamed AT&T Bell Labs, and its Western Electric manufacturing division became AT&T Technologies. See RBOC. divide overflow Program error in which a number is accidentally divided by zero or by a number that creates a result too large for the computer to handle. DL/1 (Data Language 1) Database language in IMS. DLC (1) (Data Link Control) See data link and OSI. (2) (Data Link Control) Protocol used in IBM's Token Ring networks. (3) (Digital Loop Carrier) See loop carrier. DLL See dynamic link library. DMA (Direct Memory Access) Specialized circuitry or a dedicated microprocessor that transfers data from memory to memory without using the CPU. Although DMA may periodically steal cycles from the CPU, data is transferred much faster than using the CPU for every byte of transfer. DME (Distributed Managment Environment) See OSF. DMPL (Digital Microprocessor Plotter Language) Vector graphics file format from Houston Instruments that was developed for plotters. Most plotters support the DMPL or HPGL standards. DNA (Digital Network Architecture) Introduced in 1978, DNA defines Digital's protocols, formats and control of message exchange over a network. DECnet is the implementation of this architecture. DNS (Domain Naming System) E-mail addressing system used in networks such as Internet and Bitnet. do loop High-level programming language structure that repeats instructions based on the results of a comparison. In a DO WHILE loop, the instructions within the loop are performed if the comparison is true. In a DO UNTIL loop, the instructions are bypassed if the comparison is true. The following DO WHILE loop prints 1 through 10 and stops.  COUNTER = 0  DO WHILE COUNTER < 10  COUNTER = COUNTER + 1  ? COUNTER  ENDDO  do nothing instruction Same as no-op. docking station Base station for a laptop that includes a power supply and expansion slots as well as monitor and keyboard connectors. docs Short for documents or documentation. document (1) Any paper form that has been filled in. (2) Word processing text file. (3) In the Macintosh, any text, data or graphics file created in the computer. document handling Procedure for transporting and handling paper documents for data entry and scanning. document imaging Scanning paper documents into electronic pictures for online retrieval and processing. Document imaging systems are used to replace paper-intensive operations in large organizations. They are often simpler to develop and implement than data processing systems, because users have been familiar with the paper documents that appear on screen. In addition, documents can be shared by all users on a network and routing can be controlled by the computer (workflow automation). Document images are created in raster graphics format, and although a small amount of text (key words) may be associated with the document in order to index it, the meaning of the document content is known only to the human viewer, not the computer. Like microfilm, signatures and other original markings remain intact. document mark In micrographics, a small optical blip on each frame on a roll of microfilm that is used to automatically count the frames. document processing Processing text documents, which includes indexing methods for text retrieval based on content. See document imaging. documentation Narrative and graphical description of a system. Documentation for an information system includes: Operating Procedures 1. Instructions for turning the system on and getting the programs initiated (loaded). 2. Instructions for obtaining source documents for data entry. 3. Instructions for entering data at the terminal, which includes a picture of each screen layout the user will encounter. 4. A description of error messages that can occur and the alternative methods for handling them. 5. A description of the defaults taken in the programs and the instructions for changing them. 6. Instructions for distributing the computer's output, which includes sample pages for each type of report. System Documentation 1. Data dictionary - Description of the files and databases. 2. System flow chart - Description of the data as it flows from source document to report. 3. Application program documentation - Description of the inputs, processing and outputs for each data entry, query, update and report program in the system. Technical Documentation 1. File structures and access methods 2. Program flow charts 3. Program source code listings 4. Machine procedures (JCL) docuterm Word or phrase in a text document that is used to identify the contents of the document. domain (1) In database management, all possible values contained in a particular field for every record in the file. (2) In communications, all resources under control of a single computer system. (3) In magnetic storage devices, a group of molecules that makes up one bit. (4) In a hierarchy, a named group that has control over the groups under it, which may be domains themselves. dominant carrier Telecommunications services provider that has control over a large segment of a particular market. dongle Same as hardware key. door (1) In a BBS system, a programming interface that lets an online user run an application program in the BBS. (2) See drive door. doorway mode In a communications program, a mode that passes function, cursor, ctrl and alt keystrokes to the BBS computer in order to use the remote application as if it were on the local machine. dopant Element diffused into pure silicon in order to alter its electrical characteristics. doping Altering the electrical conductivity of a semiconductor material, such as silicon, by chemically combining it with foreign elements. It results in an excess of electrons (n-type) or a lack of electrons (p-type) in the silicon. DOS (1) (Disk Operating System)  Pronounced "dahss." Generic term for operating system. (2) (Disk Operating System) Single-user operating system for the PC, PS/1 and PS/2 series from IBM. DOS is also called PC-DOS to distinguish it from MS-DOS, the version for non-IBM PCs. DOS and MS- DOS are developed by Microsoft, are almost identical, and both are referred to as DOS. IBM has participated in DOS development in varying degrees. See "Operating Environment" in the PC definition. In this Glossary, DOS refers to both PC-DOS and MS-DOS. See DOS abc's. DOS / Slashes are used to identify switches, or parameters, in a DOS command. They precede letters or numbers and their meaning is pertinent only to the command they are used with. There are many examples of this in the Glossary. See DOS backslash (\). DOS % Percent signs are used in DOS batch files to define user input. The following batch file example would copy a file and then delete it: copy %1 %2  del %1 If the above file were named MOVEIT.BAT, the following example moves file ABC into the \HOLD directory and then deletes it from the current directory: moveit abc \hold DOS . The single dot in a DOS command refers to all files in the current directory. For example, del . is the same as del *.*, which deletes all files. DOS .. The double dots refer to the directory one level above the current directory. The command cd .. switches you to the higher directory. Double clicking on a [..] in a file menu does the same thing. DOS 5 Major DOS upgrade in 1991 that includes an enhanced DOS shell with task swapping, undelete commands, a full-screen text editor and online help. It includes memory managers that support extended and expanded memory and allow part of DOS to be loaded into the high memory area (HMA). It supports 2GB hard disks and 2.88MB floppies. DOS 5 includes Microsoft's QBasic language, which supersedes GW-BASIC in the MS-DOS version and accompanies BASICA in the IBM version. Major DOS 5 features in this Glossary are: DOS Dos DOS Doskey DOS Editor DOS EMM386.EXE DOS Loadhigh DOS Mirror DOS online help DOS Setver DOS Task Swapper DOS Undelete DOS Unformat An excellent, comprehensive book on DOS 5 that includes handy utilities on disk, is "DOS 5" by Alfred Glossbrenner, ISBN 0-679-73925-4. For a thorough understanding of DOS memory management, read "DOS Beyond 640K" by James S. Forney, ISBN 0-8306-3744-3. DOS 6 Upgrade introduced in 1993 that includes built-in realtime compression and new utilities for memory management, backup, file transfer, disk optimization, antivirus and for managing multiple startup configurations. Following is a list of major DOS 6 features in this Glossary. To review them sequentially, go into Search Definitions and search on "DOS 6." DOS Defrag DOS Deltree DOS DoubleSpace DOS Interlink DOS Memmaker DOS Move DOS MSAV DOS MSbackup DOS MSD DOS startup options DOS 7 The next version of DOS (code named Chicago) is expected to be a 32-bit operating system that will only run in 386s and up. It should be a significant change to DOS. DOS :: Double colons are used to make a comment in a DOS batch file. For example, the following line will not be processed by DOS or displayed on screen: :: sbl.exe is the screen blanker program DOS abc's This is an overview of DOS concepts. For details, look up each DOS definition. To keep your place in the abc's, set a bookmark by pressing Ctrl-B for the DOS version or clicking SET BOOKMARK in the Windows version. Press Ctrl-F or click FIND BOOKMARK to come back. If you'd like hard copy of this tutorial, look up and print "DOS abc's" and "DOS abc's continued." Look up the definition, then press Ctrl-P if you're using the DOS version or select Print from the File menu if you're using the Windows version.  敖陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳朕  WHAT THIS COVERS...    1. Examples of DOS commands in this    Glossary cover ALL the things users   do MOST of the time. Refer to your  DOS manual for more options.   2. This is geared to users who have   computers with a hard drive and who   are using DOS Version 3.0 and higher.   青陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳潰  WHAT IS DOS? DOS (pronounced "dawss") stands for disk operating system. It is a master control program that is automatically run when you start your PC. DOS stays in the computer all the time letting you run a program and manage files. To use DOS, you must know where your program is stored  and how to talk to DOS. WHERE YOUR PROGRAM IS STORED Everything DOS does... absolutely everything... is based on the "default drive and current directory." The default drive is the drive DOS uses unless you tell it otherwise. When you start the computer, the default drive is normally C. Floppy drives are named A: and B:. The hard drive is named C:. DOS Versions 2.x and 3.x can manage disks up to 32MB (megabytes) in size, so in these versions larger hard disks are broken up into several "logical" drives (C:, D:, E:, etc.). DOS 4.01 manages disks up to 512MB. Starting with DOS 5, DOS will manage disks up to 2GB. Even though these versions can handle large hard disks, sometimes users still break them up into several smaller ones to help organize their data. Hard disks Floppy 敖陳DOS versions陳陳陳陳陳陳陳陳陳 Disks 2.x, 3.x 4.01 5 & 6 敖陳陳朕 敖陳陳陳陳朕 敖陳陳朕 敖陳陳陳陳朕 A: C: (32M) C: C: 青陳陳潰 団陳陳陳陳調 D: (32M) (512M) (2G) 敖陳陳朕 団陳陳陳陳調 B: E: (32M) 青陳陳潰 青陳陳陳陳潰 青陳陳潰 青陳陳陳陳潰 Directories Disks are further divided into simulated file drawers, called "directories," the size of which is limited only by the unused space left on the disk.   敖陳陳陳 敖陳陳陳 敖陳陳陳  Data Words Numbers  嬪 嬪 嬪  青陳陳陳 青陳陳陳 青陳陳陳  Your software package's install program usually creates the directory for you and copies the appropriate files into it. But there are times when you'll want to create your own directories and move files among them. Suppose you'd like to transfer office work to your home computer. DOS lets you copy files into the appropriate directories on each machine. Root Directory The current directory is the file drawer you're in on each disk. When you start the computer, the current directory is the "root" directory. All other directories stem from the root. You can store anything in the root directory, but typically the hard disk's root directory is used for utility programs and batch files, not applications. Applications are stored in their own directories, one for database, one for word processing, etc.:   敖陳陳陳  Root  嬪  青陳堕陳  敖陳陳陳陳田陳陳陳陳  敖陳祖陳 敖陳祖陳 敖陳祖陳  Data Words Numbers  嬪 嬪 嬪  青陳陳陳 青陳陳陳 青陳陳陳  When you start DOS, the default drive is C and the current directory is the root. When you first switch to another drive, the current directory is the root directory of that disk. Every disk has a root directory as is noted in the following illustration (each rectangle represents a directory or subdirectory). Floppy Hard disk Hard disk Disks DOS 2.x and 3.x DOS 4.01 and up A: C: C: 敖陳陳朕 敖陳陳堕陳陳堕陳朕 敖陳陳堕陳陳賃陳朕  root root  root 団陳陳田陳堕祖賃調 団陳陳田陳陳汰陳調 青陳陳潰 青陳陳祖陳祖陳珍潰 団陳堕田陳堕 B: D: 敖陳陳朕 敖陳堕陳陳堕陳堕 団陳田祖陳田祖陳調  root root 団陳津陳陳津陳珍調 団陳祖陳陳 青陳陳潰 青陳珍陳陳珍陳陳潰 E: 青陳陳陳陳祖陳陳潰 敖陳陳堕陳陳賃陳朕 root 青陳陳祖陳陳珍陳潰 Note! On a floppy, everything is typically stored in the root directory, because floppies are usually dedicated to one purpose. Remember! DOS's reference point is the default drive and current directory. You can think of them as the "current" drive and directory, or "working" drive and directory, or "default" drive and directory. HOW TO TALK TO DOS DOS is command-driven. You type in a command, and DOS carries it out. Entering a Command at the DOS Prompt DOS commands are entered when DOS displays its "prompt" on screen. The prompt also informs you which drive and directory you're currently in. The following prompt means C drive and root directory: C:\> The C: means drive C. The backslash \ means root directory. The > is an end symbol. If you switched to the DATA directory, your prompt would change to: C:\DATA>.  C: C drive \ root directory DATA data directory > end of prompt Are We in Sync? Does your on-screen prompt look like the examples above? If it doesn't, and all you see is C> or D> no matter which directory you're in, you're missing an important command in your AUTOEXEC.BAT file. For now, type the following command at the DOS prompt: prompt $p$g Later on, you will want to set this prompt permanently. See DOS prompt and DOS AUTOEXEC.BAT. Can't Get the DOS Prompt? All DOS commands in this tutorial are run from the DOS prompt. If your computer starts up with a menu of programs to run, you'll have to exit this menuing system (also called a shell) first. Usually there's a "To DOS," "DOS prompt" or "Command Prompt" option in the menu. Select it to get your DOS prompt. Pressing Enter Executes the Command After you type in your command, pressing the Enter key causes DOS to begin the action. The following command renames a file from RED to BLUE. The action is taken when you press the Enter key: C:\>rename red blue(ENTER) You must have a space between the command verb Rename and the next word. In further examples, you won't see the (ENTER) notation. It is however always implied. Nothing happens until you press Enter! Switching Directories Assume you have the following directories on your hard disk:  C:\>  敖陳陳陳  Root  嬪  青陳堕陳   敖陳陳陳陳津陳陳陳陳陳朕  C:\DATA> C:\WORDS> C:\NUMBERS>  敖陳陳陳 敖陳陳陳 敖陳陳陳  Data Words Numbers  嬪 嬪 嬪  青陳陳陳 青陳陳陳 青陳陳陳  If you're in the C:\DATA> directory now, and you want to go to the C:\NUMBERS> directory, you would type: Explanation C:\DATA>cd \numbers change to NUMBERS C:\NUMBERS> prompt has changed cd \numbers means CHANGE DIRECTORY TO ROOT then NUMBERS DIRECTORY cd \ numbers Switch back to the root directory by typing: Explanation C:\NUMBERS>cd \ change to root directory C:\> prompt has changed CHANGE DIRECTORY TO ROOT  cd \  Subdirectories Subdirectories are directories subordinate to your main directories. The following example organizes files separately for two writers:  敖陳陳陳  Directory Words   青陳堕陳  敖陳珍陳陳  敖陳祖陳 敖陳祖陳  Subdirectories Joseph Helene  嬪 嬪  青陳陳陳 青陳陳陳  For more on directories and subdirectories, look up DOS directories. Switching Drives To switch from one drive to another, type the drive letter and colon as in the following examples: Explanation C:\>d: change from C to D D:\> prompt has changed to show new drive Switch to A: D:\>a: change from D to A A:\> prompt has changed Remember! Don't forget the colon. The letter A by itself would be a file name, not a drive ID. The a: identifies the A drive. DOS abc's (continued) This is a continuation of DOS abc's above. To review... DOS is a master control program that lets you  run a program and manage files. RUNNING A PROGRAM To run a program, go to the directory the program is in and type in the program's name. For example, to go to the LOTUS directory and run the 123.EXE program, you would type: C:\>cd \lotus go to directory C:\LOTUS>123 run 123.EXE program The .EXE is a file extension for a program that is ready to run (EXEcute). You'll learn about file extensions in DOS file names. You can usually (but not always) run a program in a different directory or even a different disk by naming the path to it. Suppose you're in the ANYWHERE directory on drive C, you could run PARADOX3.EXE in directory DATA on E by typing: C:\ANYWHERE>e:\data\paradox3 Note: You don't enter the .EXE extension when naming a program to run. Also note: The "ANYWHERE" above is a prompt used in examples to indicate that the command will work no matter which directory you're currently in. Command Sytax Most programs are run by typing in their name. For example, the DOS version of the Glossary is loaded and run by typing gloss at the DOS prompt. Sometimes, additional information can be given to the program when it is run. For example, in the Windows version of this Glossary, adding the word mono to the program name changes the display for a laptop; for example:  wingloss mono When managing your files with DOS, the commands often require additional input; for example, the Format command must be typed with the name of the disk you want to format: format a: MANAGING FILES To learn how to create directories and subdirectories, copy files back and forth and use DOS to manage your computer, look up the following topics in the Glossary. At this point, the DOS topics are in alphabetical order, not in lesson order. ............................................. Why don't you print out the following summary and keep it handy. To do this, move the dotted line to the top of the text window with the Up or Down Arrow keys. Be sure your printer is turned on, and then press Ctrl-P if you're using the DOS version of the Glossary, or select Print from the File Menu if you are in the Windows version. WHAT YOU NEED TO LEARN    DOS file names  Learn about names and extensions.   DOS wild cards Learn how to select groups of files. DOS directories More examples on switching directories.  DOS Dozen  12 commands that do everything.  DOS batch file  How to automate procedures.  DOS AUTOEXEC.BAT  How to automatically set up your computer each time you turn it on.  DOS CONFIG.SYS How to configure the computer.   敖陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳朕  End of the ABC's.   The rest of the DOS commands are  in A-Z order under DOS xxxx.  青陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳潰  DOS Abort, Retry See DOS error messages. DOS ANSI.SYS Driver used for screen control (cursor movement, screen clearing) and as a keyboard macro processor to assign commands to a function key or reassign awkwardly placed keys. Some applications require ANSI.SYS. See DOS CONFIG.SYS. DOS antivirus See DOS MSAV. DOS Append External command as of DOS 3.3 that lets programs open data files as if they were in the current directory. It is used only with older programs that cannot access different directories. append display appended paths append e:\abc append E:\ABC append; cancel appends Want to Combine Files? If you want to append one file to another, look up DOS combining files. DOS Assign External command used to reassign drives when programs work only with specific drives. In DOS 6, this command is no longer installed, although it still resides on the DOS 6 Supplemental Disk. The following example allows an install program that requires the floppy to be in drive A: to run from drive B:.  assign a=b  To cancel assignments, type: assign If your program is ancient and works only with drive A:, you can fake it into accessing the hard disk with: assign a=c Important! Cancel assignments before using Backup, Diskcopy, Format, Join, Label, Print, Restore or Subst. DOS Attrib External command that displays and changes file attributes, which are settings in every DOS file. FILE ATTRIBUTES A - Archive H - Hidden file R - Read only S - System file To display the current attributes in all files in the current directory, type: attrib *.* files only attrib *.* /s files & subdirectories (DOS 3.3 and up) READ ONLY STATUS When a file is read-only, it can't be changed or deleted. To set and reset VITAL.TXT, type: attrib vital.txt +r set to read-only attrib vital.txt -r reset to read/write ARCHIVE ATTRIBUTE As of DOS 3.3, all files are set to archive status, which assists in making backups. When files are copied (Xcopy and Backup), the archive status is turned off and not turned on again until the file has been modified (changed by some program). The following example removes and restores the archive status in XYZ.TXT. attrib xyz.txt -a turn off attrib xyz.txt +a turn back on To back up only modified files (archive status on), use the /m switch with the Xcopy and Backup commands. After copying, the archive status is turned off (archive bit set to zero). For example, to Xcopy only modified files (archive bit on) to the B drive, type:   xcopy *.* b: /m SYSTEM AND HIDDEN ATTRIBUTE (as of DOS 5) These attributes are assigned to important DOS files and other files that your applications may generate. As a rule, you should not tamper with them unless you know what you are doing. Prior to DOS 5, you needed a third-party utility to do this. As of DOS 5, you can reset these attributes in most, but not all files, in which case you may still need a third-party program. attrib xyz +s make XYZ a system file attrib xyz -s clear system file status attrib xyz +h make XYZ a hidden file attrib xyz -h clear hidden status DOS AUTOEXEC.BAT Special DOS batch file that is automatically executed whenever the computer is started or restarted. It must be stored in the root directory. It is used to load TSR (Terminate and Stay Resident) programs that stay in memory and "pop up" whenever you call them. It's also used to start an application when the computer is turned on, perhaps a menu program that launches a variety of applications. Two common commands in AUTOEXEC.BAT are: PROMPT - Usually prompt $p$g. PATH - The Path line contains the directories you want access to no matter which directory you're in. To load or run a program, enter the program name on a separate line. Any DOS commands in AUTOEXEC.BAT will be executed like a normal DOS batch file. The following example sets the prompt and path, loads the Doskey program in the DOS directory switches to the LOTUS directory and runs the 123 program: prompt $p$g  path c:\data;d:\words;e:\budget  c:\dos\doskey  cd \lotus  123 Remember! AUTOEXEC.BAT must be stored in the root directory.   Your Configuration Files Get Tampered With Install programs may edit your AUTOEXEC.BAT and CONFIG.SYS files during installation. For example, they may want to add the new directory to the path or to set an environment variable (see DOS Set). They made also need to add a new driver. You are generally informed that this is being done and often shown the changes as they are made. The original files are usually renamed with a different extension and left on the disk. If you want to delete the application soon after it was installed, you can rename these files back to AUTOEXEC.BAT and CONFIG.SYS (after deleting the current ones). However, after several software installations, you may not remember which is which, and all these previous configuration files may have little value unless carefully inspected. DOS backslash (\) Backslashes are used to represent the root directory when it precedes the first directory of file name in a path. Used elsewhere in the path, it is a symbol that separates file and directory names. See DOS abc's. DOS Backup/Restore (For DOS 6 users, see DOS MSbackup.) Backup and Restore are external commands that let you back up your hard disk onto as many floppies as required. To back up all the files in directory WORK on drive C onto floppies in drive A, type: backup c:\work a: BACK UP AND FORMAT If you don't have a lot of formatted floppies, you can format them at the same time you're backing up. In DOS 3.3 and lower, add /f:  backup c:\work a: /f As of DOS 4.01, Backup automatically runs the Format program if it finds an unformatted disk. BACK UP ONLY UPDATED FILES To back up only those files that have been changed since the last update, add /m (see Archive Attribute in DOS Attrib): backup c:\work a: /m BACK UP SUBDIRECTORY FILES TOO To back up the files in WORK as well as all files in subdirectories attached to WORK, add /s: backup c:\work a: /s ADDING FILES When running Backup, existing files on the floppies are erased. To add to the disks (keep existing files), use /a: backup c:\work a: /a You can mix any of the switches (/s, /m, /f, etc.); such as: backup c:\work a: /m /s CREATE A BACKUP LOG Starting with DOS 3.3, the /l switch lets you create a file containing the names of each file backed up along with its backup disk number. If you don't name the file, BACKUP.LOG will be created in the root directory of the current drive. If the log file exists, file names will be added to the list. The following example creates MYLOG in MYDIR on drive E: backup c:\work a: /m /s /l:e:\mydir\mylog RESTORING FILES To restore files, you must explicitly state which files. To restore all files back into the C:\WORK directory from the A drive, type: restore a: c:\work\*.* To restore only EXE files, type: restore a: c:\work\*.exe To restore all files, including the subdirectory files, add the /s: restore a: c:\work\*.* /s DOS batch file File of DOS commands for "batch" processing. Each line of a batch file is executed by DOS until the end of the file is reached. To create a batch file, use Copy Con, a text editor such as Edlin or Edit or a word processor. If using a word processor, save your batch file as an ASCII text file, not as a standard document. Name it, and always include the .BAT extension. The following batch file switches to the E drive, goes to the PAT directory and runs the MYPROG program: e:  cd \pat  myprog If the above file was PAT.BAT in the root directory, you would execute it by typing: C:\>pat Since the batch file switches drives and goes to the required directory, it doesn't matter which drive or directory you're in when you run it. Tip! If you use batch files to launch applications, put the batch files in the root and make sure the root is in the path. That way, you can run a batch file from whichever directory you're in. Another option is to create a directory called \BATCH and put C:\BATCH in the path. Stopping a Batch File To stop a batch file in operation, press Ctrl-C or Ctrl-Break. 敖陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳朕 The following commands are here for quick reference only. If you are not an experienced batch file programmer, consult a good book on the subject, such as Kris Jamsa's "DOS Batch File Power" published by SAMS. 青陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳潰  Additional Batch Commands  cls Clear the screen rem Remarks (documentation)  :: Non-displayable remarks (see DOS ::) echo off Turn off display.  @echo off Turn off display (3.3 and up).  echo on Turn on display.  echo Display message; for example, echo Press any key to continue.  call Call other batch file.  pause Stop (wait for keystroke). choice (in DOS 6) more organized method for getting user input    Advanced Batch Commands For reference only. Refer to your DOS manual.  if not exist filename goto :line  if not string1==string2 goto :line  if not errorlevel 0 goto :line  for %%varname in (files) do command  %0 - Batch file name.  %1 - %9 - Input variables.  %varname% - Variable used with Set. Following is an example of the choice batch file command in DOS 6. It loads three different programs depending on receiving A, B or C from the user. If A is entered, errorlevel is 1, B is 2 and C is 3. IF ERRORLEVEL always tests for >=, which is why the largest number is tested first. choice /c:abc Run A. Run B. Run C. if errorlevel 3 goto runC if errorlevel 2 goto runB :runA run program A goto end :runB run program B goto end :runC run program C :end DOS box DOS compatibility mode. The "box" is an OS/2 or Windows window that is running a standard DOS application. DOS Break Ctrl-C and Ctrl-Break are key commands that stop the current operation; however, certain functions such as disk I/O cannot normally be halted. Break is a CONFIG.SYS setting that tests the keyboard more frequently for Ctrl-C and Ctrl-Break. To extend Ctrl-C checking, add the following to your CONFIG.SYS file: break=on Note that applications can be programmed to ignore Ctrl-C and Ctrl-Break regardless of the Break setting. DOS buffers= See DOS CONFIG.SYS. DOS cache See DOS SmartDrive. DOS Cd Internal command that changes the current directory. Chdir is an alternate form. To change to the DATA directory type: C:\ANYWHERE>cd \data or type: C:\ANYWHERE>chdir \data See DOS directories and DOS abc's. DOS changing directories See DOS Cd and DOS directories. DOS Chdir See DOS Cd. DOS Chkdsk External command that reports free memory and disk space. To display memory and disk status, type: chkdsk Improperly closed files, caused by rebooting from a frozen application for example, generate lost clusters, which are unidentifiable files. Most of the time, these are temporary files not worth recovering. To reclaim these lost clusters, run Chkdsk with the /f switch. When you're asked "Convert lost chains to files?", answering Y for yes will convert lost clusters to FILE0000.CHK files, which you can examine. Answering N will remove them. For example:  chkdsk /f To list recovered files, type: dir *.chk Important! Don't go to the DOS prompt (shell out) from within Windows or any other program and then run the Chkdsk utility. You may get invalid results and possibly destroy data. DOS CHKSTATE.SYS Software driver used by Memmaker exclusively during its optimization process. The line is placed into CONFIG.SYS and then removed when Memmaker is finished. See DOS SIZER.EXE. DOS clean boot See DOS startup options. DOS Cls Internal command that clears the screen. To clear the screen, type: cls DOS combining files To combine text files, use the Copy command. For example, to combine the files FIRST and SECOND, creating a new file named COMBINED, type: copy first+second combined To append SECOND to the end of FIRST, type: copy first+second After the copy, SECOND still exists as a single file, and it has also been appended to FIRST. DOS command history See DOS Doskey. DOS COMMAND.COM Command interpreter that displays the DOS prompt and accepts and executes your typed-in commands. If a command interpreter other than COMMAND.COM is used, it is specified with the Shell command (see DOS Shell). DOS loads COMMAND.COM from the disk at startup. Part of COMMAND.COM is always resident in memory. The rest of it, or transient part, may be overwritten when a program is executed. When the program is done, the transient portion is reloaded into memory. See DOS Sys. DOS Comp External command that compares two files for identical content and reports up to 10 mismatches. In DOS 6, this command is no longer installed, although it still resides on the DOS 6 Supplemental Disk. To compare file RED with GREEN, type:  comp red green Mismatches are reported as follows: Compare error at OFFSET AA File 1 = BB File 2 = BB AA = location of characters BB = characters (in hex) As of DOS 5, these optional switches can be added to the command: /a Show ASCII characters (not hex) /l Display line numbers (not offset) /c Non case-sensitive compare See also DOS FC. DOS comparing files See DOS FC and DOS Comp. DOS compressing files See DOS DoubleSpace. DOS compression ratios To see the compression ratios of your DoubleSpace files, use the /c switch with the Dir command to list each file's ratio and an average for the selected group. The following example displays ratios for all .EXE files: dir *.exe /c DOS Comspec DOS environment variable that holds the path to COMMAND.COM. See DOS COMMAND.COM and DOS Set. DOS CONFIG.SYS Configuration file that DOS looks for in the root directory upon startup. It is used to load drivers and change system settings. Adding a new type of peripheral to the computer usually requires installing the driver program to make it operate.  Common  Commands Purpose DEVICE Names a driver to be loaded. FILES Files open at one time (8-255). Default is 8, but this is often set to 20-40. Some apps open a lot of files. BUFFERS 528-byte areas of RAM reserved for input and output (1-99). Default is usually 15, but this is often set to 20 or 30. The more buffers, the faster the I/O.  /x switch in 4.01 puts buffers in EMS. LASTDRIVE Last drive letter (see DOS Subst). Look up DOS Loadhigh for storing drivers in high memory in DOS 5 and up. Following is an example of the contents of a CONFIG.SYS file for a 386:  device=c:\dos\himem.sys  device=c:\dos\emm386.exe ram  device=c:\dos\ansi.sys  device=c:\mouse\mouse.sys  files=30  buffers=40  dos=high,umb   Common  Drivers Purpose ansi.sys Screen and keyboard control. display.sys Supports code-page switching. driver.sys Identifies 3rd & 4th floppy and allows copying from/to same drive. mouse.sys Mouse driver. printer.sys Code-page support for printers. himem.sys Extended memory (XMS) manager. emm386.exe 386 EMS manager. qemm386.sys Quarterdeck's 386 EMS manager. ramdrive.sys RAM disk (extended or EMS memory). smartdrv.sys Disk cache (extended or EMS memory). DOS Copy Internal command for making duplicate disk files. The command format is: COPY FROM TO COPY TO/FROM FLOPPIES copy a:*.* b: all A files to B  copy b:*.* a: all B files to A copy b:sales a: SALES file in B to A COPY FROM FLOPPY TO CURRENT HARD DISK DIRECTORY copy a:sales SALES file on A  copy a:*.* all A files COPY FROM CURRENT HARD DISK DIRECTORY TO FLOPPY copy sales b: SALES file in  to B copy *.* b: all files to B copy . b: shortcut of above COPY FROM CURRENT DIRECTORY TO ANOTHER DIRECTORY copy filex \text copy FILEX to TEXT directory copy *.* \text all files to TEXT directory copy . \text shortcut of above COPY FROM ANOTHER DIRECTORY INTO CURRENT DIRECTORY copy \abc\x.bat X.BAT from ABC directory copy \abc\*.* all files from ABC copy \abc shortcut of above COPY AND RENAME AT THE SAME TIME The following example duplicates and renames a PC Paintbrush file within the same directory: copy logo.pcx logo2.pcx YOU CAN VERIFY YOUR COPY To be extra sure that the copy is correct, add the /v switch to compare the new file with the old file; for example: copy *.* a: /v Remember! There's less typing if you're in the directory you want to copy to. For example, from any directory, you could issue: D:\ANYWHERE>copy a:*.* c:\budgets\1992 But, if you're already in C:\BUDGETS\1992, the TO is implicit: C:\BUDGETS\1992>copy a:*.*  LOOK UP THESE COPY COMMANDS COPY only copies files, but XCOPY copies both files and subdirectories and creates the directory names on the target disk. DISKCOPY makes exact copies of floppy disks and formats them at the same time. REPLACE is great for backup and copies only files that have been changed. DOS Copy con Internal command for creating a quick batch file. For example, to create the WRITE batch file, type:  copy con write.bat After pressing Enter, you'll get a blank line. Type your text and press Enter to end the line. When done, press F6 (ctrl-Z), then press Enter. Copy Con works a line at a time. You can't go back and change lines, but you can use backspace to delete characters on the same line. DOS Ctty Internal command that redirects the keyboard and screen to the serial port. This is used to connect a remote keyboard to a PC. ctty aux change to serial port ctty con restore keyboard and screen DOS data recovery See DOS Recover, DOS Unformat, DOS Undelete and "There's More to Mirror" in DOS Mirror. DOS Date See DOS Time/Date. DOS Debug External command that performs a variety of machine language functions. Debug is used to edit memory, executable files, input/output ports, assemble small programs and perform hex arithmetic. To load Debug, type: C:\>debug load Debug - Debug prompt (-) Some simple Debug commands follow for reference only. See your DOS manual for details.  Commands Purpose  ? Online help (as of DOS 5). q Quit. d cs: 100 Display 128 bytes of RAM at 100h in the CS segment (current program). d Display next 128 bytes. h xxxx yyyy Hex math. X and y are hex numbers. Results are x+y x-y. g=C800:5 Go to address C800:5 DOS Defrag Starting with DOS 6, Defrag is a utility that defragments the hard disk. Some users run a defragmenter every day, others every couple of months. It's up to you. Defragmenting will improve the performance of applications in which you continuously update the data. If done routinely, it will help reduce wear and tear on the hard disk. Follow this procedure to defragment your hard disk: 1. Delete all unnecessary files on the disk. 2. Quit all running programs, including Windows. 3. Check for lost clusters by typing chkdsk /f. If prompted "Convert lost chains to files?", answer Y. 4. Run Defrag by typing defrag. DOS Del Internal command that removes a file from the disk. To erase a file named OLD.TXT, type: del old.txt or erase old.txt To erase all files in your current directory, type:  del *.* or  erase *.* To delete all DOC files, type: del *.doc or erase *.doc Before DOS 5, there was no undelete. However, deleted files can be recovered, because deleting only changes the name entry in the directory. The data is still there. If you accidentally delete vital data, do this: In DOS 3.x and 4.01:  1. Stop!  2. Turn the computer off. If you must save  what you're working on, save it to a  different disk drive.  3. Get a file recovery program and follow its  instructions.  In DOS 5 and DOS 6: Just type the following and follow the prompts: undelete See DOS Undelete. DOS Deltree Starting with DOS 6, an external command that removes directories. It differs from the Rd command in that the directories do not have to be empty. All files contained in the directory and all subdirectories attached to that directory as well as any files contained in them will be deleted. Like the Rd command, you must not currently be in the directory that you want to delete. For example, to delete the C:\BUDGETS directory, you could type: C:\>deltree budgets from the root C:\WORK>deltree budgets from a non-related directory If BUDGETS contained subdirectories; for example, \BUDGETS\1992 and \BUDGETS\1993, those subdirectories and files will also be deleted. DOS device names DOS reserved names for common input and output devices. See DOS redirection, DOS Sort and DOS Dir.  Reserved name Device  AUX First connected serial port PRN First connected parallel port COM1 thru COM4 Serial ports (modem, mouse, etc.) LPT1 thru LPT3 Parallel ports (printer) CON Keyboard and screen NUL Dummy (testing purposes) DOS device= See DOS CONFIG.SYS. DOS Devicehigh See DOS Loadhigh. DOS Dir Internal command for displaying the names of files within a single directory. To list all file names in the current directory, type: dir To display only files with an .EXE extension, type: dir *.exe or dir .exe See DOS wild cards for more on selecting file names. A Dir list contains the following information (see example below):  Line 1 Drive name. "Has no label" means it hasn't been named.  Line 2 Drive serial no. (DOS 4.01 and up)  Line 3 Current directory name.  Line 4 The "." line represents the entire current directory and shows the creation date. Let it remind you of the shortcut for "*.*".  Line 5 The ".." line means the directory is attached to a higher level (they all are except for the root).  Lines 6, 7 & 9  Name, extension, size, creation date/time of each file selected.  Line 8 Name of subdirectory attached to this directory. Volume in drive C has no label   Line 1 Volume Serial Number is NNNNNNNNN Line 2 Directory of D:\DIRNAME Line 3 . MM-DD-YY H:MM Line 4 .. MM-DD-YY H:MM Line 5 NAME EXT SIZE MM-DD-YY H:MM Line 6 NAME EXT SIZE MM-DD-YY H:MM Line 7 NAME MM-DD-YY H:MM Line 8 NAME EXT SIZE MM-DD-YY H:MM Line 9  Important Variations LIST ONLY DIRECTORIES To display subdirectory names attached to the directory you're in, type: dir *. Starting with DOS 5, use the /ad switch to list directories. Only directories will be displayed, whereas with the DIR *. example above, depending on DOS version, you may also get file names that do not have extensions. dir /ad WIDE DISPLAY To display names across the full width of the screen rather than in one column, add /w: dir /w PRINT THE LIST To print a Dir list, redirect the output to the printer. The following example prints the list rather than displaying it. Add the > prn to any of these examples to print instead of display.  dir > prn ONE SCREENFUL AT A TIME To display a screenful at a time and pause, add the /p switch:  dir /p LIST FILES ALPHABETICALLY (Before DOS 5) To list file names alphabetically no matter what DOS version is installed in your machine (DOS 2.0 and up), you can pipe the output to the Sort external command as follows: dir *.exe | sort LIST FILES ALPHABETICALLY (As of DOS 5) To list file names alphabetically, type: dir /o subdirectories 1st, files 2nd dir /on subdirectories and files mixed By extension: dir /oe subdirectories and files mixed dir /oe /og separate By file size: dir /os  low to high (mixed)  dir /os /og separate   dir /o-s high to low (mixed)  dir /o-s /og separate By date: dir /od  earliest to latest (mixed)  dir /od /og separate   dir /o-d latest to earliest (mixed)  dir /o-d /og separate SEARCH FOR DUPLICATE FILE NAMES (As of DOS 5) You can use Dir to find all files with the same name in the current directory and its subdirectories. For example, to find out where X.BAT is located, type: dir x.bat /s LOWER CASE OPTION (As of DOS 5) To display all names in lower case, add /l: dir /l DISPLAY FILE ATTRIBUTES (As of DOS 5) Use the /a switch to display the various attributes that can be assigned to a file: dir /ar read only files dir /ah hidden files dir /aa files ready for archiving dir /as system files CHANGE DIR COMMAND DEFAULTS (As of DOS 5) Use can change the defaults for the Dir command by setting the DIRCMD environment variable. The following example sets alpha order and a screenful at a time: set dircmd=/o /p change defaults set  view current settings set dircmd= restore defaults Add the Set Dircmd line in your AUTOEXEC.BAT file to change defaults each time you start. SHOW COMPRESSION RATIOS (As of DOS 6) To see how effective your DoubleSpace compression is, see DOS compression ratios. DOS Dircmd Environment variable that lets you set the default options for the Dir command. The explanation is at the end of DOS Dir (Page Up once). DOS directories Simulated file drawers on a disk. To understand directory basics, look up DOS abc's. Directories and Subdirectories DOS directories are hierarchical in structure. The starting point is the root directory. In fact, when several people use the same computer, the "directory tree" looks like an organization chart:   root   敖陳陳陳堕陳陳祖陳陳堕陳陳陳 karen sam pat robin  敖陳祖陳 budget text A subdirectory is a directory that is subordinate to (below, or attached to) another directory like BUDGET and TEXT above. Since all directories are below the root directory, all directories are technically subdirectories. The two terms become intertwined. Don't worry about this. More importantly, don't set up too many levels in the hierarchy or you'll drive yourself nuts trying to manage them at the DOS prompt. However, if you have a menu system that let's you point to the directory you want, you can manage several levels of directories more easily.  A Real Bummer The hardest thing about DOS commands is creating the proper path name to the files you want to work with. It's tricky because the structure for naming the path isn't clearcut. The culprit is the backslash symbol (\), which means two entirely different things depending on its position in the path. The first time it's used, it stands for root directory. The second and subsequent times it's used, it's a symbol that separates file and directory names. The following commands for creating, removing and changing directories will show you many ways path names are used. There are plenty of examples that follow: Creating a Stand-alone Directory A stand-alone directory is one attached to the root. To create stand-alone directory KAREN, type: C:\ANYWHERE>cd \ go to the root C:\>md karen make directory off the root C:\> you're still in the root To go to that directory, type: C:\>cd karen change directories C:\KAREN> prompt changed to Karen Note! Directories are named the same as files, with a name up to eight characters and an optional extension of up to three. See DOS file names. Creating a Subdirectory To create a subdirectory called BUDGET that is located within the KAREN directory, type: * C:\ANYWHERE>cd \karen go to KAREN C:\KAREN>md budget make subdirectory ** C:\KAREN>cd budget go to budget C:\KAREN\BUDGET> prompt has changed * Going to KAREN requires a backslash in front of KAREN, because the first backslash means ROOT directory, and KAREN is off the root. ** Going to BUDGET does not use the backslash, because BUDGET is off KAREN, not off the root. More on this in a moment. Also Note! The above methods were chosen for demonstration, because the syntax is the same for creating both stand-alone directories and subdirectories. However, you should know that you can create both types of directories no matter which directory you're in. For example, from the ANYWHERE directory, you could have created KAREN by typing md \karen being sure you have the backslash in front of KAREN. You could then attach the BUDGET subdirectory to KAREN with md \karen\budget. Removing a Directory First, be sure all files in the directory have been erased. Second, move back a level to the directory before it. The following example switches to the KAREN directory, deletes all files, moves back one level and removes the KAREN directory: C:\>cd karen go to KAREN C:\KAREN>del *.* delete all files C:\KAREN>cd .. move back one level C:\>rd karen remove KAREN directory Remember! 1. You can't be in the directory you're deleting. Go to the level before it. 2. You can't delete a directory that's not empty. Switching Directories The CD (change directory) command means go to another directory. What actually changes is the DOS prompt, which displays the name of the directory you've switched to. Suppose you have three subdirectories under the PLANS directory: C:\PLANS\1991 C:\PLANS\1992 C:\PLANS\1993 If you're in the 1991 directory and you want to go to the 1992 directory, you have to state the path starting at the root: C:\PLANS\1991>cd \plans\1992 C:\PLANS\1992> Another way is to type: C:\PLANS\1991>cd .. back up one level ** C:\PLANS>cd 1992 go to 1992 C:\PLANS\1992> **Note: When going from PLANS to 1992, you don't use the backslash (\), because 1992 is subordinate to PLANS, not the root. Let's examine this some more. In the command: cd \plans\1991 The first \ means ROOT. The second \ separates one directory name from another. Therefore, if you're in PLANS already, you cannot type: C:\PLANS>cd \1991 You'll get an "Invalid directory" message, because 1991 is not off the root.  \1991 means root 1991 Using the PLANS directories again: C:\PLANS\1991 C:\PLANS\1992 C:\PLANS\1993 Only the first example below is correct: correct C:\PLANS>cd 1991 1991 is off PLANS no good C:\>cd 1991 You're in the root no good C:\>cd \1991 1991 is not off root Switching Between Drives When switching between directories on different drives, you must switch drives first. For example, to switch from C:\PLANS\1991> to D:\BUDGETS>, you would type: C:\PLANS\1991>d: switch drives first D:\>cd budgets then change directories D:\BUDGETS> prompt has changed Think of drives as buildings and directories as floors. You can't get to the 3rd floor of the college if you're on the 2nd floor of the high school by simply switching floors. You have to leave the college and go to the high school first. Using Paths with Other Commands Drive letters ARE NOT used with the CD command. Drive letters ARE used with all other commands whenever the drives are not implicit. For example, to copy the SALES worksheet from C:\PLANS to D:\BUDGETS, you would type: E:\ANYWHERE>copy c:\plans\sales.wk1 d:\budgets Notice that, because you're in drive E, both FROM and TO drive letters must be used (C: and D:). Also notice that the SALES file name is simply added to the end of the path, separated by a backslash. If you were already in C:\PLANS, you would only need to reference the file name: C:\PLANS>copy sales.wk1 d:\budgets Remember! Drive letters must be stated whenever a drive is not implicit. If you're not sure, state the drive letters anyway. Both examples below work:   C:\PLANS>copy c:\plans\sales.wk1 a:   C:\PLANS>copy sales.wk1 a: DOS directory rules  DIRECTORY RULE #1 When going to a directory on a different drive, change drives first, then change directories.  DIRECTORY RULE #2 The backslash represents the root directory. It is also used as a separator symbol between directory and file names.  DIRECTORY RULE #3 When using the CD command to go to a directory on the same or previous level, the path name must begin with the root (\). DOS disk cache See DOS SmartDrive. DOS disk recovery See DOS Recover, DOS Unformat, DOS Undelete and "There's More to Mirror" in DOS Mirror. DOS Diskcomp External command that compares two floppy disks track by track and reports the side and track number if it finds a mismatch.  diskcomp a: b: two identical drives  diskcomp a: one drive On one-drive compares, you'll be prompted to insert the source and target diskettes a few times. DOS Diskcopy External command that makes an exact copy of a floppy disk. Disk types MUST BE THE SAME. You can't Diskcopy a 720KB disk onto a 1.44MB disk. If the target disk is unformatted, Diskcopy will format it. diskcopy a: b: two identical drives diskcopy a: a: one-drive On one-drive copies, you'll be prompted to insert the source and target diskettes a few times. DOS Dos CONFIG.SYS setting as of DOS 5 that allows part of DOS to be loaded into the HMA area (1024-1088K). In order to do this, HIMEM.SYS or some other XMS driver must precede the Dos command in CONFIG.SYS, for example: device=himem.sys dos=high To allow drivers and programs to be loaded into unused memory blocks (UMBs) in the UMA area (640- 1024K), use: dos=umb or activate both with dos=high,umb See DOS Loadhigh and DOS HIMEM.SYS. DOS Doskey External command starting with DOS 5 that provides command history and macros (typed-in commands stored for later use). The command buffer (reserved space) is 512 bytes long unless you specify otherwise. Three examples for loading Doskey follow: doskey 512 byte buffer doskey /bufsize=1000 1K buffer doskey /bufsize=256 minimum size Use Up and Down Arrow to move through command history, and press Page Up and Page Down for the oldest and most recent command. Doskey uses these additional key commands: Key Function F7 Display command history Alt-F7 Clear command history Alt-F10 Clear macros F9 Recall command by number Ctrl <-- --> Cursor previous/next word Home/End Cursor beginning/end line Esc Clear line Ins Insert mode for this line F1, F3 and F6 work as usual. See DOS key commands. CREATING MACROS Doskey macros are useful for shortening phrases that are hard to type; for example, suppose you often copy the file D:\PKWARE\PKUNZIP.EXE to different directories or disks. You could create a macro named PK as follows: doskey pk = copy d:\pkware\pkunzip.exe $1 The $1 creates a blank field for data entry. Now that the macro is created, to copy PKUNZIP.EXE to the B drive, you would type: pk b: Entering the command above converts the macro into the following command (the b: replaces the $1):  pk = copy d:\pkware\pkunzip.exe b:  To see the macros you've created, type: doskey /macros Doskey macros last for only the current session. If you save them in a batch file and add the word DOSKEY in front of each one, you can execute the batch file and recreate the macros in the next session. To store your macros in MYMACRO.BAT, type: doskey /macros > mymacro.bat In order to make the resulting file a command file, you have to type the word DOSKEY at the beginning of each line. DOS DoubleSpace DoubleSpace is a realtime compression capability built into DOS 6 that increases the disk's storage capacity as much as twofold. The actual compression obtainable depends on the data being stored. DOS 6 does not compress your drives automatically. You must run the DoubleSpace program to do it. To compress your hard disk, type dblespace. The first time you run DoubleSpace, you'll have a choice of Express or Custom Setup. To compress your C: drive including all existing files, select Express Setup. To compress another drive or to compress part of your C: drive leaving your existing files uncompressed, select Custom Setup. The compressed drives that DoubleSpace creates are actually files with names such as DBLSPACE.000 and DBLSPACE.001 that reside on an uncompressed drive as hidden "compressed volume files" or CVFs. The uncompressed drive, known as the host drive, is either the C: drive if you did not compress all of it or some other drive that DoubleSpace creates. If you're curious, you can view the hidden CVFs in the uncompressed host drive by typing dir /ah. However, do not restore them to normal status or tamper with them in any manner! When viewing them, you will notice DBLSPACE.BIN. This program file is loaded at startup and gives DOS access to the compressed DoubleSpace disks. To review the status of your compressed drives, to change them or to make new ones, type dblspace and select the appropriate menu options. You can see how effective the DoubleSpace compression is on your files by using the Dir command (see DOS compression ratios). DOS Dozen Twelve DOS commands that let you do almost everything. The DOS Dozen (tm) format  Initialize a floppy dir   List file names del  Remove a file rename Change names type  Display a text file xcopy  Copy files and directories copy   Copy files md Make directory cd Go to a directory rd Remove directory chkdsk Test for corrupted files cls  Clear screen DOS drive identification DOS drives are identified with a letter and colon. A: First floppy B: Second floppy C: Main hard drive D: Second hard drive, second partition within the main hard disk or some other device such as a CD ROM drive. Drive letters E: through Z: also used. To switch drives, type drive letter and colon; for example, to go to drive D, type: C:\>d: switch drives D:\> prompt has changed DOS DRIVER.SYS Driver used to add newer devices (typically floppy disks) to older PCs that did not originally support them. It's also used to assign a second drive letter to a single drive to allow you to copy to and from the same drive. The following codes are used to define drives and drive types:  Drive /d: Factor /f: Switches Default  0 - First 0 - 360KB /h: Heads (1-99) (2) 1 - Second 1 - 1.2MB  /s: Sectors (1-99) (9) 2 - Third 2 - 720KB  /t: Tracks (1-999) (80) 3 - Fourth 7 - 1.44MB /c Change line support etc. 9 - 2.88MB /n Nonremovable device The following lines in CONFIG.SYS add support for a third floppy disk: device=driver.sys /d:2 /f:0 /t:40 360KB device=driver.sys /d:2 /f:1 /s:15 1.2MB device=driver.sys /d:2 /f:2  720KB device=driver.sys /d:2 /f:7 /s:18  1.44MB device=driver.sys /d:2 /f:9 /s:36  2.88MB The following line creates a second "logical" drive for a 1.2MB A: drive. If drive C was the last drive letter, this CONFIG.SYS line will create drive D:, which references A:. device=driver.sys /d:0 /f:1 s:15 If you type: copy a:*.* d: DOS will inform you when to switch disks, and you can Copy or Diskcopy to and from the same drive. Note! DRIVER.SYS differs from Drivparm as it will always make the device the highest drive letter. For example, if a 3.5" drive is added to a PC with an A: and C: drive, DRIVER.SYS will assign it drive D: rather than B:. DOS Drivparm CONFIG.SYS command that redefines the current settings for a device and maintains the same drive letter. The following codes are used:  Drive /d: Factor /f: Switches  0 - First 0 - 360KB /h: Heads (1-99) 1 - Second 1 - 1.2MB  /s: Sectors (1-99) 2 - Third 2 - 720KB  /t: Tracks (1-999) 3 - Fourth 5 - Hard disk /c Change line support etc. 6 - Tape  /n Nonremovable device 7 - 1.44MB 8 - Read/write optical disk 9 - 2.88MB floppy The following line in CONFIG.SYS would define a tape unit on drive B: that writes 10 tracks with 128 sectors per track: drivparm=/d:1 /f:6 /h:1 /s:128 /t:10 Note! To add a device and create a new drive letter, see DOS DRIVER.SYS. Also, Drivparm should not be used experimentally. Get the right specs before you proceed. DOS Editor Full-screen text editor starting with DOS 5 for creating ASCII text files (batch files). To create or edit a file, type edit followed by the name of the file. For example, to edit AUTOEXEC.BAT, type: edit autoexec.bat DOS Editor is easy to use and help is online. Use the Arrow keys to move around. Press Alt-F for the File menu and select Exit when you're done. Note! You must have the QBASIC.EXE program in your DOS directory to run the DOS Editor (EDIT.COM). For DOS versions previous to 5, see DOS Edlin. DOS Edlin Text editor that comes with every version of DOS. However, in DOS 6, it is no longer installed, but still resides on the DOS 6 Supplemental Disk. It allows only one line to be edited at a time. Starting with DOS 5, use the full-screen editor (see DOS Editor). To create or edit a file, type edlin followed by the name of the file. For example, to edit AUTOEXEC.BAT, type: edlin autoexec.bat The screen will display "End of input file" followed by the Edlin asterisk prompt ("*"). Press L and Enter to list the file's contents. TO EDIT A LINE Type the line number and press Enter. Press Right Arrow to bring one character at a time into view, or press F3 to restore the whole line. When you're done editing the line, press Enter for the "*" prompt. Press Enter again for the next line. Ctrl-C cancels changes to the current line. TO INSERT TEXT Type i to insert text in front of the current line, which is marked with an asterisk; for example: 3:*. To change to a different line, type the line number and press Enter. After typing new text, press Enter to end the line. Then press Ctrl-C to end insert mode or keep typing more text. TO QUIT At the "*" prompt, press e and Enter. Basic Edlin commands  L List contents (for specific lines, type: start,stop L; for example: 5,25 L).  i Insert at current line. Ctrl-C ends  #i Insert at end of file. insert mode n Line number to edit. nd Delete line (for example, 5d deletes line 5).  q Abandon edit.  e End Edlin.  r Search/replace. (start,stoprsearchreplace) For example: 1,20rBlueRed changes all Blue to Red in lines 1 to 20. F6 enters a Ctrl-Z. Ctrl-V[ Insert an escape character. DOS EMM386.EXE Starting with DOS 5 and Windows 3.0, EMM386.EXE is an expanded memory manager (EMM) for 386s and up, which is software that converts extended memory into EMS memory. It also allows TSRs and drivers to be stored in the upper memory area (UMA) between 640K and 1M. It is activated with a statement in the CONFIG.SYS file. The HIMEM.SYS driver must also be activated before EMM386.EXE: device=himem.sys device=emm386.exe To provide access to the UMA, either the RAM or NOEMS parameters must be added: device=emm386.exe ram UMA and EMS device=emm386.exe noems UMA only The default amount of memory used is 256K, but you can allocate from 16 to 32768K, for example: device=emm386.exe 1300 ram For DOS 6 Users: The EMM386.EXE that comes with DOS 6 can dynamically convert extended memory into EMS memory when an application requires it. To free up all of extended memory until some of it is required for your EMS application, type: device=emm386.exe min=0 ram EMM386.EXE is an executable program, which can be run after it has been initialized in order to change settings. For example, you can turn off EMS memory management off by typing: emm386 off emm386 on turn it back on DOS environment Reserved area in DOS for holding values used by DOS and other applications. The values stored in this area are called "environment variables" and are created with the Set command (see DOS Set). DOS Erase See DOS del. DOS error messages There are hundreds of error messages in DOS. Messages that generally occur more frequently are explained below:  Access denied The file you are deleting is protected. See DOS Attrib.  Bad command or file name Means that DOS does not understand the command you entered, or it cannot find the program you asked it to run.  Data error reading drive X Means that an area of the disk is unreadable. Press R to retry. Most likely, you'll have to press A to stop (abort). If the data or program is critical and there's no backup, use a utility program to try to reconstruct the damaged area. See DOS Recover. Duplicate file name or file not found Means that you are referencing a file that does not exist or that you are renaming a file to a file name that already does exist.  Exception error 12 Means that DOS does not have enough room to handle hardware interrupts. Increase the number of stacks in the STACKS= command in the CONFIG.SYS file (see DOS Stacks).  General failure (error) reading drive X  Abort, Retry, Ignore? (Fail?) Usually means that an unformatted floppy is being used. Press A to Abort, format the floppy and try again. You'll also get this if you try to read a high-density disk in a low-density drive. High- density disks require high-density drives.  Not ready (error) reading drive X  Abort, Retry, Fail? (Ignore?) Means the drive door is left open, or the floppy disk is not in the drive. Either put the appropriate floppy disk in the drive or close the drive door (turn lever) and press R. To switch to another drive, press A. If you get the message "Current drive is no longer valid>", type the drive (c:, d:, etc.) you want to go back to. If you get this message again, press F (or I for DOS 3.3 and earlier).  Not ready (error) writing device PRN  Abort, Retry, Ignore? (Fail?) Means the printer is turned off or unavailable. Press A to cancel, or turn the printer on and press R. You might also check the cable connection to the printer. Non-system disk or disk error Replace and press any key when ready Usually means there's a non-bootable floppy in drive A. The computer looks for DOS on a floppy before it looks for DOS on the hard disk. If an ordinary floppy is in drive A at startup, it causes this error. Remove the disk and press any key. Incorrect DOS Version Means that the command you are using belongs to another version of DOS. Somehow an earlier or later version of a command is on your hard disk. Commands from one DOS version often do not work in other versions. Internal Stack Failure Means that DOS has gotten completely confused. Turn off the computer and restart. Invalid directory Means that you entered the name of a directory that does not exist. Invalid drive specification If you get this message on a valid drive such as C:, it may mean that your hard disk has become corrupted. See DOS Mirror. Invalid parameter Means DOS doesn't understand the command line. It indicates that a switch is used incorrectly. If you're typing path names, be sure to use a backslash (\), not a forward slash (/). The forward slash is used to enter parameters (see DOS switch and DOS abc's). Packed file is corrupt See DOS Loadfix.  Path not found Means that you entered an invalid path name. Stack overFlow Means that DOS does not have enough room to handle hardware interrupts. Increase the number of stacks in the STACKS= command in the CONFIG.SYS file (see DOS Stacks). Write protect error Means that the floppy disk has been protected and data cannot be recorded on it. Either unprotect it or use another disk. See file protection. DOS Exit Internal command that returns control from DOS to the previous level. Many applications can "shell out" to DOS, letting you run DOS commands and then return to the application. Simply type exit to return. DOS extender Software that is combined with a DOS application to allow it to run in extended memory (beyond 1MB). Some DOS extenders work with 286s and up, others require a 386 minimum. To gain access to extended memory, it runs the application in Protected Mode. When the application requests DOS services, the DOS extender either handles them itself or, with functions such as disk accesses, resets the machine to Real Mode, lets DOS service the request and then switches back into Protected Mode. DOS-extended programs can run by themselves in a DOS machine, but the VCPI specification was developed to enable them to run cooperatively with DESQview and other VCPI-compliant applications. The DPMI spec was developed for compliance with Windows 3.0. If an XMS driver is present, DOS extenders will use XMS to allocate memory. DOS extensions Names used to identify DOS file types. See extension and DOS file names. DOS external command Separate utility program that comes with DOS, such as Format, Diskcopy, XCopy, Tree, Backup and Restore, but is not resident within DOS, such as Copy and Dir. The directory that contains these programs should be on the path so that you can run them no matter which directory you're in. Contrast with DOS internal command. DOS Fastopen External command starting in DOS 3.3 that reopens hard disk files quickly. If a drive is specified with Fastopen, the locations of the files opened are stored in memory. When opened again within the same session, their exact location is known. Fastopen is put in the AUTOEXEC.BAT file with the number of files you want to hold in memory: fastopen c:=50 hold 50 file names on C: fastopen c:=50 d:=75 50 on C:, 75 on D: DOS 4.01 can optionally keep track of all the file fragments. This second number is usually four times greater than the number of names: fastopen c:=(50,200) Caution! Fastopen cannot be used on network drives, and it can be used only once per computer session. DOS FAT (DOS File Allocation Table) The part of the DOS and OS/2 file system that keeps track of where data is stored on disk. When the disk is high-level formatted, the FAT is recorded twice and contains a table with an entry for each disk cluster. The directory list, which contains file ID (name, extension, date of last update...) points to the FAT entry where the file starts. If a file is larger than one cluster, that entry points to another entry and so on. If a cluster becomes damaged, its FAT entry is marked and not used again. DOS FC External command that compares two files for content. .EXE, .COM, .SYS, .OBJ, .LIB and .BIN files are compared byte for byte, otherwise, comparison is line by line. To compare text files FILE1 and FILE2, type: fc file1 file2  blank areas must match character for character fc file1 file2 /w blank areas can be of different sizes fc file1 file2 /a show only start and end text on mismatches Mismatches in ASCII files show as:  ***** first file  start ... ... end  ***** second file  start ... ... end  *****  To compare program files ABC.EXE and XYZ.EXE, type: fc abc.exe xyz.exe Mismatches in binary files show as: AAAAAAAA BB BB A = Hex location from start of file. B = Hex characters in first and second files. DOS FCB (DOS File Control Block) Method of handling files in DOS 1.0. Applications still exist that remain compatible with 1.0 and use this method. See DOS Share. DOS Fdisk External command used to partition a hard disk, which is necessary before high-level formatting. For the procedure, see "How to Format a Hard Disk" under DOS Format. DOS file (1) Any computer file created under DOS. (2) ASCII text file. See DOS batch file. DOS file names On a disk, every independent collection of instructions or data is a "file." Programs, databases, word procesing documents, spreadsheets and graphics images are examples of files. All files have a file name, and most files have an extension. Extensions are attached to the name with a period (no spaces in between). For example, the following files make up the DOS and Windows versions of this Glossary: Name Extension  Purpose WINGLOSS.EXE Windows Glossary program WINGLOSS.HLP Windows Version help GLOSS.EXE DOS Glossary program GLOSS.HLP DOS Version help GLOSS.ABC Configuration data GLOSS.TXT Text file GLOSS.NDX Index The name can be from one to eight characters in length. The extension, if used, can be from one to three characters long. All runnable programs in DOS have either a BAT, COM or EXE extension (look up "extension" for a list of over 100 common DOS extensions). Valid characters in names and extensions are: A-Z, a-z, 0-9 ! @ # $ % & ( ) ' ` - { } ~ The Dot is Sacred If an extension is used, it is added to the file name with a period, for example, GLOSS.TXT. As a result, the dot can't be used in a file name. For example, GL.OSS.TXT isn't valid. Your Own Filing System. Most applications use proprietary extensions for the data files that they create. However, several word processors do not, and if you can organize your documents with your own filing system. For example, the NOV extension could be a novel with chapters INTRO.NOV, MAIN.NOV and END.NOV. Note! Directories are named just like files with a name and optional extension. DOS files= See DOS CONFIG.SYS. DOS filters & pipes Filters are external commands that change data in some manner. The filters are: FIND - Searches for text SORT - Rearranges data in alpha order MORE - Displays data a screenful at a time Pipes let you direct the output of one command as input to another. The pipe symbol is a vertical bar (shift backslash key). Pipes are used with filters as follows. To get a Dir list of all the files that have "ZIP" somewhere in their names, you would type: C:\>dir | find "ZIP" command PKUNZIP EXE results displayed PKZIP EXE C:\> The pipe redirects the Dir list output to the find command, which looks for ZIP and filters only lines with "ZIP" in them through to output. See DOS Find, DOS Sort and DOS Dir. DOS Find External command used to search for a particular string of text in a text file. The following example will display the line numbers of the lines that contain c: in the RUNJOB.BAT batch file: find "c:" runjob.bat Find is case sensitive. "C:" will not find "c:". See DOS filters & pipes. DOS Format File structure used by DOS to keep track of data on a disk. All disks must be formatted (initialized) before use. This process creates the sectors on the disk (low-level format) that are later filled with data and also generates the tables that DOS uses (high-level format) to keep track of the data. Hard disks are regularly formatted at the factory, but floppies are usually not. The Format external command creates both low- and high-level format on floppies, but only a high- level format on hard disks.  Formatting a Floppy To format an unformatted floppy fresh from the box, put it into drive A or B and type: format a: or format b: and answer the prompts. FLOPPY DISK SIZES There are five floppy disk capacities:  Diameter Capacity Name  5.25" 1.2MB High density 5.25" 360KB Low density (Double Density) 3.5" 2.88MB Extra high density 3.5" 1.44MB High density 3.5" 720KB Low density (Double Density) Higher-density drives can read and write low- density disks. But to format a low-density disk in a high-density drive, you must modify the command as follows. FORMATTING 5.25" DISKS To format a 360K disk in a 1.2M drive, type:  format a: /4 All versions format a: /f:360 DOS 4.01 and up Caution! 360K disks formatted on very early 1.2MB drives may cause reading problems. FORMATTING 3.5" DISKS To format a 720KB disk in a 1.44MB drive, type:  format a: /n:9 /t:80 All versions format a: /f:720 DOS 4.01 and up To format a 1.44M disk in a 2.88M drive, type: format a: /f:1.44  REFORMATTING A FLOPPY (As of DOS 5) The /q switch causes Format to bypass checking for bad sectors. To quickly reformat a formatted disk that you know is OK, type: format a: /q Previous to DOS 5, the format program completely formatted a floppy losing all data if previously formatted. As of DOS 5, Format creates a "safe format" by saving additional data on the disk. This takes a bit longer but allows the disk to be unformatted. Since you will not have to unformat blank disks, you can format "unconditional" and speed up the format process with the /u switch: format a: /u Also previous to DOS 5, any bad sector on a diskette eliminated the entire track. As of 5, only that sector is marked as bad. CREATING A BOOTABLE FLOPPY To format a floppy and make it "bootable" by copying DOS from the hard disk onto it, type: format a: /s The DOS COMMAND.COM file is also necessary on the bootable floppy. Starting with DOS 5, the Format command copies COMMAND.COM to the floppy automatically. In DOS 4.01 and earlier, you have to copy COMMAND.COM manually. Formatting a Hard Disk A hard disk format requires: 1. Low-level format 2. Create partitions (Fdisk) 3. High-level format (Format) LOW-LEVEL FORMAT If your hard drive is not already low-level formatted from the factory (most IDE drives are), the low-level format is accomplished by running a utility program that comes from the disk manufacturer or other software provider. The program may also be resident in the BIOS of the disk controller card. CREATE PARTITIONS Fdisk is an external command that creates partitions and "logical drives" on the hard disk. To run Fdisk on your C: drive, boot the computer with a floppy in drive A that contains DOS as well as the Fdisk program. If you're adding a second or subsequent hard drive, load Fdisk from your C: drive. Type fdisk to load the program and follow the menu options. DOS 3.3 and under handles disks up to 32MB in size, therefore after making a primary partition of up to 32MB, you'll be making an extended partition if your disk exceeds 32MB. DOS 4.01 handles disks up to 512MB, and DOS 5 up to 2GB, in which case you only need to create the primary partition. After making the primary partition, make an extended partition if you require logical drives (D:, E:, etc.) either for convenience or because you want to install two operating systems on your disk. After making the extended partition, make one or more logical drives. The active partition (the one to boot from) is assumed to be the C: drive. If not, you can change that from the Fdisk menu. Starting with DOS 5, Fdisk only creates DOS partitions. If you have to create a partition for another operating system, refer to that operating system's manual. HIGH-LEVEL FORMAT The final step is to run Format for each logical drive (C:, D:, etc.). This step prepares the root directory, FAT tables and places startup data in the boot sector. To format your C: drive, boot the computer with a floppy in drive A that contains DOS as well as the Format program. Use the /s switch to transfer DOS at the end of the format. To format drive C, type:  format c: /s To format a second or subsequent hard drive, load Format from your C: drive. DOS hidden file DOS file with a status that prevents it from being altered, erased or normally recognized. DOS system files are all hidden files. See DOS Attrib. DOS high memory Area between 640K and 1024K reserved for system use. Also may refer to the area between 1024K and 1088K (HMA). See PC memory map. DOS HIMEM.SYS Starting with DOS 5 and Windows 3.0, HIMEM.SYS is an XMS driver, which is software that manages extended memory in the PC. It allows part of DOS to be loaded into the high memory area (HMA) to free up more conventional memory. HIMEM.SYS is required if you use EMM386.EXE to load TSRs and drivers in the upper memory area (UMA) or to turn extended memory into expanded memory. HIMEM.SYS is activated in the CONFIG.SYS file and must precede all drivers that use extended memory; for example: device=himem.sys device=emm386.exe EMS memory manager  device=smartdrv.sys disk cache  device=ramdrive.sys /e RAM disk Note: Windows requires extended memory and comes with its own HIMEM.SYS driver that is automatically installed. However, HIMEM.SYS from DOS 5 supersedes the HIMEM.SYS from Windows 3.0. Only one program can reside in the HMA at one time. In order to reserve it for the largest program, you can specify the minimum size the program must be with the HMAMIN switch. In the following example, a program must be at least 50K to use the HMA: device=himem.sys /hmamin=50 See DOS Dos and DOS EMM386.EXE. DOS history See DOS Doskey. DOS installing from drive B: See DOS Assign. DOS Interlink Starting with DOS 6, the Interlink utility lets you transfer files between two PCs connected via their serial or parallel ports. The serial port cable can be a 3-wire file transfer cable or a 7-wire null modem cable, and the parallel cable must be a bidirectional parallel cable. The PC with DOS 6 and the INTERLNK.EXE program is the client PC, and the second machine (DOS 3.0 and up) is the server PC. The program INTERSVR.EXE must be transferred to the server PC via floppy or by remote copy (see below). Once the link is established, the disks on the server become different drive letters on the client. For example, if the server has an A:, B: and C: drive, those drives would be assigned as follows on the client: Client Server A: B: C: D: A: E: B: F: C: You can copy and move files between the client and server, and you can even delete and run programs on the server as if they were on the client by using the new drive letters. SETTING UP THE CLIENT Add up the total number of drives on both PCs, add the following line to the bottom of your CONFIG.SYS file and reboot the computer. The following example assumes five total drives: device=c:\dos\interlnk /drives:5 SETTING UP THE SERVER Transfer the INTERSVR.EXE program from the client to the server via floppy or use the following procedure for a remote transfer: 1. Cable PCs together. 2. Type interlnk /rcopy on the client. 3. Follow instructions. ESTABLISHING THE LINK 1. Cable PCs together. 2. Type intersvr on the server. 3. Type interlnk on the client. The server will display a status screen during the link, but the client will return to the DOS prompt so you can use the Copy command to transfer files. To review the new drive assignments, type interlnk on the client. Note that the INTERLNK.EXE driver loaded by CONFIG.SYS will take up memory each time you start up the computer unless you remove that line. DOS internal command Command capability within DOS (COMMAND.COM) at all times, such as Dir, Copy, Del, Ren, Type and Cls. Contrast with DOS external command. DOS Join External command that assigns a drive to a directory. For example, if a program accesses files on C only, but you want it to use files on B, you can make the B drive appear to be a directory of C. Join creates the directory, but it must be off the root.  join b: c:\bdrive join B to C:\BDRIVE join b: /d unjoin B join display join status Don't use Join with Assign, Subst, Backup, Chkdsk, Diskcomp, Diskcopy, Fdisk, Format, Label, Recover, Restore or Sys commands on a joined drive. DOS key commands The following keyboard keys can be used: Ctrl-Alt-Del Reset computer Ctrl-C or Ctrl-Break Cancel operation Ctrl-S Stop scrolling Ctrl-P Print what's displayed (on/off) Shift-PrtSc Print current screen F1 or --> Redisplay last DOS entry a character at a time F3 Redisplay last DOS entry F6 Enter Ctrl-Z (end-of-file character) Alt-Digit Enter ASCII character by value (use numeric keypad) DOS Label External command that names a disk (volume label). The name can be up to 11 characters long, and it can contain spaces. To name the disk in A 1992 BUDGET, type: label a:1992 budget Important! Don't use Label on a network drive, or one that has been ASSIGNed, JOINed or SUBSTituted. DOS Lastdrive Used in the CONFIG.SYS file, it specifies the maximum number of drives that can be accessed. The following line in CONFIG.SYS sets the last drive letter to M: lastdrive=m DOS Loadfix External command starting with DOS 5 that loads a program beyond the first 64K of RAM, solving a problem with some earlier programs. As of DOS 5, part of DOS can be loaded into high memory, thus freeing up more lower memory. Some programs cannot run in this lower RAM and generate a "Packed file corrupt" error. "Packed" refers to an older method for compressing EXE files, and this method had a bug in it that prevents it from running in lower RAM. The following example loads the program ABC beyond the first 64K: loadfix abc DOS Loadhigh Internal command starting with DOS 5 that loads a program into the UMA (upper memory area: 640K-1M) in 386s and up. It requires that the HIMEM.SYS and EMM386.EXE memory managers be loaded and the dos=umb command be present. If you have programs that need expanded memory (EMS), the following three lines in CONFIG.SYS are required to use Loadhigh. The RAM parameter informs EMM386 to manage both the UMA and expanded memory:  device=\dos\himem.sys  device=\dos\emm386.exe ram  dos=umb  The following example uses the NOEMS parameter to inform EMM386 to manage only the UMA and not expanded memory:  device=\dos\himem.sys  device=\dos\emm386.exe noems  dos=umb  If the lines above are in your CONFIG.SYS file, you can load programs into upper memory. The following example, which can be run from the DOS prompt or in your AUTOEXEC.BAT file, loads POPUP into the UMA. If POPUP is too big to fit into an available, contiguous memory block, it will load below 640K. loadhigh popup or lh popup To load a device driver into upper memory, use the Devicehigh command in CONFIG.SYS instead of Device; for example: device=ansi.sys below 640K devicehigh=ansi.sys above 640K See DOS Dos and DOS Mem. DOS Md Internal command that makes a new directory. Mkdir is an alternate form. To create the HARRY directory off the root, type: C:\>md harry or type: C:\>mkdir harry See DOS directories and DOS abc's. DOS Mem External command starting with DOS 4.01 that displays the amount of memory currently used and free. Type: mem Starting with DOS 5, to display the contents of memory by program name and show the available free memory blocks (UMBs) in upper memory (UMA), type: mem /c DOS Memmaker Starting with DOS 6, Memmaker is a utility that optimizes memory on 386s and up by determining the best order to load TSRs and drivers in the upper memory area (UMA). Memmaker may change device= statements to devicehigh= in your CONFIG.SYS file in order to load drivers in the UMA. It may add the loadhigh command to TSRs loaded in your AUTOEXEC.BAT file to load them "high" as well. To run Memmaker, type memmaker. Choosing Express Setup will configure your system automatically. If certain TSRs and drivers placed in the upper memory area cause conflicts, you can exclude them by running Memmaker and choosing Custom Setup or by adding their names to the MEMMAKER.INF file. Use the DOS Editor to open MEMMAKER.INF and read the instructions. Choosing Custom Setup lets you specify further optimization. For example, if you use an EGA or VGA monitor and not Super VGA, answer Yes to "Use monochrome region for running programs." If you run only Windows applications, choose "No" to "Optimize upper memory under Windows?" See DOS CHKSTATE.SYS and DOS SIZER.EXE. DOS memory manager Software that expands DOS' ability to manage more than one megabyte of memory or to manage its first megabyte more effectively. Since the early days of DOS, third party memory managers, such as QEMM and 386MAX, have used every trick in the book to move TSRs and drivers out of the lower 640K and into the 384K upper memory area (UMA). Starting with DOS 5, DOS includes its own memory managers. HIMEM.SYS manages extended memory, and EMM386.EXE manages expanded memory. See DOS HIMEM.SYS, DOS EMM386.EXE, DOS Memmaker, memory allocation, PC memory map, EMS, XMS, VCPI and DPMI. Also see "Operating Environment" in the PC definition.  DOS Memory Areas Conventional memory 0-640K Upper memory area (UMA) 640-1024K High memory area (HMA) 1024-1088K Extended memory 1024 and up Expanded memory Bank switched memory DOS Mirror External command in DOS 5 that loads the Delete Tracker memory-resident program (TSR). It takes 6K of RAM and monitors the files you delete. It doesn't provide a 100% guarantee, but it adds a level of protection in case you have to undelete a file later. In DOS 6, the Undelete command is used to activate Delete Tracker. Also, Delete Sentry is even better (see DOS Undelete). In DOS 6, Mirror is not installed, but still resides on the DOS 6 Supplemental Disk. Also note "There's More to Mirror" below. Mirror creates and uses a MIRROR.FIL file and also creates hidden MIRORSAV.FIL and PCTRACKR.DEL files. To automatically load it each time you start up, place the command in your AUTOEXEC.BAT file. The following example tracks drives C and D:  mirror c: d: /tc /td If you must unload Delete Tracker from memory, type: mirror /u Use the Undelete command to undelete a file. For example, to undelete SALES.DBF, type: undelete sales.dbf THERE'S MORE TO MIRROR Mirror is also used to save information about your hard disk partition, directories and FAT table, which could get corrupted in the event of a power failure while writing to the hard disk. This command, initiated in DOS 5, has been relegated to the DOS 6 Supplemental Disk. Most DOS 6 books don't even mention it, no doubt because data recovery is not an exact science. One DOS 6 book that does elaborate on Mirror is "MS-DOS 6, The Ultimate Guide for Experienced DOS Users" by Minasi, Camarda, Stang and Ashton, ISBN 1-56205-132-6. Nevertheless, if you want to provide more protection, you can run Mirror in both DOS 5 and DOS 6 as follows. SNAPSHOT YOUR PARTITION TABLE To save vital data about your hard disk partition in a file called PARTNSAV.FIL on a floppy disk, type: mirror /partn Put the floppy in a safe place. If you ever get an "Invalid drive specification" on your valid drive, the partition table may be corrupted. To restore your partion, find your PARTNSAV.FIL floppy, and type (see warning below): unformat /partn SNAPSHOT YOUR DRIVES DAILY Take a snapshot of your hard disk directories and FAT table every time you start up by placing the Mirror command in your AUTOEXEC.BAT file. A MIRROR.FIL and a hidden MIRORSAV.FIL file will be created. For example, to snapshot drives C and D, type: mirror c: d: The following procedure is used to restore your C drive, providing you take daily snapshots that have not become corrupted (see warning below): 1. type unformat /partn to restore partition 2. insert PARTNSAV.FIL floppy disk 3. insert bootable floppy to reboot 4. type unformat c: /j test outcome of step #5 5. type unformat c: /u to restore directories and FAT ! W A R N I N G ! You can try the above procedure if you absolutely cannot get to your data at all, but there is no guarantee you will succeed. The success ratio of users trying to do their own data recovery on badly corrupted disks is most likely the reason Microsoft has all but abandoned Mirror in DOS 6. However, if you experience problems, one of the worst things you can do is to keep rebooting from your hard drive, providing you can reboot. Although Mirror keeps a previous and current snapshot, rebooting over and over can easily cause you to take new snapshots of bad disks. You're better off rebooting from a bootable floppy. You're also far better off getting help from an experienced data recovery expert, such as the tech support rep from your hardware supplier or the software company that you purchased data recovery utilities from, such as Central Point Software, Symantec or Fifth Generation. BETTER THAN ALL OF THIS IS TO MAKE BACKUPS OF YOUR DATA REGULARLY. Your vital data takes up less room than you think. Even if you have a 200MB drive, you may be surprised to find out that most of it is software, which you can re-install, even if it takes several hours and is a royal pain. You may be able to store all your vital data on less than a dozen floppies if you compress it with PKZIP or some other backup or compression utility. If you have DOS 6, see DOS MSbackup. Important! Don't run Mirror on any drive that has been redirected with Join or Subst. If using the Assign command, do the Assign before executing Mirror. DOS Mkdir See DOS Md. DOS Mode External command that allows changes to a variety of settings. Following are common examples: SET THE SERIAL PORT FOR COMMUNICATIONS To set the first serial port to 2400 baud, No parity, 8 bits and 1 stop bit, type: mode com1:2400,n,8,1 SET THE SERIAL PORT FOR THE PRINTER To set the first serial port to 4800 baud and even parity for a printer, type: mode com1:4800,e,,,p REDIRECT THE PRINTER PORT To redirect printing from the parallel port to serial port #1, type: mode lpt1:=com1: reroute data mode lpt1 cancel rerouting CHANGE KEYBOARD SPEED As of DOS 4.01, Mode changes keyboard repeat rate and amount of delay before repeating. To change rate to 20 and delay to .5 sec, type: mode con rate=20 delay=2 Rates: 1-32 Delays: 1-4 (.25 .50 .75 1.0 sec.) LEFT HANGING IN 40-COLUMN MODE? If a program leaves you in 40-column mode (extra wide text characters on screen), you can switch back to 80 column mode with mode 80 DOS Move External command starting with DOS 6 that moves a file to a new location (it copies first, then deletes the source file). The syntax is like the Copy command; however, you must always enter a target destination. That means even though you are already in the directory you want to move the file into, you still have to state it. For example, to move file ABC from the B: drive into the UTILITY directory, type: C:\UTILITY>move b:abc \utility Note: The C: drive is implicit, but the \UTILITY directory is not and must be explicitly stated even though you are already in it. DOS MSAV (DOS MicroSoft AntiVirus) Starting with DOS 6, MSAV is a menu-driven utility that scans memory and disk for viruses. To run it, type msav. To run the program automatically each time you start the computer, add one of the following lines in your AUTOEXEC.BAT file: msav /p scan memory and drives msav /p /l limit scan to local drives if network drives are used A memory resident antivirus utility is also included that will continually check for viruses. To load it, type vsafe. To unload it, press Alt-V and Alt-U. For Windows Users A Windows version of MSAV.EXE is included with DOS 6 called MWAV.EXE. This is run from an icon in Windows, which is installed in the Microsoft Tools Program Group. DOS MSbackup Starting with DOS 6, the MSbackup program provides a menu-driven backup and restore utility for floppy disks that contains its own help. To run it, type msbackup. The first time you run it, it will ask you to perform a compatibility test to adjust to your computer's hardware configuration. See backup types. For Windows Users A Windows version of MSBACKUP.EXE is included with DOS 6 called MWBACKUP.EXE. This is run from an icon in Windows, which is installed in the Microsoft Tools Program Group. DOS MSD (DOS MicroSoft Diagnostics) Starting with DOS 6, MSD is a diagnostic utility that reports the current hardware and software configuration of your system. Type msd to load the program. DOS multiple startups See DOS startup options. DOS online help Starting with DOS 5, online help is available from the DOS prompt. For example, in DOS 5, to see a summary of syntax and switches for the Xcopy command, type: help xcopy or xcopy /? To display a list of all DOS commands, type help by itself. Starting with DOS 6, there are two kinds of help. Typing help loads a help system with hypertext links to related commands. To load the system and immediately go to a specific command, type the name of the command; for example, help xcopy. Typing xcopy /? will generate a summary help screen as it does in DOS 5. DOS optimizing memory See DOS memory manager and DOS Memmaker. DOS Path Internal command that sets up a search path to one or more directories. If DOS can't find a program in the current directory, it looks in the path. For example, the DOS directory, which holds DOS's external commands (Format, Xcopy, etc.) is always put in the path so you can use the commands from whichever directory you happen to be in. The path command is placed into the AUTOEXEC.BAT file, which is executed on startup. The following example sets up a search path to C:\(root), C:\DOS and E:\UTILITY. Directory names are separated with a semicolon (;):  path c:\;c:\dos;e:\utility To add the C:\123 directory to the example above, you would add ;c:\123 to the end of the line, resulting in:  path c:\;c:\dos;e:\utility;c:\123 See DOS AUTOEXEC.BAT. DOS pipes See DOS filters & pipes. DOS Print External command that prints text files or pre- formatted word processing files in the background allowing you to continue work on something else. To print files ABC and XYZ, type: print abc xyz To print all files with a .TXT extension, type: print *.txt Specified files are placed in a queue and printed one after the other. Print queue commands are: print display status print /t cancel all printing To increase the number of files allowable in the queue from 10 (default) to 20 (max 32), type: print *.txt /q:20 Other Print Options You can also print text files with DOS's Type command (see DOS Type). To display the current text screen, press Shift-Print Screen. In addition, to print directory lists, press Ctrl-P before typing the Dir command. The text on screen will be sent to the printer. Press Ctrl-P again when you're done. DOS prompt Message DOS displays when ready to accept user input. The default prompt (C>, D>...) displays the current drive and doesn't say which directory you're in. Since this can be changed, PCs are usually configured with the following line in the AUTOEXEC.BAT file, which creates the prompt used in our examples:  prompt $p$g  Prompt  Code  Displays $p Current drive/directory $g > $l < $b | $$ $ $n Default drive $t Time $d Date $v DOS version $_ Go to next line The command, prompt XYZ Company$_$d $p$b would generate the following DOS prompt: XYZ Company Tue 04-30-1993 C:\| DOS RAM disks RAM disks simulate a disk drive in memory and provide fast retrieval of programs and data. If operations are disk intensive, they can be speeded up using RAM disks; for example, copying files within a RAM disk is almost instantaneous. However, some operations may benefit only slightly. You'll have to try it to find out. RAM disk contents are lost if the power fails or the computer is turned off, thus, data updated in RAM disks should be periodically copied to real disks. RAM disks take on the next available drive letter. To copy files into RAM disks on startup, put Copy commands in your AUTOEXEC.BAT file. RAM disks are activated by adding a line in CONFIG.SYS. The following examples assume that VDISK.SYS and RAMDRIVE.SYS are in the root directory. Number of directory entries Sector size (128-256-512)朕 RAM disk size (KBytes) Install RAM disk in this memory: DOS 3.x  device=vdisk.sys 100 512 5 conventional  device=vdisk.sys 2000 512 150 /e extEnded  device=vdisk.sys 1000 512 50 /a expAnded (EMS) DOS 4.01 and up: device=ramdrive.sys 100 512 5 conventional device=ramdrive.sys 2000 512 150 /e extEnded device=ramdrive.sys 1000 512 50 /a expAnded (EMS) Starting with DOS 5, 4096K is the maximum disk size for one RAMDRIVE.SYS disk. For multiple RAM disks, use multiple DEVICE= lines. Use 128 sector size for small files; 512 for large ones. The default is 128 in VDISK and 512 in RAMDRIVE. If you leave this out, you can't include a directory entry number. Number of directory entries is 2 to 512 for VDISK; 2 to 1024 for RAMDRIVE. The default is 64. Note! In order to use extended or expanded (EMS) memory for your RAM disk, you must load the extended memory or EMS driver from CONFIG.SYS before loading your RAM disk driver. See DOS HIMEM.SYS and DOS EMM386.EXE. DOS RAMDRIVE.SYS See DOS RAM disks. DOS Rd Internal command that removes a directory. Rmdir is an alternate form. Directories must be empty first, and the command must be entered from the previous level or from a non-related directory. To remove the HARRY directory directly off the root, type: C:\>rd harry or type: C:\>rmdir harry HARRY can also be removed while in another directory by stating the full path to it; for example: C:\WORK>rd \harry For DOS 6 Users: See DOS Deltree to remove directories that contain files and subdirectories. See DOS directories and DOS abc's. DOS Recover External command up to but not including DOS 6 that reads data on disks that are physically damaged. It reads files a sector at a time recovering whatever data it can and puts the recovered files into the root directory. You can recover an entire disk by specifying only the drive letter, but recovered files are renamed starting with FILE0001.REC, and you won't know which is which. It is best to recover one file at a time; for example: recover a:sales.dbf DOS redirection Redirecting keyboard input and screen output (see DOS Mode to redirect the printer port). Normally, DOS gets input from the keyboard and displays output on screen. However, you can redirect input from the keyboard to another file and redirect output from the screen to the printer or a disk file. The symbols are: < Redirect input > Redirect output to a new file >> Redirect output to an existing file For example, to redirect the output of a Dir list to the printer, type: dir > prn PRN is the name of the parallel port (see DOS device names). The following example redirects input to sort a text file named FIRST into alphabetical order and display it on screen: sort < first Using both input and output redirection, the sorted file can be copied into a new file called SECOND. Think of < as "input from," and > as "output to." sort < first > second Redirection can be used with the Pipe command, which funnels output of one command into another. The following example, using the pipe's vertical bar symbol, funnels output of the Dir list to the Sort filter before redirecting it to a disk file called NEWLIST:   dir | sort > newlist Since the pipe and redirection symbols act as word separators, you could type the above command as: dir|sort>newlist See DOS Sort. DOS Rem Remarks statement in DOS batch files and CONFIG.SYS file. For example, the following REM line is for documentation purposes only: rem the following driver activates the mouse device=mouse.sys You can bypass the command on the line by adding REM at the beginning. In the following example, MOUSE.SYS will not be loaded:  rem device=mouse.sys DOS Rename Internal command that changes the name of one file at a time. To change from ABC.DOC to XYZ.DOC, type: rename file.abc file.xyz or ren file.abc file.xyz Put a space between words and names. DOS Replace External command (DOS 3.3 and up) that copies files that have been updated. The /u checks time and date and copies only files from the source directory that are newer than the files in the target directory. To update .TXT files on drive B, type: replace *.txt b: /u DOS restoring disks See DOS Recover, DOS Unformat, DOS Undelete, DOS Backup/Restore and "There's More to Mirror" in DOS Mirror. DOS Rmdir See DOS Rd. DOS root First directory on a disk. See DOS abc's and root directory. DOS Set Internal command that sets environment variables, which are stored values used by DOS as well as many applications. PATH, APPEND, COMSPEC and PROMPT are actually environment variables too. An environment variable is often used to indicate where temporary files are stored, such as in the following example: set temp=c:\dos This Glossary softwware also uses an environment variable. For example, if the Glossary is shared on a network server, lookup history will be common. If you want to review tomorrow what you looked up today, and not what your neighbor looked up, you have to create a private file for lookup history and tell the Glossary software where it is. Copy GLOSS.ABC from the network server into your local machine. Then add a line in your AUTOEXEC.BAT file that sets the Glossary environment variable GLOSSPATH to your local machine. For example, if you stored a copy of GLOSS.ABC in your C:\UTILITY directory, add the following line in your AUTOEXEC.BAT file: set glosspath=c:\utility To display the current values for all the environment variables, type: set Important! In other DOS commands, spaces after the equals sign don't matter. With Set, they do. The command set state = IL would make the first character of the STATE variable a blank (" IL"). DOS Setver External command starting with DOS 5 that updates a version table containing names of programs and the DOS version number they need to run under. Programs may test version numbers and function differently as a result (all DOS's are not the same), but some programs didn't plan on 5 as a future number. This command "fakes them out" by supplying them with the version number they need. A list of known programs in the version table is included, and the DOS install program puts a device=setver.exe line in the CONFIG.SYS file, which loads the version table. To see the current list, type: setver You can add and delete programs to the list. To set the program OLDPROG.EXE to Version 3.3, type: setver oldprog.exe 3.30 To remove it from the list, type: setver oldprog.exe /delete DOS Share External command that provides file sharing and file locking in a network environment. To load Share, type: share Starting with DOS 5, load SHARE.EXE in the CONFIG.SYS file with the Install command: install=\dos\share.exe Important for DOS 4.01 Users! In DOS 4.01, which increased disk handling from 32MB to 512MB, Share lets applications written for compatibility with DOS 1.0 work properly with disks over 32MB. You'll never know if you've got such an application, so if you're running large disks under DOS 4.01, be sure to put Share in your AUTOEXEC.BAT. Note: Share is not used this way as of DOS 5. See DOS AUTOEXEC.BAT and DOS FCBs. DOS shell Shells provide the user interface in DOS, or the way you interact with the system. COMMAND.COM is the program that provides the command-driven user interface described in this tutorial. Other shells can be substituted for COMMAND.COM, by adding the Shell command in the Config.sys file; for example: shell=xyzmenu.com As of DOS 4.01, an optional user interface called DOSSHELL is provided that lets you command DOS with menus. The 4.01 install program (Select) creates the DOSSHELL.BAT batch file, which loads DOSSHELL when executed. Type: dosshell As of DOS 5, the menu-driven user interface has been completely revised, and the DOSSHELL.COM is used to start it. Run it by typing: dosshell /t text (character) mode dosshell /g graphics mode dosshell /bw black & white (laptops) DOS SIZER.EXE Utility used by Memmaker exclusively during its optimization process that checks the size of each program loaded. The command is placed into CONFIG.SYS and AUTOEXEC.BAT and then removed when Memmaker is finished. See DOS CHKSTATE.SYS. DOS SmartDrive Disk cache software included with DOS and Windows starting with DOS 4.01 and Windows 3.0. SmartDrive speeds up hard disk performance by reserving a block of memory and reading and writing larger chunks from the disk (see cache). There are two versions of SmartDrive depending on DOS and Windows version. File name DOS Windows SMARTDRV.SYS 4.01, 5 3.0 SMARTDRV.EXE 6 3.1 DOS 4.01 & 5 and Windows 3.0 The SMARTDRV.SYS driver is loaded from CONFIG.SYS, and its default setting uses 256K of extended memory, for example: device=c:\dos\smartdrv.sys You can reserve more memory by adding the number of K's to the line; for example, to reserve two megabytes, type: device=smartdrv.sys 2048 extended memory device=smartdrv.sys 2048 /a expAnded memory Note! In order to use extended or expanded (EMS) memory for your disk cache, you must load the extended memory or EMS driver from CONFIG.SYS before loading SMARTDRV.SYS. See DOS HIMEM.SYS, DOS EMM386.EXE and cache. DOS 6 and Windows 3.1 The SMARTDRV.EXE program is loaded from the AUTOEXEC.BAT file. If a SCSI drive was detected on installation, SMARTDRV.EXE is also loaded from CONFIG.SYS as in the following example: No SCSI drive detected c:\dos\smartdrv in AUTOEXEC.BAT SCSI drive detected c:\dos\smartdrv in AUTOEXEC.BAT CONFIG.SYS:  device=c:\dos\smartdrv.exe /double_buffer To determine if the device= line can be removed from CONFIG.SYS, type smartdrv (after SMARTDRV has been loaded in AUTOEXEC.BAT). If every line under the column "buffering" reads NO, you can remove the line. SmartDrive's default setting uses 1 to 2MB of extended memory depending on the amount of RAM installed. You can reserve more memory by adding the number of K's to the line. The following AUTOEXEC.BAT example reserves 4MB (4096KB) of extended memory for DOS applications. The second number (2048KB) limits Windows to reducing the cache size to 2MB. After Windows is exited, the cache is restored to 4096K.  c:\dos\smartdrv 4096 2048 Note! In order to use extended memory for your disk cache, you must load the extended memory driver from CONFIG.SYS before loading SMARTDRV.SYS. See DOS HIMEM.SYS. DOS Sort External command that sorts a text file or Dir list into alphabetical order. Lines in the text files must be uniform and columns (fields) must line up, such as the text within the BBS definition in this Glossary. The following example sorts the text file ABC (starting at column 1), creating ABC2. The < means "input from," and the > means "output to." sort < abc > abc2 Let's assume that the text in our BBS definition is stored in a file called BBS. The following examples create a new file in telephone number sequence. They use the /+ switch to indicate that the telephone numbers begin in column 40 (character position 40):  sort /+40 < bbs > bbs2 a-z order sort /+40 /r bbs2 z-a order (reverse) To sort the file and print it without saving the results, type: sort /+40 < bbs > prn To display a sorted Dir list, type: dir | sort You can sort Dir lists by file characteristics. Use the /+ switch to begin the sort on other than column one of the line: dir | sort /+10 by extension dir | sort /+14 by file size dir | sort /+23 by month dir | sort /+29 by year To write the sorted Dir list to a disk file, type: dir | sort > xyz create new XYZ file dir | sort >> xyz add to existing XYZ file To append the current sorted directory list to the end of a file called XYZ, type: dir | sort >> xyz Note! As of DOS 5, additional sorting options for Dir are provided (see DOS Dir). DOS Stacks CONFIG.SYS command that reserves memory for hardware interrupts. The Stacks command has become more of an issue with Windows, as mouse interrupts must be stored until Windows finishes its current operation and can service them. The stacks=9,256 line is placed in the CONFIG.SYS file by Windows 3.1's install program. This allocates nine stacks of 256 bytes taking up 2,304 bytes of conventional memory. Some computers save memory for this function and can operate without additional stacks (stacks=0,0); however, Microsoft recommends that if your PC hangs up when you move your mouse, try the following entries in CONFIG.SYS, one at a time: stacks=12,128  stacks=9,256  stacks=12,256  stacks=0,0 The first number in the command allocates the number of stacks from 8 to 64. The second number is the size of the stack in bytes from 32 to 512. The stacks=0,0 command allocates no stacks. DOS startup options Starting with DOS 6, there are multiple startup options for the CONFIG.SYS and AUTOEXEC.BAT files. You can bypass them, decide which lines to execute or set up multiple configurations for selection at startup. Clean Boot You can "boot the computer clean" by bypassing the CONFIG.SYS and AUTOEXEC.BAT files. This is useful if you want to test something without any TSRs or drivers loaded. In addition, if you changed CONFIG.SYS or AUTOEXEC.BAT and the computer locks up, you can still boot from the hard disk rather than having to boot from a floppy. To clean boot, press and release F5 as soon as the "Starting MS-DOS..." message appears on screen. Execute a Line at a Time If a new driver or TSR causes problems, you have the option of bypassing it at startup. This is helpful for testing purposes until you change the CONFIG.SYS file permanently. To select this option, press and release F8 as soon as the "Starting MS-DOS..." message appears. Each line in CONFIG.SYS will be displayed for confirmation. Press Y to execute or N to bypass. After CONFIG.SYS is read, you will be prompted to run AUTOEXEC.BAT in its entirety or to bypass it. Multiple Configurations You can create multiple configurations within the same CONFIG.SYS and AUTOEXEC.BAT files. If there isn't enough memory to load the TSRs and drivers for all the applications in a PC, or if one TSR or driver conflicts with another, users typically set up separate CONFIG.SYS and AUTOEXEC.BAT files to run different sets of software. In order to activate them before DOS 6, the current CONFIG.SYS and AUTOEXEC.BAT are renamed and the required set is given those names. DOS 6 lets you place multiple configurations in CONFIG.SYS and in AUTOEXEC.BAT and prompts you for your choice at startup. To do this, create a menu in CONFIG.SYS that defines two or more configuration blocks. The following example simulates stand-alone and network versions of CONFIG.SYS. The optional text "Select this for..." next to the MENUITEM= lines is used by DOS as the menu option at startup. If no text is placed to the right of the line, then the name of the configuration block is used as the menu option. The menu and configuration block headers must be enclosed in left and right brackets ([ ]).  [menu]  menuitem=nonet Select this for no network.  menuitem=net Select this for network.  menudefault=nonet,5 <- default to "nonet" in 5 seconds if no choice made [nonet]  <- configuration block "nonet"  device=c:\driver1.sys <-statements that pertain  device=c:\driver2.sys <-to "nonet"   [net]  <- configuration block "net"  device=c:\netdrivr.sys   [common]  <- common configuration block  files=40    <-statements that pertain  buffers=20 <-to all configurations  etc.  You may use an include= line in a configuration block that includes all the items in another configuration block. Important! Be sure to put the [common] configuration block last as many install programs add lines to the CONFIG.SYS file. CONFIGURING AUTOEXEC.BAT You can create multiple configurations in AUTOEXEC.BAT, but they must correspond to the CONFIG.SYS configuration blocks. To do this, add the goto %config% line at the end of all common statements in AUTOEXEC.BAT; for example:   all common lines in AUTOEXEC.BAT goto %config%  :nonet <- be sure to use colon all statements for "nonet"  goto end  :net  all statements for "net"  goto end :end <- last line in AUTOEXEC.BAT DOS Subst External command that creates a virtual drive and provides a shortcut for referencing long path names. For example, to reference C:\KAREN\BUDGETS with drive K:, type: subst k: c:\karen\budgets If you were in the root, you could display MYFILE by typing: C:\>type k:myfile instead of C:\>type c:\karen\budgets\myfile To cancel the K disk, type: subst k: /d Important! The last drive letter is normally E. See DOS Lastdrive. Do not use Assign, Backup, Chkdsk, Diskcomp, Diskcopy, Fdisk, Format, Join, Label, Recover, Restore and Sys on a virtual drive. DOS switch Code that modifies a command. DOS switches use a forward slash (not backslash) followed by some letter, digit or code. For example, the /w changes the Dir command to list "wide" across the screen instead of in a column: dir /w DOS switching directories See DOS Cd and DOS directories. DOS Sys External command that transfers hidden DOS system files. To make a bootable diskette, copy DOS from the hard disk to a floppy with the Sys command. The COMMAND.COM file must also be copied, which, previous to DOS 5, must be done manually. Starting with DOS 5, COMMAND.COM is copied automatically by the Sys command. Previous to DOS 5 C:\>sys a: copy system Starting with DOS 5 C:\>sys a: copy system C:\>copy command.com a: copy COMMAND.COM DOS is made up of IBMBIO.COM and IBMDOS.COM or IO.SYS and MSDOS.SYS hidden system files along with COMMAND.COM. Hidden files can be listed with the Attrib command starting with DOS 5 or a utility such as Norton's File Attribute program. DOS Sys files DOS extension used with driver programs. See DOS CONFIG.SYS. DOS system file DOS file that contains the fundamental part of DOS (the kernel). See DOS Sys. DOS Task Swapper Starting with DOS 5, you can run multiple applications and switch between them. Do the following: 1. Load DOSSHELL.COM by typing dosshell. 2. To see your active tasks on screen, select Program/File Lists from the View menu (Alt V F). 3. Select Enable Task Swapper from the Options menu (Alt O E). Note: This will stay in effect for future sessions. 4. Run the first program either by selecting Run from the File menu (Alt F R) and typing in the program's name, or by selecting it from the directory list on screen (double click it or highlight and press Enter). After the program is running, press Ctrl-Esc to return to the Shell. You can alternatively put the program into the Active Task List without running it, by selecting the program name from the on-screen directory list and pressing Shift-Enter. 5. Repeat step 4 for each program. 6. To switch between active programs, hold down the Alt key and press Tab until you see the name of the program you want at the top of the screen. Then release Alt. To switch between the two last programs, press Alt-Tab. You can also select a program from the Active Task List at the bottom of the Shell screen. There are a variety of ways to switch between active tasks. Look up Keyboard, Active Task List Keys from the Shell's Help menu. DOS text file Text file that does not contain any proprietary coding schemes. Batch files and source language programs are examples. It contains only ASCII characters and has a CR/LF (carriage return/line feed) code at the end of each line. Text files are read by text editors as well as word processors with "ASCII" or "text" input options. DOS Time/Date Internal commands that set the system time and date and update the internal battery-powered clock. Versions previous to 3.3 do not set the internal clock. A separate setup program is used. time display time time 14:30 set to 2:30pm date display date date 12-11-92 set to 12-11-92 TO UPDATE A FILE'S TIME AND DATE To give a file a current time and date without changing it, use the Copy command. For example, to update XYZ.BAT, type: copy /b xyz.bat+,, Be sure to add the plus, comma, comma after the file name. The /b ensures that no change is made to the file. DOS Tree External command that displays a list of the subdirectories in the current directory. To display a directory tree, type: tree To display files names and subdirectories, type: tree /f DOS tutorial See DOS abc's. DOS Type Internal command that displays the contents of text files. To display the contents of XYZ.BAT, type: type xyz.bat Type lets you view only text files (batch files). If garbage appears on screen, the file is a program or data file, not straight text. To print the file, redirect Type's output to the printer: type xyz.bat > prn DOS Undelete Prior to DOS 5, bringing a file back that has just been deleted requires an undelete utility such as found in Symantec's Norton Utilities, Central Point's PC Tools or Fifth Generation's Mace Utilities. Starting with DOS 5, an undelete command is provided. For example, to restore VITAL.TXT after having deleted it, type the following and follow the prompts: undelete vital.txt If you don't mention a file name, Undelete will undelete all deleted files, prompting you one at a time. DELETE TRACKER Starting with DOS 5, the Delete Tracker option provides an extra level of protection in case you have to undelete a file. This is activated with the Mirror command. If you use DOS 5, see DOS Mirror. If you use DOS 6, read the following. In DOS 6, Delete Tracker is activated with the Undelete command. It's not as much protection as Delete Sentry (see below), but you would use this if you have little room left on your hard disk. Tracker takes up 13K of RAM and creates hidden MIRORSAV.FIL and PCTRACKR.DEL files. To automatically load Tracker on startup, place the command in your AUTOEXEC.BAT file. The following example tracks drives C and D:  undelete /tc /td USE DELETE SENTRY FOR MAXIMUM PROTECTION In DOS 6, the Delete Sentry intercepts the files you delete and actually moves them to a hidden \SENTRY directory, renaming them with coded file names. Sentry will purge (really remove) the files after seven days or when 20% of the hard disk is used up with deleted files and it needs room for more newly-deleted files. Sentry also creates a hidden CONTROL.FIL file in the \SENTRY directory. Like Tracker, Sentry will take up 13K or RAM. To automatically load Sentry on startup, place the command in your AUTOEXEC.BAT file. The following example activates Sentry for drives C and D: undelete /sc /sd If you must remove Tracker or Sentry from memory, type: undelete /u EDITING UNDELETE.INI The first time Sentry is loaded, it creates an UNDELETE.INI configuration file in the \DOS directory that can be edited with a text editor. To change the drives Sentry intercepts, you can add or delete DRIVELETTER= lines. For example, to bypass protection on floppy drives, delete the A= or B= lines. To change when Sentry purges deleted files from seven to four days, change days=7 to days=4. To change the maximum amount of space Sentry uses to hold deleted files from 20% to 10%, change percentage=20 to percentage=10. UNDELETE.INI excludes certain types of files from being intercepted, such as temporary files. It also excludes .IMG files. If you work with .IMG files and want protection for them, remove -*.IMG, from the sentry.files= line. You may wish to exclude other types of files; for example, .BAK files. To exclude .BAK files, add ,-*.BAK to the end of the sentry-files= line. Once UNDELETE.INI is created, you can also load Sentry with undelete /s or undelete /load. For Windows Users A Windows version of Undelete is included with DOS 6 called MWUNDEL.EXE. This is run from an icon in Windows, which is installed in the Microsoft Tools Program Group. If you're in Windows, use MWUNDEL.EXE first. It also lets you undelete directories, which you cannot do with Undelete for DOS. However, if you cannot undelete a file with MWUNDEL.EXE under Windows, go to the DOS prompt and try to undelete it with Undelete. DOS Unformat External command starting with DOS 5 that restores a formatted disk to its previous contents, providing it was formatted under DOS 5 without the /S switch. The /S switch bypasses saving unformat information during the format process (see DOS Format). Unformatting is not guaranteed. However, you can find out if you can unformat the disk before doing it. For example, to test the disk in drive A, type: unformat a: /test To unformat the disk in drive A, type: unformat a: /u Also see DOS Mirror for additional ways Unformat is used in data recovery. DOS upgrading Starting with DOS 5, Microsoft provides upgrade packages that make it easy to upgrade a PC that has a previous version of DOS installed on it. The install program records data on "uninstall" disks during the conversion. If the new version doesn't work properly, you can revert to the previous one. To install the DOS 5 or DOS 6 upgrade: 1. Start computer as usual. 2. Have one blank high-density floppy or two blank low-density floppies handy (formatted or unformatted). 3. Insert disk 1 into drive A or B. 4. Type a:setup or b:setup. DOS upper memory See UMA and UMB. DOS/V Japanese version of DOS that supports two-byte-long characters for handling the Kanji character set. It can switch between English and Japanese and is geared for 286s and up with VGA graphics. Backed by IBM Japan and the OADG. In Japan, NEC is the major personal computer vendor with its PC-9801 series. DOS VDISK.SYS See DOS RAM disks. DOS Ver Internal command that displays the DOS version. Type: ver DOS Verify Internal command that tests each write operation by reading it back. verify on turn on verify off turn off verify display status DOS versions Like most software, DOS improves with age: Version Major new features  1.0 1981 8-sector 160KB floppy (SS). 1.05 Bug fix. 1.1 1982 8-sector 320KB floppy (DS). 2.0 1983 10M hard disk, 9-sector 360KB floppy, directories, more batch commands. 2.1 1983 PCjr cartridge support and bug fixes. 3.0 1984 20MB hard disk, 1.2MB floppy, VDISK, PATH, new commands. 3.1 1985 Network support, bug fixes. 3.2 1986 720KB floppy, new commands. 3.3 1987 1.44MB floppy, FDISK partitions. 4.0 1988 Menu and mouse support (DOS shell), improved commands, EMS support, 512MB hard disks. 4.01 1988 Bug fix (4.0 rarely used). 5 1991 Major upgrade: new DOS shell, ability to use high memory, task swapping, online help, new text editor, 2GB hard disks, 2.88MB floppies, enhanced commands. 6 1993 Includes built in disk compression and various utilities for antivirus, backup, undelete and file transfer. DOS Vol Internal command that displays the name of the current drive (volume). Type: vol DOS Vsafe See DOS MSAV. DOS/VSE See VSE. DOS wild cards Wild cards are symbols that let you reference groups of related files. As in card games, wild cards take on any value. DOS wild cards are the "*" and "?." The Asterisk (*) The asterisk takes the value of any number of characters; for example, if you typed in: dir gloss* GLOSS1, GLOSS10 and GLOSSARY files would be selected: To delete all files with a TXT extension, type: del *.txt To delete all the files in the current directory, type: del *.* The Question Mark (?) The question mark matches any single character. For example, ?GLOSS would find 1GLOSS, 2GLOSS and XGLOSS. Note that *GLOSS is not valid for this. To copy CHP files that begin with CO, type: copy CO*.CHP a: To list files that begin with CO and have an extension that begins with D, type: dir CO*.D* Tip! The dot is a shortcut for *.*. The following commands both copy all files to the B drive: copy *.* b:  copy . b: DOS Xcopy External command starting with DOS 3.2 that copies files and subdirectories. The following examples copy from the root directory on C to the D drive: C:\>xcopy *.* d: all files in the root C:\>xcopy *.* d: /s all files and subdirectories that contain files C:\>xcopy *.* d: /s /e all files and all subdirectories (whether empty or not) To be prompted each time Xcopy copies a source file, add /p: xcopy *.* d: /s /e /p To be extra sure the copy is correct, add the /v switch, which compares the new file with the old one; for example: xcopy *.* d: /v Xcopy can copy files and create a new directory at the same time. The following example creates the NEW directory and copies all the files from the OLD directory: C:\OLD>xcopy *.* \new Use Xcopy's /m switch to back up only files that have been changed since the last time they were Xcopied. The following example backs up all files onto the B disk: xcopy *.* b: /m Note! In versions previous to DOS 5, Xcopy copies hidden and system files. Starting with DOS 5, you must remove the hidden and system attributes with Attrib first. DOS \ See DOS backslash. DOSmark Unit of performance based on Ziff-Davis' PC Labs tests. It rates a PC's ability to run DOS applications, which is a composite of CPU, memory, disk and video tests. See Winmark. Dosshell See DOS shell. dot (1) Tiny round, rectangular or square spot that is one element in a matrix, which is used to display or print a graphics or text image. See dot matrix. (2) A period; for example, V dot 22 is the same as V.22. dot addressable Ability to program each individual dot on a video display, dot matrix printer or laser printer. dot chart Same as scatter diagram. dot gain Increase in size of each dot of ink when printed due to temperature, ink and paper type. dot matrix Pattern of dots that form character and graphic images on video screens and printers. Display screens use a matrix (rows and columns) of dots just like TVs. Serial printers use one or two columns of dot hammers that are moved across the paper. Laser printers "paint" dots of light a line at a time onto a light-sensitive photographic drum. The more dots per square inch, the higher the resolution of the characters and graphics. dot matrix printer Printer that forms images out of dots. The common desktop dot matrix printer uses one or two columns of dot hammers that are moved serially across the paper. The more dot hammers used, the higher the resolution of the printed image. 24-pin dot matrix printers produce typewriter-like output. dot pitch Distance between a red (or green or blue) dot and the closest red (or green or blue) dot on a color monitor (typically from .28 to .51mm; large presentation monitors may go up to 1.0mm). The smaller the dot pitch, the crisper the image. A .28 dot pitch means dots are 28/100ths of a millimeter apart. A dot pitch of .31 or less provides a sharp image, especially on text. Dot pitch measurements between conventional tubes and Sony's Trinitron tubes are roughly, but not exactly equivalent. Sony's CRTs use vertical stripes, not dots, and its measurement is the distance between stripes, not the diagonal distance between dots. double buffering Programming technique that uses two buffers to speed up a computer that can overlap I/O with processing. For example, data in one buffer is being processed while the next set of data is read into the second buffer. double click To press the mouse button twice in rapid succession. double density Twice the capacity of the prior format. Yesterday's double density can be today's low density (see DD). double dots See DOS ... double precision Using two computer words instead of one to hold a number used for calculations, thus allowing twice as large a number for more arithmetic precision. Contrast with single precision. double scan CGA Hardware circuit that improves CGA resolution. double sided disk Floppy disk that is recorded on both of its sides. double strike Printing a character twice in order to darken the image. double twist Same as supertwist. double word Twice the length of a single computer word. A double word is typically 32 bits long. See word. DoubleSpace Realtime compression technique built into DOS 6. See DOS DoubleSpace. down Refers to a computer that fails to operate due to hardware or software failure. A communications line is down when it is unable to transfer data. downlink Communications channel from a satellite to an earth station. Contrast with uplink. download To transmit a file from one computer to another. When conducting the session, download means receive, upload means transmit. It implies sending a block of data rather than interacting in a conversational mode. downloadable font Same as soft font. downsizing Converting mainframe and mini-based systems to personal computer LANs. downtime Time during which a computer is not functioning due to hardware or system software failure. That's when you truly understand how important it is to have reliable hardware. downward compatible Also called backward compatible. Refers to hardware or software that is compatible with earlier versions. Contrast with upward compatible. DP See data processing and dot pitch. DPCM (Differential PCM) Audio digitization technique that codes the difference between samples rather than coding an absolute measurement at each sample point. See ADPCM. dpi (Dots Per Inch) Measurement of printer resolution. A 300 dpi printer means 90,000 dots are printable in one square inch (300x300). 400 dpi generates 160,000 dots; 500 dpi yields 250,000 dots. DPMA (Data Processing Management Assn.) Membership organization founded in 1951 with over 40,000 managers of DP installations, programmers, systems analysts and research specialists. It founded the CDP examinations, now administrated by ICCP. Offers many educational programs and seminars, in addition to sponsoring student organizations around the country interested in DP. Address: 505 Busse Highway, Park Ridge, IL 60068, 312/825-8124. DPMI (DOS Protected Mode Interface) DOS extender specification for 286s and up that allows DOS extended programs to cooperatively run under Windows 3.x. Developed by Microsoft, it keeps a DOS-extended application from crashing the computer and usurping Windows' control. It is not compatible with VCPI, the first DOS extender standard, but Windows 3.1 is more tolerant of VCPI applications than Windows 3.0. DPPX (Distributed Processing Programming EXecutive) Operating system for the 8100, now defunct. DPPX/370 is a version allowing users to migrate to 9370s. DPS Minicomputer series from Bull HN. DPSK (Differential Phase Shift Keying) Common form of phase modulation used in modems. It does not require complex demodulation circuitry and is not susceptible to random phase changes in the transmitted waveform. Contrast with FSK. DR DOS (Digital Research DOS) DOS-compatible operating system from Novell noted for its many features. Version 5.0 includes built-in help, passwords, disk cache, file transfer, the ability to store itself and drivers in high memory and an optional graphical interface. Version 6.0 includes file compression that doubles hard disk space. Drafix 2-D and 3-D CAD packages for PCs and Atari STs from Foresight Resources Corp., Kansas City, MO. It features professional functions and provides constant on-screen information during drawing. draft mode Highest-speed, lowest-quality printing mode. drag To move an object on screen in which its complete movement is visible from starting location to destination. The movement may be activated with a stylus, mouse or keyboard keys. drag & drop Ability to execute a function graphically without typing in a command. For example, in the Macintosh, selecting a floppy disk icon and dragging it onto the trashcan icon causes the floppy to be ejected. drag lock Ability to lock onto a screen object so that it can be dragged with the mouse without continuously holding down the mouse (or trackball) button. drain Output (receiving) side of the bridge in a field effect transistor. When the gate is charged, current flows from the source to the drain. Same as collector in a bipolar transistor. DRAM See dynamic RAM. DRAW (Direct Read After Write) Reading data immediately after it has been written to check for recording errors. drawing program Graphics software that allows the user to design and illustrate products and objects. It maintains an image in vector graphics format, which allows all elements of the graphic object to be isolated and manipulated individually. Drawing programs and CAD programs are similar; however, drawing programs usually provide a large number of special effects for fancy illustrations, while CAD programs provide precise dimensioning and positioning of each graphic element in order that the objects can be transferred to other systems for engineering analysis and manufacturing. Contrast with paint program. DRDA (Distributed Relational Database Architecture) SAA-compliant enhancement that allows data to be distributed among DB2 and SQL/DS databases. Users or programs can access data from SAA or non-SAA systems that implement DRDA. DRDBMS (Distributed Relational DBMS) Relational DBMS that manages distributed databases. See distributed database. DRI See Digital Research. dribbleware Software that is publicly displayed and previewed well in advance of its actual release. Dribbleware is one stage beyond vaporware. drift Change in frequency or time synchronization of a signal that occurs slowly. drill down To move from summary information to the detailed data that created it. drive (1) Electromechanical device that spins disks and tapes at a specified speed. Also refers to the entire peripheral unit such as disk drive or tape drive. (2) To provide power and signals to a device. For example, "this control unit can drive up to 15 terminals." drive bay Slot for a disk drive in a computer cabinet. drive door Panel, gate or lever used to lock a disk in a disk drive. In a 5.25" floppy drive, the drive door is the lever that is turned down over the slot after inserting the disk. drive type See hard disk. driver (1) Also called a device driver, a program routine that links a peripheral device or internal function to the operating system. It contains the precise machine language necessary to activate all device functions and includes detailed knowledge of its characteristics, such as sectors per track or the number of pixels of screen resolution. Basic drivers come with the operating system, and drivers are added when new peripheral devices are installed. For example, if you add a mouse or CD ROM player to your personal computer, you have to install the appropriate driver so that the operating system knows how to handle it. In the DOS world, applications provide their own screen and printer drivers in order to provide complete control over the display and printing of a document. Memory managers, RAM disks and disk caches are also activated by drivers. See DOS CONFIG.SYS. (2) Device that provides signals or electrical current to activate a transmission line or display screen. See line driver. drop cap In typography, a large first letter that drops below the first line, for example:  栩栩 his is an example  of a drop cap in  printing.  drop-down menu See pull-down menu. drop in Extraneous bit on a magnetic medium that was not intentionally written, due to a surface defect or recording malfunction. drop out (1) On magnetic media, a bit that has lost its strength due to a surface defect or recording malfunction. (2) In data transmission, a momentary loss of signal that is due to system malfunction or excessive noise. droupie (Data gROUPIE) Person who likes to spend time in the company of programmers and data processing professionals. drum See magnetic drum. drum plotter Graphics plotter that wraps the paper around a drum. The drum turns to produce one direction of the plot, the pen moves to provide the other. drum printer Line printer that uses formed character images around a cylindrical drum as its printing mechanism. There is a band of characters for each print position. When the desired character for the selected print position has rotated around to the hammer line, the hammer hits the paper from behind and pushes it into the ribbon and onto the character. dry plasma etching Method for inscribing a pattern on a wafer by shooting hot ions through a mask to evaporate the silicon dioxide insulation layer. Dry plasma etching replaces the wet processing method that uses film and acid for developing the pattern. drystone See Dhrystone. DS (Digital Signal) Speed measurements: DS-0 64Kbps DS-1 1.544Mbps (T1) DS-1C 3.152Mbps DS-2 6.312Mbps (T2) DS-3 44.736Mpbs (T3) DS-4 274.176Mpbs (T4) DS/DD (Double Sided/Double Density) Refers to floppy disks, such as the 5.25" 360KB PC format and 3.5" 720KB PC and 800KB Mac formats. DS/HD (Double Sided/High Density) Refers to floppy disks, such as the 5.25" 1.2MB PC format and 3.5" 1.44MB PC and Mac formats. DSA (1) (Distributed Systems Architecture) Bull HN network architecture. (2) (Directory Systems Agent) X.500 routine that looks up the location of a message recipient. It accepts requests from the Directory User Agent counterpart in the workstation. (3) (Digital Storage Architecture) Disk controller standard from Digital. (4) (Digital Signal Analyzer) Tektronix oscilloscope that samples high-frequency signals. DSP See digital signal processing. DSR (Data Set Ready) RS-232 signal sent from the modem to the computer or terminal indicating that it is able to accept data. Contrast with DTR. DSS (1) (Decision Support System) Information and planning system that provides the ability to interrogate computers on an ad hoc basis, analyze information and predict the impact of decisions before they are made. DBMSs let you select data and derive information for reporting and analysis. Spreadsheets and modeling programs provide both analysis and "what if?" planning. However, any single application that supports decision making is not a DSS. A DSS is a cohesive and integrated set of programs that share data and information. A DSS might also retrieve industry data from external sources that can be compared and used for historical and statistical purposes. An integrated DSS directly impacts management's decision-making process and can be a very cost- beneficial computer application. See EIS. (2) (Digital Signature Standard) National Security Administration standard for authenticating an electronic message. See RSA and digital signature. DSTN (Double SuperTwisted Nematic) LCD display that uses an extra display layer (compensating layer) between the main display and the rear polarizer, resulting in an almost-pure black and white display with little color tinge. DSU/CSU (Data Service Unit/Channel Service Unit) Pair of communications devices that connect an inhouse line to an external digital circuit (T1, DDS, etc.). The CSU terminates the external line at the customer's premises and provides signal regeneration and remote testing. The DSU provides buffering and flow control between the customer's internal line and the CSU. The DSU/CSU is similar to a modem, but connects a digital circuit rather than an analog one. DTA (Design and Test Alliance) Group of ATE, EDA, chip makers and systems houses dedicated to improving testing of complicated electronic systems. DTE (Data Terminating Equipment) Communications device that is the source or destination of signals on a network. It is typically a terminal or computer. Contrast with DCE. DTP See desktop publishing. DTR (Data Terminal Ready) RS-232 signal sent from the computer or terminal to the modem indicating that it is able to accept data. Contrast with DSR. DTS (1) (Digital Termination Service) Microwave-based, line-of-sight communications provided directly to the end user. (2) (DeskTop Server) Motorola 68000-based network server from Banyan. (3) (Developer Technical Support) Tech-support group for developers at Apple. DUA (Directory User Agent) X.500 routine that sends a request to the Directory Systems Agent to look up the location of a user on the network. dual boot Computer that can be started with either one of two different operating systems. dual in-line package See DIP. dumb terminal Display terminal without processing capability. It is entirely dependent on the main computer for processing. Contrast with smart terminal and intelligent terminal. dump To print the contents of memory, disk or tape without any report formatting. See memory dump. duplex channel See full-duplex. duplexed system Two systems that are functionally identical. They both may perform the same functions, or one may be standby, ready to take over if the other fails. duplicate keys Identical key data in a file. Primary keys, such as account number cannot be duplicated, since no two customers or employees should be assigned the same number. Secondary keys, such as date, product and city, may be duplicated in the file or database. DVE (Digital Video Effects) Video effects such as fades, wipes, dissolves, page flips, and iris and funnel effects performed by computer. DVI (Digital Video Interactive) Intel compression technique for data, audio and full-motion video. On a CD ROM, it provides up to 72 minutes of full- screen video, 2 hours of half-screen video, 40,000 medium-resolution or 7,000 high-resolution images. It compresses full-motion video at ratios greater than 100 to 1 and still images at 10 to 1. Split screen capabilities allow still and moving images side by side. For example, a training course could show an operation taking place along with pictures of the components being used. DVI uses standard storage devices, but requires a DVI controller board in the personal computer. Developed by RCA's Sarnoff Research labs in Princeton, Intel acquired it in 1988. Software-only versions of DVI are also forthcoming. See CD, CD ROM, CD-I. Dvorak keyboard Keyboard layout designed in the 1930s by August Dvorak, Univ. of Washington, and his brother-in- law, William Dealey. 70% of words are typed on the home row compared to 32% with qwerty, and, more words are typed using both hands. In eight hours, fingers of a qwerty typist travel 16 miles, but only one for the Dvorak typist.  Qwerty  52% Q W E R T Y U I O P    32%  A S D F G H J K L ; '   16%  Z X C V B N M , . /   Dvorak   22%   ' , . P Y F G C R L ?   70%   A O E U I D H T N S -    8%   ; Q J K X B M W V Z  DVST (Direct View Storage Tube) Early graphics screen that maintained an image without refreshing. The entire screen had to be redrawn for any change. DX See 386 and 486. DX2 See 486. DXF AutoCAD 2-D graphics file format. Many CAD systems import and export the DXF format for graphics interchange. dyadic Two. Refers to two components being used. dye diffusion See thermal dye diffusion. dye polymer recording Optical recording technique that uses dyed plastic layers as the recording medium. A single dye polymer layer is used in some WORM devices. Erasable optical disks use two dyed plastic layers, a top retention layer and a bottom expansion layer. A bit is written by shining a laser through the retention layer onto the expansion layer, which heats the area and forms a bump that expands into the retention layer. The retention layer bumps are the actual bits read by the unit. To erase a bit, another laser (different wavelength) strikes the retention layer and the bump subsides. dynamic Refers to operations performed while the program is running. The expression, "buffers are dynamically created," means that space was created when actually needed, not reserved beforehand. dynamic address translation In a virtual memory system, the ability to determine what the real address is at the time of execution. dynamic binding Linking a routine or object at runtime based on the conditions at that moment. See polymorphism. dynamic compression Ability to compress and decompress data in realtime; for example, as it's being written to or read from the disk. dynamic link Connection established at runtime from one program to another. dynamic link library Executable routines available to applications at runtime. They are typically written in reentrant code so they can serve more than one application at the same time. dynamic network services Realtime networking capabilities, such as adaptive routing, automatically reconfiguring the network when a node is added or deleted and the ability to locate any user on the network. dynamic RAM Most common type of computer memory, also called D- RAM ("dee-RAM") and DRAM. It usually uses one transistor and a capacitor to represent a bit. The capacitors must be energized hundreds of times per second in order to maintain the charges. Unlike firmware chips (ROMs, PROMs, etc.) both major varieties of RAM (dynamic and static) lose their content when the power is turned off. Contrast with static RAM. In memory advertising, dynamic RAM is often erroneously stated as a package type; for example, "DRAMs, SIMMs and SIPs on sale." It should be "DIPs, SIMMs and SIPs," as all three packages typically hold dynamic RAM chips. dynamic range Range of signals from the weakest to the strongest. dynamic SQL SQL statements interpreted by the SQL database at runtime. Dynamic SQL may be generated by programs or entered interactively by the user. Contrast with embedded SQL. dynlink See dynamic link. E See exponent. e-beam See electron beam. e-disk (Emulated-disk) Same as RAM disk. e-mail See electronic mail. E-time See execution time. E1 European counterpart to T1, which transmits at 2.048 Mbits/sec. EAM (Electronic Accounting Machine) Same as tabulating equipment. early binding Assigning types in the compilation phase. See binding time. EAROM (Electrically Alterable ROM) Same as EEPROM. earth station Transmitting/receiving station for satellite communications. It uses a dish-shaped antenna for microwave transmission. easy to learn and use Easy to learn refers to software that is well designed and capable of being used right away. If you make the program work with little problem, it's easy to learn. Easy to learn implies easy to use right away, but it does not imply easy to use after you're familiar with it. The menus that coddled you in the beginning can become tiresome when used constantly. Advanced programs have a macro recorder that lets you store a series of menu selections and execute them automatically. EasyCAD 2 Full-featured PC CAD program from Evolution Computing, Tempe, AZ, that is known for its ease of use. EasyCAD users can migrate to FastCAD, which looks almost identical on screen, but provides multiple windows and is designed for high-speed operations. EBCDIC (Extended Binary Coded Decimal Interchange Code) Pronounced "eb-suh-dick." IBM data code originating with System/360, used in its mainframes and most midrange computers. It is an 8-bit code (256 combinations) that stores one alphanumeric character or two decimal digits in a byte. EBCDIC and ASCII are the two codes most widely used to represent data. EBCDIC chart 浜様様様様様様様様様様様様様様様様様様様様様様様融 EBCDIC Extended Binary Coded Decimal Interchange Code 00 Null 40 (3) 80 C0 { 01 Start of heading 41 (4) 81 a C1 A 02 Start of text 42 82 b C2 B 03 End of text 43 83 c C3 C 04 Select 44 84 d C4 D 05 Horizontal Tab 45 85 e C5 E 06 Required New Line 46 86 f C6 F 07 Delete 47 87 g C7 G 08 Graphic Escape 48 88 h C8 H 09 Superscript 49 89 i C9 I 0A Repeat 4A 8A CA (5) 0B Vertical Tab 4B . 8B CB 0C Form Feed 4C < 8C CC 0D Carriage return 4D ( 8D CD 0E Shift out 4E + 8E CE 0F Shift in 4F 8F CF 10 Data link escape 50 & 90 D0 } 11 Device control 1 51 91 j D1 J 12 Device control 2 52 92 k D2 K 13 Device control 3 53 93 l D3 L 14 Rest/Enable Pres 54 94 m D4 M 15 New Line 55 95 n D5 N 16 Backspace 56 96 o D6 O 17 Prog/Oper Comm 57 97 p D7 P 18 Cancel 58 98 q D8 Q 19 End of medium 59 99 r D9 R 1A Unit Backspace 5A ! 9A DA 1B Customer Use 1 5B $ 9B DB 1C File Separator 5C 9C DC 1D Group Separator 5D ) 9D DD 1E Record Separator 5E ; 9E DE 1F (1) 5F 朕 9F DF 20 Digit Select 60 - A0 E0 \ 21 SOS 61 / A1 ~ E1 (6) 22 Field Separator 62 A2 s E2 S 23 Word Underscore 63 A3 t E3 T 24 (2) 64 A4 u E4 U 25 Line Feed 65 A5 v E5 V 26 End Trans Block 66 A6 w E6 W 27 Escape 67 A7 x E7 X 28 Set Attribute 68 A8 y E8 Y 29 Start Field Ext. 69 A9 z E9 Z 2A Set Mode/Switch 6A | AA EA 2B Ctrl Seq Prefix 6B , AB EB 2C Modify Field Atr 6C % AC EC 2D Enquiry 6D - AD ED 2E Acknowledge 6E > AE EE 2F Bell 6F ? AF EF 30 70 B0 F0 0 31 71 B1 F1 1 32 Synchronous Idle 72 B2 F2 2 33 Index Return 73 B3 F3 3 34 Pres Position 74 B4 F4 4 35 Transparent 75 B5 F5 5 36 Numeric Backspace 76 B6 F6 6 37 End of Trans 77 B7 F7 7 38 Subscript 78 B8 F8 8 39 Indent Tab 79 ` B9 F9 9 3A Required Frm Feed 7A : BA FA 3B Customer Use 3 7B # BB FB 3C Device Ctrl 4 7C @ BC FC 3D Negative Ack 7D ' BD FD 3E 7E = BE FE 3F Substitute 7F " BF FF (7) 藩様様様様様様様様様様詫様様様溶様様様様詫様様様夕 (1) Bypass/Inhibit Presentation (2) Intermediate Trans Block/ Interchange Unit Separator (3) Space (4) Required Space (5) Syllable Hyphen (6) Numeric Space (7) Eight Ones EBL (Extended Batch Language) Shareware programming language by Frank Canova that allows for more complex programming in DOS batch files. ECF (Enhanced Connectivity Facilities) IBM software that allows DOS PCs to query and download data from mainframes as well as issue mainframe commands. It also allows printer output to be directed from the PC to the mainframe. It uses the SRPI interface and resides in the PC (client) and mainframe (server). Applications issue SRPI commands to request services. echo (1) Same as echoplex. (2) DOS and OS/2 screen command that displays messages and turns off/on screen responses. See DOS batch file. echo cancellation High-speed modem technique that isolates and filters out unwanted signals caused by echoes from the main transmitted signal. This permits full- duplex modems to send and receive on the same frequency. Telephone networks often use echo cancellers in addition to or in place of echo suppressors. Network-based echo cancellation can interfere with modems that do their own, such as V.32, so a method is provided for those modems to disable network echo cancellers. echo check In communications, an error checking method that retransmits the data back to the sending device for comparison with the original. echo suppressor Communications technique that turns off reverse transmission in a telephone line, thus effectively making the circuit one way. It is used to reduce the annoying effects of echoes in telephone connections, especially in satellite circuits. echoplex Communications protocol that transmits the received data back to the sending station allowing the user to visually inspect what was received. ECL (Emitter-Coupled Logic) Variety of bipolar transistor that is noted for its extremely fast switching speeds. ECLIPSE Series of 32-bit minicomputers from Data General. The development of the initial 32-bit ECLIPSE MV/Family supermini, the MV/8000, was the subject of Tracy Kidders' best selling book, "Soul of a New Machine." ECMA (European Computer Manufacturers Assn.) Organization devoted to international standards. Address: Rue du Rhone 114, CH-1204 Geneva, Switzerland. ED (1) (Extra High Density) Refers to 2.88M floppy disks. (1) (EDitor) Early UNIX line editor that contained functionality later incorporated into vi. EDA (1) (Electronic Design Automation) Using the computer to design and simulate the performance of electronic circuits on a chip. See ATE. (2) (EDA/SQL) (Enterprise Data Access/SQL) Software from Information Builders, Inc., New York, that provides a common interface between a wide variety of SQL programs and SQL databases. It also allows queries on data from different types of databases at the same time. (3) (Electronic Document Authorization) Authorizing certificates used to identify public keys for encrypting data under the RSA method. edge connector Row of etched lines on the edge of a printed circuit board that is inserted into an expansion slot. EDI (Electronic Data Interchange) Electronic communication of transactions between organizations, such as orders, confirmations and invoices. Independent service organizations provide EDI services that enable users to interconnect with another organization's network regardless of type of equipment used. See X12, Tradacoms and EDIFACT. EDIFACT (Electronic Data Interchange For Administration Commerce and Transport) ISO standard for EDI that is proposed to supersede both X12 and Tradacoms standards to become the worldwide standard. edit To make a change to existing data. See update. edit checking Same as validity checking. edit instruction Computer instruction that formats a field for display or printing. Using an edit mask, it inserts decimal points, commas and dollar signs into the data. edit key Key combination or function key that changes the program into edit mode when pressed. edit mask Pattern of characters that represent formatting codes through which data is filtered for display or printing. See picture. edit mode Operational state in a program that allows existing data to be changed. edit program (1) Data entry program that validates user input and stores the newly created records in the file. (2) Program that allows users to change data that already exists in a file. See update. edit routine Routine in a program that tests for valid data. See validity checking. editable PostScript File of PostScript commands that can be edited by a word processor or other program. This allows PostScript documents to be changed without requiring the use of the application that originally created it. editor See text editor and linkage editor. Edlin Archaic text editor used in DOS. The OS/2 counterpart is SSE. See DOS Edlin. EDP (Electronic Data Processing) First name used for the computer field. education Teaching concepts and perspectives. Computer education includes computer systems and information systems. Contrast with training. edutainment Entertaining educational material. EE See Extended Edition. EEMS See EMS. EEPROM (Electrically Erasable Programmable Read Only Memory) Memory chip that holds its content without power. It can be erased, either within the computer or externally and usually requires more voltage for erasure than the common +5 volts used in logic circuits. It functions like non-volatile RAM, but writing to EEPROM is slower than writing to RAM. EEPROMs are used in devices that must keep data up-to-date without power. For example, a price list could be maintained in EEPROM chips in a point of sale terminal that is turned off at night. When prices change, the EEPROMs can be updated from a central computer during the day. eesa See EISA and ESA/370. EFF (Electronic Frontier Foundation) Organization founded in 1990 by Mitchell Kapor and John Perry Barlow dedicated to raising public awareness of the opportunities and challenges posed by computing and telecommunications. Address: 155 Second St., Cambridge, MA 02141, 617/864-0665. EFT (Electronic Funds Transfer) Transfer of money from one account to another by computer. EGA (Enhanced Graphics Adapter) IBM video display standard that provides medium-resolution text and graphics. It supports previous display modes and requires a digital RGB Enhanced Color Display or equivalent monitor. EGA has been superseded by VGA. See PC display modes. EGP (Exterior Gateway Protocol) Gateway protocol that broadcasts TCP/IP IP addresses to the gateway of another self-contained network. EIA (Electronic Industries Assn.) Membership organization founded in 1924 as the Radio Manufacturing Assn. It sets electronic interface standards and sponsors shows and seminars. In 1984, the TIA (Telecommunications Industry Assn.) became part of EIA. Address: 2001 Pennsylvania Ave., N.W., Washington, DC 20006, 202/457-4900. EIA-232 See RS-232. EIA-422, 423, 449 See RS-422, 423, 449 EIA-485 See RS-485. EIA-568 EIA standard for telecommunications wiring in a commercial building. EIS (Executive Information System) Information system that consolidates and summarizes ongoing transactions within the organization. It should provide management with all the information it requires at all times from internal as well as external sources. See DSS. EISA (Extended ISA) Pronounced "e-suh." PC bus standard that extends the AT bus (ISA bus) to 32 bits and provides bus mastering. It was announced in 1988 as a 32-bit alternative to the Micro Channel that would preserve investment in existing boards. PC and AT cards (ISA cards) can plug into an EISA slot. EL See electroluminescent. electricity Flow of electrons in a circuit. The speed of electricity is the speed of light (approx. 186,000 miles per second). In a wire, it is slowed due to the resistance in the material. Its pressure, or force, is measured in volts and its flow, or current, is measured in amperes. The amount of work it produces is measured in watts (amps X volts). electrode Device that emits or controls the flow of electricity. electroluminescent Flat panel display that provides a sharp, clear image and wide viewing angle. It contains a powdered or thin film phosphor layer sandwiched between an x-axis and a y-axis panel. When an x-y coordinate is charged, the phosphor in that vicinity emits visible light. Phosphors are typically amber, but green is also used. electrolyte In a rechargeable battery, the material that allows electricity to flow from one plate to another by conducting ions. electromagnet Magnet that is energized by electricity. A coil of wire is wrapped around an iron core. When current flows in the wire, the core generates an energy called magnetic flux. electromagnetic radiation Energy that exists in all things, including humans, which incorporates cosmic rays, gamma rays, x-rays, ultraviolet light, visible light, infrared light and radar. electromagnetic spectrum Range of electromagnetic radiation. electromechanical Use of electricity to run moving parts. Disk drives, printers and motors are examples. Electromechanical systems must be designed for the eventual deterioration of moving parts. electromotive force Pressure in an electric circuit measured in volts. electron Elementary particle that circles the nucleus of an atom. Electrons are considered to be negatively charged. electron beam Stream of electrons, or electricity, that is directed towards a receiving object. electron gun Device which creates a fine beam of electrons that is focused on a phosphor screen in a CRT. electron tube Same as vacuum tube. electronic Use of electricity in intelligence-bearing devices, such as radios, TVs, instruments, computers and telecommunications. Electricity used as raw power for heat, light and motors is considered electrical, not electronic. Although coined earlier, "Electronics" magazine (1930) popularized the term. The magazine subheading read "Electron Tubes - Their Radio, Audio, Visio and Industrial Applications." The term was derived from the electron (vacuum) tube. electronic circuit See circuit and digital circuit. electronic mail Transmission of memos and messages over a network. Users can send mail to a single recipient or broadcast it to multiple users. Sophisticated systems prompt recipients for a reply if they haven't responded within a certain time frame. With multitasking workstations, mail can be delivered and announced while the user is working in an application. Otherwise, mail is sent to a simulated postal box in the network server or host computer, which must be interrogated. The fax machine has become the most universal electronic mail today, showing the power of a common standard. However, it isn't called e-mail as the text cannot be edited at the other end without scanning and using text recognition software. See X.400, X.500 and EDI. Electronic Mail Assn. Membership organization founded in 1983 with over 250 vendor and user companies involved in electronic messaging and information exchange. Concerns include marketing e-mail within the corporation, privacy, security, interconnection and standards. Address: 1555 Wilson Blvd., Suite 300, Arlington, VA 22209, 703/875-8620. Electronic Message Service See EMS (2). electronic messaging Same as electronic mail. electronic printer Printer that uses electronics to control the printing mechanism, such as a laser printer and certain line printers. electronic publishing Providing information in electronic form to readers or subscribers of the service. See information utility and videotex. electronic switch On/off switch activated by electrical current. electronic typewriter See memory typewriter and word processing. electrophotographic Printing technique used in copy machines and laser printers. A negative image made of dots of light is painted onto a photosensitive drum or belt that has been electrically charged. The light comes from a laser, LEDs or liquid crystals that shutter a light source. Wherever light is applied, the drum becomes uncharged. A toner (dry ink) is applied and adheres to the charged areas of the drum. The drum transfers the toner to the paper, and pressure and heat fuse the toner and paper permanently. Some electrophotographic systems use a positive approach in which the toner is attracted to the laser-produced latent image. electrosensitive printer Dot matrix printer that burns away dots on the outer silver coating of a special black paper. electrostatic Stationary electrical charges in which no current flows. electrostatic plotter Plotter that uses a special paper that is charged as it passes by a line of electrodes. Toner is then applied to the charged paper. Models print in in black and white or color, and some handle paper up to six feet wide. electrostatic printer Same as electrostatic plotter. elegant program Program that is simple in design, uses the least amount of memory and runs fast. ELF (Extemely Low Frequency) See low radiation. elite Typeface that prints 12 cpi. em In typography, a unit of measure equal to the width of the capital letter M in a particular font. EMA (1) (Enterprise Management Architecture) Digital's stategic plan for integrating network, system and application management. It provides the operating environment for managing a multi-vendor network. (2) See Electronic Mail Assn. EMACS (Editor MACroS) UNIX text editor developed at MIT that is used for writing programs. It provides a wide variety of editing features including multiple windows. embedded command (1) Command inserted within text or other codes. (2) In word processing, a command within the text that directs the printer to change fonts, print underline, boldface, etc. The command is inserted when the user selects a layout change. Commands are often invisible on screen, but can be revealed if required. Embedded commands in a document are proprietary to the word processor used. When a document is printed, the text is copied to a temporary file, and the embedded commands are converted into printer commands for the printer. When printing is finished, the temporary file is erased. See print to disk. embedded SQL SQL statements written into a high-level language source program, such as C or Pascal. In a separate compiling phase, the SQL may be optimized and converted into special function calls. Contrast with dynamic SQL. embedded system Specialized computer used to control a device such as an automobile, appliance or space vehicle. Operating system and application functions are often combined in the same program. Emerald Bay PC database engine from Ratliff Software Productions, Inc., Montrose, CA, that is designed to interface with different languages. Introduced in 1988 and written by Wayne Ratliff (dBASE II), it provides a binary field that can store any type of information. EMI (ElectroMagnetic Interference) Electromagnetic waves that eminate from an electrical device. It often refers to both low-frequency waves from electromechanical devices and high-frequency waves (RFI) from chips and other electronic devices. Allowable limits are governed by the FCC. emitter Supply of current in a bipolar transistor. Same as source in a MOS transistor. emitter-coupled logic See ECL. EMM (Expanded Memory Manager) Software that manages expanded memory (EMS). In XTs and ATs, expanded memory boards must also be used. In 386s and up, the EMM converts extended memory into EMS. EMM386 See DOS EMM386.EXE. emoticon (EMOTional ICON) In e-mail, expressing emotion by typing character combinations. The following examples are viewed sideways. :) original smiley face :-) smile :-( frown ;-) wink :-D big smile :-O mouth open in amazement :-Q tounge hanging out in nausea :-{) smile (user has moustache) :-{)} moustache and beard 8-) smile (user wears glasses) (-: smile (user left handed or Australian) :*) red nosed smile, suggesting inebriation *<|:{)} Santa Claus! @:{)=== sikh with turban and long beard EMS (1) (Expanded Memory Specification) Technique for increasing memory in DOS PCs. EMS Version 4.0 allows DOS to work with up to 32MB of extra memory by bank switching 16K segments of EMS memory, known as the "page frame," into conventional memory. In XTs and ATs, EMS is installed by plugging in an EMS memory board and adding an EMS driver. In 386s and up, EMS is created by expanded memory manager (EMM) software that turns extended memory into EMS. In order to use EMS, the application is either written to use it directly (Lotus 1-2-3 Ver. 2.x, AutoCAD, etc.) or the application is run in an environment that uses it, such as DESQview. In 1984, Lotus, Intel and Microsoft introduced EMS (LIM EMS), which allowed up to 8MB of EMS memory. By Version 3.2, it was widely-supported, but limited to one 64K page frame (four 16K pages) only in the UMA (640K-1M region). AST, Quadram and Ashton-Tate later introduced Enhanced EMS (EEMS), letting the page frame take the full 1M address space (64 16K pages), allowing programs such as DESQview to multitask large applications within conventional memory. In 1987, Lotus, Intel and Microsoft introduced Version 4.0, increasing memory to 32MB and incorporating the EEMS standard.  Extended  Memory   -----団陳1M陳陳陳  UMA 敖陳陳陳陳陳陳陳   Range 咳臼臼臼臼臼営朕 EMS memory  of page frame  DOS 青陳臼臼臼臼臼臼   団陳640K陳陳調 Circuits on  the EMS board  User remap the  Conv. Memory requested EMS  Memory area into the  page frame,  which DOS  can address.  青陳陳陳陳陳陳陳  -----青陳0K陳陳陳  Expanded versus Extended Expanded memory (EMS) and extended memory are not the same. EMS can be installed in XT-class machines and up, whereas extended memory requires at least a 286. EMS broke the 1MB memory barrier in the early days, however, now that 286s are the low-end CPU, extended memory is finally being utilized due to the widespread use of Windows 3.x and DOS-extended applications. See "Operating Environment" in the PC definition. For an excellent, detailed book on EMS, extended memory and more, read "DOS Beyond 640K," 2nd Ed., by James Forney, ISBN 0-8306-3744-3. (2) (Electronic Message Service) Part of the radio spectrum assigned to electronic messaging over digital satellite circuits. EMS emulator Before the 386, it referred to a driver for 8086/88s and 286s that simulated EMS memory in extended memory or disk. It is slower than an EMS board that provides high-speed bank switching, because the emulator copies data within memory or between memory and disk. Since the 386, it refers to a memory manager (EMM) that runs in 386s and up and creates EMS out of extended memory. Technically, the 386 is really not emulating anything. The 386 can map any memory to any other memory, thus it is merely mapping memory according to the EMS specification. EMS memory manager See EMM and EMS emulator. emulation mode Operational state of a computer when it is running a foreign program under emulation. emulator Device that is built to work like another. A computer can be designed to emulate another model and execute software that was written to run in the other machine. A terminal can be designed to emulate various communications protocols and connect to different networks. The emulator can be hardware, software or both. en In typography, a unit of measure equal to one half the width of an em. An en is typically the width of one numeric digit. enable To turn on. Contrast with disable. Enable/OA Integrated software package for PCs from Enable Software, Inc., Ballston Lake, NY. It is noted for being a very comprehensive package rivaling many stand-alone programs. Version 4.0 also runs under UNIX. Encapsulated PostScript PostScript file format that contains PostScript code for the document as well as optional preview images in TIFF, Windows Metafile or Macintosh PICT formats. The PostScript code drives a PostScript printer directly, and the preview formats allow the image to be manipulated on screen. DOS and OS/2 files use an EPS extension. encapsulation (1) In object-oriented programming, making the data and processing private within an object, which allows it to be modified without causing problems elsewhere in the program. (2) In communications, inserting the frame header and data from a higher level protocol into the data frame of a lower level protocol. encipher To encode data for security purposes. See encryption. encode (1) To assign a code to represent data, such as a parts code. (2) Same as encipher or encrypt. encryption Encoding data for security purposes by converting it into a proprietary code. To be used, it must be decoded. It is used to transmit documents over a network or to encode data so that it cannot be easily changed with common software. See DES. end key Keyboard key commonly used to move the cursor to the bottom of the screen or file or to the next word or end of line. end points In vector graphics, the two ends of a line (vector). In 2-D graphics, each end point is typically two numbers representing coordinates on x and y axes. In 3-D, each end point is made up of three numbers representing coordinates on x, y and z axes. end user Same as user. end user computing Using personal computers. endian See big endian. endless loop Series of instructions that are constantly repeated. It can be caused by an error in the program or it can be intentional; for example, a screen demo on continuous replay. endnote See footnote. engine (1) Specialized processor, such as a graphics processor. Like any engine, the faster it runs, the quicker the job gets done. (2) Software that performs a primary and highly repetitive function such as a database engine, graphics engine or dictionary engine. (3) Slang for processor. engineering cylinder See diagnostic tracks. engineering drawing sizes A - 8 1/2 x 11 B - 11 x 17 C - 17 x 22 D - 22 x 34 E - 34 x 44 Enhanced keyboard IBM 101-key keyboard that superseded the PC and AT keyboards. It has a separate cursor key cluster located between the original numeric/cursor keypad and the letter keys. enhancement Any improvement made to a software package or hardware device. ENIAC (Electronic Numerical Integrator And Calculator) First operational electronic digital computer developed for the U.S. Army by John Eckert and John Mauchly at the Univ. of Pennsylvania. Completed in 1946, it was decimal-based, used 18,000 vacuum tubes, took up 1,800 square feet and performed 5,000 additions/second. enquiry character In communications, a control character that requests a response from the receiving station. enter key See return key. enterprise data Centralized data that is shared by many users throughout the organization. enterprise model Model of how an organization does business. Information systems are designed from this model. enterprise network Geographically-dispersed network under the jurisdiction of one organization. It often includes several different types of networks and computer systems from different vendors. entity In a database, anything about which information can be stored; for example, a person, concept, physical object or event. Typically refers to a record structure. entity relationship model In a database, a data model that describes attributes of entities and the relationships among them. entity type In a database, a particular kind of file; for example, a customer or product file. entropy In data compression, a measure of the amount of non-redundant, non-compressible information in an object. entry Input of an item or set of items at a terminal. See data entry. entry point In programming, the starting point of the instructions in a subroutine. enumerate To count or list one by one. An enumerated data type defines a list of all possible values for a variable, and no other value can then be placed into it. envelope (1) Range of frequencies for a particular operation. (2) Group of bits or items that is packaged and treated as a single unit. environment Computer configuration that includes the CPU model and system software (operating system, data communications and database systems). It may also include the programming language used. It sets the standards for the applications that run in it. The term often refers only to the operating system; for example, "This program is running in a UNIX environment." environment variable See DOS Set. EOF (End Of File) File status when its end has been reached or when an instruction or command resets the file pointer to the end. EOL (End Of Line) EOM (End Of Message) EOT (End Of Transmission) epitaxial layer In chip making, a semiconductor layer that is created on top of the silicon base rather than below it. See molecular beam epitaxy. epoch date Starting point from which time is measured as the number of days, minutes, etc., from that time. EPP (1) (Enhanced Parallel Port) Standard that provides fast parallel port transfer, up to 2Mbytes/sec. It is built into the 386SL chip set. (2) (Ethernet Packet Processor) Chip from Kalpana, Inc., Santa, Clara, CA, that doubles speed of Ethernet transmission to 20Mbits/sec. EPROM (Erasable Programmable ROM) Reusable PROM chip that holds its content until erased under ultraviolet light. See PROM programmer. EPS See Encapsulated PostScript. Epson emulation Compatible with Epson dot matrix printers. The command set in the Epson MX, RX and FX printers has become an industry standard. Useful codes are: ASCII VALUE COMMAND 12 Form feed 27 48 8 LPI 27 50 6 LPI 15 Condensed on 18 Condensed off 27 81 1 Double width on 27 81 0 Double width off 27 69 Emphasized on 27 70 Emphasized off 27 83 1 Subscript on 27 83 0 Superscript on 27 84 Sub/super off 27 45 1 Underline on 27 45 0 Underline off EPSS (Electronic Performance Support System) Computer system that provides quick assistance and information without requiring prior training to use it. It may incorporate all forms of multimedia delivery as well as AI techniques such as expert systems and natural language recognition. EQ (EQual to) See relational operator. equalization In communications, techniques used to reduce distortion and compensate for signal loss (attenuation) over long distances. equation Arithmetic expression that equates one set of conditions to another; for example, A = B + C. In a programming language, assignment statements take the form of an equation. The above example would assign the sum of B and C to the variable A. ER model See entity relationship model. ERA (Electrically Reconfigurable Array) Programmable logic chip (PLD) technology from Plessey Semiconductor that allows the chip to be reprogrammed electrically. erase See delete. erase head In a magnetic tape drive, the device that erases the tape before a new block of data is recorded. ergonomics Science of people-machine relationships. An ergonomically-designed product implies that the device blends smoothly with a person's body or actions. Erlang Unit of traffic use that specifies the total capacity or average use of a telephone system. One Erlang is equivalent to the continuous usage of a telephone line. Traffic in Erlangs is the sum of the holding times of all lines divided by the period of measurement. error checking (1) Testing for accurate transmission of data over a communications network or internally within the computer system. See parity checking and CRC. (2) Same as validity checking. error control Same as error checking. error detection & correction See error checking and validity checking. error-free channel Interface (wire, cable, etc.) between devices that is not subject to external interference; specifically not the dial-up telephone system. error handling Routines in a program that respond to errors. The measurement of quality in error handling is based on how the system informs the user of such conditions and what alternatives it provides for dealing with them. error rate Measurement of the effectiveness of a communications channel. It is the ratio of the number of erroneous units of data to the total number of units of data transmitted. ES See expert system. ES/3090 High-end IBM mainframe that incorporates the ESA/370 enhancements. ES/9000 IBM System/390 computer line introduced in late 1990 that uses 31-bit addressing with maximum memory capacities from 256MB to 9GB. It's 18 models (Model 120 to Model 900) introduced the widest range of power in a single series at one time with prices ranging from $70K to $23M. Vector processing is optional on high-end water-cooled and certain air-cooled models. See System/390. ESA/370 (Enterprise System Architecture/370) IBM enhancements that increase the performance of high- end 4381 and 3090 mainframes. Introduced in 1988, it increases virtual memory from 2GB to 16TB and adds techniques for managing it more effectively. This architecture is built into System/390 ES/9000 computers. ESA/390 (Enterprise System Architecture/390) Extensions to ESA/370 for System/390 series. It includes MVS/ESA, VM/ESA and VSE/ESA operating systems. Esc See escape character and escape key. escape character Control character often used to precede other characters to control a printer or other device. For example, escape, followed by &l10, sets the LaserJet to landscape mode. In ASCII, escape is decimal 27, hex 1B; in EBCDIC, it is hex 27. escape key Keyboard key commonly used to exit a mode or routine, or cancel some function. escape sequence (1) Machine command that starts with an escape character. Printers are often commanded by escape sequences. See escape character. (2) In a modem, a unique sequence of characters that precedes a command. It allows modem commands (dial, hang up, etc.) to be transmitted with the data. See TIES and Hayes Smartmodem. ESCON (Enterprise Systems CONnection) IBM System/390 fiber optic channel that transfers 10 Mbytes/sec up to 5.6 miles. An ESCON Director is the coupling device that provides 8-16 ports (Model 1) or 28-60 ports (Model 2). ESD (1) (ElectroStatic Discharge) Sparks (electrons) that jump from an electrically-charged object to an approaching conductive object. (2) (Electronic Software Distribution) Installing software by transmitting it to the destination machines over a network. (3) (Entry Systems Division) Personal computer and workstation division within IBM. ESDI (Enhanced Small Device Interface) Hard disk interface that transfers data in the one to three MByte/sec range. ESDI has always been the high- speed interface for small computers, but is now being superseded by IDE and SCSI drives. See hard disk. ESDS (Entry Sequence DataSet) VSAM structure that stores records one after the other without regard to content. Records are retrieved by address. Contrast with KSDS. ESF (1) (Extended SuperFrame) Enhanced T1 format that allows a line to be monitored during normal operation. It uses 24 frames grouped together (instead of the 12-frame D4 superframe) and provides room for CRC bits and other diagnostic commands. (2) (External Source Format) Specification language for defining an application in IBM's CSP/AD application generator. ESP (1) (Enhanced-Service Provider) Organization that adds value to basic telephone service by offering such features as call-forwarding, call-detailing and protocol conversion. (2) (E-tech Speedy Protocol) Proprietary protocol of E-Tech Research used in its modems. (3) (Electronic Still Photography) Digitizing and transmitting images over a telephone line. (4) (Emulex SCSI Processor) Proprietary chip used in Emulex's SCSI disk controller. ESS (1) (Electronic Switching System) Large-scale computer used to switch telephone conversations in a central office. (2) (Executive Support System) See EIS. (3) (Electronic SpreadSheet) See spreadsheet. Ethernet Local area network (LAN) that conforms to the IEEE 802.3 standard, originally developed by Xerox, Digital and Intel. It uses the CSMA/CD access method, transmits at 10Mbps and can connect up to 1,024 nodes in total. Standard Ethernet (also called thick Ethernet) uses a bus topology with a maximum cable segment length of 1,640 ft. without the use of a repeater. Attachment is made to the cable by clamping a transceiver onto it. Thin Ethernet (also called ThinNet and CheaperNet) uses a bus topology with a maximum cable length of 607 feet. Nodes are daisy chained together with T-type BNC connectors as the transceivers are contained within the network adapter cards. Twisted pair Ethernet allows installed telephone wire to be used (if the right type) and Fiber Optic Ethernet is impervious to external radiation. Both use a star topology, which is considered easier to debug as networks expand.  Maximum devices per segment  Maximum segment length  Ethernet type Topology  10Base5 Standard 1,640 ft. 100 bus 10Base2 Thin 607 ft. 30 bus 10BaseT Twisted pair 328 ft. 2 star 10BaseF Fiber Optic 1.3 mi. 2 star An emerging Ethernet standard is Fast Ethernet (10BaseX), which proposes 100Mbits/sec speeds over twisted pair. Details to be ironed out in 1993. EtherTalk Macintosh software from Apple that accompanies its Ethernet Interface NB Card and adapts the Mac to Ethernet networks. Eurocard Family of European-designed printed circuit boards that uses a 96-pin plug rather than edge connectors. The 3U is a 4x6" board with one plug; the 6U is a 6x12" board with two plugs; the 9U is a 14x18" board with three plugs. even parity See parity checking. event driven Application that responds to input from the user or other application at unregulated times. It's driven by choices that the user makes (select menu, press button, etc.). Contrast with procedure oriented. EVGA (Extended VGA) See VGA. Exabyte (Exabyte Corp., Boulder, CO) Maker of high- capacity, proprietary 8mm tape backup systems. Single-tape units are in the 2 to 25GB range, and multi-tape library units can hold terabytes. Excel Full-featured spreadsheet for PCs and the Macintosh from Microsoft. It can link many spreadsheets for consolidation and provides a wide variety of business graphics and charts for creating presentation materials. exception report Listing of abnormal items or items that fall outside of a specified range. exclusive NOR See NOR. exclusive OR See OR. EXE file (EXEcutable file) Runnable program in DOS, OS/2 and VMS. In DOS, if a program fits within 64K, it may be a COM file. executable Program in machine language that is ready to run in a particular computer environment. execute To follow instructions in a program. Same as run. execution time Time in which a single instruction is executed. It makes up the last half of the instruction cycle. executive Same as operating system. exit (1) To get out of the current mode or quit the program. (2) In programming, to get out of the loop, routine or function that the computer is currently in. expanded memory See EMS, EMM and expanded storage. expanded memory emulator Memory manager for 386s and up that converts extended memory into EMS memory. See EMM. expanded storage Auxiliary memory in IBM mainframes. Data is usually transferred in 4K chunks from expanded storage to central storage (main memory). expansion board (1) Printed circuit board that plugs into an expansion slot. (2) See bus extender. expansion bus (1) The computer's bus comprised of a series of receptacles or slots into which expansion boards (video display, disk controller, etc.) are plugged. (2) Sometimes refers to bus extender (3). expansion card Same as expansion board. expansion slot Receptacle inside a computer or other electronic system that accepts printed circuit boards. The number of slots determines future expansion. In personal computers, expansion slots are connected to the bus. ExperLogo Macintosh version of Logo from ExperTelligence, Inc., Goleta, CA. It contains more functions similar to LISP than most versions of Logo. expert system AI application that uses a knowledge base of human expertise for problem solving. Its success is based on the quality of the data and rules obtained from the human expert. In practice, expert systems perform both below and above that of a human. It derives its answers by running the knowledge base through an inference engine, which is software that interacts with the user and processes the results from the rules and data in the knowledge base. Examples of uses are medical diagnosis, equipment repair, investment analysis, financial, estate and insurance planning, vehicle routing, contract bidding, production control and training. See EPSS. 敖陳陳陳陳 敖陳陳陳陳 敖陳陳陳陳 Knowledge Inference User  Base 団陳 Engine 団陳Interface 青陳陳陳陳 青陳陳陳陳 青陳陳陳陳 If-then-else Forward chain Ability to ask rules Backward chain questions, get input and explain rationale for answer   Expert System  expireware Software with a built-in expiration date, either by date or number of uses. explode (1) To break down an assembly into its component pieces. Contrast with implode. (2) To decompress data back to its original form. exponent Number written above the line and to the right of a number that indicates the power of a number, or how many zeros there are in it. For example 10 to the 3rd power indicates three zeros. The number 467,000 can be stated as 467 x 10 to the 3rd. On a screen or printout, the number is expressed as 467E3. See floating point. exponential growth Extremely fast growth. On a chart, the line curves up rather than being straight. Contrast with linear. exponential smoothing Widely-used technique in forecasting trends, seasonality and level change. Works well with data that has a lot of randomness. export To convert a data file in the current application program into the format required by another application program. expression In programming, a statement that describes data and processing. For example, VALUE=2*COST and PRODUCT="HAT" AND COLOR="GRAY". extended application DOS application that runs in extended memory under the control of a DOS extender. extended ASCII Second half of the ASCII character set (128 through 255). The symbols are defined by ANSI, by IBM for the PC (see ASCII chart or hex chart) and by other vendors for proprietary uses. It is non-standard ASCII. Extended Edition IBM version of OS/2 that includes communications and database management. The Communications Manager has built-in LU 6.2 and X.25 protocols. The Database Manager uses IBM's SQL. extended maintenance On-call service that is ordered for periods in addition to the primary period of maintenance. extended memory In Intel 286s and up, standard memory above one megabyte. Extended memory is used directly by Windows and OS/2 as well as DOS applications that run with DOS extenders. It is also used under DOS for RAM disks and disk caches. Contrast with expanded memory (EMS), which is specialized memory above one megabyte. Memory boards can usually be set up as a mix of the two. See EMS, XMS and DOS extender. extender See bus extender. extensible Capable of being expanded or customized. For example, with extensible programming languages, programmers can add new control structures, statements or data types. extension DOS and OS/2 file category added to the end of the file name with a dot. An extension can have up to three letters or digits. Executable files use .EXE, .COM and .BAT extensions; for example, GLOSS.EXE is the software program for the DOS version of this Glossary. All programs and most data files use extensions. However, some word processing files do not, in which case you could create your own filing system; for example, CHAP1.NOV and CHAP2.NOV could be chapters in a novel.  敖 File extension  Type of file ABC Glossary configuration AD After Dark image AFM Windows Type 1 font metrics AI Adobe Illustrator graphics ARC ARC, ARC+ compressed ASM Assembly source code BAK Backup BAS BASIC source code BAT DOS, OS/2 batch file BIN Driver, overlay BMP Windows & OS/2 bitmap C C source code CAL Windows calendar CAL SuperCalc spreadsheet CAP Ventura Pub. captions CDR Corel Draw vector graphics CFG Configuration CGM CGM vector graphics CHP Ventura Pub. chapter CHK DOS Chkdsk chained file CIF Ventura Pub. chapter info. COB COBOL source code CLP Windows clipboard COM Executable program CPI DOS code page CPP C++ source code CSV Comma delimited CUT Dr. Halo graphics DAT Data DB Paradox table DBF dBASE database DBT dBASE text DCA IBM text DCT Dictionary DIB Device independent BMP DIC Dictionary DIF Spreadsheet DLL Dynamic link library DOC Document (Multimate, Word...) DOX MultiMate V4.0 document DPI Pointline raster graphics DRV Driver DRW Micrografx Designer vector graphics DWG & DXF AutoCAD vector formats EPS Encapsulated PostScript EXE Executable program FAX Group 3 fax FDX Force index FLC, FLI AutoDesk animation FMT dBASE Screen format FNT Windows font FON Font or telephone no. FOR FORTRAN source code FOT Windows TrueType font info. FOX FoxBase compiled program FRM dBASE report layout GCA IBM MO:DCA graphics GED Arts & Letters graphics GEM GEM vector graphics GIF CompuServe raster graphics GRF Micrografx Charisma vector graphics GRP Windows ProgMan Group GX1 & GX2 Show Partner raster graphics HLP Help text HPL HP Graphics language HYC WordPerfect hypen list ICA IBM MO:DCA raster graphics ICO Windows icons IDX FoxBase index IL Icon library (hDC Computer) IMG GEM Paint raster graphics INF Information INI Initialization JT JT Fax LBL dBASE label LBM Deluxe Paint graphics LIB Function library LZH LHARC compressed MAC MacPaint raster MAP Linkage editor map MET OS/2 Metafile MEU Menu items MDX dBASE IV multi-index MID MIDI sound file MSP Microsoft Paint raster graphics NDX dBASE index NG Norton Guides text OAZ OAZ Fax OBJ Object module OVL Overlay module OVR Overlay module PAS Pascal source code PCL HP LaserJet PCM LaserJet cartridge info. PCT PC Paint raster and Mac PICT format PCW PC Write document PCX PC Paintbrush raster graphics PDF Printer driver PDV PC Paintbrush printer driver PFA Type 3 font PFB Type 1 font PFM Windows Type 1 font metrics PGL HPGL graphics PIC Vector vector formats: Lotus 1-2-3, Micrografx Draw, Mac PICT format IBM Storyboard raster format PIF Windows info. for DOS programs, IBM Picture Interchange PM PageMaker graphics/text PMx PageMaker document (x=ver.) PTx PageMaker template (x=ver.) PRD Word printer driver PRG dBASE source code PRN XyWrite printer driver PRN Temporary print file PRS WordPerfect printer driver PRT Formatted text PS PostScript page description QLC ATM font info. RAS Sun raster graphics RIB Renderman graphics RIC Roch FaxNet RIX RIX virtual screen RLE Compressed RTF Microsoft text/graphics R8P LaserJet portrait font R8L LaserJet landscape font SAM Ami Pro document SBP IBM Storyboard vector graphics SC Paradox source code SCx ColoRIX raster (x=res.) SCR dBASE screen layout SCR Script SCT Lotus Manuscript screen capture text SET Setup parameters SFP LaserJet portrait font SFL LaserJet landscape font SFS PCL 5 scalable font SLD AutoCAD slide SND Aristosoft sound SPD Speedo scalable font STY Ventura Pub. style sheet SYL SYLK format (spreadsheets) SYS DOS, OS/2 driver TAL Adobe Type Align shaped text TDF Speedo typeface definition TFM Intellifont font metrics TIF TIFF raster graphics TMP Temporary TTC TrueType font compressed TTF TrueType font TXT ASCII text USP LaserJet portrait font USL LaserJet landscape font VGR Ventura Pub. chapter info. VOC Sound Blaster sound VUE dBASE relational view WAV Windows sound WKQ Quattro spreadsheet WKS Lotus 1-2-3 ver. 1a spreadsheet WK1 Lotus ver. 2.x WK3 Lotus ver. 3.x & Windows WMF Windows Metafile WPG WordPerfect vector graphics WPM WordPerfect macro WRI Windows Write document WRK Sympohony spreadsheet XFX JetFax XLS Excel spreadsheet XLC Excel chart ZIP PKZIP compressed ZOO Zoo compressed $$$ Temporary extent Contiguous space on a disk reserved for a file or application. external command (1) In DOS and OS/2, a function performed by a separate utility program that accompanies the operating system. (2) A user-developed HyperCard command. See XCMD. external interrupt Interrupt caused by an external source such as the computer operator, external sensor or monitoring device, or another computer. external modem Self-contained modem that can be connected to the serial port of any computer. It gets its power from a wall outlet. Contrast with internal modem. external reference In programming, a call to a program or function that resides in a separate, independent library. external sort Sort program that uses disk or tape as temporary workspace. Contrast with internal sort. external storage Storage outside of the CPU, such as disk and tape. f See farad. F connector Coaxial cable connector used to connect antennas, TVs and VCRs. It is easily recognized: the plug's inner wire is stripped bare and sticks out of the connector looking very unfinished. F keys See function keys. facilities management Management of a user's computer installation by an outside organization. All operations including systems, programming and the datacenter can be performed by the facilities management organization on the user's premises. facsimile See fax. factorial Number of sequences that can exist with a set of items, derived by multiplying the number of items by the next lowest number until 1 is reached. For example, three items have six sequences (3x2x1=6): 123, 132, 231, 213, 312 and 321. fail safe Same as fault tolerant. fail soft Ability to fail with minimum destruction. For example, a disk drive can be built to automatically park the heads when power fails. Although it doesn't correct the problem, it minimizes destruction. FAMOS (Floating gate Avalanche-injection Metal Oxide Semiconductor) Type of EPROM. fan-fold paper Same as continous forms. fan in To direct multiple signals into one receiver. fan out To direct one signal into multiple receivers. far pointer In an Intel x86 segmented address, a memory address that includes both segment and offset. Contrast with near pointer. farad Unit of electrical charge that is used to measure the storage capacity of a capacitor. In microelectronics, measurements are usually in microfarads or picofarads. Fast Asynchronous communications protocol used to quickly transmit files over high-quality lines. Error checking is done after the entire file has been transmitted. Fast Eddy Code name for Apple/Sony devlopment of a consumer- oriented CD ROM product that connects to the TV, similar to CD-I and CDTV. Fast Fourier Transform Class of algorithms used in digital signal processing that break down complex signals into elementary components. FastCAD Full-featured PC CAD program from Evolution Computing, Tempe, AZ, known for its well-designed user interface. It requires a math coprocessor. Users with less sophisticated requirements can start out with FastCAD's baby brother, EasyCAD. FastDisk Windows 3.1 driver that accesses the hard disk directly to improve performance. See WinDisk. FAT See DOS FAT. fatal error Condition that halts processing due to read errors, program bugs or anomalies. FatBits MacPaint option in the "Goodies" menu that lets a user edit an image a pixel at a time. father file See grandfather, father, son. fault tolerant Continous operation in case of failure. A fault tolerant system can be created using two or more computers that duplicate all processing, or having one system stand by if the other fails. It can also be built with redundant processors, control units and peripherals architecturally integrated from the ground up (Tandem, Stratus, etc.). Fault tolerant operation requires backup power in the event of power failure. It may also imply duplication of systems in disparate locations in the event of natural catastrophe or vandalism. fax (FACSimile) Originally called telecopying, it is the communication of a printed page between remote locations. Fax machines scan a paper form and transmit a coded image over the telephone system. The receiving machine prints a facsimile of the original. A fax machine is made up of a scanner, printer and modem with fax signalling. Groups 1 and 2, used in the 1970s and 1980s, transmit at six and three minutes per page respectively. Group 3 transmits up to 9,600 baud using data compression at less than one minute per page. This speed increase led to the extraordinary rise in usage in the late 1980s, resulting in today's most universal form of electronic mail. Group 3 resolution is 203x98 dpi in standard mode and 203x196 dpi in fine mode. Higher-speed Group 4 machines rely on all-digital (ISDN) networks which may not be prevalent until the mid 1990s. fax board Fax transmission on an expansion board. It uses software that generates fax signals directly from disk files or the screen and transmits a sharper image than a fax machine, which gets its image by scanning. Incoming faxes are printed on the computer's printer. fax/modem Combination fax board and data modem available as an external unit or expansion board. It includes a fax switch that routes the call to the fax or the data modem. fax switch Device that tests a phone line for a fax signal and routes the call to the fax machine. When a fax machine dials a number and the line answers, it emits an 1,100Hz tone to identify itself. Some devices handle voice, fax and data modem switching and may require keying in an extension number to switch to the modem. FCB See DOS FCB. FCC (Federal Communications Commission) Regulatory body for U.S. interstate telecommunications services as well as international service originating in the U.S. It was created under the U.S. Communications Act of 1934, and its board of commissioners is appointed by the President. FCC Class FCC certification of radiation limits on digital devices. Class A certification is for business use. Class B for residential use is more stringent in order to avoid interference with TV and other home reception. See Part 15, Subpart B, of the Federal Register (CFR 47, Parts 0-19). FCFS First come, first served. fci (Flux Changes per Inch) Measurement of polarity reversals on a magnetic surface. In MFM, each flux change is equal to one bit. In RLL, a flux change generates more than one bit. FD (Floppy Disk) For example, FD/HD refers to a floppy disk/hard disk device. FD:OCA (Formatted Data:Object Content Architecture) SAA- compliant (CCS) specification for formatting data in fields. FDDI (Fiber Distributed Data Interface) ANSI standard token passing LAN that uses optical fiber cabling and transmits at 100 Mbits/sec up to 62 miles. FDDI specifications deal with OSI layers 1 and 2. It provides an optional "dual counter-rotating ring" topology that contains primary and secondary rings with data flowing in opposite directions. If the line breaks, the secondary ring is used to bypass the fault.  栩枋陳陳P陳壷栩 栩枋陳陳P陳壷栩  栩枋陳陳S陳栩 栩枋陳陳S陳栩  崖 崖 崖 崖       崖 崖 崖 崖  栩枋陳陳陳壷栩 栩枋陳 陳壷栩  栩枋陳陳陳壷栩 栩枋陳 陳壷栩  Normal Operation Rerouted  Stations can be configured as Single Attached Stations (SAS) connected to concentrators, or as Dual Attached Stations (DAS), connected to both rings. Groups of stations are typically wired to concentrators connected in a hierarchical tree to the main ring. Large networks may be configured as a "dual ring of trees," in which the dual ring provides the backbone to which multiple hierarchies of concentrators are attached. FDDI provides a quantum leap in speed over Ethernet, Token Ring and other LANs and allows high-resolution graphics and digital video to be quickly transmitted. See CDDI. FDISK See DOS Fdisk. FDM (Frequency Division Multiplexing) Method used to transmit multiple signals over a single channel. Each signal (data, voice, etc.) modulates a carrier with a different frequency and all signals travel simultaneously over the channel. Contrast with TDM. See baseband. FDX See full-duplex. FEA (Finite Element Analysis) Mathematical technique for analyzing stress, which breaks down a physical structure into substructures, called finite elements. The finite elements and their interrelationships are converted into equation form and solved mathematically. Graphics-based FEA software can display the model on screen as it is being built and, after analysis, display the object's reactions under load conditions. Models created in popular CAD packages can often be accepted by FEA software. feasibility study Analysis of a problem to determine if it can be solved effectively. The operational (will it work?), economical (costs and benefits) and technical (can it be built?) aspects are part of the study. Results of the study determine whether the solution should be implemented. feature negotiation See automatic feature negotiation. FEC See forward error correction. federal regulations See NCSC and Computer Security Act. female connector Receptacle into which the male counterpart of the connector is plugged. femtosecond One quadrillionth of a second. See space/time. FEP See front end processor. ferric oxide (Fe2O3) Oxidation of iron used in the coating of magnetic disks and tapes. ferromagnetic Capability of a material, such as iron and nickel, to be highly magnetized. FET (Field Effect Transistor) Type of transistor used in MOS integrated circuits. fetch To locate the next instruction in memory for execution by the CPU. FF See form feed. FFT See Fast Fourier Transform. Fiber Channel Future ANSI standard under development for a high- speed computer channel that incorporates IPI, SCSI and HiPPI command sets. Speeds range from 12.5 to 100 MBytes/sec using coax and optical fiber. fiber optic Communications systems that use optical fibers for transmission. See optical fiber. Fibonacci numbers Series of whole numbers in which each number is the sum of the two preceding ones: 1, 1, 2, 3, 5, 8, 13, etc. It is used to speed up binary searches by dividing the search into the two lower numbers; for example, 13 items would be divided into 5 and 8 items; 8 items would be divided into 5 and 3. fiche Same as microfiche. FidoNet E-mail protocol that originated from the Fido BBS created by Tom Jennings in 1984. Over 10,000 FidoNet nodes are in use. Users must have their networks active for one universal hour in the early morning, and the software must adhere to the FTSC- 001 specification. The FidoNet address format is zone:local net/node; for example, Boardwatch Magazine's address is 1:104/555. field Physical unit of data that is one or more bytes in size. A collection of fields make up a record. A field also defines a unit of data on a source document, screen or report. Examples of fields are NAME, ADDRESS, QUANTITY and AMOUNT DUE. The field is the common denominator between the user and the computer. When you interactively query and update your database, you reference your data by field name. A field is a physical unit of storage, whereas a data item refers to the data itself. For example, the data items, Chicago, Dallas and Phoenix are stored in the CITY field. The terms field, data element, data item and variable refer to the same unit of data and are often used interchangeably. field engineer Person who is responsible for hardware installation, maintentance and repair. Formal training is in electronics, although many people have learned on the job. field name Assigned name for a field (NAME, ADDRESS, CITY, STATE, etc.) that will be the same in every record. field separator Character used to mark the separation of fields in a record. See comma delimited and tab delimited. field service See field engineer. field squeeze In a mail merge, a function that eliminates extra blank spaces between words when fixed-length fields are inserted into the document text. See line squeeze. field template See picture. FIF (Fractal Image Format) Graphics file format from Iterated Systems, Inc., Norcross, GA, that stores fractal images with compression ratios as high as 2,500:1. FIFO (First In-First Out) Storage method that retrieves the item stored for the longest time. Contrast with LIFO. fifth-generation computer Computer designed for AI applications. Appearing in the late 1990s, these systems will represent the next technology leap. file (1) In data management, a collection of related records. (2) In word processing, a single text document. (3) In computer graphics, a set of image descriptors for one picture, either in TV-like format (raster graphics) or in line, or object, format (vector graphics). (4) In programming, the source program and machine language program are stored as individual files. (5) In computer operations, any collection of data that is treated as a single unit on a peripheral device, such as any of the examples in items 1 through 4 above. file and record locking First-come, first-served technique for managing data in a multiuser environment. The first user to access the file or record prevents, or locks out, other users from accessing it. After the file or record is updated, it is unlocked and available. file attribute File access classification that allows a file to be retrieved or erased. Typical attributes are read/write, read only, archive and hidden. file compression See data compression. file conversion. See conversion. file extension See extension. file extent See extent. file format Structure of a file. There are hundreds of proprietary formats for database, word processing and graphics files. See record layout. file layout Same as record layout. file maintenance (1) Periodic updating of master files. For example, adding/deleting employees and customers, making address changes and changing product prices. It does not refer to daily transaction processing and batch processing (order processing, billing, etc.). (2) Periodic reorganization of the disk drives. Data that is continuously updated becomes physically fragmented over the disk space and requires regrouping. An optimizing program is run (daily, weekly, etc.) that rewrites all files contiguously. file manager (1) Software that manages data files. Often erroneously called database managers, file managers provide the ability to create, enter, change, query and produce reports on one file at a time. They have no relational capabilty and usually don't include a programming language. (2) Software used to manage files on a disk. It provides functions to delete, copy, move, rename and view files as well as create and manage directories. file name Name assigned by the user or programmer that is used to identify a file. file protect ring Plastic ring inserted into a reel of magnetic tape for file protection. file protection Preventing accidental erasing of data. Physical file protection is provided on the storage medium by turning a switch, moving a lever or covering a notch. On 1/2" tape, a plastic ring in the center of the reel is removed (no ring-no write). In these cases, writing is prohibited even if the software directs the computer to do so. Logical file protection is provided by the operating system, which can designate a single file as read only. This method allows both regular (read/write) and read only files to be stored on the same disk volume. Files can also be designated as hidden files, which makes them invisible to most software programs. Protecting Floppies 3.5" On the back of the disk (metal door at top), slide the square, plastic window (bottom right) downward uncovering a hole through the disk. 5.25" Cover the side notch with a stick-on label. 8" Remove stick-on label covering the side notch. file recovery program Software that recovers disk files that have been accidentally deleted or damaged. file server High-speed computer in a LAN that stores the programs and data files shared by users on the network. Also called a network server, it acts like a remote disk drive. See database server. file sharing protocol Communications protocol that provides a structure for file requests (open, read, write, close, etc.) between stations in a network. If file sharing is strictly between workstation and server, it is also called a client/server protocol. It refers to layer 7 of the OSI model. file size Length of a file in bytes. See "Byte Specifications" in the term byte. file spec (file SPECification) Reference to the location of a file on a disk, which includes disk drive, directory name and file name. For example, in DOS and OS/2, c:\wordstar\books\chapter is a file spec for the file CHAPTER in the BOOKS subdirectory in the WORDSTAR directory on drive C. file system (1) Method for cataloging files in a computer system. See hierarchical file system. (2) Data processing application that manages individual files. Files are related by customized programming. Contrast with relational database. file transfer protocol Communications protocol that can transmit files without loss of data. It implies that it can handle binary data as well as ASCII data. Common examples are Xmodem, Ymodem, Zmodem and Kermit. file viewer Software that displays the contents of a file as it would be normally displayed by the application that created it. It is usually capable of displaying a variety of common formats. FileMaker II Macintosh file manager from Claris. It is a popular program for general data management and provides a variety of statistical functions, fast search capabilities and extensive reporting features. FileMan (1) Public-domain MUMPS software that provides a stand-alone, interactive DBMS as well as a set of utilities for the MUMPS programmer. (2) Slang for Windows' file manager, which is precisely named "File Manager." filespec See file spec. fill (1) In a paint program, to change the color of a bordered area. (2) In a spreadsheet, to enter common or repetitive values into a group of cells. fill pattern (1) Color, shade or pattern used to fill an area of an image. (2) Signals transmitted by a LAN station when not receiving or transmitting data in order to maintain synchronization. film recorder Device that takes a 35mm slide picture from a graphics file, which has been created in a CAD, paint or business graphics package. It generates very high resolution, typically 2,000 to 4,000 lines. It typically works by recreating the image on a built-in CRT that shines through a color wheel onto the film in a standard 35mm camera. Some units provide optional Polaroid camera backs for instant previewing. Film recorders can be connected to personal computers by plugging in a controller board cabled to the recorder. filter (1) Process that changes data, such as a sort routine that changes the sequence of items or a conversion routine (import or export filter) that changes one data, text or graphics format into another. (2) Pattern or mask through which only selected data is passed. For example, certain E-mail systems can be programmed to filter out important messages and alert the user. In dBASE, set filter to file overdue, compares all data to the matching conditions stored in OVERDUE. financial planning language Language used to create data models and command a financial planning system. financial planning system Software that helps the user evaluate alternatives. It allows for the creation of a data model, which is a series of data elements in equation form; for example, gross profit = gross sales - cost of goods sold. Different values can be plugged into the elements, and the impact of various options can be assessed (what if?). It is a step above spreadsheets by providing additional analysis tools; however, some of these capabilities are being added to spreasheets. For example, sensitivity analysis assigns a range of values to a data element, which causes that data to be highlighted if it ever exceeds that range. Goal seeking provides automatic calculation. For example, by entering gross margin = 50% as well as the minimums and maximums of the various inputs, the program will calculate an optimum mix of inputs to achieve the goal (output). Finder The part of the Macintosh operating system that manages the desktop. It keeps track of icons, controls the Clipboard and Scrapbook and allows files to be copied. Finder manages one application at a time. Multifinder manages multiple applications on screen. fingerprint reader Scanner used to identify a person's fingerprint for security purposes. After a sample is taken, access to a computer or other system is granted if the fingerprint matches the stored sample. A PIN may also be used with the fingerprint sample. finite element See FEA. firmware Category of memory chips that hold their content without electrical power and include ROM, PROM, EPROM and EEPROM technologies. Firmware becomes "hard software" when holding program code. first-generation computer Computer that used vacuum tubes as switching elements; for example, the UNIVAC I. fixed disk Non-removable hard disk such as is found in most personal computers. Programs and data are copied to and from the fixed disk. fixed-frequency monitor Monitor that accepts one type of video signal, such as VGA only. Contrast with multiscan monitor. fixed head disk Direct access storage device, such as a disk or drum, that has a read/write head for each track. Since there is no access arm movement, access times are significantly improved. fixed length field Constant field size; for example, a 25-byte name field takes up 25 bytes in each record. It is easier to program, but wastes disk space and restricts file design. Description and comment fields are always a dilemma. Short fields allow only abbreviated remarks, while long fields waste space if lengthy comments are not required in every record. Contrast with variable length field. fixed length record Data record that contains fixed length fields. fixed point Method for storing and calculating numbers in which the decimal point is always in the same location. Contrast with floating point. Fkey (Function key) Macintosh command sequence using command, shift and option key combinations. For example, Fkey 1 (command-shift 1) ejects the internal floppy. flag (1) In communications, a code in the transmitted message which indicates that the following characters are a control code and not data. (2) In programming, a "yes/no" indicator built into certain hardware or created and controlled by the programmer. flame Slang for communicating emotionally and/or excessively via electronic mail. flash memory Memory chip that holds its content without power, but must be erased in bulk. Originally coined by Toshiba, the term comes from its ability to be erased "in a flash." Derived from EEPROMs, flash memory chips are less expensive and provide higher bit densities. As future designs provide for less-than-whole- chip erasure, and ultimately, byte by byte erasure, flash memory may provide an alternative to current- day RAM. flat address space Memory addressing in which each byte is referenced by a different sequential number starting with 0. Contrast with segmented address space. flat file Stand-alone data file that does not have any pre- defined linkages or pointers to locations of data in other files. The term usually refers to files managed by file managers with no relational capability. In the past, this referred to the very type of file used in relational databases. flat panel display Thin display screen that uses any of a number of technologies, such as LCD, electroluminscent or plasma. Used today in laptops to reduce size and weight, they will eventually supersede CRTs. flat shading In computer graphics, a technique for computing a one-tone shaded surface to simulate simple lighting. flatbed plotter Graphics plotter that draws on sheets of paper that have been placed in a bed. The size of the bed determines the maximum size sheet that can be drawn. flexible disk Same as floppy disk and diskette. flicker Fluctuating image on a video screen. flip-flop Electronic circuit that alternates between two states. When current is applied, it changes to its opposite state (0 to 1 or 1 to 0). Made of several transistors, it is used in the design of static memories and hardware registers. flippy board PC expansion board that connects to both ISA/EISA and Micro Channel buses. ISA/EISA connectors are on one edge of the board, MCA on the other. flippy-floppy Single-sided 5.25" floppy converted to double-sided use by punching a second notch into the disk so that it can be flipped over and inserted upside down. This is not recommended as the disk's rotation is alternated. float In programming, a declaration of a floating point number. floating point Method for storing and calculating numbers in which the decimal points don't line up as in fixed point numbers. The significant digits are stored as a unit called the mantissa, and the location of the radix point (decimal point in base 10) is stored in a separate unit called the exponent. Floating point methods are used for calculating a large range of numbers quickly. Floating point operations can be implemented in hardware (math coprocessor), or they can be done in software. They can also be performed in a separate floating point processor that is connected to the main processor via a channel.  Mantissa Exponent Value  敖陳陳陳賃陳陳陳陳堕陳陳陳陳朕  6508 0 6508  6508 1 65080  6508 -1 650.8  青陳陳陳珍陳陳陳陳祖陳陳陳陳潰   Floating Point  floating point processor Arithmetic unit designed to perform floating point operations. It may be a coprocessor chip in a personal computer, a CPU designed with built-in floating point capabilities or a separate machine, often called an array processor, which is connected to the main computer. floppy disk Reusable magnetic storage medium. It is the primary method for distributing personal computer software. It's also used to transfer data between users, although local area networks can eliminate much of this "sneakernet." Also called a diskette, the floppy is a flexible disk, similar to tape, with both surfaces used for magnetic recording. The disk drive grabs the floppy's center and spins it inside its housing, and the read/write head makes contact with the surface through an opening in the floppy's envelope, case or cartridge. Floppies are much slower than hard disks, because they spin at 300 rpm, a tenth the rotation of a hard disk, and they are at rest until a data transfer is requested. In order of first to last developed, the major types are:  Creator External format Capacity  IBM 8" flexible envelope 100 - 500KB Shugart 5.25" flexible envelope 100KB - 1.2MB Sony 3.5" rigid case 400KB - 4MB + Although floppy disks look the same, what's recorded on them determines their capacity and compatibility. Each new floppy must be "formatted," which records the sectors on the disk that will hold the data. PC, Mac, Apple II, Amiga and Atari formats are different, although most can read and write PC (DOS) diskettes. See format program, Floptical and magnetic disk. FLOPS (FLoating point Operations Per Second) Unit of measurement of floating point calculations. For example, 100 megaflops is 100 million floating point operations per second. Floptical Floppy disk from Insite Peripherals, Inc., San Jose, CA, that records data magnetically, but uses grooves in the disk to optically align the head over the tracks. The first 3.5" Floptical drive uses 21MB diskettes and can also read and write 720KB and 1.44MB diskettes. flow chart Graphical representation of the sequence of operations in an information system or program. Information system flow charts show how data flows from source documents through the computer to final distribution to users. Program flow charts show the sequence of instructions in a single program or subroutine. Different symbols are used to draw each type of flow chart. flow control (1) In communications, the management of data transmission. It ensures that the receiving station can process the data before the next block is sent. (2) In programming, the if-then and loop statements that make up the program's logic. flush To empty the contents of a memory buffer onto disk. flush center In typography, refers to centering text uniformly between the left and right margins as is this paragraph. flush left In typography, the alignment of all text uniformly to the left margin. All text is typically set flush left as is this paragraph. flush right In typography, the alignment of all text uniformly to the right margin while the left margin is set ragged left as is this paragraph. flux Energy field generated by a magnet. FM (1) (Frequency Modulation) Transmission technique that blends the data signal into a carrier by varying (modulating) the frequency of the carrier. See modulate. (2) (Frequency Modulation) Earlier magnetic disk encoding method that places clock bits onto the medium along with the data bits. It has been superseded by MFM and RLL. Fn key (FuNction key) Keyboard key that works like a shift key to activate the second function on a dual-purpose key, typically found on laptops to reduce keyboard size. It is different than the function keys F1, F2, etc. FOCA (Font Object Content Architecture) See MO:DCA. FOCUS (1) DBMS from Information Builders, Inc., New York, that runs on PCs, mainframes and minis. It allows relational, hierarchical and network data structures and can access a variety of databases, including standard IBM mainframe files, DB2, IMS, IDMS and others. It includes a fourth-generation language and a variety of decision support facilities. (2) (Federation On Computing in the U.S.) U.S. representative of IFIP. Address: IEEE Computer Society, 1730 Mass. Ave. N.W., Washington, DC 20036, 202/371-0101. FOIRL (Fiber Optic Inter Repeater Link) IEEE standard for fiber optic Ethernet. folder In the Macintosh, a simulated file folder that holds documents (text, data or graphics), applications and other folders. A folder is like a DOS directory. A folder within a folder is like a DOS subdirectory. Folio (1) Text management software for PCs from Folio Corp., Provo, UT, that provides storage, retrieval and hypertext capability for text databases. It can import text from over 40 file formats. Folio files are called "Infobases." (2) (folio) In typography, a printed page number. For example, folio 3 could be the 27th physical page in a book. font Set of type characters of a particular typeface design and size. Each typeface (Times Roman, Helvetica, etc.) generally includes normal weight and bold, italic and bold italic variations of the typeface, which consitute four fonts. For bitmapped fonts, which include pre-defined bitmaps for each point size, four fonts are required for each point size. For scalable fonts, which create bitmaps in the required size on the fly, only four fonts are required for each typeface. Fonts are either built into the printer or are available as plug-in cartriges or as soft fonts, which reside in the computer. See bitmapped font and scalable font. font cartridge Set of bitmapped or outline fonts for one or more typefaces contained in a plug-in module for the printer. The fonts are stored in a ROM chip within the cartridge. Contrast with soft font and internal font. font characteristics Font selection in an HP LaserJet is made by sending a coded command to the printer with the following criteria:  Code Characteristic Typeface Design (Courier, Times Roman, etc.) Orientation Portrait or landscape Symbol set Country or special characters Spacing Proportional or fixed spacing (width) Pitch Characters per inch (if fixed spacing) Point size Height of characters Style Upright or italic Stroke Light, medium or bold appearance weight font compiler Same as font generator. font editor Software that allows fonts to be designed and modified. font family Set of fonts of the same typeface in assorted sizes, including bold, italic and bold italic variations. font generator Software that converts an outline font into a bitmap (dot pattern required for a particular font size). Font generation is not linear, simply expanding a letter to any size. As fonts get bigger, their characteristics must change in order to make them attractive. Font generation implies creating fonts in advance of printing and storing them on disk. Font scaling implies creating fonts on the fly as needed. See font scaler. font metric Typographic information (width, height, kerning) for each character in a font. font number Identification number assigned to a font. A program references the font by this number. font rasterizer See font scaler. font scaler Software that converts scalable fonts into bitmaps on the fly as required for display or printing. Examples are TrueType, Adobe Type Manager and Bitstream's Facelift. See font generator and scalable font. font style Typeface variation (normal, bold, italic, bold italic). font utility Software that provides functions for managing fonts, including the ability to download, install, design and modify fonts. font weight Thickness of characters (light, medium or bold). Fontware Font generator for PCs from Bitstream Inc., Cambridge, MA, that includes a library of outline fonts. Typeface packages include normal, italic, bold and bold italic weights. foo Popular name for a temporary file, function or variable, or example of same. Often used in conjunction with "bar," from "fubar" (Fouled Up Beyond All Recognition). footer In a document or report, common text that appears at the bottom of every page. It usually contains the page number. footnote Text that appears at the bottom of a page, which adds explanation. It is often used to give credit to the source of information. When accumulated and printed at the end of a document, they are called endnotes. footprint Amount of geographic space covered by an object. A computer footprint is the desk or floor surface it occupies. A satellite's footprint is the earth area covered by its downlink. for statement High-level programming language structure that repeats a series of instructions a specified number of times. It creates a loop that includes its own control information. The following examples print "Hello" 10 times:  BASIC C  for x = 1 to 10 for (x = 0; x < 10; x++)  print "hello" printf ("hello\n");  next x  Force dBASE compiler from Sophco, Inc., Boulder, CO, that combines C and dBASE structures. It is noted for generating very small executable programs. foreground/background Priority assigned to programs running in a multitasking environment. Foreground programs have highest priority, and background programs have lowest. Online users are given the foreground, and batch processing activities (sorts, updates, etc.) are given the background. If batch activities are given a higher priority, terminal response times may slow down considerably. In a personal computer, the foreground program is the one the user is currently working with, and the background program might be a print spooler or communications program. Forest & Trees Data analysis program for PCs from Channel Computing, Inc., Newmarket, NH, that integrates data from a variety of applications. It provides a control room interface that lets users monitor important business information. form (1) Paper form used for printing. (2) Screen display designed for a particular application. form factor Physical size of a device. form feed Advancing a printer form to the top of the next page. It is done by pressing the printer's form feed (FF) button or by sending the form feed code (ASCII 12) to the printer from the computer. form view Screen display showing one item or record arranged like a preprinted form. Contrast with table view. format Structure, or layout, of an item. Screen formats are fields on the screen. Report formats are columns, headers and footers on a page. Record formats are the fields within a record. File formats are the structure of data files, word processing documents and graphics files (display lists and bitmaps) and all associated codes. See format program, disk format, DOS Format and style sheet. format program Software that initializes a disk. There are two formatting levels. The low-level initializes the disk surface by creating the physical tracks and storing sector identification in them. Low-level format programs are geared to the drive technology used (IDE, SCSI, etc.). The high-level format lays out the indexes used by the operating system (Mac, DOS, etc.) to keep track of data stored in the sectors. Floppy disk format programs perform both levels on a diskette. See DOS Format. formula (1) Arithmetic expression that solves a problem. For example, (fahrenheit-32)*5/9 is the formula for converting fahrenheit to centigrade. (2) In spreadsheets, an algorithm that identifies how the data in a specific number of cells is to be calculated. For example, +C3*D8 means that the contents of cell C3 are to be multipled by the contents of cell D8 and the results are to be placed where the formula is located. FORTH (FOuRTH-generation language) High-level programming language created by Charles Moore in the late 1960s as a way of providing direct control of the computer. Its syntax resembles LISP, it uses reverse polish notation for calculations, and it is noted for its extensibility. It is both compiler and interpreter. The source program is compiled first and then executed by its operating system/interpreter. It is used in process control applications that must quickly process data acquired from instruments and sensors. It is also used in arcade game programming as well as robotics and other AI applications. The following polyFORTH example converts Fahrenheit to Celsius:  : CONV ( n) 32 - 5 9 * / . ." Celsius  : USER_INPUT ." Enter Fahrenheit " CONV ;  FORTRAN (FORmula TRANslator) First high-level programming language and compiler, developed in 1954 by IBM. It was originally designed to express mathematical formulas, and although it is used occasionally for business applications, it is still the most widely used language for scientific, engineering and mathematical problems. FORTRAN IV is an ANSI standard, but FORTRAN V has various proprietary versions. The following example converts Fahrenheit to Celsius:  WRITE(6,*) 'Enter Fahrenheit '  READ(5,*) XFAHR  XCENT = (XFAHR - 32) * 5 / 9  WRITE(6,*) 'Celsius is ',XCENT  STOP  END  FORTUNE 500 The following figures are the 1991 and 1992 FORTUNE 500 ranking of computer and electronics firms. Reprinted with permission of FORTUNE Magazine. See vendors and software vendors. (c) 1992-1993 The Time Inc. Magazine Company. All rights reserved.  1 9 9 2 COMPUTERS/OFFICE EQUIPMENT  Sales Profit Employees Rank Company (000,000) (000) 4 IBM 65,096 (4,965) 308 24 Hewlett-Packard 16,427 549 93 27 Digital Equipment 14,027 (2,796) 114 62 Unisys 8,422 361) 54 76 Apple Computer 7,087 530 15 119 Compaq Computer 4,132 213 10 139 Sun Mircosystems 3,628 173 13 144 Pitney Bowes 3,460 100 29 164 Seagate Technology 2,889 63 43 182 Amdahl 2,554 (7) 9 203 Conner Peripherals 2,273 121 13 217 Tandem Computers 2,058 (41) 11 225 Wang Laboratories 1,910 (357) 13 270 Storage Technology 1,521 15 10 315 Intergraph 1,182 8 10 327 Quantum 10,128 47 18 328 Data General 1,127 (63) 7 331 Gateway 2000 1,107 70 18 348 SCI Systems 1,045 4 10 351 Maxtor 1,039 7 8 367 AST Research 951 69 4 370 Western Digital 940 (73) 7 385 Dell Computer 890 51 3 392 Silicon Graphics 867 (118) 4 408 Cray Research 798 (15) 5  TOTAL 146,557 (6,051) 794   1 9 9 2 ELECTRONICS/ELECTRICAL  Sales Profit Employees Rank Company (000,000) (000) 5 General Electric 62,202 4,725 268 32 Motorola 13,341 453 107 35 Westinghouse 12,100 (1,291) 109 43 Rockwell Int'l. 10,995 (1,036) 79 54 Raytheon 9,119 635 64 70 Emerson Electric 7,706 663 69 71 Texas Instruments 7,470 247 61 73 Whirlpool 7,309 205 39 89 Cooper Industries 6,159 (229) 53 90 N. American Philips 6,138 50 43 93 Intel 5,922 1,067 26 95 Litton Industries 5,741 174 50 148 AMP 3,337 290 25 151 Harris 3,042 75 28 157 Maytag 3,041 (315) 21 163 Teledyne 2,891 33 24 165 Loral 2,882 122 22 214 E-Systems 2,099 (69) 19 243 Nat'l Semiconductor 1,726 (120) 27 255 Nat'l Service Ind. 1,634 74 20 257 General Signal 1,623 (83) 14 259 Duracell Int'l. 1,617 128 8 266 Reliance Electric 1,553 26 14 269 Advanced Micro Dev. 1,531 245 12 295 Raychem 1,296 (25) 11 304 Zenith Electronics 1,271 (106) 25 310 Magnetek 1,230 22 16 333 J.M. Huber 1,102 43 7 340 General Instrument 1,076 (53) 9 344 Thomas & Betts 1,057 51 8 354 Pittway 1,019 47 5 364 Sunbeam/Oster 967 48 9 407 Hubbell 800 78 6 415 Molex 782 67 7 455 Vishay Intertechnology 664 30 11 482 LSI Logic 617 (110) 3 490 Harman Int'l Ind. 604 3 5 495 Exide 594 7 5  TOTAL 194,259 6,172 1,326   1 9 9 1 COMPUTERS/OFFICE EQUIPMENT  Sales Profit Employees Rank Company (000,000) (000) 4 IBM 64,792 (2,827) 345 26 Hewlett-Packard 14,541 755 89 28 Digital Equipment 14,024 (617) 121 58 Unisys 8,696 (1,393) 60 81 Apple Computer 6,309 310 14 137 Pitney Bowes 3,417 295 29 145 Compaq Computer 3,271 131 10 146 Sun Microsystems 3,260 190 12 166 Seagate Technology 2,691 67 43 201 Wang Laboratories 2,127 (386) 18 217 Tandem Computers 1,940 35 11 233 Amdahl 1,702 11 9 239 Storage Technology 1,653 93 10 248 Conner Peripherals 1,627 92 8 272 DR Holdings 1,391 - 7 295 Data General 1,237 86 9 300 Intergraph 1,205 71 10 314 SCI Systems 1,129 13 10 363 Quantum 878 74 1 365 Maxtor 875 (45) 8 370 Cray Research 862 113 5 431 AST Research 697 65 3 457 Bell & Howell 625 (5) 6 488 Silicon Graphics 557 33 3 490 Dell Computer 546 27 2  TOTAL 140,054 (2,812) 845  1 9 9 1 ELECTRONICS/ELECTRICAL  Sales Profit Employees Rank Company (000,000) (000) 5 General Electric 60,236 2,636 284 30 Westinghouse 12,794 (1,086) 114 35 Rockwell Int'l. 12,028 601 87 39 Motorola 11,341 454 102 51 Raytheon 9,356 592 72 64 Emerson Electric 7,427 632 70 77 Texas Instruments 6,812 (409) 63 78 Whirlpool 6,770 170 38 86 Cooper Industries 6,163 393 54 91 N. American Philips 6,065 8 43 99 Litton Industries 5,313 64 52 106 Intel 4,779 819 25 147 Teledyne 3,218 (25) 29 150 AMP 3,095 260 25 151 Harris 3,081 19 31 153 Maytag 2,971 79 23 200 Loral 2,136 90 24 210 E-Systems 1,998 110 19 229 Nat'l Semiconductor 1,711 (151) 30 251 General Signal 1,620 54 15 254 Nat'l Service Ind. 1,602 32 21 260 Duracell Int'l. 1,524 (34) 8 261 Reliance Electric 1,516 34 14 274 Varian Associates 1,381 58 9 282 Zenith Electronics 1,322 (52) 28 291 Raychem 1,250 (23) 11 296 Advanced Micro Dev. 1,227 145 11 312 Magnetek 1,134 35 15 339 Western Digital 986 (134) 7 340 Pittway 984 26 8 349 Mark IV Industries 937 26 11 356 Sunbeam/Oster 886 48 11 407 Hubbell 768 91 6 413 Exide 743 (12) 6 418 Molex 716 65 7 422 LSI Logic 713 8 4 473 Harman Int'l Ind. 587 (20) 4 478 Thomas & Betts 573 48 5 493 Analog Devices 539 8 5  TOTAL 188,298 5,656 1,389  forward chaining In AI, a form of reasoning that starts with what is known and works toward a solution. Known as bottom-up approach. Contrast with backward chaining. forward compatible Same as upward compatible. forward error correction Communications technique that can correct bad data on the receiving end. Before transmission, the data is processed through an algorithm that adds extra bits for error correction. If the transmitted message is received in error, the correction bits are used to repair it. fourth-generation computer Computer made up almost entirely of chips with limited amounts of discrete components. We are currently in the fourth generation. fourth-generation language Computer language that is more advanced than traditional high-level programming languages. For example, in dBASE, the command LIST displays all the records in a data file. In second- and third- generation languages, instructions would have to be written to read each record, test for end of file, place each item of data on screen and go back and repeat the operation until there are no more records to process. First-generation languages are machine languages; second-generation are machine dependent assembly languages; third-generation are high-level programming languages, such as FORTRAN, COBOL, BASIC, Pascal, and C. Although many languages, such as dBASE, are called fourth-generation languages, they are actually a mix of third and fourth. The dBASE LIST command is a fourth- generation command, but applications programmed in dBASE are third-generation. Query language and report writers are also fourth-generation languages. Any computer language with English-like commands that doesn't require traditional input-process-output logic falls into this category. FoxBASE+ dBASE III PLUS-compatible DBMS for the Macintosh from Microsoft. Originally developed by Fox Software for the PC, FoxBASE gained a reputation for its speed and compatibility. FoxPro dBASE IV-compatible DBMS from Microsoft for PCs. An enhanced version of FoxBASE, FoxPro includes windowing, SQL and QBE interfaces and "Rushmore" technology for fast queries on large databases. FPGA (Field Programmable Gate Array) Programmable logic chip with a high density of gates. fps (1) (Frames Per Second) See frame. (2) (FPS) (Floating Point Systems, Inc., Beaverton, OR) Supercomputer manufacturer. FPU (Floating Point Unit) Computer circuit that handles floating point operations. fractals Technique for describing and greatly compressing images, especially natural objects, such as trees, clouds and rivers. Fractals, or "fractional mathematics," comes from the science of chaos. It turns an image into a set of data and an algorithm for expanding it back to the original. fractional T1 Service that provides less than full T1 capacity. One or more 64Kbits/sec channels are provided. fragmentation Non-contiguous storage of data on disk. As files are updated, new data is stored in available free space, which may not be contiguous. Fragmented files cause extra head movement, slowing disk accesses. A disk maintenance, or optimizer, program is used to rewrite and reorder all the files. FRAM (1) (Ferroelectronic RAM) Non-volatile semiconductor memory that retains its content without power for up to 10 years. (2) (Ferromagnetic RAM) Non-volatile memory that records microscopic bits on a magnetic surface. frame (1) In computer graphics, one screenful of data or its equivalent storage space. (2) In communications, a group of bits that make up an elementary block of data for transmission by certain protocols. (3) In AI, a data structure that holds a general description of an object, which is derived from basic concepts and experience. frame buffer Separate memory component that holds a graphic image. It can have one plane of memory for each bit in the pixel; for example, if eight bits are used per pixel, there are eight separate memory planes. frame grabber Device that accepts standard TV signals and digitizes the current video frame into a bitmap image. frame relay High-speed packet switching protocol that provides faster transmission than X.25. It is suited for data and image transfer rather than voice. FrameMaker Desktop publishing program from Frame Technology Corp., San Jose, CA, that runs on UNIX platforms, Macintosh and Windows. It is noted for its integrated text and graphics capabilities. Optional viewers let documents run on machines without FrameMaker, providing a way to distribute hypertext-based help systems. framework (1) In object-oriented programming, a generalized subsystem design for building applications. It consists of abstract classes and their object collaboration as well as concrete classes. While object-oriented programming supports software reuse, frameworks support design reuse. (2) (FrameWork) One of the first integrated software packages for PCs that included a programming language. From Ashton-Tate. framing bit Same as start bit and stop bit. free-form database Database system that allows entry of text without regard to length or order. Although it accepts data as does a word processor, it differs by providing better methods for searching, retrieving and organizing the data. free-form language Language in which statements can reside anywhere on a line or even cross over lines. It does not imply less syntax structure, just more freedom in placing statements. For example, any number of blank spaces are allowed between symbols. Most high- level programming languages are free-form. Free Software Foundation Non-profit organization founded in 1985 by Richard Stallman, dedicated to eliminating restrictions on copying and modifying programs by promoting the development and use of freely re-distributable software. It is developing the GNU computing environment, including kernel, utilities, editor, compiler and debugger. GNU programs, X Windows and others are available for a transaction charge. Address: 675 Mass. Ave., Cambridge, MA 02139, 617/876-3296, Internet: gnu@prep.ai.mit.edu. See League for Programming Freedom. FreeHand Full-featured Macintosh drawing program from Aldus Corp., Seattle, WA, that combines a wide range of drawing tools with special effects. freeware Software distributed without charge. Ownership is retained by the developer who has control over its redistribution, including the ability to change the next release of the freeware to payware. See shareware and public domain software. frequency Number of oscillations (vibrations) that are in an alternating current within one second. See carrier. frequency division multiplexing See FDM. frequency modulation See FM. frequency shift See FSK. friction feed Mechanism that allows cut paper forms to be used in a printer. The paper is passed between the platen and a roller that presses tightly against it. Contrast with tractor feed. frob From frobnicate. Slang for manipulating and adjusting dials and buttons for fun. front-end CASE CASE tools that aid in systems analysis and design. Contrast with back-end CASE. front end processor Computer that handles communications processing for a mainframe. It connects to the communications lines on one end and the mainframe on the other. It transmits and receives messages, assembles and dissassembles packets and detects and corrects errors. It is sometimes synonymous with a communications controller, although the latter is usually not as flexible. frontware Software that adds a graphical user interface to mainframe applications. The frontware application is processed in the personal computer which is used as a terminal to the mainframe. FSK (Frequency Shift Keying) Simple modulation technique that merges binary data into a carrier. It creates only two changes in frequency: one for 0, another for 1. FSR (Free System Resource) In Windows, the amount of unused memory in a 64K block (128K for Version 3.1) reserved for managing current applications. Every open window takes some space in this area. FT1 See fractional T1. FTAM (File Transfer Access and Management) Communications protocol for the transfer of files between systems of different vendors. FTP (File Transfer Protocol) TCP/IP protocol that is used to log onto the network, list directories and copy files. It can also translate between ASCII and EBCDIC. See TFTP. FTS 2000 (Federal Telecommunications System 2000) Digital fiber-optic network providing voice, video, e-mail and high-speed data communications for the U.S. government. AT&T and Sprint are the major equipment providers. FUD factor (Fear Uncertainty Doubt factor) Marketing strategy by a dominant or privileged organization that restrains competition by not revealing future plans. full backup See backup types. full-duplex Transmitting and receiving simultaneously. In pure digital networks, this is achieved with two pairs of wires. In analog networks or in digital networks using carriers, it is achieved by dividing the bandwidth of the line into two frequencies, one for sending, one for receiving. full featured Hardware or software that provides capabilities and functions comparable to the most advanced models or programs of that category. full path Path name that includes the drive, starting or root directory, all attached subdirectories and ending with the file or object name. full project life cycle Project from inception to completion. full-screen mode Programming capability that allows data to be displayed in any row or column on screen. Contrast with teletype mode. fully populated Circuit board whose sockets are completely filled with chips. function In programming, a software routine that does a particular job. The function performs the job and returns control to the instruction following the calling instruction. Programming languages provide a set of standard functions and may allow programmers to define others. The C language is built entirely of functions. function keys Set of keyboard keys used to command the computer (F1, F2, etc.). F1 is often the help key, but the purpose of any function key is determined by the software currently running. function library Collection of program routines. See function. functional decomposition Breaking down a process into non-redundant operations. functional specification Blueprint for the design of an information system. It provides documentation for the database, human and machine procedures, and all the input, processing and output detail for each data entry, query, update and report program in the system. fuse (1) Protective device that is designed to melt, or blow, when a specified amount of current is passed through it. PROM chips are created as a series of fuses that are selectively blown in order to create the binary patterns in the chip. (2) To bond together. fusible link Circuit line in a PROM chip or similar device that is designed to be blown apart. See PROM programmer. Futurebus+ IEEE standard multisegment bus that can transfer data at 32, 64, 128 and 256-bits and can address up to 64 bits. Clock speeeds range from 25 to 100MHz. At 100MHz and 256 bits, it transfers 3.2 Gbytes/sec. fuzzy computer Specially-designed computer that employs fuzzy logic. Using such architectural components as analog circuits and parallel processing, fuzzy computers are designed for AI applications. fuzzy logic Mathematical technique for dealing with imprecise data and problems that have many solutions rather than one. It can deal with values between 0 and 1 and is more analogous to human logic than digital logic. Results can be mostly true and mostly false rather than true and false. fuzzy search Inexact search for data that finds answers that come close to the desired data. It can get results when the exact spelling is not known or help users obtain information that is loosely related to a topic. G See giga. G-byte See gigabyte. gain Amount of increase that an amplifier provides on the output side of the circuit. GAL (Generic Array Logic) Programmable logic chip (PLD) technology from Lattice Semiconductor. gallium arsenide Alloy of gallium and arsenic compound (GaAs) that is used as the base material for chips. It is several times faster than silicon. game port I/O connector used to attach a joy stick. It is typically a 15-pin socket on the back of a PC. gamma correction In computer graphics, using a formula to provide a range of intensities that appear uniform to the human eye. gang punch To punch an identical set of holes into a deck of punched cards. Gantt chart Form of floating bar chart usually used in project management to show resources or tasks over time. gap (1) Space between blocks of data on magnetic tape. (2) Space in a read/write head over which magnetic flux (energy) flows causing the underlying magnetic tape or disk surface to become magnetized in the corresponding direction. gapless Magnetic tape that is recorded in a continuous stream without interblock gaps. garbage collection Routine that searches memory for program segments or data that are no longer active in order to reclaim that space. garbage in... See GIGO. gas discharge display See plasma display. gas plasma See plasma display. gate (1) Open/closed switch. (2) Pattern of transistors that makes up an AND, OR or NOT Boolean logic gate. See gate array. (2) In a MOS transistor, the line that triggers the switch. gate array Chip type that contains unconnected logic elements. The finished, customized chip is obtained by adhering the top metal layer of pathways between the elements. This final masking stage is less costly than designing the chip from scratch. It usually contains only two-input NAND gates, which can be used singularly or connected with other NAND gates to provide all the Boolean operations required for digital logic. gated Switched "on" or capable of being switched on and off. gateway Computer that interconnects and performs the protocol conversion between two types of networks. For example, a gateway between a personal computer LAN and a mainframe network. See bridge. gather write To output data from two or more noncontiguous memory locations with one write operation. See scatter read. GatorBox Gateway from Cayman Systems, Inc., Cambridge, MA, that interconnects LocalTalk and Ethernet networks and supports TCP/IP and NFS protocols. It also functions as a router to connect AppleTalk-based computers on a LAN with remote AppleTalk devices. gauss Unit of measurement of magnetic energy. Gaussian distribution Random distribution of events that is often graphed as a bell-shaped curve. It is used to represent a normal or statistically probable outcome. Gaussian noise In communications, a random interference generated by the movement of electricity in the line. Also called white noise. GB, Gb See gigabyte and gigabit. Gbit See gigabit. Gbits/sec (GigaBITS per SECond) Billion bits per second. GBps, Gbps (GigaBytes Per Second, GigaBits Per Second) Billion bytes per second. Billion bits per second. GByte See gigabyte. Gbytes/sec (GigaBYTES per SECond) Billion bytes per second. GCOS Bull HN operating system used in its minis and mainframes (formerly Honeywell's product). GCR (1) (Group Code Recording) Encoding method used on magnetic tapes and Apple II and Mac 400K and 800K floppy disks. (2) (Gray Component Replacement) Method for reducing amount of printing ink used. It substitutes black for the amount of gray contained in a color, thus black ink is used instead of the three CMY inks. See UCR and dot gain. GDDM (Graphical Data Display Manager) Software that generates graphics images in the IBM mainframe environment. It contains routines to generate graphics on terminals, printers and plotters as well as accepting input from scanners. Programmers use it for creating graphics, but users can employ its Interactive Chart Utility (ICU) to create business graphics without programming. GDDM/graPHIGS is a programming environment that combines graphics capability with a user interface similar to the Presentation Manager in OS/2. GDI (Graphics Device Interface) Windows graphics language used to provide output to the screen, printer or other device. Applications create images on screen by calling GDI functions. A GDI driver executes these Windows functions directly. GDM See CGM. GE (Greater than or Equal to) See relational operators. GEM (Graphics Environment Manager) Graphical user interface from Digital Research similar to the Mac/Windows environment. It is built into ROM in several Atari computers, and the DOS version of Ventura Publisher comes with a runtime version. gender changer Coupler that reverses the gender of one of the connectors in order that two male connectors or two female connectors can be joined together. General Magic (General Magic, Inc., Cupertino, CA) Spin off of Apple Computer in 1990. Its mission is to create new personal intelligent communications products and services by developing and licensing technology to a wide variety of manufacturers and service providers. It has formed an alliance with large organizations such as AT&T, Sony, Philips and Motorola in order to reach the widest possible audience. See Telescript and Magic Cap. general-purpose computer Refers to computers that follow instructions, thus virtually all computers from micro to mainframe are general purpose. Even computers in toys, games and single-function devices follow instructions in their built-in program. In contrast, computational devices can be designed from scratch for special purposes (see ASIC). general-purpose controller Peripheral control unit that can service more than one type of peripheral device; for example, a printer and a communications line. general-purpose language Programming language used to solve a wide variety of problems. All common programming languages (FORTRAN, COBOL, BASIC, C, Pascal, etc.) are examples. Contrast with special-purpose language. generalized program Software that serves a changing environment. By allowing variable data to be introduced, the program can solve the same problem for different users or situations. For example, the electronic versions of this Glossary could be programmed to read in a different title and thus be used for any type of dictionary. generator (1) Software that creates software. See application generator and macro generator. (2) Device that creates electrical power or synchonization signals. Generic CADD Full-featured PC CADD package from Generic Software, Inc., Bothell, WA, that offers levels for beginner, intermediate and advanced users. GEnie (General Electric Network for Information Exchange) Online information service from GE Information Services that provides business information, news and access to special interest groups. See online services. Genifer dBASE application generator from Bytel Corp., Berkeley, CA, that creates dBASE source code. genlock (generator lock) Circuitry that synchronizes video signals for mixing. In personal computers, a genlock display adapter converts screen output into an NTSC video signal, which it synchronizes with an external video source. geostationary Same as geosynchronous. geosynchronous Earth aligned. Refers to communications satellites that are placed 22,300 miles above the equator and travel at the same speed as the earth's rotation, thus appearing stationary. GeoWorks Ensemble Popular graphical operating environment for DOS from GeoWorks, Inc., Berkeley, CA, that includes word processing, drawing, communications, card file and calendar applications. It provides complete DOS file management and simulates file folders like the Macintosh. Users can launch all applications from within Ensemble. GeoWorks Pro includes the Quattro Pro spreadsheet. germanium (Ge) Material used in making the first transistors. Although still used in very limited applications, germanium was replaced by silicon years ago. gesture recognition Ability to interpret simple hand-written symbols such as check marks and slashes. get In programming, a request for the next record in an input file. Contrast with put. Gflops See gigaflops. ghost (1) Faint second image that appears close to the primary image on a display or printout. In transmission, it is a result of secondary signals that arrive ahead of or later than the primary signal. On a printout, it is caused by bouncing print elements as the paper passes by. (2) To display a menu option in a dimmed, fuzzy typeface, indicating it is not selectable at this time. GHz (GigaHertZ) One billion cycles per second. GIF (Graphics Interchange Format) Popular raster graphics file format developed by CompuServe that handles 8-bit color (256 colors) and uses the LZW method to achieve compression ratios of approximately 1.5:1 to 2:1. giga Billion. Abreviated "G." It often refers to the precise value 1,073,741,824 since computer specifications are usually binary numbers. See binary values and space/time. gigabit One billion bits. Also Gb, Gbit and G-bit. See giga and space/time. gigabyte One billion bytes. Also GB, Gbyte and G-byte. See giga and space/time. gigaflops (GIGA FLoating point OPerations per Second) One billion floating point operations per second. GIGO (Garbage In Garbage Out) "Bad input produces bad output." Data entry is critical. All possible tests should be made on data entered into a computer. GIGO also means "Garbage In, Gospel Out." People put too much faith in computer output! GIS (1) (Geographic Information System) Digital mapping system used for exploration, demographics, dispatching and tracking. (2) (Generalized Information System) Early IBM mainframe query and data manipulation language. GKS (Graphical Kernel System) Device-independent graphics language for 2-D, 3-D and raster graphics images. It allows graphics applications to be developed on one system and easily moved to another with minimal or no change. It was the first true standard for graphics applications programmers and has been adopted by both ANSI and ISO. glare filter Fine mesh screen that is placed over a CRT screen to reduce glare from overhead and ambient light. glitch Temporary or random hardware malfunction. It's possible that a bug (permanent error) in a program may cause the hardware to appear as if it had a glitch in it and vice versa. At times it can be extremely difficult to determine whether a problem lies within the hardware or the software. global Pertaining to an entire file, database, volume, program or system. global variable In programming, a variable that is used by all modules in a program. glossary Term used by Microsoft Word and adopted by other word processors for the list of shorthand, keyboard macros created by a particular user. glue chip Support chip that adds functionality to a microprocessor, for example, an I/O processor or extra memory. GNU (Gnu's Not UNIX) Project sponsored by the Free Software Foundation that is developing a complete software environment including operating system kernel and utilities, editor, compiler and debugger. Many consultants and organizations provide support for GNU software. goal seeking Ability to calculate a formula backward to obtain a desired input. For example, given the goal gross margin = 50% as well as the range of possible inputs, goal seeking attempts to obtain the optimum input. GOCA (Graphics Object Content Architecture) See MO:DCA. gooey See GUI. GOSIP (Government Open Systems Interconnection Profile) U.S. government mandate that after 8/15/90, all new network procurements must comply with OSI. Testing is performed at the NIST, which maintains a database of OSI-compliant commercial products. (TCP/IP protocols can also still be used.) GOTO (1) In a high-level programming language, a statement that directs the computer to go to some other part of the program. Low-level language equivalents are branch and jump. (2) In dBASE, a command that directs the user to a specific record in the file. (3) In word processing, a command that directs the user to a specific page number. GOTO-less programming Writing a program without using GOTO instructions, an important rule in structured programming. A GOTO instruction points to a different part of the program without a guarantee of returning. Instead of using GOTOs, structures called subroutines or functions are used, which automatically return to the next instruction after the calling instruction when completed. Gouraud shading In computer graphics, a technique developed by Henri Gouraud that computes a shaded surface based on the color and illumination at the corners of polygonal facets. GPF (1) (General Protection Fault) Application program abend in Windows 3.1. See UAE. (2) (GUI Programming Facility) OS/2 application generator from GPF Systems, Inc., Moodus, CT. GPI (Graphical Programming Interface) Graphics language in OS/2 Presentation Manager. It is a derivative of the GDDM mainframe interface and includes Bezier curves. GPIB (General Purpose Interface Bus) IEEE 488 standard parallel interface used for attaching sensors and programmable instruments to a computer. It uses a 24-pin connector. HP's version is the HPIB. GPS (Global Positioning System) Series of continuously-transmitting satellites used for identifying earth locations. By triangulation from three satellites, a receiving unit can pinpoint where it is on earth. GPSS (General Purpose Simulation System) Programming language for discrete event simulation, which is used to build models of operations such as manufacturing environments, communications systems and traffic patterns. Originally developed by IBM for mainframes, PC versions are available, such as GPSS/PC by Minuteman Software and GPSS/H by Wolverine Software. grabber hand Pointer in the shape of a hand that is moved by a mouse to "grab" and relocate objects on screen. graceful degradation A system that continues to perform at some reduced level of performance after one of its components fails. graceful exit Ability to get out of a problem situation in a program without having to turn the computer off. grade Transmission capacity of a line. It refers to a range or class of frequencies that it can handle; for example, telegraph grade, voice grade and broadband. gradient Color spread from light to dark to shade an object or give it a sense of depth. It is also used to create a colorful background. GRAFCET (GRAPHe de Commande Etape-Transition - stage transition command graph) PLC specification and programming language. GrafPort See graphics port (2). grammar checker Software that checks the grammar of a sentence. It can check for and highlight incomplete sentences, awkward phrases, wordiness and poor grammar. Grammatik Popular grammar checking program for DOS, Windows, Macintosh and UNIX from Reference Software, Int'l, San Francisco. U.S. Government versions check for usage according to the Government Printing Office and other military and civilian guides. grandfather, father, son Method for storing previous generations of master file data that are continuously updated. The son is the current file, the father is a copy of the file from the previous cycle, and the grandfather is a copy of the file from the cycle before that one. granularity Degree of modularity of a system. The more granularity (grains or granules), the more customizable or flexible the system. graph Pictorial representation of information. See business graphics. graphic character Printable symbol that includes digits and letters. graphical interface See GUI. graphics Usually called "computer graphics," it is the creation and management of picture images in the computer. It is defined as "graphics" in this Glossary to keep it next to other "graphics" entries. A graphics computer system requires a graphics display screen, a graphics input device (tablet, mouse, scanner, camera, etc.), a graphics output device (dot matrix printer, laser printer, plotter, etc.) and a graphics software package; for example, a CAD, drawing or paint program. Vector Graphics and Raster Graphics Two methods are used for storing and maintaining pictures in a computer. The first method, called vector graphics (also known as object-oriented graphics), maintains the image as a series of points, lines, arcs and other geometric shapes. The second method, called raster graphics, resembles television, where the picture image is made up of dots. Understanding these two methods and how they intertwine in today's graphics systems is essential for mastering computer graphics. When you create an image on the computer, you may not know which method is used, but when you try to manipulate that image, it will become obvious. Vector Graphics for CAD and Drawing Vector graphics is the method employed by CAD (computer-aided design) and drawing packages. As you draw, each line of the image is stored as a vector (two end points on an x-y matrix). For example, a square becomes four vectors, one for each side. A circle is turned into dozens or hundreds of tiny straight lines, the number of which is determined by the resolution of the drawing. The entire image is commonly stored in the computer as a list of vectors, called a display list. Older CAD systems used vector display screens that "drew" the image directly from the vectors. Today, most screens are raster graphics displays (made up of dots), and the vectors are "rasterized" into the required dot patterns by hardware or software. Vector graphics is used when you need geometric knowledge about the object created. Geometric shapes keep their integrity: a line can always be picked, extended or erased. It never turns into just a string of dots in the database. Vector graphics can be transmitted directly to x-y plotters that "draw" the images from the list of vectors. Raster Graphics for Imaging and Painting Raster graphics is the TV-like method that uses dots to display an image on screen. Raster graphics images are created by scanners and cameras and are also generated by paint packages. A picture frame is divided into hundreds of horizontal rows, with each row containing hundreds of dots, called pixels. Unlike TV, which uses one standard (NTSC) for the country, there are dozens of raster graphics standards. Also, unlike TV, which records and displays the dots as infinitely variable shades and colors (analog), computer graphics have a finite number of shades and colors (digital). When you scan an image or paint an object into the computer, the image is created in a reserved area of memory called a bitmap, with some number of bits corresponding to each dot (pixel). The simplest monochrome bitmap uses one bit (on/off) for each dot. Gray scale bitmaps (monochrome shades) hold a number for each dot large enough to hold all the gray levels. Color bitmaps require three times as much storage in order to hold the intensity of red, green and blue. The image in the bitmap is continuously transmitted to the video screen, dot for dot, a line at a time, over and over again. Any changes made to the bitmap are instantly reflected on the screen. Since colors are designated with numbers, changing red to green is simply searching for the red number and replacing it with the green number. Animation is accomplished by continuously copying new sequences from other areas in memory into the bitmap, one after the other. Raster graphics images may take up more space on disk than their vector graphics counterpart, because storage for each pixel is required even if it's part of the background. A small object in vector graphics format will take up only a few vectors in the display list file. graphics accelerator High-performance video display board for graphical user interfaces that has line drawing and pixel block move functions (bitblt) built into hardware. In Windows, such boards provide fast scrolling and line drawing. Windows applications will run better on a slower PC with a graphics accelerator than on a faster PC without one. See Winmark and graphics engine. graphics adapter Same as video display board graphics based Display of text and pictures as graphics images; typically bitmapped images. Contrast with text based. graphics card Same as video display board. graphics engine Hardware that performs graphics processing independently of the computer's CPU. Under directives from a graphics language, it can perform a variety of functions, such as converting vectors to rasters, compression and matrix multiplication (for fast rotation). It is typically designed for CAD systems and is more specialized than a graphics accelerator. graphics file File that contains only graphics data. Contrast with text file and binary file. graphics interface See graphics language and GUI. graphics language High-level language used to create graphics images. The language is translated into images by software or specialized hardware. See graphics engine. graphics mode Screen display mode that displays graphics. Contrast with text mode and character mode. graphics port (1) Socket on the computer for connecting a graphics monitor. (2) Macintosh graphics structure that defines all the characteristics of a graphics window (also called GrafPort). graphics primitive Elementary graphics building block, such as a point, line or arc. In a solid modeling system, a cylinder, cube and sphere are examples of primitives. graphics processor Same as graphics engine. graphics tablet See digitizer tablet. graphics terminal (1) I/O device that displays pictures in raster graphics, vector graphics format or both. Images are received via communications or entered with a mouse or light pen. The keyboard may have specialized function keys, wheels or dials. (2) Terminal or personal computer that displays graphics. graPHIGS See GDDM. gray scale Series of shades from white to black. The more shades, or levels, the more realistic an image can be recorded and displayed, especially a scanned photo. Scanners differentiate typically from 16 to 256 gray levels. Although compression techiques help reduce the size of graphics files, high-resolution gray scale requires huge amounts of storage. At a printer resolution of 300 dpi, each square inch is made up of 90,000 pixels. At 256 levels, it takes one byte per pixel, or 90,000 bytes per square inch of image. See halftone. greek To display text in a representative form in which the actual letters are not discernible, because the screen resolution isn't high enough to display them properly. Desktop publishing programs let you set which font sizes should be greeked. grep (Global Regular Expression and Print) UNIX pattern matching utility that searches for a string of text and outputs any line that contains the pattern. ground Electrically conductive body, such as the earth, which maintains a zero potential (not positively or negatively charged) for connecting to an electrical circuit. ground current Current found in a ground line. May be caused by imbalanced electrical sources; for example, the ground line in a communications channel between two computers deriving power separately. ground fault Temporary current in the ground line, caused by a failing electrical component or interference from an external electrical source such as a thunderstorm. ground loop Unwanted ground current flowing back and forth between two devices that are grounded at two or more points. ground noise injection Intentional insertion of unwanted noise by a power supply into the ground line. groupware Software that is designed for use in a network and serve a group of users that work on a related project. GSOS (GS Operating System) Graphical operating system for the Apple IIGS that also accepts ProDOS applications. GT (Greater Than) See relational operator. guard band Frequency that insulates one signal from another. In an analog telephone line, the low band is 0-300; the high band is 3300-4000Hz. GUI (Graphical User Interface) Graphics-based user interface that incorporates icons, pull-down menus and a mouse. Macintosh, Windows, Presentation Manager (OS/2), OSF/Motif and Open Look are examples. See desktop manager and window manager. See also Star. Contrast with CUI. GUI accelerator See graphics accelerator. gulp Some number of bytes! gutter In typography, the space between two columns. GVPN (Global Virtual Private Network) Service from cooperating carriers that provides international digital communications for multinational companies. GW-BASIC (Gee Whiz-BASIC) BASIC interpreter that accompanied MS-DOS in versions prior to 5.0. See QBasic. h (Hexadecimal) Symbol that refers to a hex number. For example, 09h has a numeric value of 9, whereas 0Ah has a value of 10. See hex chart. H&J (Hyphenation and Justification) Alignment of the right margin in a document. Hyphenation breaks up words that exceed the margin. Justification aligns text uniformly at the right margin while spacing text evenly between both margins. H.261 CCITT standard for a video codec that uses intraframe and interframe compression and transmits over Px64 ISDN lines. It transmits at 9.115 Mbits/sec (QCIF), with 36.45 Mbits/sec (CIF) optional. hacker Person who writes programs in assembly language or in system-level languages, such as C. Although it may refer to any programmer, it implies very tedious "hacking away" at the bits and bytes. The term has become widely used for people that gain illegal entrance into a computer system. HAL (1) (Hardware Abstraction Layer) Hardware- dependent routines within Windows NT, which provides the translation layer between hardware- independent applications. (2) Spaceship computer in the film, "2001," which takes command by itself. From I-B-M, the letters preceding H-A-L. half-adder Elementary electronic circuit in the ALU that adds one bit to another, deriving a result bit and a carry bit. half-duplex Transmission of data in both directions, but only one direction at a time. Two-way radio was the first to use half-duplex, for example, while one party spoke, the other party listened. Contrast with full-duplex. half height drive 5.25" disk drive that takes up half the vertical space of first-generation drives. It is 1 5/8" high by 5.75" wide. halftone In printing, the simulation of a continuous-tone image (shaded drawing, photograph) with dots. All printing processes, except for Cycolor, print dots. In photographically-generated halftones, a camera shoots the image through a halftone screen, creating smaller dots for lighter areas and larger dots for darker areas. Digitally-composed printing prints only one size of dot. In order to simulate varying size halftone dots in computer printers, dithering is used, which creates clusters of dots in a "halftone cell." The more dots printed in the cell, the darker the gray. As the screen frequency gets higher (more lines per inch), there is less room for dots in the cell, reducing the number of gray levels that can be generated. This tradeoff is a compromise in a 300 dpi printer, since realistic gray-scale printing reduces the resolution; for example, the 8x8 halftone cell required to create 64 grays results in a coarse 38 lpi resolution (300 dpi 8). In high-resolution imagesetters, the highest screen frequencies can be used with ample gray scale. 敖賃陳堕陳 cells  津陳田津陳田陳陳陳 顎朿栩  This simplistic example uses lpi 津陳田津陳田 a 2x2 halftone cell 顎潦  allowing only white (no dots), 津陳田津 black (all four dots) and three  interim shades (1, 2 and 3 dots). In a 300 dpi printer, this would allow for a 150 lpi resolution (3002). A 4x4 cell would provide 16 shades and 75 lpi.  Halftone Cell hammer In a printer, the mechanism that pushes the typeface onto the ribbon and paper or pushes the paper into the ribbon and typeface. Hamming code Communications error correction method that intersperses three check bits at the end of each four data bits. At the receiving station, the check bits are used to detect and correct one-bit errors automatically. handle (1) In computer graphics, a location on an image that can be grabbed for reshaping. It is usually a tiny square. (2) Temporary name or number assigned to a file, font or other object. For example, an operating system may assign a sequential number to each file that it opens as a way of identifying and keeping track of it. (3) Nickname used when teleconferencing on a bulletin board, like a "CB handle" used between truck drivers. handler Software routine that performs a particular task. For example, upon detection of an error, an error handler is called to recover from the error condition. handset The part of the telephone that contains the speaker and the microphone. handshaking Signals transmitted back and forth over a communications network that establish a valid connection between two stations. hanging paragraph Paragraph in which the first line starts at the left margin, but subsequent lines are indented as is this paragraph. hard boot Same as cold boot. hard coded Software that performs a fixed number of tasks or works with only a fixed number of devices. For example, a program could be written to work with only two types of printers and not allow any other types to be introduced. Hard coded solutions to problems are usually the fastest, but do not allow for future flexibility. hard copy Printed output. Contrast with soft copy. hard disk Primary computer storage medium that is made of rigid disks with a magnetic recording surface. Personal computer hard disks hold from 20MB to over 1GB. Mini and mainframe hard disks can hold several gigabytes. Fixed hard disks are permanently sealed in the drive. Removable hard disks are encased in disk pack or disk cartridge modules that can be moved between computers with the same kinds of drives. Hard disks provide fast retrieval because they rotate at 3,600 rpm and higher and spin constantly, although laptops turn them off to preserve battery. Hard disks are made of one or more aluminum platters (two to 15" diameter), each side coated with a ferromagnetic material. Hard disks are usually low-level formatted from the factory, which records the original sector identification on them. See floppy disk, magnetic disk and format program.  HARD DISK SPECIFICATIONS Interface Encoding Transfer Rate Storage Type Method* (Bytes/sec) Capacities ST506 MFM 625K 5M - 100M ST506 RLL RLL 937K 30M - 200M IDE RLL .625-2M 20M - 1G ESDI RLL 1-3M 80M - 2G SCSI-1 RLL 1-5M 20M - 1.5G SCSI-2 RLL 1-40M 40M - 3G SMD RLL 1-4M 200M - 2G IPI RLL 10-25M 200M - 3G *(Most disks use RLL, but the encoding method is not prescribed by all interfaces.) Hard Disk Measurements Capacity is measured in bytes, and speed is measured in bytes per second (transfer rate) and in milliseconds (access time). Fast personal computer hard disk access times range from 12 to 28ms; in larger computers as fast as 1ms. For Technical Specs "Hard Drive Bible," $24.95 Corporate Systems Center, Sunnyvale, CA 408/737-7312. "Hard Disk Technical Guide," $49.95 "Hard Disk Encyclopedia." $119.95 Micro House, Clearwater, FL, 800/741-3282 hard error (1) Permanent, unrecoverable error such as a disk read error. Contrast with soft error. (2) Group of errors that requires user intervention and includes disk read errors, disk not ready (no disk in drive) and printer not ready (out of paper). hard hyphen Hyphen that always prints. Contrast with soft hyphen. hard return Code entered into a text document by pressing the return (enter) key. DOS and OS/2 text files use a CR/LF (carriage return/line feed) pair, but this is not standard (WordPerfect uses only an LF). The Macintosh uses a CR and UNIX uses an LF. It may be represented by a visible symbol on screen, such as the "<" in WordStar or the "" in XyWrite, or it may remain invisible until revealed in an expanded screen mode. Contrast with soft return. hard sectored Sector identification technique that uses a physical mark. For example, hard sectored floppy disks have a hole in the disk that marks the beginning of each sector. Contrast with soft sectored. hard space Special space character that acts like a letter or digit, used to prevent multiple-word proper names from breaking between lines. Hardcard Family of hard disks from Plus Development Corp., Milpitas, CA, that house the disk drive and the controller electronics on an expansion board that plugs into a PC. It allows for a simple installation and does not use up a drive bay. HardFacts Database service for PC hardware from HardFacts, Inc., Beverly, MA, that includes retail and street prices, distributor and mail order info on 14,000+ PCs and peripherals. Monthly updates, product review abstracts and manufacturer's data sheets by fax are included in the subscription. hardware Machinery and equipment (CPU, disks, tapes, modem, cables, etc.). In operation, a computer is both hardware and software. One is useless without the other. The hardware design specifies the commands it can follow, and the instructions tell it what to do. See instruction set. Hardware Is "Storage and Transmission" The more memory and disk storage a computer has, the more work it can do. The faster the memory and disks transmit data and instructions to the CPU, the faster it gets done. A hardware requirement is based on the size of the databases that will be created and the number of users or applications that will be served at the same time. How much? How fast? Software Is "Logic and Language" Software deals with the details of an ever-changing business and must process transactions in a logical fashion. Languages are used to program the software. The "logic and language" involved in analysis and programming is generally far more complicated than specifying a storage and transmission requirement. hardware failure Malfunction within the electronic circuits or electromechanical components (disks, tapes) of a computer system. Contrast with software failure. hardware interrupt Interrupt caused by some action of a hardware device, such as the depression of a key or mouse movement. See interrupt. hardware key Copy protection device supplied with software that plugs into a computer port. The software interrogates the key's serial number during execution to verify its presence. The hardware key acts as a pass-through, but tests for a special code that reads the serial number. hardware monitor Device connected to the circuits of a computer in order to analyze its performance. hardware virtual memory Virtual memory management built into a chip. Although virtual memory can be performed by software only, it is far more efficient to do it in hardware. See DAT and PMMU. hardwired (1) Electronic circuitry that is designed to perform a specific task. See hard coded. (2) Devices that are closely or tightly coupled. For example, a hardwired terminal is directly connected to a computer without going through a switched network. harmonic distortion In communications, frequencies that are generated as multiples of the original frequency due to irregularities in the transmission line. Harvard Graphics Popular PC business graphics program from Software Publishing Corp., Mountain View, CA. It was one of the first business graphics packages and provides the ability to create columnar and free form text charts. hash total Method for ensuring the accuracy of processed data. It is a total of several fields of data in a file, including fields not normally used in calculations, such as account number. At various stages in the processing, the hash total is recalculated and compared with the original. If any data has been lost or changed, a mismatch signals an error. Hayes compatible Refers to modems controlled by the Hayes command language. See AT command set. Hayes Smartmodem Family of intelligent modems for personal computers from Hayes Microcomputer Products, Inc., Atlanta, GA. Hayes developed the intelligent modem for first-generation personal computers in 1978, and its command language (Hayes Standard AT Command Set) for modem control has become an industry- standard. The Intelligent Modem An intelligent modem has a command state and an online state. In the command state, it accepts instructions. In the online state, it dials, answers, transmits and receives. Once connected, it performs the handshaking with the remote modem, which is similar to the opening exchange of a telephone call. The called party says "hello," the calling party says "hello, this is..." After this, the real conversation begins. If the modem's speaker is on, you can hear the whistles and tones used in the handshake. Once the handshake is completed, you are online with the other computer, and data can be transmitted back and forth. An important part of the Hayes standard is the escape sequence, which tells the modem to switch from online to the command state. It usually consists of three plus signs in sequence (+++) with a Hayes-patented, one-second guard time interval before and after it, which prevents the modem from mistaking a random occurrence of the escape sequence. The escape sequence and guard time interval can be programmed in the modem's Status registers. To issue an escape sequence, hold down the shift key and press + + +. Pause one second before and after the sequence. The modem will return the OK result code, indicating it is ready to accept commands. HC See high color. HD (1) (High Density) Designation for high-density diskettes; for example, the 5.25" 1.2MB and 3.5" 1.44MB floppies. Contrast with DD. (2) (Hard Disk) For example, FD/HD refers to a floppy disk/hard disk device such as a controller. HDA (Head Disk Assembly) Mechanical components of a disk drive (minus the electronics), which includes the actuators, access arms, read/write heads and platters. HDD (Hard Disk Drive) See hard disk. HDLC (High-level Data Link Control) ISO communications protocol used in X.25 packet switching networks. It provides error correction at the data link layer. SDLC, LAP and LAPB are subsets of HDLC. HDTV (High Definition TV) TV standard with 1125 lines of resolution compared to the 525-line NTSC standard. Japan is currently broadcasting HDTV, and 36" to 50" TV sets cost as much as $15,000. U.S. standards are forthcoming. HDX See half-duplex. head See read/write head. head crash Physical destruction of a hard disk. Misalignment or contamination with dust can cause the read/write head to collide with the disk's recording surface. The data is destroyed, and both the disk platter and head have to be replaced. The read/write head touches the surface of a floppy disk, but on a hard disk, it hovers above its surface at a distance that is less than the diameter of a human hair. It has been said that the read/write head flying over the disk surface is like trying to fly a jet plane six inches above the earth's surface. head-per-track disk Disk drive that has a read/write head positioned over each track, thus eliminating the access arm movement from track to track. head skew Offset distance from the start of the previous track so that the head has time to switch from top of platter to bottom of platter and be at the start of the new track. See cylinder skew. header (1) In data processing, the first record in a file, used for identification. File name, date of last update and other status data are stored in it. (2) In a document or report, common text printed at the top of every page. (3) In communications, the first part of the message, which contains controlling data, such as originating and destination stations, message type and priority level. (4) Any caption or description used as a headline. header label Record used for file identification that is recorded at the beginning of the file. heap In programming, the free memory currently available to load and run programs. heat sink Material that absorbs heat. helical scan Diagonal tracking used on videotape and digital audio tape (DAT), which increases storage capacity over parallel methods. help On-screen instruction regarding the use of a program. On PCs, pressing F1 is the de facto standard for getting help. With graphics-based interfaces (Mac, Windows, etc.), clicking a "?" or HELP button gets help. See context sensitive help. help compiler Software that translates text and compiler instructions into an online help system. Hercules Graphics Video display standard for PCs from Hercules Computer Technology Inc., Berkeley, CA, that provides monochrome graphics and text with a resolution of 720x348 pixels. IBM's first PC monochrome display did not provide graphics, and Hercules introduced its display adapter to fill the void in 1982. It quickly became a de facto standard incorporated into all monochrome display boards. Hermes Code name for Microsoft's enterprisewide network management system that will provide centralized control of resources and manage Windows and Windows NT environments. Expected late 1993. Hertz Frequency of electrical vibrations (cycles) per second. Abbreviated "Hz," one Hz is equal to one cycle per second. In 1883, Heinrich Hertz detected electromagnetic waves. heterogeneous environment Equipment from a variety of manufacturers. heuristic Method of problem solving using exploration and trial and error methods. Heuristic program design provides a framework for solving the problem in contrast with a fixed set of rules (algorithmic) that cannot vary. Hewlett-Packard See HP. hex (HEXadecimal) Hexadecimal means 16. Base 16 numbering system used as a shorthand for representing binary numbers. Each half byte (four bits) is assigned a hex digit as follows:  Dec Hex Binary Dec Hex Binary Dec Hex Binary 0 0 0000 6 6 0110 10 A 1010 1 1 0001 7 7 0111 11 B 1011 2 2 0010 8 8 1000 12 C 1100 3 3 0011 9 9 1001 13 D 1101 4 4 0100 14 E 1110 5 5 0101 15 F 1111 In a hex number, each digit position has a value 16 times greater than the one to its right. Two hex digits make up one byte; for example, A7h (h means hex) is equivalent to decimal 167 (10x16 + 7x1). See hex chart. A 7  敖陳賃陳陳堕陳賃陳陳  4096 256 16 1  青陳珍陳陳祖陳珍陳陳  The hex number A000 (pronounced "A thousand") is equivalent to 40,960 in decimal (4096x10); however, for PC addressing, hex addresses are interpreted uniquely (see paragraph). $, h and H Sometimes a $ is used to represent hex values as well as upper and lower-case H; for example, $3E0, 3E0h and 3E0H are the same hex number. hex chart The following chart is ASCII code in hexadecimal. 浜様様様様様様様様様様様様様様様僕様様様様様様様様 Standard ASCII Extended ASCII The first 32 characters are (IBM PC) control codes. 00 Null 21 ! 51 Q 80 AE DC 楮 01 Start of heading 22 " 52 R 81 AF DD 欹 02 Start of text 23 # 53 S 82 B0 鯵 DE 涅 03 End of text 24 $ 54 T 83 B1 嘘 DF 澪 04 End of transmit 25 % 55 U 84 B2 桶 E0 犧 05 Enquiry 26 & 56 V 85 B3 崖 E1 畉 06 Acknowledge 27 ' 57 W 86 B4 干 E2 盧 07 Audible bell 28 ( 58 X 87 B5 騎 E3 禳 08 Backspace 29 ) 59 Y 88 B6 恭 E4 篋 09 Horizontal tab 2A * 5A Z 89 B7 軍 E5 綺 0A Line feed 2B + 5B [ 8A B8 験 E6 羣 0B Vertical tab 2C , 5C \ 8B B9 抗 E7 膾 0C Form feed 2D - 5D ] 8C BA 些 E8 荳 0D Carriage return 2E . 5E ^ 8D BB 山 E9 藝 0E Shift out 2F / 5F _ 8E ｳ BC 竺 EA 蟶 0F Shift in 30 0 60 ` 8F BD 蹴 EB 觝 10 Data link escape 31 1 61 a 90 BE 廠 EC 貂 11 Device control 1 32 2 62 b 91 BF 審 ED 躡 12 Device control 2 33 3 63 c 92 C0 棲 EE 邵 13 Device control 3 34 4 64 d 93 C1 然 EF 鏈 14 Device control 4 35 5 65 e 94 C2 続 F0 雕 15 Neg. acknowledge 36 6 66 f 95 C3 坦 F1 餾 16 Synchronous idle 37 7 67 g 96 C4 蝶 F2 鮑 17 End trans. block 38 8 68 h 97 C5 迭 F3 鷓 18 Cancel 39 9 69 i 98 C6 導 F4 19 End of medium 3A : 6A j 99 C7 燃 F5 1A Substitution 3B ; 6B k 9A C8 罰 F6 1B Escape 3C < 6C l 9B C9 紐 F7 1C Figures shift 3D = 6D m 9C CA 奮 F8 1D Group separator 3E > 6E n 9D CB 乏 F9 1E Record separator 3F ? 6F o 9E CC 務 FA 1F Unit separator 40 @ 70 p 9F CD 由 FB 20 Blank space 41 A 71 q A0 CE 粒 FC 42 B 72 r A1 ヽ CF 漏 FD 43 C 73 s A2 D0 亞 FE 44 D 74 t A3 ３ D1 儚 FF 45 E 75 u A4 こ D2 匈 46 F 76 v A5 コ D3 啌 47 G 77 w A6 Τ D4 坡 48 H 78 x A7 С D5 娚 49 I 79 y A8 ┳ D6 岾 4A J 7A z A9 D7 彝 4B K 7B { AA D8 愕 4C L 7C | AB D9 抒 4D M 7D } AC DA 擲 4E N 7E ~ AD DB 朿 4F O 7F  50 P 藩様様様様様様様様様溶様様詫様様瞥様様詫様様詫様様 hexadecimal See hex. HFS (Hierarchical File System) Macintosh file system that allows files to be placed into folders, and folders to be placed within other folders. HGC See Hercules Graphics. hi res Same as high resolution. hidden file File classification that prevents a file from being accessed. It is usually an operating system file; however, utility programs let users hide files to prevent unauthorized access. hierarchical Structure made up of different levels like a company organization chart. The higher levels have control or precedence over the lower levels. Hierarchical structures are a one to many relationship; each item having one or more items below it. In communications, a hierarchical network refers to a single computer that has control over all the nodes connected to it. hierarchical communications Network controlled by a host computer that is responsible for managing all connections. Contrast with peer-to-peer communications. hierarchical file system File organization method that stores data in a top- to-bottom organization structure. All access to the data starts at the top and proceeds throughout the levels of the hierarchy. In DOS and OS/2, the root directory is the starting point. Files can be stored in the root directory, or directories can be created off the root that hold files and subdirectories. In the Macintosh, the disk window is the starting point. Files can be stored in the disk window, or folders can be created that can hold files and additional folders. high color Ability to generate 32,768 colors (15 bits) or 65,536 colors (16-bit). 15-bit color uses five bits for each red, green and blue pixel. The 16th bit may be a color, such as XGA with 5-red, 6-green and 5-blue, or be an overlay bit that selects pixels to display over video input. See true color. high definition TV See HDTV. high density Refers to increased storage capacity of bits and/or tracks per square inch. See HD. high DOS memory Same as UMA. high-level format Indexes on a disk that the operating system uses to keep track of the data stored on the disk. See format program. high-level language Machine-independent programming language, such as FORTRAN, COBOL, BASIC, Pascal and C. It lets the programmer concentrate on the logic of the problem to be solved rather than the intricacies of the machine architecture such as is required with low- level assembly languages. high memory (1) Uppermost end of memory. (2) In PCs, the area between 640K and 1M, or the 64K high memory area (HMA) between 1024 and 1088K. High-Performance Computing Federal initiative to enhance U.S. computing capability that includes a T3-speed network linking agencies, private companies and schools to supercomputer centers. high resolution High-quality image on a display screen or printed form. The more dots used per square inch, the higher the quality. To display totally realistic images including the shades of human skin requires about 1,000x1,000 pixels on a 12" diagonal screen. Desktop laser printers print respectable text and graphics at 300 dpi, but typesetting machines print 1,270 and 2,540 dpi. High Sierra First CD ROM standard named for an area near Lake Tahoe where it was conceived in 1985. Later evolved into the ISO 9660 standard. high tech Refers to the latest advancements in computers and electronics as well as to the social and political environment and consequences created by such machines. highlight To identify an area on screen in order to select, move, delete or change it in some manner. highlight bar Currently-highlighted menu item. Choice is made by moving the bar to the desired item and pressing enter or clicking the mouse. The bar is a different color on color screens or reverse video on monochrome screens. HiJaak Graphics file conversion and screen capture program for PCs from Inset Systems Inc., Brookfield, CT. It supports a wide variety of raster and vector graphics formats as well as fax boards. It also handles conversion between PC and Mac formats. HIMEM.SYS XMS driver in DOS 5 and Windows 3.0 that allows programs to cooperatively allocate extended memory in 286s and up. See XMS and DOS HIMEM.SYS. hints Font instructions that alter space and other features to improve the typeface image at low resolutions. Hints help to make a character uniform and legible especially at small point sizes; for example, they ensure that serifs and accents appear in proper proportion. Hints will have less meaning for printing as common desktop resolutions approach 600 and 800 dpi and more, but rendering typefaces on screens, which have less resolution than printers, will still be valuable. HIPO (Hierarchy plus Input-Process-Output) Pronounced "hy-po." IBM flow-charting technique that provides a graphical method for designing and documenting programs. HiPPI (HIgh Performance Parallel Interface channel) ANSI-standard high-speed (100 Mbytes/sec) supercomputer channel. histogram Chart displaying horizontal or vertical bars. The length of the bars are in proportion to the values of the data items they represent. history User input within the current session. A history feature keeps track of user commands and/or retrieved items so that they can be quickly reused or reviewed. HLLAPI (High Level Language Application Program Interface) IBM programming interface that allows a PC application to communicate with a mainframe application. The hardware hookup is handled via normal micro to mainframe 3270 emulation. HLS (Hue Lightness Saturation) Variation of the HSV color model that uses double hexcones (six-sided pyramids). Black is at the bottom, white on top, and the hue coordinates surround the center. HMA (High Memory Area) In PCs, the first 64K of extended memory from 1024K to 1088K, which can be accessed by DOS. It is managed by the HIMEM.SYS driver. HMOS (High-density MOS) Chip with a high density of NMOS transistors. Hobbit Microprocessor from AT&T used in a variety of portable devices. hog Program that uses an excessive amount of computer resources, such as memory or disk, or takes a long time to execute. Hollerith machine First automatic data processing system. It was used to count the 1890 U.S. census. Developed by Herman Hollerith, a statistician who had worked for the Census Bureau, the system used a hand punch to record the data in dollar-bill-sized punched cards and a tabulating machine to count them. It was estimated that, with manual methods, the 1890 census wouldn't be completed until after 1900. With Hollerith's machines, it took two years and saved five million dollars. Hollerith formed the Tabulating Machine Company and sold his machines throughout the world for a variety of accounting functions. In 1911, his company was merged into the company that was later renamed IBM. home brew Products that are developed at home by hobbyists. home button Icon that represents the beginning of a file or a set of operations. home computer Low-priced personal computer such as the Apple II, Commodore 64 and 128, Tandy Color Computer and Atari ST. home key Keyboard key used to move the cursor to the top of the screen or file or to the previous word or beginning of line. See home button. Honeywell See Bull HN. hook In programming, instructions that provide logical breakpoints for future expansion. Hooks may be changed to call some outside routine or function or may be places where additional processing is added. hooked vector Trapped interrupt in a PC. The pointer for a particular interrupt in the interrupt vector table has been modified to jump to a new routine to service that interrupt. hookemware Free software that contains a limited number of features designed to entice the user into purchasing the more comprehensive version. hop count Number of gateways and routers in a transmission path. hopper Tray, or chute, that accepts input to a mechanical device, such as a disk duplicator. horizontal resolution Number of elements, or dots, on a horizontal line (columns in a matrix). Contrast with vertical resolution. horizontal scan frequency Number of lines illuminated on a video screen in one second. For example, a resolution of 400 lines refreshed 60 times per second requires a scan rate of 24KHz plus overhead (time to bring the beam back to the beginning of the next line). Same as horizontal sync frequency in TV. Contrast with vertical scan frequency. horizontal sync See horizontal scan frequency. HOS (Higher Order Software) Design and documentation technique used to break down an information system into a set of functions that are mathematically correct and error free. It uses a rigid set of rules for the decomposition of the total system into its elementary components. The resulting specifications are complete enough to have machine language programs generated directly from them. host Main computer in a distributed processing environment. It typically refers to a large timesharing computer or a central computer that controls a network. host adapter Device that connects a peripheral unit to a computer (computer may be any size). It contains less electronics than a controller. For example, an IDE disk drive has a built-in controller and connects to a non-IDE-ready motherboard via an IDE host adapter (often erroneously called an IDE controller). host based Communications system that is controlled by a large, central computer system. host mode Communications mode that allows a computer to answer an incoming telephone call and receive data without human assistance. hot fix Capability of being repaired while in operation. For example, many SCSI drives can move the data in sectors that are becoming hard to read to spare sectors on the fly without even the SCSI host adapter being aware of it. In some fault tolerant systems, circuit boards and components can be removed and replaced without turning the system off (also called hot swapping). hot link Predefined connection between programs so that when information in one database or file is changed, related information in other databases and files are also updated. See compound document and OLE. hot spot Exact location of the screen cursor that points to and affects the screen object when the mouse is clicked. It is typically the tip of an arrow or finger pointer, but can be elsewhere with other cursor designs. hot swap ~See hot fix. hotkey Key or key combination that causes some function to occur in the computer, no matter what else is currently running. It is commonly used to activate a memory resident (TSR) program. housekeeping Set of instructions that are executed at the beginning of a program. It sets all counters and flags to their starting values and generally readies the program for execution. HP (Hewlett-Packard Company, Palo Alto, CA) Major manufacturer of computers and electronics. It was founded in 1939 by William Hewlett and David Packard in a garage behind the Packard's California home. Its first product, an audio oscillator for measuring sound, was the beginning of a line of electronics that made HP an international supplier of electronic test and measurement instruments. Walt Disney Studios, HP's first big customer, purchased eight oscillators to develop and test a new sound system for the movie "Fantasia." HP entered the computer field in 1966 with the 2116A, the first of the HP 1000 series designed to gather and analyze the data produced by HP instruments. HP 1000 computers are used for CIM applications, such as process monitoring and control, alarm management and machine monitoring. In 1972, HP branched into business computing with the 3000 series, a multiuser system that became well known for its extremely high reliability, especially for that time. The successful 3000 family has continued to be HP's major computer series and has evolved into a full family of computers from micro to mainframe. Also in 1972, HP introduced the first scientific handheld calculator, the HP-35, obsoleting the slide rule and ushering in a new age of pocket- sized calculators. In 1982, the first HP 9000 workstation was introduced. HP's first personal computer was the Touchscreen 150, an MS-DOS personal computer that gained only modest acceptance. In 1985, it introduced the Vectra, a 286-based machine that was the first of a complete line of IBM-compatible PCs. In 1984, HP revolutionized the printer market with its desktop LaserJet printer, which has set the standard for the industry. In 1986, it introduced a new internal design for its 3000 and 9000 families that will carry the company into the 1990s. The new HP Precision Architecture provides a significant increase in performance. In 1989, HP acquired Apollo Computer, which combined with its own line, made HP the market leader in workstations. HP sells over 10,000 different products in the electronics and computer field, and it has gained a worldwide reputation for its rugged and reliable engineering. HP 1000 Family of realtime computers from HP introduced in 1966. They are sensor-based computers used extensively in laboratory and manufacturing environments for collecting and analyzing data. HP 3000 Family of business-oriented computers from HP. Introduced in 1972, these midrange computers set a standard for reliability and rugged engineering. It evolved into a complete line from micros to medium-scale mainframes and has been HP's major computer line. New models are RISC machines that are compatible with the original 3000s. HP 9000 Family of high-performance UNIX workstations and business servers from HP. Introduced in 1982, it is used extensively in CAD and engineering applications. Business servers provide commercial functionality. New models use HP's RISC architecture. HP-PA See HP Precision Architecture. HP Precision Architecture Proprietary RISC architecture from HP introduced in 1986 that is incorporated into new models of its 3000 and 9000 computer families. HP-UX HP's version of UNIX that runs on its 9000 family. It is based on SVID and incorporates features from BSD UNIX along with several HP innovations. HPC See High-Performance Computing. HPFS (High Performance File System) File system, introduced with OS/2 Version 1.2, that handles larger disks (2TB volumes; 2GB files), long file names (256 bytes) and can launch the program by referencing the data as in the Macintosh. It coexists with the existing FAT system. HPGL (Hewlett-Packard Graphics Language) Vector graphics file format from HP that was developed as a standard plotter language. Most plotters support the HPGL and DMPL standards. HPIB (Hewlett-Packard Interface Bus) HP's version of the IEEE 488 standard GPIB. HSB (Hue Saturation Brightness) See HSV. HSL (Hue Saturation Lightness) See HLS. HST (1) Asymetrical modem protocol from U.S. Robotics that includes error control and compression and transmits from 4800 to 14400 bps in one direction and from 300 to 400 bps in the other. (2) (Hubble Space Telescope) Launched in April 1990, it views star material some 10 to 12 billion light years from earth. HSV (Hue Saturation Value) Color model that uses a cylindrical coordinate system structured as an inverted hexcone (six-sided pyramid). Hue is measured by the angle around the vertical axis with red at 0, yellow 60, green 120, cyan 180, blue 240 and magenta 300. Saturation is amount of color from 0 to 1 or 0 to 100%. Value is from black to white (0-1 or 0-100%). Pure green would be H=120, S=1 and V=1. hub Central connecting device for communications lines in a star topology. "Passive hubs" add nothing to the data being transmitted. "Active hubs" regenerate signals and may monitor traffic for network management. "Intelligent hubs" are computers that provide network management and may also include bridging, routing and gateway capabilities. The hub's star topology improves troubleshooting over bus topology, in which all nodes are connected to a common cable. Hubs can be added to Ethernet (bus) networks for improved network management. Both hubs and routers may be inserted into the middle of a network in order to improve performance and network management. See router. hub ring Flat ring pressed around the hole in a 5.25" floppy disk for rigidity. The drive's clamping ring presses the hub ring onto the spindle. hue In computer graphics, a particular shade or tint of a given color. Huffman coding Statistical compression method that converts characters into variable length bit strings. Most- frequently-ocurring characters are converted to shortest bit strings; least frequent, the longest. Compression takes two passes. The first pass analyzes a block of data and creates a tree model based on its contents. The second pass compresses the data via the model. Decompression decodes the variable length strings via the tree. See LZW. hybrid circuit See hybrid microcircuit. hybrid computer Digital computer that processes analog signals which have been converted into digital form. It is used in process control and robotics. hybrid microcircuit Electronic circuit composed of different types of integrated circuits and discrete components, mounted on a ceramic base. Used in military and communications applications, it is especially suitable for building customized analog circuits (A/D, D/A converters, amplifiers, modulators, etc.). hybrid network In communications, a network made up of equipment from multiple vendors. Hydra (1) (Hybrid Document Reproduction Apparatus) A printer, photocopier, scanner and fax built into one machine. (2) Device that converts analog signals to ISDN Basic Rate Interface (BRI). (3) Utility from the Austin Mac Developer's Assn. that tests Macintosh graphics card performance. Hyperaccess PC communications program from Hilgraeve, Inc., Monroe, MI, that provides data compression, has its own script language and supports a variety of terminals and protocols. HyperCard Application development system from Apple that runs on the Macintosh and Apple IIGS. Using visual tools, users build "stacks" of "cards" that hold data, text, graphics, sound and video with hypertext links between them. The HyperTalk programming language allows complex applications to be developed. Third-party compilers can compile HyperCard stacks into executable programs, eliminating the need to have HyperCard running in order to execute the stacks. HyperCard used to be more popular with many commercial and shareware stacks being developed routinely. Today Apple includes only a runtime version with its Macs, not the full development version, which is available from Claris. HyperCard's visual programming approach was brought to PCs with Brightbill-Robert's HyperPad and Asymetrix's ToolBook. hypercube Parallel processing architecture made up of binary multiples of computers (4, 8, 16, etc.). The computers are interconnected so that data travel is kept to a minimum. For example, in two eight-node cubes, each node in one cube would be connected to the counterpart node in the other. hypermedia Use of data, text, graphics, video and voice as elements in a hypertext system. All the various forms of information are linked together so that a user can easily move from one to another. HyperPAD Application development system for PCs from Brightbill-Roberts & Company, Ltd., Syracuse, NY. It is a HyperCard-like program that works in text mode and includes the PADtalk scripting language. HyperScript Advanced macro (scripting) language that is provided with the WINGZ spreadsheet. HyperTalk Programming language used in HyperCard. hypertext Linking related information. For example, by selecting a word in a sentence, information about that word is retrieved if it exists, or the next occurrence of the word is found. The concept was coined by Ted Nelson as a method for making the computer respond to the way humans think and require information. In the electronic versions of this Glossary, you can hypertext to the definition of any term used within the definitions by clicking on it or highlighting it with the mouse. hyperware Hypertext products. hyphen ladder Hyphens on two or more consecutive lines, which causes distraction to the reader. hyphenation Breaking words that extend beyond the right margin. Software hyphenates words by matching them against a hyphenation dictionary or by using a built-in set of rules, or both. See discretionary hyphen. hyphenation dictionary Word file with predefined hyphen locations. hyphenation zone Distance from the right margin within which a word may be hyphenated. hysteresis Lag between making a change, such as increasing or decreasing power, and the response or effect of that change. Hz (HertZ) See Hertz. I-CASE (Integrated CASE) CASE systems that generate applications code directly from design specifications. Features include support for rapid prototyping, modeling the data and processing and drawing logic diagrams. I/E time See instruction cycle. I/O (Input/Output) Transferring data between the CPU and a peripheral device. Every transfer is an output from one device and an input into another. I/O area Reserved segment of memory used to accept data from an input device or to accumulate data for transfer to an output device. See buffer. I/O bound Refers to an excessive amount of time getting data in and out of the computer in relation to the time it takes for processing it. Faster channels and disk drives improve the performance of I/O bound computers. I/O card See expansion board and PC card. I/O channel See channel. I/O interface See port and expansion slot. I/O processor Circuitry specialized for I/O operations. See front end processor. I/O statement Programming instruction that requests I/O. I-time See instruction time. i486 See 486. i750 Programmable compression chip from Intel that supports a variety of techniques including DVI, MPEG and JPEG. i860 RISC-based, 64-bit from Intel that uses a 64-bit data bus, has built-in floating point and 3-D graphics capability and contains over one million transistors. It can be used as a stand-alone CPU or to accelerate performance in existing systems. IAC (InterApplication Communications) IPC capability in Macintosh System 7.0. IBM (International Business Machines Corp., Armonk, NY) World's largest computer company. It started in New York in 1911 when the Computing-Tabulating- Recording Co. (CTR) was created by a merger of The Tabulating Machine Co. (Hollerith's punched card company in Washington), International Time Recording Co. (time clock maker in NY state), Computing Scale Co. (maker of scales and food slicers in Dayton, Ohio), and Bundy Manufacturing (time clock maker in Poughkeepsie, NY). CTR started out with 1,200 employees and a capital value of $17.5 million. In 1914, Thomas J. Watson, Sr., became general manager. During the next 10 years, he dispensed with all non-tabulating business and turned it into an international enterprise renamed IBM in 1924. Watson instilled a strict, professional demeanor in his employees that set IBMers apart from the rest of the crowd. IBM achieved spectacular success with its tabulating machines and the punched cards that were fed into them. From the 1920s through the 1960s, it developed a huge customer base that was ideal for conversion to computers. IBM launched its computer business in 1953 with the 701 and introduced the 650 a year later. By the end of the 1950s, the 650 was the most widely used computer in the world with 1,800 systems installed. The 1401, announced in 1959, was its second computer winner, and by the mid 1960s, an estimated 18,000 were in use. In 1964, it announced System/360, the first family of compatible computers ever developed. The 360s were enormously successful and set a standard underlying IBM mainframes to this day. During the 1970s and 1980s, IBM made a variety of incompatible minicomputer systems, including the System/36 and System/38. Its highly-successful AS/400, introduced in 1988, provides a broad family of compatible machines in this segment. In 1981, IBM introduced the PC into a chaotic personal computer field and set the standard almost overnight. IBM is still the largest single supplier of PCs, but the majority of sales come from the PC industry at large, from companies such as Compaq and Dell to mom and pop shops by the thousands. The 1990s will be the most challenging era for this industry giant. With technology advancing in an never-ending spiral, with PC networks springing up daily, and with downsizing on the lips of every budget-conscious IS manager, IBM will use every ounce of its marketing genius. In 1991, IBM surprised everyone by forming an alliance with Apple to integrate Macintoshes into IBM enterprise networks and to jointly develop a new line of future desktop systems (see Apple for details). No doubt, more surprises are in store! IBM-compatible PC Personal computer that is compatible with the IBM PC and PS/2 standards. IBM mainframes Large-scale computers from IBM. The following series all stem from the System/360 architecture introduced in 1964. Date  Intro. Series name and models  1964 System/360 (Models 20 thru 195) 1970 System/370 (Models 115 thru 168) 1977 303x series (3031, 3032, 3033) 1979 43xx series (4300 thru 4381, ES/4381) 1980 308x series (3081, 3083, 3084) 1986 3090 series (Models 120 thru 600, ES/3090) 1986 9370 series (Entry level; 9370, ES/9370) 1990 System/390 (ES/9000 Models 120 to 900) IBM minicomputers Midrange computers from IBM. The following series comprise IBM's minicomputers over the years.   Date  Intro. Series name  1969 System/3 1975 System/32 1976 Series/1 1977 System/34 1978 System/38 1978 8100 1983 System/36 1985 System/88 1988 AS/400 IBM PC Personal computer from IBM. May refer to the first IBM PC (1981) or to any IBM personal computer model. PC Yr. Intro. CPU Features PC '81 8088 No. 1 (floppy only) XT '83 8088 Slow hard disk XT 286 '86 286 Slow hard disk XT/370 '83 8088 370 emulation AT '84 286 Medium-speed hard disk 3270 PC '83 8088 3270 emulation PCjr '83 8088 Floppy-based home use PC Portable '84 8088 Floppy-based portable Convertible '86 8088 Microfloppy laptop PS/2 Intro. CPU Features (MCA bus unless noted otherwise) 25 '87 8086, PC bus (limited expansion) 30 '87 8086, PC bus 30-286 '88 286, ISA bus 35 LS '91 386SX, ISA bus, diskless 35 SX '91 386SX, ISA bus L40 SX '91 386SX, ISA bus, laptop 40 SX '91 386SX, ISA bus 50 '87 286 50 Z '88 286, faster 50 N51 SX '92 386SX, notebook N51 SLC '92 386SLC, notebook 55 SX '89 386SX 55 LS '90 386SX, diskless 56 SLC '92 386SLC 56 SX '92 386SX, upgradeable 57 SLC '92 386SLC 57 SX '91 386SX, 2.88MB floppy CL57 SX '92 386SX, notebook, active matrix color 60 '87 286 65 '90 386SX 70 '88 386 70 486 '89 486 P70 '89 386 portable P75 486 '90 486 portable, 22 lbs. 76 '92 486SX, OS/2 77 '92 486SX, OS/2 80 '87 386, tower 90 '90 486, XGA, SCSI, upgradable 90 '92 486DX2/66 95 '90 486, tower 90 SX '91 486SX 95 SX '91 486SX, tower Thinkpad laptops 300 '92 386SLC 700 '92 486SLC 700C '92 486SLC, active matrix color IC See integrated circuit and information center. IC card See PC card and memory card. ICCP (Institute for Certification of Computer Professionals) Organization founded in 1973 that offers industry certification and provides worldwide test centers. The Associate Computer Professional exam is open to all. The Certified Computer Programmer (CCP), Certified Data Processor (CDP) and Certified Systems Professional (CSP) require job experience (academic credit may substitute). Address: 2200 E. Devon Ave., Des Plaines, IL 60018, 708/299-4227. icon Small, pictorial, on-screen representation of an object (file, program, disk, etc.) used in graphical interfaces. For example, to delete a file in the Macintosh, the file icon is moved into the wastebasket icon. iconic interface User interface that uses icons. IDA (Intelligent Drive Array) High-performance hard disk interface from Compaq that controls a disk array via the EISA bus. IDAPI (Independent Database API) Programming interface for accessing databases on a network proposed by Borland and supported by IBM, Novell and others. IDC (Int'l. Data Corp., Framingham, MA) Largest market research, analysis, consulting and publishing firm in the information field. It provides annual briefings and in-depth reports on all aspects of the industry. IDE (1) (Integrated Drive Electronics) Hard disk that contains a built-in controller. IDE drives are widely used in PCs and range in capacity from 40MB up to 1GB. The drive connects via a 40-line flat ribbon cable to an IDE host adapter (often called an IDE controller) that plugs into an expansion slot in the PC. The host adapter controls up to two IDE drives, but advanced host adapters control up to four. Some motherboards are built with a 40-pin IDE connector directly on the board thus freeing up an expansion slot for use by another device. The IDE drive uses the ATA interface (AT Attachment), although ATA is often only referenced in technical manuals. See hard disk. Installing a Second IDE Drive Installing a disk drive correctly requires more mechanical skill than it does knowledge of computers or electronics. Fitting the drive into the bays and pushing and pulling on wires is the hard part. Many PCs come with one IDE drive, but the IDE host adapter can usually control two, and the 40- line flat, signal cable between the host adapter and the first drive generally has an open connector for the second drive. Be sure you have two jumpers in hand (available from your hardware supplier) and follow this procedure to install the second drive: 1. DETERMINE IF YOUR BIOS SUPPORTS THE NEW DRIVE Note the cylinder, heads and sectors (spt) identified on the second drive. Go into your BIOS setup and determine if you can define this new drive properly. To get into setup, many PCs display on startup the key to press (often the Del key). If not, look in your hardware manual for the keys to press (sometimes Ctrl-Alt-Esc). Cursor down to the second hard drive, which is either D: or 1 (drives are either indicated as C and D or 0 and 1) and see if you can select either a predefined type that matches your new drive or select User-defined type 47 and enter the cylinders, heads and sectors to derive the total size in megabytes. This time, exit setup without saving anything. If you were able to define the new drive successfully, proceed with step #2, otherwise do not proceed and review the problem with your hardware support personnel. 2. INSTALL THE DRIVE Turn the computer off. Look at your drives and make sure each drive has two sets of pins, one named Master, the other named Slave (possibly only M and S will be printed). Do not proceed if the pins are not present on both drives. Next, place a jumper on Master on the first drive and Slave on the second. Insert the new drive into a drive bay and screw it in. Do not over-tighten screws into the drive. If you want to put a 3.5" drive into a 5.25" drive bay, get an adapter that holds the drive and fits into the 5.25" bay. Plug an available four-wire (red-black-black- yellow/orange) power cable into the drive (it only fits one way). If none is available, get a power cable splitter, pull out an existing power connection to another drive and insert the splitter. Attach both drives to the splitter. The connectors on the flat signal cable can be inserted up or down, so be sure to connect the second drive in the same direction as the first drive. If the cable isn't long enough, a longer 40-pin IDE ribbon cable can be purchased. The three connectors on the cable are common, and either one can be used for either drive or the host adapter. One side of the cable is usually colored. Line that side up with pin 1 on the host adapter and the drives if you have to start from scratch. After installing the drives, turn on the computer and go immediately into setup mode and re- enter the data from step #1 above. This time, select the option that saves the new data to the CMOS RAM. The computer will reboot, and the second drive is now ready for Fdisk and Format (see Formatting a Hard Disk under DOS Format). (2) (Integrated Development Environment) Set of programs run from a single user interface. For example, programming languages often include a text editor, compiler and debugger, which are all activated and function from a common menu. IDE controller (1) Controller built into an IDE drive. (2) Often (erroneously) refers to an IDE host adapter that connects an IDE drive to a non-IDE- ready motherboard. IDMS (Integrated Data Management System) Full-featured relational DBMS from Computer Associates that runs on minis and mainframes. It was developed at GE in the 1960s and marketed by Cullinane, later renamed Cullinet. In 1989, Cullinet was acquired by Computer Associates and IDMS was renamed CA- IDMS/DB. IE See information engineering. IEC (Int'l. Electrotechnical Commission) Organization that sets international electrical and electronics standards founded in 1906 and headquartered in Geneva. It is made up of national committees from over 40 countries. Contact via ANSI, New York, NY. IEEE (Institute of Electrical and Electronic Engineers) Membership organization that includes engineers, scientists and students in electronics and allied fields. Founded in 1963, it has over 300,000 members and is involved with setting standards for computers and communications. Address: 345 E. 47th St., New York, NY 10017, 212/705-7900. The Computer Society of the IEEE has over 100,000 members and holds meetings and technical conferences on computers. Address: 1730 Mass. Ave. N.W., Washington, DC 20036, 202/371-0101. IEEE 488 See GPIB. IEEE 802 IEEE standard for local area networks. See "LANs" under data link protocol. 敖802.1陳Covers network management, etc.陳陳陳朕 敖陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳潰 敖802.2陳Specifies data link layer for陳陳 the following access methods 青陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳潰 敖陳802.3陳 敖802.4陳 敖陳陳802.5陳陳陳 CSMA/CD token token ring "Ethernet" bus "IBM Token Ring" 青潰 青陳陳陳陳潰 青陳陳陳陳 青陳陳陳陳陳陳陳潰 IEF (Information Engineering Facility) CASE software from TI that runs on PCs and MVS mainframes and generates COBOL code for PCs, MVS mainframes, VMS, Tandem, AIX, HP-UX and other UNIX platforms. It is a fully-integrated set of CASE tools. IEW (Information Engineering Workbench) CASE software from Knowledgeware, Inc., Atlanta, GA, that runs on DOS PCs and generates COBOL, CICS and IMS code for MVS mainframes. if-then-else High-level programming language statement that compares two or more sets of data and tests the results. If the results are true, the THEN instructions are taken; if not, the ELSE instructions are taken. The following is a BASIC example:  10 IF ANSWER = "Y" THEN PRINT "Yes"  20 ELSE PRINT "No"  In certain languages, THEN is implied. All statements between IF and ELSE are carried out if the condition is true. All instructions between ELSE and ENDIF are carried out if not true. The following dBASE example produces the same results as above:  IF ANSWER = "Y"  ? "Yes"  ELSE  ? "No"  ENDIF  IFIP (Int'l. Federation of Information Processing) Multinational affiliation of professional groups concerned with information processing, founded in 1960. There is one voting representative from each country (U.S. representative is FOCUS). Address: 16 Place Longemalle, CH-1204 Geneva, Switzerland, 41 22 28 2649. IFS (Installable File System) OS/2 feature that supports multiple file systems. Different systems can be installed (UNIX, CD ROM, etc.) just like drivers are installed for new peripherals. IGES (Initial Graphics Exchange Specification) ANSI graphics file format that is system independent and also intended for human interpretation. It evolved out of the Air Force's Integrated Computer Automated Manufacturing (ICAM) program in 1979. For more on IGES and PDES, contact: IGES Organization, National Institute of Standards & Technology, Building 220, Room A-353, Gaithersburg, MD 20899, 301/921-3691. IIA (1) (Information Industry Assn.) Trade organization that includes members from all aspects of the information field. Its purpose is to conduct active government relations that safeguard the interests of a healthy, competitive information industry. IIA sponsors seminars and conferences and provides newsletters, newspapers and books. Address: 555 New Jersey Ave. N.W., Washington, DC 20001, 201/639-8262. (2) (Information Interchange Architecture) IBM formats for exchanging documents between different systems. illustration program Same as drawing program. Illustrator 88 Macintosh drawing program from Adobe Systems, Inc., that enhanced the original Illustrator program in 1988. It provides sophisticated tracing and text manipulation capabilities, as well as colors and color separations. IM See information management. image (1) A picture (graphic). (2) See system image. image enhancement Improving graphics images either manually using a paint program or by using software routines that change contrast, smooth lines or filter out unwanted data. See anti-aliasing. image processing (1) Analysis of a picture using techniques that can identify shades, colors and relationships that cannot be perceived by the human eye. It is used to solve identification problems, such as in forensic medicine or in creating weather maps from satellite pictures and deals with images in raster graphics format that have been scanned in or captured with digital cameras. (2) Image improvement, such as refining a picture in a paint program that has been scanned or entered from a video source. (3) Same as imaging. imagesetter Typesetting machine that handles text and graphics and typically accepts PostScript input. See phototypesetter. imaging Creating a film or electronic image of any picture or paper form. It is accomplished by scanning or photographing an object and turning it into a matrix of dots (raster graphics), the meaning of which is unknown to the computer, only to the human viewer. Scanned images of text may be encoded into computer data (ASCII or EBCDIC) with page recognition software (OCR). See micrographics, image processing and document imaging. imaging model Set of rules for representing images. imaging system See document imaging, image processing and image enhancement. immediate access Same as direct access. impact printer Printer that uses a printing mechanism that bangs the character image into the ribbon and onto the paper. See printer for examples. impedance Resistance to the flow of alternating current in a circuit. implementation (1) Computer system implementation is the installation of new hardware and system software. (2) Information system implementation is the installation of new databases and application programs and the adoption of new manual procedures. implode To link component pieces to a major assembly. It may also refer to compressing data using a particular technique. Contrast with explode. import To convert a file in a foreign format to the format of the program being used. Improv Multidimensional Windows spreadsheet from Lotus that allows for easy switching to different views of the data. Data is referenced by name as in a database rather than the typical spreadsheet row and column coordinates. Improv was originally developed for the NeXt computer. IMS (Information Management System) IBM hierarchical DBMS for mainframes under MVS. It was widely implemented throughout the 1970s and continues to be used. IMS/DC is its transaction processing component (like CICS) that handles the details of communications and SNA networking. IMS/DC is also used to access DB2 databases. in hardware Refers to logic that has been placed into the electronic circuits of the computer. in software Refers to logic in a program. For example, "that routine is done in software." incident light In computer graphics, light that strikes an object. The color of the object is based on how the light is absorbed or reflected by the object. increment To add a number to another number. Incrementing a counter means adding 1 to its current value. incremental backup See backup types. incremental spacing See microspacing. IND$FILE IBM mainframe program that transfers files between the mainframe and a PC functioning as a 3270 terminal. indent To align text some number of spaces to the right of the left margin. See hanging paragraph. index (1) In data management, the most common method for keeping track of data on a disk. Indexes are directory listings maintained by the OS, DBMS or the application. An index of files contains an entry for each file name and the location of the file. An index of records has an entry for each key field (account no., name, etc.) and the location of the record. (2) In programming, a method for keeping track of data in a table. See indexed addressing. index hole Small hole punched into a hard sectored floppy disk that serves to mark the start of the sectors on each track. index mark Physical hole or notch, or a recorded code or mark, that is used to identify a starting point for each track on a disk. index register High-speed circuit used to hold the current, relative position of an item in a table (array). At execution time, its stored value is added to the instructions that reference it. indexed addressing Technique for referencing memory that automatically increments the address with the value stored in an index register. See subscript (2). indexed sequential See ISAM. indexing (1) Creating indexes based on key data fields or key words. (2) Creating timing signals based on detecting a mark, slot or hole in a moving medium. indirect addressing Address mode that points to another pointer rather than the actual data. This mode is prohibited in RISC architecture. inductance Opposition to the changing flow of current in a circuit, measured in Henrys. induction Process of generating an electric current in a circuit from the magnetic influence of an adjacent circuit as in a transformer or capacitor. inference engine Processing program in an expert system. It derives a conclusion from the facts and rules contained in the knowledge base using various artificial intelligence techniques. infix notation Common way arithmetic operators are used to reference numeric values. For example, A+B/C is infix notation. Contrast with Polish notation and reverse Polish notation. Info Select Popular personal information manager (PIM) for PCs from Micro Logic Corp., Hackensack, NJ, that includes automatic phone dialing via modem. It is noted for its exceptional ease of use and ability to store random information and instantly retrieve it. It is based on an earlier product called Tornado conceived by Paul Mendelsohn. infopreneur Person who is in business to gather and disseminate electronic information. informate To dispense information, as coined by Harvard Professor Shoshana Zuboff. information Summarization of data. Technically, data are raw facts and figures that are processed into information, such as summaries and totals. But since information can also be raw data for the next job or person, the two terms cannot be precisely defined. Both terms are used synonymously and interchangeably. As office automation and data processing merge, it may be more helpful to view information the way data is defined and used, namely: data, text, spreadsheets, pictures, voice and video. Data are discretely defined fields. Text is a collection of words. Spreadsheets are data in matrix (row and column) form. Pictures are lists of vectors or frames of bits. Voice is a continuous stream of sound waves. Video is a sequence of frames. Future databases will routinely integrate all these forms of information. information appliance Type of future home or office device that can transmit to or plug into common public or private networks. Envisioned is a "digital highway," like telephone and electrical power networks. information center Division within the IS department that supports end-user computing. Responsible for training users in applications and solving related personal computer problems. information engineering Integrated set of methodologies and products used to guide and develop information processing within an organization. It starts with enterprise-wide stategic planning and ends with running applications. information hiding Keeping details of a routine private. Programmers only know what input is required and what outputs are expected. See encapsulation and data abstraction. information industry (1) Information publishing. Organizations that provide information via online services or through distribution by diskette or CD ROM. (2) All computer, communications and electronics- related organizations, including hardware, software and services. information management Discipline that analyzes information as an organizational resource. It covers the definitions, uses, value and distribution of all data and information within an organization whether processed by computer or not. It evaluates the kinds of data/information an organization requires in order to function and progress effectively. Information is complex because business transactions are complex. It must be analyzed and understood before effective computer solutions can be developed. See data administration. information processing Same as data processing. information resource management See Information Systems and information management. information science See information management. information service Any information retrieval, publishing, timesharing or BBS facility. See online services. Information Services See Information Systems. information system Business application of the computer. It is made up of the database, application programs, manual and machine procedures and encompasses the computer systems that do the processing. The database stores the subjects of the business (master files) and its activities (transaction files). The application programs provide the data entry, updating, query and report processing. The manual procedures document how data is obtained for input and how the system's output is distributed. Machine procedures instruct the computer how to perform the batch processing activities, in which the output of one program is automaticaly fed into another program. The daily processing is the interactive, realtime processing of the transactions. At the end of the day or other period, the batch processing programs update the master files that have not been updated since the last cycle. Reports are printed for the cycle's activities. The periodic processing of an information system is the updating of the master files, which adds, deletes and changes the information about customers, employees, vendors and products.  Relationships Between Systems  STRUCTURE (is) FUNCTION (does) 陳Management system陳賃陳陳陳陳陳陳陳陳陳陳陳陳陳 Sets organization's goals 1. PEOPLE and objectives, strategies 2. MACHINES and tactics, plans, schedules and controls 陳Information system陳田陳陳陳陳陳陳陳陳陳陳陳陳陳 1. DATABASE Defines data structures 2. APPLICATION Data entry, updating, PROGRAMS queries and reporting 3. PROCEDURES Defines data flow 陳Computer system陳陳津陳陳陳陳陳陳陳陳陳陳陳陳陳 1. CPU Processes (The 3 C's) 2. PERIPHERALS Store and retrieve 3. OPERATING SYSTEM Manages computer system Information Systems Formal title for a data processing, MIS, or IS department. Other titles are Data Processing, Information Processing, Information Services, Management Information Systems, Management Information Services and Information Technology. information theory Study of encoding and transmitting information. From Claude Shannon's 1938 paper, "A Mathematical Theory of Communication," which proposed the use of binary digits for coding information. information utility (1) Service bureau that maintains up-to-date databases for public access. (2) Central source of information for an organization or group. information warehouse Collection of all databases in an enterprise across all platforms and departments. INFORMIX Family of DBMSs from Informix Software, Inc., Menlo Park, CA, that includes an SQL-based relational DBMS, fourth-generation language and toolkits for embedding SQL in application programs. infoware Information sold electronically, such as the electronic versions of this Glossary. InfoWindow Trade name for IBM display screens. infrared Invisible band of radiation at the low-frequency end of the light spectrum. Contrast with ultraviolet. INGRES (INteractive Graphics and REtrieval System) Relational DBMS from Ingres Corp., Alameda, CA, that runs on VAXs and UNIX workstations. It includes a 4GL, QBE and lets users create and manage a database as a series of forms. Its Knowledge Management extension allows rules to be programmed into the database. Ingres Corp. was formerly Relational Technology, a company founded in 1980 to market a commercial version of INGRES, which was developed at the Univ. of California at Berkeley in the early 1970s. inheritance In object-oriented programming, the ability of one class of objects to inherit properties from a higher class. inhouse Operation that takes place on the user's premises. INIT (INITiate) Macintosh routine that is run when the computer is started or restarted. It is used to load and activate drivers and system routines. Many INITs are memory resident and may conflict with each other like TSRs in the PC environment. initial program load See IPL. initialization string Same as setup string. initialize To start anew, which typically involves clearing all or some part of memory or disk. ink jet Printer mechanism that sprays one or more colors of ink onto paper and produces high-quality printing like that of a laser printer. The continuous stream method produces droplets that are aimed onto the paper by electric field deflectors. The drop-on-demand method uses a set of independently controlled injection chambers, the newest of which use solid ink developed by Exxon in 1983. Solid ink liquefies quickly when heated and solidifies instantly when it reaches the paper. INMARSAT (INternational MARitime SATellite) International organization involved in providing satellite communications to and from ships and offshore rigs. It is represented in the U.S. and partially owned by COMSAT. innoculate To store characteristics of an executable program in order to detect a possible unknown virus if the file is changed. input (1) Data that is ready for entry into the computer. (2) To enter data into the computer. input area Reserved segment of memory that is used to accept data from a peripheral device. Same as buffer. input device Peripheral device that generates input for the computer such as a keyboard, scanner, mouse or digitizer tablet. input/output See I/O. input program Same as data entry program. input queue Reserved segment of disk or memory that holds messages that have been received or job control statements describing work to be done. input stream Collection of job control statements entered in the computer that describe the work to be done. inquiry program Same as query program. Ins key (INSert key) A keyboard key that is used to switch between insert and overwrite mode or to insert an object at the current cursor location. insert mode Data entry mode that causes new data typed on the keyboard to be inserted at the current cursor location on screen. Contrast with overwrite mode. install program Software that prepares a software package to run in the computer. It copies the files from the distribution diskettes to the hard disk and decompresses them, if required. It may ask you to identify your computer environment in order to link in the drivers for the display, printer and other devices that you have. installation conflicts See PC conflicts. installation spec Documentation from an equipment manufacturer that describes how a product should be properly installed within a physical environment. instance In object-oriented programming, a member of a class; for example, "Lassie" is an instance of the class "dog." When an instance is created, the initial values of its instance variables are assigned." instance variable In object-oriented programming, the data in an object. instant print Ability to use the computer as a typewriter. Each keystroke is transferred to the printer. instantiate In object-oriented programming, to create an object of a specific class. See instance. instruction (1) Statement in a programming language. (2) Machine instruction. instruction cycle Time in which a single instruction is fetched from memory, decoded and executed. The first half of the cycle transfers the instruction from memory to the instruction register and decodes it. The second half executes the instruction. instruction mix Blend of instruction types in a program. Often refers to writing generalized benchmarks, which requires that the amount of I/O versus processing versus math instructions, etc., reflects the type of application the benchmark is written for. instruction register High-speed circuit that holds an instruction for decoding and execution. instruction repertoire Same as instruction set. instruction set Repertoire of machine language instructions that a computer can follow (from a handful to several hundred). It is a major architectural component and is either built into the CPU or into microcode. Instructions are generally from one to four bytes long. instruction time Time in which an instruction is fetched from memory and stored in the instruction register. It is the first half of the instruction cycle. insulator Material that does not conduct electricity. Contrast with conductor. int Programming statement that specifies an interrupt or that declares an integer variable. See interrupt and integer. int 13 DOS interrupt used to activate disk functions, such as seek, read, write and format. integer Whole number. In programming, the integer function would yield 123 from 123.898. Integer BASIC Apple version of BASIC for the Apple II that handles only fixed point numbers (non-floating point). Due to its speed, many games are written in it. integrated Collection of distinct elements or components that have been built into one unit. integrated CASE See I-CASE. integrated circuit Formal name for chip. integrated injection logic Type of bipolar transistor design known for its fast switching speeds. integrated software package Software that combines several applications in one program, typically database management, word processing, spreadsheet, business graphics and communications. Such programs (Microsoft Works, AppleWorks, etc.) provide a common user interface for their applications plus the ability to cut and paste data from one to the other. User interfaces, such as found on the Macintosh and Windows, provide this capability with all applications written for their environments. integrator In electronics, a device that combines an input with a variable, such as time, and provides an analog output; for example, a watt-hour meter. integrity See data integrity. Intel (Intel Corp., Santa Clara, CA) Leading manufacturer of semiconductor devices founded in 1968 by Bob Noyce and Gorden Moore in Mountain View, CA. A year later it introduced its first product, a 64-bit bipolar static RAM chip. By 1971, its very successful memory chips began to obsolete magnetic core storage. Intel is known for its x86 microprocessor family, but it also developed the first microprocessor in 1971. In response to a calculator chip order from Japanese manufacturer Busicom, Intel engineer Marcian E. "Ted" Hoff decided it would make more sense to design a general-purpose machine. The resulting 4004 chip was the world's first microprocessor. Over the years, Intel has developed a wide variety of chips and board-level products, including the MULTIBUS bus used in industrial applications. Intel started with 12 people and first year revenues of $2672. In 1990, it had 24,000 employees and revenues of four billion. Intellect Natural language query program from AI Corp., Waltham, MA, that runs on IBM mainframes and other computers. It can answer many English language questions; for example, "Tell me the number of employees in the personnel department." Intellifont Scalable font technology from Agfa CompuGraphic. Intellifont typefaces are built into LaserJet IIIs and 4s (see LaserJet). The Intellifont for Windows font scaler creates matching screen fonts for Windows from Intellifont and compatible typefaces. intelligence Processing capability. Every computer is intelligent! intelligent cable Same as smart cable. intelligent controller Peripheral control unit that uses a built-in microprocessor for controlling its operation. intelligent database Database that contains knowledge about the content of its data. A set of validation criteria are stored with each field of data, such as the minimum and maximum values that can be entered or a list of all possible entries. See DBMS (Intelligent Databases). intelligent form Data entry application that provides help screens and low levels of AI in aiding the user to enter the correct data. intelligent hub Network hub that performs a variety of functions such as regenerating signals, monitoring transmission for network management, allowing connections to a variety of cable types and routing. Contrast with passive hub. See hub. intelligent modem Modem that responds to commands and can accept new instructions during online transmission. It was originally developed by Hayes. intelligent paper Same as intelligent form. intelligent terminal Terminal with built-in processing capability, but no local disk or tape storage. It may use a general-purpose CPU or may have specialized circuitry as part of a distributed intelligence system. Contrast with dumb terminal. INTELSAT (INt'l. TELecommunications SATellite) International organization involved in launching and operating commercial satellites. It was created in 1964 with only 11 countries participating. Today, over 100 nations have ownership. It is represented in the U.S. and partially owned by COMSAT. inter To cross over boundaries; for example, internetwork means from one network to another. Contrast with intra. interactive Back-and-forth dialog between the user and a computer. interactive cable TV Service in which viewers take part in TV programs by reacting to issues. It implies full TV viewing, in contrast with videotex or teletext. In time, all of these services may be provided over cable TV channels. A decoder and keyboard are required. interactive session Back-and-forth dialogue between user and computer. Contrast with batch session. interactive video Use of videodisc or CD ROM controlled by computer for an interactive education or entertainment program. See videodisc and CD ROM. InterBase Relational DBMS from Borland that runs on UNIX workstations and VAXes, designed to handle online complex processing (OLCP). It can be a peer-to- peer or client/server system and uses SQL plus its own data manipulation language. interblock gap Same as interrecord gap. interface Connection and interaction between hardware, software and the user. Hardware interfaces are the plugs, sockets, wires and the electrical pulses travelling through them in a particular pattern. Also included are all electrical timing considerations. Examples are RS-232 transmission, the Ethernet and Token Ring network topologies and the IDE, ESDI, SCSI, ISA, EISA and Micro Channel interfaces. Software, or programming, interfaces are the languages, codes and messages programs use to communicate with each other and to the hardware. Examples are the applications that run under the Mac, DOS and Windows operating systems as well as the SMTP e-mail and LU 6.2 communications protocols. User interfaces are the keyboards, mice, commands and menus used for communication between you and the computer. Examples are the command lines in DOS and UNIX and the Mac, Windows and Motif graphical interfaces. Interfacing is a major part of what engineers, programmers and consultants do. Users "talk to" the software. The software "talks to" the hardware and other software. Hardware "talks to" other hardware. All this is interfacing. It has to be designed, developed, tested and redesigned, and with each incarnation, a new specification is born that may become yet one more de facto or regulated standard. Format & Function Every interface implies a structure. Electrical signals are made up of voltage levels, frequencies and duration. The data passed from one device or program to another has a precise format (header, body, trailer, etc.). Every interface implies a function. At the hardware level, electronic signals activate functions; data is read, written, transmitted, received, analyzed for error, etc. At the software level, instructions activate the hardware (access methods, data link protocols, etc.). At higher levels, the data transferred or transmitted may itself request functions to be performed (client/server, program to program, etc.). Language & Programming An interface is activated by programming language commands. The complexity of the functions and the design of the language determine how difficult it is to program. Interface, Protocol, API and ABI The interface between the user and the computer is called a user interface; between components in a network, a protocol; between two programs, an API, and between an application and a computer environment, an API or ABI. All these interactions are interfaces, and the terms are used interchangeably. Regardless of what they're called, they all imply a set of rules that must be followed. interface adapter In communications, a device that connects the computer or terminal to a network. interframe coding In video compression, coding only the differences between frames. See intraframe coding. interlaced Illuminating a CRT by displaying odd lines and then even lines (every other line first; then filling in the gaps). TV signals are interlaced and generate 60 half frames (30 full frames) per second. Computer display systems may also be interlaced, but usually only at the highest resolution. Rather than send every line of information to the screen (non-interlaced), interlacing sends half the information in the same time frame, thus requiring less-complicated and less-expensive circuits. TV's constant animation has always provided acceptable viewing using the interlaced method, although reading a still image on TV is not all that pleasing. Interlaced screens used on computers can provide an annoying flicker that causes headaches and eye strain (see below). Interlaced Non-interlaced 1 臆臆臆臆臆臆 臆臆臆臆臆臆臆 2 旭旭旭旭旭旭 臆臆臆臆臆臆臆 3 臆臆臆臆臆臆 臆臆臆臆臆臆臆 4 旭旭旭旭旭旭 臆臆臆臆臆臆臆 5 臆臆臆臆臆臆 臆臆臆臆臆臆臆 Where's the Flicker? When you purchase a video display adapter and monitor, the interlaced vs non-interlaced issue comes up when you get into the highest modes. For example, most VGA adapters and monitors support the following three resolutions: 640x480, 800x600 and 1024x768. Advanced models support 1280x1024 and higher. The lower resolutions (640x480 and 800x600) are usually non-interlaced, but the highest mode 1024x768 or 1280x1024 may be interlaced. When you start up under DOS, you are always at the lowest, non-interlaced 640x480 resolution. It's only when you get into Windows or AutoCAD that you get into the higher modes. An interlaced resolution does not cause flicker like a badly-synchronized movie projector. Rather it provides a faint overall flutter that is often very noticeable on tiny, complex graphic elements such as icons. A related issue is the vertical scan frequency, or the number of times the entire screen is refreshed per second. Since the refresh rate may go down as resolution goes up, this is another consideration. The number can range from 45 to over 100; however, 60 is the smallest refresh recommended. For CAD and destop publishing, a non-interlaced 1280x1024 resolution with a 70Hz refresh rate on a 21" monitor is recommended. Depending on the size of the page you are working with, a non-interlaced 1024x768 resolution on a 17" screen may suffice. The high resolutions required to see full pages and facing pages of text provide enough strain on the eyes. Interlaced screens and low refresh rates only add to the burden. Interleaf Full-featured desktop publishing software for 386 and higher PCs from IBM. Includes text and graphics editing, free-hand drawing, supports PostScript and provides connectivity to shared AS/400 folders. interleave See sector interleave and memory interleaving. interlock Device that prohibits an action from taking place. intermediate language Same as pseudo language. intermediate node routing Routing a message to non-adjacent nodes; for example, if three computers are connected in series A--B--C, data transmitted from A to C can be routed through B. intermittent error Error that occurs sporadically, not consistently. It is very difficult to diagnose and repair. internal bus Data pathway between closely-connected components, such as between the CPU and memory. See local bus. internal font Set of characters for a particular typeface that is built into a printer. Contrast with font cartridge and soft font. internal interrupt Interrupt that is caused by processing, for example, a request for input or output or an arithmetic overflow error. Contrast with external interrupt. internal modem Modem that plugs into a particular computer's expansion slot from which it derives its power. Contrast with external modem. internal sort Sorting accomplished entirely in memory without using disks or tapes for temporary files. internal storage Same as memory. internet (1) Large network made up of a number of smaller networks. (2) (Internet) National research-oriented network comprised of over 3,000 government and academic networks in more than 40 countries. Access to the Internet is available through many online services such as CompuServe, BIX and America Online. See online services. Internet address The format for addressing a message to an Internet user is: recipient@location.domain. For example, the address of the Free Software Foundation is gnu@prep.ai.mit.edu, which means transmitting to the GNU mailbox via nodes PREP, AI and MIT.  Internet Domains  com - business edu - educational gov - government mil - military site net - gateway or host org - other organization InterNet Router Macintosh software from Apple that internetworks different access methods (LocalTalk, EtherTalk, TokenTalk, etc.) and can reside in any network station. Each Router can connect up to eight networks with a maximum of 1,024 networks and 16 million nodes. internetwork To go between one network and another. interoperable Ability for one system to communicate or work with another. interpolate To estimate values that lie between known values. Interpress Page description language from Xerox used on the 2700 and 9700 page printers (medium to large-scale laser printers). Ventura Publisher provides output in Interpress. interpret To run a program one line at a time. Each line of source language is translated into machine language and then executed. interpreter High-level programming language translator that translate and runs the program at the same time. It translates one program statement into machine language, executes it, then proceeds to the next statement. Interpreted programs run slower than their compiler counterparts, because the compiler translates the entire program before it is run. However, it's convenient to write an interpreted program, since a single line of code can be tested interactively. Interpreted programs must always be run with the interpreter. For example, in order to run a BASIC or dBASE program, the BASIC or dBASE interpreter must be in the computer. If a language can be both interpreted and compiled, a program may be developed with the interpreter and compiled for production. interpretive language Programming language that requires an interpreter to run it. interprocess communication See IPC. interrecord gap Space generated between blocks of data on tape, created by the starting and stopping of the reel. interrogate (1) To search, sum or count records in a file. See query. (2) To test the condition or status of a terminal or computer system. interrupt Signal that gets the attention of the CPU and is usually generated when I/O is required. For example, hardware interrupts are generated when a key is pressed or when the mouse is moved. Software interrupts are generated by a program requiring disk input or output. An internal timer may continually interrupt the computer several times per second to keep the time of day current or for timesharing purposes. When an interrupt occurs, control is transferred to the operating system, which determines the action to be taken. Interrupts are prioritized; the higher the priority, the faster the interrupt will be serviced. interrupt-driven Computer or communications network that uses interrupts. interrupt latency Time it take to service an interrupt. It becomes a critical factor when servicing realtime functions such as a communications line. See UART overrrun. interrupt mask Internal switch setting that controls whether an interrupt can be processed or not. The mask is a bit that is turned on and off by the program. interrupt priorities Sequence of importance assigned to interrupts. If two interrupts occur simultaneously, the interrupt with the highest priority is serviced first. In some systems, a higher-priority interrupt can gain control of the computer while it's processing a lower-priority interrupt. interrupt vector In the PC, one of 256 pointers that reside in the first 1KB of memory. Each vector points to a routine in the ROM BIOS or elsewhere in memory, which handles the interrupt. intersect In relational database, to match two files and produce a third file with records that are common in both. For example, intersecting an American file and a programmer file would yield American programmers. intra Within a boundary; for example, intraoffice refers to operations that take place within the office. Contrast with inter. intraframe coding Compressing redundant areas within a video frame. See interframe coding. inverse video Same as reverse video. inverted file In data management, a file that is indexed on many of the attributes of the data itself. For example, in an employee file, an index could be maintained for all secretaries, another for managers. It's faster to search the indexes than every record. Inverted file indexes use lots of disk space; searching is fast, updating is slower. inverted list Same as inverted file. inverter (1) Logic gate that converts the input to the opposite state for output. If the input is true, the output is false, and vice versa. An inverter performs the Boolean logic NOT operation. (2) Circuit that converts DC current into AC current. Contrast with rectifier. invoke To activate a program, routine, function or process. IOCA (Image Object Content Architecture) See MO:DCA. IOCS (Input Output Control System) Early, rudimentary IBM operating system (1950s). It was a set of I/O routines for tapes and disks. Today's counterpart in the PC is the ROM BIOS. ion deposition Printing technology used in high-speed page printers. It is similar to laser printing, except instead of using light to create a charged image on a drum, it uses a printhead that deposits ions. After toner is attracted to the ions on the drum, the paper is pressed directly against the drum fusing toner to paper. Quality approaches that of a laser printer; however, the ink has not been embedded as deeply, and the paper can smear more easily. IOS (Integrated Office System) See office automation. IP (1) (Internet Protocol) IP part of the TCP/IP protocol, which routes a message across networks. See TCP/IP and datagram. (2) See image processing. IPC (InterProcess Communication) Exchange of data between one program and another either within the same computer or over a network. It implies a protocol that guarantees a response to a request. Examples are OS/2's Named Pipes, Windows' DDE, Novell's SPX and Macintosh's IAC. Although IPCs are performed automatically by the programs, an analogous function is performed interactively when users cut and paste data from one file to another using the clipboard. IPDS (Intelligent Printer Data Stream) IBM format for sending full pages of text and graphics from a mainframe or mini to a laser printer. IPI (Intelligent Peripheral Interface) High-speed hard disk interface used with minis and mainframes that transfers data in the 10 to 25 MBytes/sec range. IPI-2 and IPI-3 refer to differences in the command set that they execute. See hard disk. IPL (Initial Program Load) Same as boot. ips (Inches Per Second) Measures the speed of tape passing by a read/write head or paper passing through a pen plotter. IPX (Internet Packet EXchange) NetWare communications protocol used to route messages from one node to another. Application programs that manage their own client/server or peer-to-peer communications in a Novell network can access IPX, or NetWare's SPX protocol, directly. IPX does not guarantee delivery of a message as does SPX. IR (Industry Remarketer) Same as VAR or VAD. IRG (InterRecord Gap) See interrecord gap. IRM (Information Resource Management) See Information Systems and information management. IRMAboard Micro to mainframe board for PCs from DCA, Inc., Alpharetta, GA. It emulates the common IBM 3270 mainframe terminal allowing a PC access to centralized mainframe applications. IRMA is DCA's trade name for a variety of communications products. It is the lady's name, not an acronym. IRMALAN Family of gateway products from DCA, Inc., Alpharetta, GA, that allow PC users connected to NetBIOS-compatible LANs to access an SNA host. It includes gateways for IEEE 802.2, SDLC and DFT environments. iron oxide Material used to coat the surfaces of magnetic tapes and lower-capacity disks. IRQ (Interrupt ReQuest) Hardware interrupt on a PC. Eight lines (0-7 on 8086/88s) and 16 lines (0-15 on 286s and up) accept interrupts from devices such as a scanner and network adapter. Unless specifically programmed to interact together, two devices cannot use the same line. If a new expansion board is preset to the IRQ used by an existing board, one of them must be changed. See PC conflicts. Starting with the 286, the PC uses two 8259A controller chips to handle the IRQs. The chips are cascaded together. IRQ 2 connects to IRQ 9 of the second chip. IRQ Assignment 0 System timer 1 Keyboard 2 Connects to IRQ 9 3 COM2, COM4 4 COM1, COM3 5 LPT2 6 Floppy disk 7 LPT1 8 Realtime clock 9 3270 emulation 10 - 11 - 12 - 13 Math coprocessor 14 Hard disk 15 - IS See Information Systems. ISA (Industry Standard Architecture) Pronounced "eye- suh." Expansion bus commonly used in PCs. It accepts the plug-in boards that control the video display, disks and other peripherals. The majority of PC expansion boards on the market are ISA boards. ISA was originally called the AT bus, because it was first used in the IBM AT (1984), and it extended the original PC bus from eight to 16 bits. Most ISA PCs provides a mix of 8-bit and 16-bit expansion slots. Contrast with EISA ("ee-sa") and Micro Channel. ISA vs Local Bus Starting with the 386, when CPU speeds began to dramatically accelerate, PCs have been built with two buses. The CPU communicates with its memory chips via a 32-bit internal path, known as the local bus, at its full clock speed, which can be as high as 50MHz. RAM chips are directly connected to the motherboard to allow for this high-speed transfer. In contrast, the PC transfers data between its peripheral devices over the 16-bit ISA bus at only 8MHz. Even the 32-bit EISA and Micro Channel buses do not normally run much faster. This local bus, reserved for high-speed memory transfer, is now being tapped to transfer data to and from peripheral devices. See local bus. ISAM (Indexed Sequential Access Method) Common disk access method that stores data sequentially, while maintaining an index of key fields to all the records in the file for direct access. The sequential order would be the one most commonly used for batch processing and printing (account number, name, etc.). ISDN (Integrated Services Digital Network) International telecommunications standard for transmitting voice, video and data over a digital line. It uses 64Kbps circuit-switched B (Bearer) channels to carry voice and data and uses a separate D (Data) channel to carry control signals via a packet-switched network. This out-of-band D channel allows a variety of services to be provided, including call forwarding, call waiting and advice of charge. The two types of service are: BASIC RATE INTERFACE (BRI) 144Kbps Includes two B channels and one 16Kbps D channel (2B+D). PRIMARY RATE INTERFACE (PRI) 1.544Kbps In North America, it includes 23 B channels and one 64Kbps D channel (23B+D), equivalent to T1. In Europe, it includes 30 B channels and one 64Kbps D channel (30B+D), equivalent to European E1 service. The Future of ISDN ISDN's 64Kbps channel speed is a big boost over today's fastest analog modems, but it can't match Ethernet and Token Ring speeds of 10Mbps and 16Mbps. However, Broadband ISDN (BISDN) should materialize by the mid 1990s, which utilizes broadband transmission and fiber optic cables, to attain speeds of 150Mbps. ISO (Int'l. Standards Organization) Organization that sets international standards, founded in 1946 and headquartered in Geneva. It deals with all fields except electrical and electronics, which is governed by the older Int'l. Electrotechnical Commission (IEC), also in Geneva. With regard to information processing, ISO and IEC created JTC1, the Joint Technical Committee for information technology. It carries out its work through more than 160 technical committees and 2,300 subcommittees and working groups and is made up of standards organizations from more than 75 countries, some of them serving as secretariats for these technical bodies. ANSI is the U.S. member body. Address: ANSI, 1430 Broadway, New York, NY 10018. isochronous Time dependent. Realtime voice, video and telemetry are examples of isochronous data. isometric view In computer graphics, a picture of a 3-D object that shows all three dimensions in equal proportions. Isometric views do not show true perspective. isotropic Refers to properties, such as transmission speed, that are the same regardless of the direction that is measured. Contrast with anisotropic. ISPF (Interactive System Productivity Facility) IBM mainframe software that executes interactive user interfaces on 3270 terminals. It is created with ISPF's PDF (Program Development Facility) software. ISR (Interrupt Service Routine) Software routine that is executed in response to an interrupt. ISV (Independent Software Vendor) Person or company that develops software. IT (Information Technology) Same as Information Systems. ITAA (Information Technology Assn. of America) Formerly Assn. of Data Processing Service Organizations (ADAPSO). Membership organization founded in 1960 that defines performance standards, improves management methods and monitors government regulations in the computer services field. Address: 1616 N. Fort Myer Dr., Arlington, VA 22209, 703/522-5055. item One unit or member of a group. See data item. iteration One repetition of a sequence of instructions or events. For example, in a program loop, one iteration is once through the instructions in the loop. iterative operation Operation that requires successive executions of instructions or processes. ITSEC See NCSC. IV See interactive video. IVD (Interactive VideoDisc) See interactive video. Iverson notation Set of symbols developed by Kenneth Iverson for writing statements in APL. IVR (Interactive Voice Response) See voice response. iWARP Systolic-array microprocessor from Intel that was originally funded by DARPA and developed by Carnegie-Mellon. IXC (IntereXchange Carrier) Organization that provides interstate communications services, such as AT&T, MCI and Sprint. IZE PC text management system from Persoft, Inc., Madison, WI, noted for its flexible searching. Key words can be entered manually or can be created from a list or condition, such as the name between "Dear" and a comma. J-lead See SOJ. jack Receptacle into which a plug is inserted. jacket Plastic housing that contains a floppy disk. The 5.25" disk is built into a flexible jacket; the 3.25" disk uses a rigid jacket. Jacquard loom Automated loom that transformed the 19th century textile industry and became the inspiration for future calculating and tabulating machines. Developed by the French silk-weaver, Joseph-Marie Jacquard (1752-1834), it used punched cards to control its operation. Although punched cards were used in earlier looms and music boxes, Jacquard's loom was a vast improvement and allowed complex patterns to be created swiftly. JAD (Joint Application Development) Approach to systems analysis and design introduced by IBM in 1977 that emphasizes teamwork between user and technician. Small groups meet to determine system objectives and the business transactions to be supported. They are run by a neutral facilitator who can move the group toward well-defined goals. Results include a prototype of the proposed system. jaggies Stairstepped appearance of diagonal lines on a low- resolution graphics screen. Javelin Plus PC spreadsheet from Information Resources, Inc., Waltham, MA. Instead of row and column numbers, it uses names to identify cells and consolidate data. Jazz Integrated Macintosh software package from Lotus. Modeled after Symphony, it never caught on. JCL (Job Control Language) Command language for mini and mainframe operating systems that launches applications. It specifies priority, program size and running sequence, as well as the files and databases used. JEDEC (Joint Electronic Device Engineering Council) International body that sets integrated circuit standards. JEIDA (Japanese Electronic Industry Development Assn.) Japanese trade and standards organization. PCMCIA has joined with JEIDA to standardize on a 68-pin memory card. JES (Job Entry Subsystem) Software that provides batch communications for IBM's MVS operating system. It accepts data from remote batch terminals, executes them on a priority basis and transmits the results back to the terminals. The JES counterpart in VM is called RSCS. jiff See GIF. jitter Flickering transmission signal or display image. job Unit of work running in the computer. A job may be a single program or a group of programs that work together. job class Descriptive category of a job that is based on the computer resources it requires when running. job control language See JCL. job management language Same as JCL. job processing Handling and processing jobs in the computer. job queue Lineup of programs ready to be executed. job stream Series of related programs that are run in a prescribed order. The output of one program is the input to the next program and so on. join (1) In relational database management, to match one file against another based on some condition creating a third file with data from the matching files. For example, a customer file can be joined with an order file creating a file of records for all customers who purchased a particular product. (2) See DOS Join. Josephson junction Ultra-fast switching technology that uses superconductor materials, originally conceived by Brian Josephson. Circuits are immersed in liquid helium to obtain near-absolute zero degrees required for operation. A Josephson junction has been observed to switch in as little as 50 femtoseconds. journal Same as log. JOVIAL (Jules' Own Version of the Int'l. Algebraic Language) ALGOL-like programming language developed by Systems Development Corp. in the early 1960s and widely used in the military. Its key architect was Jules Schwartz. joy stick Pointing device used to move an object on screen in any direction. It employs a vertical rod mounted on a base that contains one or two buttons. It is used extensively in video games and in some CAD systems. JPEG (Joint Photographic Experts Group) ISO/CCITT standard for compressing images using discrete cosine transform. It provides lossy compression at variable ratios, providing 20 to 30:1 without noticeable loss. Ratios of 50:1 to 100:1 may be used if the loss in image can be tolerated. JPEG is implemented in hardware as well as software; for example, a PC with a 1992-vintage JPEG board can compress a full-color 25MB image into 1MB in one second. C-Cube Microsystems introduced the first JPEG chip. See MPEG. JRP (Joint Requirements Planning) Systems planning performed cooperatively by a team of users and technicians. Functions should be prioritized and related to the organization's goals and business opportunities. JTC1 (Joint Technical Committee 1) See ISO. Julian date Representation of month and day by a consecutive number starting with Jan. 1. For example, Feb. 1 is Julian 32. Dates are converted into Julian dates for calculation. jump Same as GOTO. jumper Metal bridge used to close a circuit. It can be a short length of wire or a plastic-covered metal block that is pushed onto two pins on a circuit board. It is often used in place of DIP switches. junction Point at which two elements make contact. In a transistor, a junction is the point where an N-type material makes contact with a P-type material. justification In typography, the alignment of text evenly between left and right margins. Contrast with ragged right. justify (1) To shift the contents of a field or register to the right or left. (2) To align text evenly between left and right margins. K See kilo. K-byte See kilobyte. K&R C (Kernighan and Ritchie C) Version of C defined by Brian Kernighan and Dennis Ritchie that preceded the ANSI standard. Kaleida (Kaleida Labs, Inc., Mountain View, CA) Joint venture of IBM and Apple that is developing multimedia software. See ScriptX. KB, Kb See kilobyte and kilobit. Kbit See kilobit. Kbits/sec (KiloBITS per SECond) Thousand bits per second. KBps, Kbps (KiloBytes Per Second, KiloBits Per Second) Thousand bytes per second. Thousand bits per second. Kbyte See kilobyte. Kbytes/sec (KiloBYTES per SECond) Thousand bytes per second. Kerberos Security system developed at MIT that authenticates users. It does not provide authorization to services or databases; it establishes identity at logon, which is used throughout the session. Kermit Aynchronous file transfer protocol developed at Columbia Univ., noted for its accuracy over noisy lines. Several extensions exist, including SuperKermit, a full-duplex, sliding window version. Kermit is popular on minis and mainframes and can also handle byte-oriented transfers over 7-bit ASCII systems. kernel Fundamental part of a program, such as an operating system, that resides in memory at all times. kerning In typography, the spacing of letter combinations, such as WA, MW and TA, where each character overlaps into some of the space of the other for improved appearance. Kerr effect Change in rotation of light reflected off a magnetic field. The polarity of a magneto-optic bit causes the laser to shift one degree clockwise or counterclockwise. key (1) Keyboard button. (2) Data that identifies a record. Account number, product code and customer name are typical key fields used to identify a record in a file or database. As an identifier, each key value must be unique in each record. See sort key. (3) Numeric code used by an algorithm to create a code for encrypting data for security purposes. key cap Replaceable, top part of a keyboard key. To identify commonly-used codes, it can be replaced with a custom-printed key cap. key click Audible feedback provided when a key is pressed. It may be adjustable by the user. key command Key combination (Alt-G, Ctrl-B, Command-M, etc.) used as a command to the computer. key driven Any device that is activated by pressing keys. key entry Data entry using a keyboard. key field See key (2). key in To enter data by typing on a keyboard. key rollover See n-key rollover. key-to-disk machine Stand-alone data entry machine that stores data on magnetic disk for computer entry. key-to-tape machine Stand-alone data entry machine that stores data on magnetic tape for computer entry. Introduced by Mohawk Data Sciences in the mid 1960s, it was the first advancement in data entry since the card keypunch. Mohawk's stock went from $2 to $200 in a couple of years. key word (1) Word used in a text search. (2) Word in a text document that is used in an index to best describe the contents of the document. (3) Reserved word in a programming or command language. keyboard Set of input keys. On terminals and personal computers, it includes the standard typewriter keys, several specialized keys and features outlined below. See PC keyboard, AT keyboard and Enhanced keyboard. Enter (Return) Key In text applications, it ends a paragraph or short line. In data applications, it signals the end of the input for that field or line. Cursor Keys The four arrow keys move the cursor on screen. They are used in conjunction with shift, alt and control to move the cursor in bigger jumps; for example, CONTROL UP ARROW might scroll the screen. Some earlier keyboards didn't have cursor keys, in which case, control or alt was used with some letter key. Control, Alt, Command and Option Keys Used like a shift key, these keys are held down while another key is pressed to command the computer in a variety of ways. Escape Key Commonly used to exit or cancel the current mode such as exiting from a menu. Also used to clear an area or repeat a function such as redrawing the screen. Numeric Lock Locks a combination number/cursor keypad into numeric mode only. Home and End Keys Commonly used to move the cursor to the extreme left or right side of the current line. Often used in conjunction with shift, control and alt; for example, CONTROL HOME and CONTROL END usually move the cursor to the beginning and end of file. Page Up and Page Down Keys Used to move the cursor up and down a page, screen or frame. Often used in combination with shift, control and alt.  Function Keys Used to call up a menu or perform a function, they are located in a cluster on the left side or in a row across the top of the keyboard (labelled F1, F2, etc.). Often used with the shift, control and alt keys providing 40 separate functions with F1 through F10. Backspace Key Used to delete the character to the left of the cursor (erase typos) and may be used with the shift, control and alt keys to erase segments of text. The extra-wide, typewriter-style key is preferred. Delete Key Used to erase the character at the current cursor location. Used in conjunction with the shift, control and alt keys, it is used to erase any segment of text, such as a word, sentence or paragraph. Insert Key Usually a toggle switch to go back and forth between insert and overwrite mode. Also used to "paste" a segment of text or graphics into the document at the current cursor location. Repeating Keys Most computer keys repeat when held down, a phenomenon first-time computer users must get used to. If you hold a key down that is used to command the computer, you'll be entering the command several times. Audible Feedback Keyboards may cause a click or beep to be heard from the computer when keys are pressed. This is done to acknowledge that the character has been entered. It should be adjustable for personal preference. All Keyboards Are Not Equal Keyboard quality is critical for experienced typists. The feel (tension and springiness) varies greatly. Key placement is important. Older keyboards and new laptop keyboards may have awkward return and shift key placements. keyboard buffer Memory bank or reserved memory area that stores keystrokes until the program can accept them. It lets fast typists continue typing while the program catches up. keyboard controller Circuit that monitors keystrokes and generates the required data bits when pressed. keyboard enhancer Same as macro processor. keyboard interrupt Signal that gets the attention of the CPU each time a key is pressed. See interrupt. keyboard macro processor See macro processor. keyboard processor See keyboard controller and keyboard enhancer. keyboard template Plastic card that fits over the function keys to identify each key's purpose in a particular software program. keyframe In computer graphics animation, a frame that indicates the beginning or end of an object in motion. keypad Small keyboard or supplementary keyboard keys; for example, the keys on a calculator or the number/cursor cluster on a computer keyboard. keypunch To punch holes in a punched card. It is sometimes used to refer to typing on a computer keyboard. keypunch department Same as data entry department. keypunch machine Punched-card data entry machine. A deck of blank cards is placed into a hopper, and, upon operator command, the machine feeds one card to a punch station. As characters are typed, a series of dies at the punch station punch the appropriate holes in the selected card column. Khornerstones Benchmark program that tests CPU, I/O and floating point performance. KHz (KiloHertZ) One thousand cycles per second. See horizontal scan frequency. kicks See CICS. kilo Thousand. Abbreviated "K." It often refers to the precise value 1,024 since computer specifications are usually binary numbers. For example, 64K means 65,536 bytes when referring to memory or storage (64x1024), but a 64K salary means $64,000. The IEEE uses "K" for 1,024, and "k" for 1,000. See binary values and space/time. kilobit One thousand bits. Also KB, Kb, Kbit and K-bit. See kilo and space/time. kilobyte One thousand bytes. Also KB, Kbyte and K-byte. See kilo and space/time. Kinetics FastPath Gateway from the Kinetics division of Excelan, Inc., that connects LocalTalk and PhoneNet systems and LaserWriters to VAXs, UNIX-based computers, PCs and other Ethernet-based hosts. It supports AppleTalk, TCP/IP and DECnet protocols. kiosk Small, self-standing structure such as a newstand or ticket booth. Unattended, multimedia kiosks dispense public information. kludge Also spelled "kluge" and pronounced "klooj." A crude, inelegant system, component or program. It may refer to a makeshift, temporary solution to a problem as well as to any product that is poorly designed or that becomes unwieldy over time. knowledge acquisition Process of acquiring knowledge from a human expert for an expert system, which must be carefully organized into IF-THEN rules or some other form of knowledge representation. knowledge base Database of rules about a subject used in AI applications. See expert system. knowledge based system AI application that uses a database of knowledge about a subject. See expert system. knowledge domain Specific area of expertise of an expert system. knowledge engineer Person who translates the knowledge of an expert into the knowledge base of an expert system. knowledge representation Method used to code knowledge in an expert system, typically a series of IF-THEN rules (IF this condition occurs, THEN take this action). Korn shell See UNIX. KSDS (Keyed Sequence DataSet) VSAM structure that uses an index to store records in available free space. Retrieval is by key field or by address. Contrast with ESDS. KSR terminal (Keyboard Send Receive terminal) Same as teleprinter. Contrast with RO terminal. kwem See QEMM. label (1) In data management, a made-up name that is assigned to a file, field or other data structure. (2) In spreadsheets, descriptive text that is entered into a cell. (3) In programming, a made-up name used to identify a variable or a subroutine. (4) In computer operations, a self-sticking form attached to the outside of a disk or tape in order to identify it. (5) In magnetic tape files, a record used for identification at the beginning or end of the file. label prefix In a spreadsheet, a character typed at the beginning of a cell entry. For example, in 1-2-3, a single quote (') identifies what follows as a descriptive label even if it's a number. LAN (Local Area Network) Communications network that serves users within a confined geographical area. It is made up of servers, workstations, a network operating system and a communications link. Servers are high-speed machines that hold programs and data shared by all network users. The workstations, or clients, are the users' personal computers, which perform stand-alone processing and access the network servers as required. Diskless and floppy-only workstations are sometimes used, which retrieve all software and data from the server. A printer can be attached to a workstation or to a server and be shared by network users. Small LANs can allow each workstation to function as a server, allowing all users access to data on all machines. These peer-to-peer networks are often simpler to install and manage, but dedicated servers provide better performance and can handle higher transaction volume. Multiple servers are used in large networks. The controlling software in a LAN is the network operating system, such as NetWare, LANtastic and Appletalk, which resides in the server. A component part of the software resides in each workstation and allows the application to read and write data from the server as if it were on the local machine. The physical transfer of data is performed by the access method (Ethernet, Token Ring, etc.) which is implemented in the network adapters that plug into the workstations and servers. The actual communications path is the cable (twisted pair, coax, optical fiber) that interconnects each network adapter. See MAN, WAN, bridge, router, gateway and hub. LAN administrator See network administrator. LAN Manager Network operating system from Microsoft that runs as a server application under OS/2 and supports both DOS, Windows and OS/2 clients. It uses the Microsoft File Sharing protocol (SMB) for file sharing, the NetBIOS protocol for its transport mechanism and uses Named Pipes for interprocess communication (IPC). See LAN Server. LAN Manager for Windows NT is a different product. It adds network management and services to Windows NT, which includes peer-to-peer networking. LAN Network Manager IBM Token Ring network management software.  LAN Station Manager is the workstation counterpart that collects data for LAN Network Manager. LAN Requester LAN Server software that resides in the workstation. LAN Server (1) Network operating system from IBM that runs as a server application under OS/2 and supports both DOS, Windows and OS/2 clients. Originally based on LAN Manager when OS/2 was jointly developed by IBM and Microsoft, Version 3.0 runs under IBM's own OS/2 Version 2.0. Version 3.0 provides disk mirroring, CID capability and Network Transport Services/2 (NTS/2) for concurrent access to NetWare servers. Options are Lan Server for the Macintosh for Mac client access and System Performance/2 (SP/2), a series of network management utilities. (2) (LAN server) Generically, a file server in a network. LAN station (1) Workstation in a local area network. (2) See LAN Network Manager. LAN Workplace Family of software products from Novell that allows DOS, Windows, Macintosh and OS/2 clients in a NetWare environment to access resources on a TCP/IP network. LAN Workplace for DOS can also encapsulate NetWare protocols and run NetWare- dependent applications entirely within a TCP/IP network. landing zone Safe non-data area on a hard disk used for parking the read/write head. Landmark rating Widely-used PC performance test from Landmark Research Int'l., Clearwater, FL, that measures CPU, video and coprocessor speed. CPU speed is rated as the clock speed required in an AT-class machine that would provide equivalent performance. landscape Printing orientation that prints data across the wider side of the form. Contrast with portrait. landscape monitor Monitor that is used to display facing text pages. It is wider than it is high. language Set of symbols and rules used to convey information. See machine language, programming language, graphics language, page description language, fourth-generation language, standards & compatibility and user interface. language processor Language translation software. Programming languages, command languages, query languages, natural languages and foreign languages are all translated by software. LanguageAccess SAA-compliant query language from IBM that translates a user's English-language request into SQL language for QMF. QMF retrieves the data. LANtastic Popular peer-to-peer LAN operating system for PCs from Artisoft, Inc., Tucson, AZ, that is noted for its ease of use. It supports Ethernet, ARCNET and Token Ring adapaters as well as its own twisted- pair adapater at two Mbits/sec. Artisoft also makes Ethernet adapters. Included are e-mail and chat functions. Voice mail and conversation are optional. LAP (Link Access Procedure) CCITT family of error correction protocols originally derived from the HDLC standard and used on X.25 packet networks. LAP-B (LAP-Balanced) Used in current X-25 networks. LAP-D (LAP-D channel) Used in the data channel of an ISDN transmission. LAP-M (LAP-Modem) Defined in CCITT V.42, which uses some of the LAPD methods and adds additional ones. LAP-X (LAP-Half-dupleX) Used for ship to shore transmission. LapLink PC file transfer program from Traveling Software, Inc., Bothell, WA, that transfers data between laptops and desktop computers. LapLink Mac transfers files between PCs and Macs. laptop computer Portable computer that has a flat screen and usually weighs less than a dozen pounds. It uses AC power and/or batteries. Most have connectors for an external monitor transforming them into desktop computers. See notebook computer and pocket computer.  Laptop Features KEYBOARD Keyboard layout is often sacrificed. The Home, End, PageUp and PageDn keys may not be dedicated keys, requiring that you hold down the Fn key in conjunction with them. This is more cumbersome. Function keys and cursor keys are often made smaller. If you have large hands, test the keyboard carefully. A full-size external keyboard can be connected to an external keyboard connector or through the serial or parallel ports with an adapter. SCREEN QUALITY Monochrome LCD screens translate colors into shades of gray. The more shades, the better the representation of full-color images. Passive matrix LCD screens provide a subdued color. Active matrix LCD screens are sharp and rich, but are costly and use more power. Stay tuned for active addressing LCD screens (see LCD). EXTERNAL DISPLAY AND KEYBOARD CONNECTORS Connect a full-size CRT and keyboard for home/office. Even if you like your laptop keyboard, you may want to use an external keyboard with your external monitor, because the laptop screen usually doesn't move out of the way for direct viewing of the monitor. LOW POWER CPU Intel's 386SL and 486SL and AMD's Am386-SXL are low-power CPUs that prolong battery life. BUILT-IN TRACKBALL Very convenient, but placement is not standard. Try it first! Keyboard keys or a specially- designed key may also be used as a mouse substitute. Barring any of these, a built-in mouse port lets you use an external mouse or trackball and frees up the serial port for something else. BUILT-IN MODEM Saves lugging an external modem. EXPANSION SLOTS Some laptops connect to an optional docking station that provides one or more slots for future expandability. AUTO RESUME Lets you return to the computer and pick up where you left off without having to reload your applications. DUAL DISPLAY Using an external monitor and laptop display at the same time. For presentations with a data projector, it may be difficult to look at a projected image off in the distance. NICKEL HYDRIDE BATTERY Provides about 20% more power per pound than NiCad and doesn't have its associated memory problem. Recharge life may be shorter, however. TRANSFORMER WEIGHT Transformer weight (often not published) is a consideration, since it is usually carried with the computer. laser (Light Amplification from the Stimulated Emission of Radiation) Device that creates a very uniform light that can be precisely focused. It generates a single wavelength or narrow band of wavelengths and is used in applications such as communications, printing and disk storage. Unlike the transmission of electricity, transmission of light pulses over optical fibers is not affected by nearby electrical interferences. See LED. The Laser Discovery In 1957, the laser was conceived by Gordon Gould, a graduate student in physics at Columbia Univ. When Gould filed for patents in 1959, he found that Columbia professor Charles Townes and Arthur Schawlow of Bell Labs had already filed for them. The year before, AT&T had, in fact, demonstrated a working laser at Bell Labs. In 1977, after years of litigation, a court awarded Gould rights to the first of three patents and later to all of them. He finally reaped millions in royalties. laser printer Printer that uses the electrophotographic method used in copy machines to print a page at a time. A laser "paints" the dots of light onto a photographic drum or belt. The toner is applied to the drum or belt and then transferred onto the paper. Desktop printers use cut sheets like a copy machine. Large printers may use rolls of paper. In 1975, IBM introduced the first laser printer, the high-speed model 3800. Later, Siemens introduced the ND 2 and Xerox introduced the 9700. These self-contained printing presses are online to a mainframe or offline, accepting print image data on tape reels or disk packs. Large-scale machines provide collating and stacking, and some models can print on very wide paper. In 1984, HP introduced the LaserJet, the first desktop laser printer, which propelled desktop publishing. The desktop laser printer has obsoleted the daisy wheel printer and competes directly with the dot matrix printer. Although high-resolution color laser printers are also available, less expensive desktop versions will become widely used throughout the 1990s. Note: All large-scale printers that print a page at a time do not use a laser. Some use ion deposition, which creates the image with electricity rather than light. laserdisc See videodisc. LaserJet Family of desktop laser printers from HP. Introduced in 1984 at $3,495, the first LaserJet revolutionized the desktop laser printer market. LaserJets print at 300 dpi and starting with the LaserJet 4, at 600 dpi. Third-party enhancements, such as the WinJet, increase resolution to 1200 dpi. PCL is the printer command language. LaserJets accept bitmapped fonts from plug-in cartridges or, except for the original model, from the computer (soft fonts). PostScript cartridges are available either from HP or from third parties for all models starting with the Series II. Starting with the LaserJet 4, native PostScript models are available. Starting with the III (PCL 5), Intellifont scalable fonts are included. In addition, the III overcomes previous limitations and can print portrait and landscape fonts on the same page and print white text on a black background.  LASERJET SPECIFICATIONS  Input paper capacity Built in fonts Canon  Year Speed   Cartridges Printer  Model Intro (ppm)   RAM Engine 陳陳陳陳陳陳陳賃陳堕陳陳賃陳陳堕陳堕陳陳陳陳堕陳陳 *LaserJet 1984 8 100 2 1 128K-2M CX *PLUS 1985 8 100 2 1 512K-2M CX *500 PLUS 1986 8 500 2 1 512K-2M CX *2000 *1 198720 500 34 3 1-5M LPB20 *Series II 1987 8 200 6 2 512K-4M SX *IID *1 1989 8 400 22 2 640K-4M SX *IIP 1989 450-300 14 1 512K-4.5 LX IIP+ 1991 Slightly faster than IIP LX *III 1990 8 200 *3 2 1-5M SX *IIID *1 1990 8 400 *3 2 1-5M SX IIIP 1991 470-320 *3 1 1-5M LX *IIIsi *2 199117 1000 *3 2 1-17M NX 陳600 dpi陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳 4 1992 8 350 *4 1 2-32M EX 4M 1992 8 350 *5 1 6-26M EX 4si *2 199317 1000 *4 2 2-34M *6 4siMX *2 199317 1000 *5 2 2-26M *6 陳陳陳陳陳陳陳珍陳祖陳陳珍陳陳祖陳祖陳陳陳陳祖陳陳 *=No longer made as of 4/93 *1=Double sided printing *2=Double sided optional *3=14 bitmapped fonts, plus two Intellifont typeface families (IIIsi has four) *4=35 Intellifont scalable fonts plus 10 TrueType scalable fonts *5=*4 plus 35 Type 1 PostScript fonts (Level 2) *6=Similar to NX (designation not yet announced) LaserMaster See WinJet. LaserWriter Family of 300 dpi desktop laser printers from Apple introduced in 1985. All models handle bitmapped fonts, and, except for the SC models, include PostScript, built-in AppleTalk connections, as well as RS-232 ports for connecting PCs via Diablo emulation. LAT (Local Area Transport) Communications protocol from Digital for controlling terminal traffic in a DECnet environment. LATA (Local Access and Transport Area) Geographic region set up to differentiate local and long distance telephone calls. Any telephone call between parties within a LATA is handled by the local telephone company. latch Electronic circuit that maintains one of two states. See flip-flop. late binding Linking routines at runtime. latency Time between initiating a request for data and the beginning of the actual data transfer. On a disk, latency is the time it takes for the selected sector to come around and be positioned under the read/write head. Channel latency is the time it takes for a computer channel to become unoccupied in order to transfer data. latent image Invisible image typically of electrical charges. For example, in a copy machine, a latent image of the page to be copied is created on a plate or drum as an electrical charge. launch To cause a program to load and run. LAWN (Local Area Wireless Network) Transmitter/receiver from O'Neill Communications, Inc., Princeton, NJ, that connects devices using radio transmission. layer (1) In computer graphics, one of several on-screen "drawing boards" for creating elements within a picture. Layers can be manipulated independently, and the sum of all layers make up the total image. (2) In communications, a protocol that interacts with other protocols to provide all the necessary transmission services. See OSI. layout setting Value used to format a printed page. Margins, tabs, indents, headers, footers and column widths are examples. LBRV (Low Bit Rate Voice) Voice sampling technique that analyzes each 15-30 millisecond speech segment independently and converts it into a 30-byte frame. LC (Low cost Color) See Macintosh. LCC See leaded chip carrier. LCD (Liquid Crystal Display) Display technology that uses rod-shaped molecules (liquid crystals) that flow like liquid and bend light. Unenergized, the crystals direct light through two polarizing filters, allowing a natural background color to show. When energized, they redirect the light to be absorbed in one of the polarizers, causing the dark appearance of crossed polarizers to show. The more the molecules are twisted, the better the contrast and viewing angle. Because it takes less power to move molecules than to energize a light-emitting device, LCDs replaced LEDs in digital watches years ago. TYPES OF LCDs Passive Display Called "passive matrix" when used for computer screens. Called "passive display" when used for digital readouts, icons, etc. All active electronics (transistors) are outside of the display screen. Provides a sharp image for monochrome screens, but more subdued for color. Submarining is common. Passive display types are: TN (twisted nematic) - low-cost displays for consumer products, instruments, etc. 90 twist; black on gray/silver background STN (supertwisted nematic) - used extensively on laptops for mono and color displays. 180 twist; green/blue on yellow background 270 twist; blue on white/blue background Active Addressing - Improves passive display by addressing pixels differently. Eliminates submarining and less expensive than active displays. Available end 1993/early 1994. Active Display (TFT LCD) Typically used for laptop color screens, thus called "active matrix" displays. Transistors are built into each pixel within the screen. For example, 640x480 color VGA screen requires 921,600 transistors; one for each red, green and blue dot. Provides a sharp, clear image with good contrast and eliminates submarining, but fabrication costs are high. Uses a 90 (TN) twist. Also called TFT LCD (thin film transistor LCD). Reflective vs Backlit Reflective screens used in many consumer appliances and some lightweight laptops require external light and only work well in a bright room or with a desk lamp. Backlit and sidelit screens have their own light source and work well in dim lighting. LCD panel Data projector that accepts computer output and displays it on a see-through liquid crystal screen placed on top of an overhead projector. LCD printer Electrophotographic printer that uses a single light source directed by liquid crystal shutters. LE (Less than or Equal to) See relational operator. lead acid Rechargeable battery technology widely used in portable gardening tools, but has been used in some portable computers. It uses lead plates and an acid electrolyte. It provides the least amount of charge per pound of the rechargeable technologies. See NiCad, nickel hydride and zinc air. leaded chip carrier Square chip housing with pin connectors on all four sides (provides more I/O paths than a DIP). Contrast with leadless chip carrier. leader (1) Length of unrecorded tape used to thread the tape onto the tape drive. (2) Dot or dash used to draw the eye across the printed page, such as in a table of contents. leading In typography, the vertical spacing between lines of type (between baselines). The name comes from the early days of typesetting when the space was achieved with thin bars of lead. leading edge (1) Edge of a punched card or document that enters the reading station first. (2) In digital electronics, a pulse as it changes from a 0 to a 1. (3) In programming, a loop that tests a condition before the loop is entered. (4) (Leading Edge Products, Inc., Westborough, MA) PC manufacturer founded in 1980. Its Model M in 1982 was the first PC-compatible from overseas. Korean Daewoo Corp. supplied it with products since 1984 and acquired it in 1989. leading zeros Zeros used to fill a field that do not increase the numerical value of the data. For example, all the zeros in 0000006588 are leading zeros. leadless chip carrier Square chip housing with flat contact connectors on all four sides (provides more I/O paths than a DIP). Contrast with leaded chip carrier. leaf In database management, the last node of a tree. League for Programming Freedom Organization of professors, students and businessmen who believe that software copyrights and patents jeopardize the industry. They are dedicated to "bringing back the freedom to write programs." Address: 1 Kendall Square, P.O. Box 9171, Cambridge, MA 02139. leapfrog test Storage diagnostic routine that replicates itself throughout the storage medium. leased line Private communications channel leased from a common carrier. It can be ordered in pairs, providing a four-wire channel for full-duplex transmission (dial-up system provides only two-wire lines). To improve line quality, it can also be conditioned. leased line modem High-speed modem used in private lines. It may have built-in lower speeds for alternate use in dial-up lines. least significant digit Rightmost digit in a number. LEC (Local Exchange Carrier) Organization that provides local telephone services. LED (Light Emitting Diode) Display technology that uses a semiconductor diode that emits light when charged. It usually gives off a red glow, although other colors can be generated. It is used in readouts and on/off lights in myriads of electronic appliances. It was the first digital watch display, but was superseded by LCD, which uses less power. LED printer ~Electrophotographic printer that uses a matrix of LEDs as its light source rather than a laser. left justify Same as flush left. Lempel Ziv Data compression algorithm that uses an adaptive compression technique. LEN (Low Entry Networking) In SNA, peer-to-peer connectivity between adjacent Type 2.1 nodes, such as PCs, workstations and minicomputers. LU 6.2 sessions are supported across LEN connections. Lessons Following are lists of definitions based on subject. Use them as a springboard to other terms. Either print the list and check off your progress on paper or set a bookmark here and return to the bookmark. Lessons Associations (Set a bookmark to return here.) ACM (Information processing) BCS (Personal computers) CBEMA (Equipment vendors) CPA (Computer press) DPMA (DP management) ICCP (Industry certificatesion) ITAA (Information technology) MMA (Microcomputer managers) MUG (Mac users) NASI (Systems integrators) NCF (Channel for donating old equipment) NCGA (Computer graphics) SPA (Software publishers) WUGNET (Windows users) STANDARDS BODIES ANSI (U.S. standards) NIST (U.S. standards) CCIA (Computer/communications industry) CCITT (International standards) IEC (International standards) ISO (International standards) EIA (Interface standards; RS-232) IEEE (Electronics standards) JEDEC (IC standards) JEIDA (Japanese electronics) PCMCIA (PC memory card standards) XAPIA (X.400 standards) Lessons Basics (Set a bookmark to return here.) hardware software data computer computer system analog digital bit binary byte peripheral magnetic recording floppy disk hard disk printer monitor modem operating sytem bus space/time chip PC Macintosh personal computer office automation standards & compatibility Lessons Communications (Set a bookmark to return here.) communications LAN OSI & OSI model data link protocol baseband Ethernet ARCNET token ring network NetWare Lantastic Appletalk SNA TCP/IP X Window LAN CONNECTIVITY repeater bridge router brouter gateway hub MODEMS BBS online services modem emoticon RS-232 V.22bis 2200 bps standard V.32 9600 bps standard V.32bis 14400 bps standard V.42 error checking V.42bis compression MNP error checking/compression Lessons Desktop pub. (Set a bookmark to return here.) desktop publishing font typeface scalable font outline font vector font halftone bitmap kerning leading color separation colors point prepress imagesetter phototypesetter page description language PDL PCL PostScript Lessons Graphics (Set a bookmark to return here.) graphics paint program drawing program CAD CAD/CAM wireframe modeling solid modeling surface modeling ray tracing Renderman JPEG AutoCAD FastCAD Bezier spline GKS PHIGS bitblt PCX GIF TIFF PIC HSV Lessons History (Set a bookmark to return here.) Pascaline Hollerith machine ABC ENIAC UNIVAC I punched card 1401 650 IBM mainframes IBM minicomputers personal computer PDP VAX Altair 8800 TRS PET System/360 Trilogy Lessons Multimedia (Set a bookmark to return here.) multimedia MPC CD CD ROM CD-I DVI CDTV THOR audio board hypertext Private Eye virtual reality Lessons Personal Computers (Set a bookmark to return here.) CATEGORIES personal computer PC Macintosh Amiga MEGA laptop palmtop HARDWARE computer memory floppy disk hard disk magnetic disk keyboard modem optical disk laser printer serial port parallel port game port mouse tape backup PC conflicts BUSES bus ISA EISA Micro Channel NuBus local bus VL-bus ENVIRONMENTS operating system DOS DOS abc's Windows DESQview DESQview/X OS/2 UNIX SOFTWARE word processing DBMS spreadsheet business graphics communications program integrated software package paint program drawing program Lessons Programming (Set a bookmark to return here.) programming assembly language high-level language machine language microcode reentrant code function object-oriented programming COBOL BASIC FORTRAN Pascal C C++ LISP Prolog LOGO MUMPS REXX PC PROGRAMMING ASCII chart hex chart binary values PC display modes PC memory map PC color codes paragraph Turbo C Microsoft C Borland C++ Lessons Slang (Set a bookmark to return here.) flame frob droupie trashware shelfware kludge RTFM hookemware phone hawk Big Blue foo TLA write only code Lessons System design (Set a bookmark to return here.) OVERVIEW information system system development cycle Systemantics PEOPLE systems analyst application programmer programmer analyst systems programmer operator DEVELOPMENT data administration prototyping functional specification documentation CASE standards & compatibility SOFTWARE query language report writer spreadsheet DBMS financial planning system DSS EIS EPSS expert system case-based reasoning Lessons UNIX (Set a bookmark to return here.) UNIX TCP/IP NFS NIS SMTP SNMP Motif Open Look USL OSF X Window X terminal BSD UNIX STREAMS emacs vi awk sed grep UNIX/PC INTEGRATION DESQview/X SCO Open Desktop Solaris 2.0 Lan Workplace UnixWare NetWare NFS Lessons Vendors (Set a bookmark to return here.) FORTUNE 500 vendors software vendors IBM Apple Atari Commodore HP Digital Equipment Data General Bull HN Intel Motorola TI Tandy Tandem Microsoft Borland Digital Research Computer Associates D&B Software letter quality Print quality of an electric typewriter. Laser printers, ink jet printers and daisy wheel printers provide letter quality printing. 24-pin dot matrix printers provide near letter quality (NLQ), but the characters are not as dark and crisp. lexicographic sort Arranging items in alphabetic order like a dictionary. Numbers are located by their alphabetic spelling. LF See line feed. LHARC Popular freeware compression program developed by Haruyasu Yoshizaki that uses a variant of the LZW (LZ77) dictionary method followed by a Huffman coding stage. It runs on PCs, UNIX and other platforms as its source code is also free. librarian Person who works in the data library. library (1) Collection of programs or data files. (2) Collection of functions (subroutines) that are linked into the main program when it is compiled. (3) See data library. library routine Subroutine that is part of a macro or function library. LIFO (Last In First Out) Queueing method in which the next item to be retrieved is the item most recently placed in the queue. Contrast with FIFO. ligature Two or more typeface characters that are designed as a single unit (physically touch). Fi, ffi, ae and oe are common ligatures. light bar Same as highlight bar. light guide Transmission channel that contains a number of optical fibers packaged together. light pen Light-sensitive stylus wired to a video terminal used to draw pictures or select menu options. The user brings the pen to the desired point on screen and presses the pen button to make contact. Screen pixels are constantly being refreshed. When the user presses the button, allowing the pen to sense light, the pixel being illuminated at that instant identifies the screen location. light source In computer graphics, used to simulate the visual effect of a light on a 3-D object. Some programs can compute multiple light sources. lightwave Light in the infrared, visible and ultraviolet ranges, which falls between x-rays and microwaves. Wavelengths are between 10 nanometers and one millimeter. lightwave system Device that transmits light pulses over optical fibers at extremely high speeds (Gbits/sec range). Many intercity telephone trunks have been converted to lightwave systems. LIM EMS See EMS. limited distance modem Same as short-haul modem. limulator See EMS emulator. Linda Set of parallel processing functions added to languages, such as C and C++, that allows data to be created and transferred between processes. It was developed by Yale professor David Gelernter, when he was a 23-year old graduate student. line (1) In text-based systems, a row of characters. (2) In graphics-based systems, a row of pixels. (3) Any communications channel. line adapter In communications, a device similar to a modem, that converts a digital signal into a form suitable for transmission over a communications line and vice versa. It provides parallel/serial and serial/parallel conversion, modulation and demodulation. line analyzer Device that monitors the transmission of a communications line. line concentration See concentrator. line conditioning See conditioning. line dot matrix printer Line printer that uses the dot matrix method. See printer. line drawing Graphic image outlined by solid lines. The mass of the drawing is imagined by the viewer. See wire frame. line driver In communications, a device that is used to extend the transmission distance between terminals and computers that are connected via private lines. It is used for digital transmission and is required at each end of the line. line editor Simple editing program that allows text to be created and changed one line at a time. line feed (1) Character code that advances the screen cursor or printer to the next line. The line feed is used as an end of line code in UNIX. In DOS and OS/2 text files, the return/line feed pair (ASCII 13 10) is the standard end of line code. (2) Printer button that advances paper one line. line frequency Number of times each second that a wave or some repeatable set of signals is transmitted over a line. See horizontal scan frequency. line level In communications, the signal strength within a transmission channel, measured in decibels or nepers. line load (1) In communications, the percentage of time a communications channel is used. (2) In electronics, the amount of current that is carried in a circuit. line number (1) Specific line of programming language source code. (2) On display screens, a specific row of text or row of dots. (3) In communications, a specific communications channel. line of code Statement in a source program. In assembly language, it usually generates one machine instruction, but in a high-level language, it may generate a series of instructions. Lines of code are used to measure the complexity of a program. However, comparisons are misleading if the programs are not in the same language or category. For example, 20 lines of code in COBOL might require 200 lines of code in assembly language. line of sight Unobstructed view from transmitter to receiver. line printer Printer that prints one line at a time. Line printers are usually connected to mainframes and minicomputers. See printer. line segment In vector graphics, same as vector. line speed See data rate. line squeeze In a mail merge, the elimination of blank lines when printing names and addresses that contain no data in certain fields, such as title, company and second address line. See field squeeze.  Without line squeeze With line squeeze  Pat Smith Pat Smith  10 South Main  10 South Main Bearcat, OR 80901  Bearcat, OR 80901  linear Sequential or having a graph that is a straight line. linear address space See flat address space. linear programming Mathematical technique used to obtain an optimum solution in resource allocation problems, such as production planning. linear video Continuous playback of videotape or videodisc. Contrast with interactive video. link (1) In communications, a line, channel or circuit over which data is transmitted. (2) In data management, a pointer embedded within a record that refers to data or the location of data in another record. (3) In programming, a call to another program or subroutine. link edit To use a linkage editor to prepare a program for running. linkage editor Utility program that links a compiled or assembled program to a particular environment. It formally unites references between program modules and libraries of subroutines. Its output is a load module, a program ready to run in the computer. linked list In data management, a group of items, each of which points to the next item. It allows for the organization of a sequential set of data in noncontiguous storage locations. linker See linkage editor. Linpack Package of FORTRAN programs for numerical linear algebra that is commonly used to create benchmark programs for testing a computer's floating point performance. Linux Freeware version of a clone of the UNIX System V Release 3.0 kernel that runs on x86 machines. It is available on programming BBSs and on the Internet. LIPS (Logical Inferences Per Second) Unit of measurement of the thinking speed of an AI application. Humans do about 2 LIPS. In the computer, one LIPS equals from 100 to 1,000 instructions. liquid crystal shutters Method of directing light onto the drum in an electrophotographic printer. A matrix of liquid crystal dots function as shutters that are opened and closed. See LCD. Lisa First personal computer to include integrated software and use a graphical interface. Modeled after the Xerox Star and introduced in 1983 by Apple, it was ahead of its time, but never caught on due to its $10,000 price and slow speed. LISP (LISt Processing) High-level programming language used in non-numeric programming. Developed in 1960 by John McCarthy, its syntax and structure is very different than traditional programming languages. For example, there is no syntactic difference between data and instructions. LISP, available in both interpreter and compiler versions, is used extensively in AI applications as well as in compiler creation. The language can be modified and expanded by the programmer. Many varieties of LISP have been developed, including versions that perform calculations efficiently. The following Common LISP example converts Fahrenheit to Celsius:  (defun convert ()  (format t "Enter Fahrenheit ")  (let ((fahr (read)))  (format t "Celsius is <126>D"  (truncate (*(-fahr 32)  (/ 5 9))))))  list (1) Arranged set of data, often in row and column format. (2) In fourth-generation languages, a command that displays/prints selected records. For example, in dBASE, list name address displays all names and addresses in the current file. list processing Processing non-numeric data. list processing language Programming language, such as LISP, Prolog and Logo, used to process lists of data (names, words, objects). Although operations such as selecting the next to first, or next to last element, or reversing all elements in a list, can be programmed in any language, list processing languages provide commands to do them. Recursion is also provided, allowing a subroutine to call itself over again in order to repetitively analyze a group of elements. listing Any printed output. literal In programming, any part of an instruction that remains unchanged when translated into machine language, such as an output message. little endian See big endian. liveware People. LLC (Logical Link Control) See "LANs" under data link protocol. LLCC See leadless chip carrier. lo-res See low resolution. load (1) To copy a program from some source, such as a disk or tape, into memory for execution. (2) To fill up a disk with data or programs. (3) To insert a disk or tape into a drive. (4) In programming, to store data in a register. (5) In performance measurement, the current use of a system as a percentage of total capacity. (6) In electronics, the flow of current through a circuit. load high To load programs into high memory. See DOS Loadhigh. load module Program in machine language form ready to run in the computer. It is the output of a link editor. load sharing Sharing the workload in two or more computers. loaded line Telephone line from customer to central office that uses loading coils to reduce distortion. loader Program routine that copies a program into memory for execution. loader routine Same as loader. loading coil Device used in local telephone loops (exceeding 18,000 ft.) that boosts voice-grade transmission. It often adds noise to high-speed data transmission and must be removed for such traffic. local area network See LAN. local bus In a 386 and higher PC, a pathway from the CPU to peripheral devices that runs at higher clock rates than the ISA, EISA and Micro Channel expansion buses. Although CPU speeds have increased dramatically over the years, the expansion buses have remained slow to accommodate all the existing expansion boards, designed for the slower speed. The local bus provides a channel that transfers data to and from the CPU at the clock speed of the CPU. For example, in a 386/33, the 16 bit ISA bus, which runs at 8MHz, can transfer 16 megabytes per second (16 bits, or two bytes, times eight million). A local bus, which uses the full 32 bits of the 386 and runs at the 33MHz clock rate can theoretically transfer 132MB/sec (four bytes times 33 million). In practice, transfers are slower than maximum in both types. First implementations of the local bus used proprietary designs and have since faded; however, VESA has standardized the VL-bus, and Intel will introduce its PCI local bus in 1993. See VL-bus, PCI and "ISA vs Local Bus" under ISA. local bypass Interconnection between two facilities without the use of the local telephone company. local loop Communications line between a customer and the telephone company's central office. See loop carrier. local memory Memory used by a single CPU or allocated to a single program or function. local storage Disk storage used by a single CPU. local variable In programming, a variable used only within the routine or function it is defined in. LocalTalk LAN access method from Apple that uses twisted pair wires and transmits at 230,400 bps. It runs under AppleTalk and uses a daisy chain topology that can connect up to 32 devices within a distance of 1,000 feet. Third party products allow it to hook up with bus, passive star and active star topologies. Apple's LocalTalk PC Card lets a PC gain access to an AppleTalk network. lockup Refers to a computer's inability to respond to user input. See abend. log Record of computer activity used for statistical purposes as well as backup and recovery. logic Sequence of operations performed by hardware or software. Hardware logic is made up of circuits that perform an operations. Software logic (program logic) is the sequence of instructions in a program. Note: Logic is not the same as logical. See logical vs physical and logical expression. logic analyzer (1) Device that monitors computer performance by timing various segments of the running programs. The total running time and the time spent in selected progam modules is displayed in order to isolate the the least efficient code. (2) Device used to test and diagnose an electronic system, which includes an oscilloscope for displaying various digital states. logic array Same as gate array or PLA. logic bomb Program routine that destroys data; for example, it may reformat the hard disk or insert random bits into data files. It may be brought into a personal computer by downloading a corrupt public-domain program. Once executed, it does its damage right away, whereas a virus keeps on destroying. logic chip Processor or controller chip. Contrast with memory chip. logic circuit Circuit that performs some processing or controlling function. Contrast with memory. logic controller See PLC. logic diagram Flow chart of hardware circuits. logic error Program bug due to an incorrect sequence of instructions. logic gate Collection of transistors and electronic components that make up a Boolean logical operation, such as AND, NAND, OR and NOR. Transistors make up logic gates. Logic gates make up circuits. Circuits make up electronic systems. logic operation Operation that analyzes one or more inputs and generates a particular output based on a set of rules. See AND, OR and NOT and Boolean logic. logic-seeking printer Printer that analyzes line content and skips over blank spaces at high speeds. logical (1) Reasonable solution to a problem. (2) Higher level view of an object; for example, the user's view versus the computer's view. See logical vs physical. logical data group Data derived from several sources. Same as view. logical drive Allocated part of a physical drive that is designated and managed as an independent unit. logical expression Expression that results in true or false. Same as Boolean expression. logical field Data field that contains a yes/no, true/false condition. logical lock Prevention of user access to data that is provided by marking the file or record through the use of software. Contrast with physical lock. logical operator One of the Boolean logical operators (AND, OR and NOT). logical record Reference to a data record that is independent of its physical location. It may be physically stored in two or more locations. logical vs physical High-level versus low-level. Logical implies a higher view than the physical. Users relate to data logically by data element name; however, the actual fields of data are physically located in sectors on a disk. For example, if you want to know which customers ordered how many of a particular product, your logical view is customer name and quantity. Its physical organization might have customer name in a customer file and quantity in an order file cross referenced by customer number. The physical sequence of the customer file could be indexed, while the sequence of the order file could be sequential. A message transmitted from Phoenix to Boston logically goes between two cities; however, the physical circuit could be Phoenix to Chicago to Philadelphia to Boston. When you command your program to change the output from the video screen to the printer, that's a logical request. The program will perform the physical change of address from, say, device number 02 to device number 04. login Same as logon. Logo High-level programming language noted for its ease of use and graphics capabilities. It is a recursive language that contains many list processing functions that are in LISP, although Logo's syntax is more understandable for novices. Logo's graphics language is called turtle graphics, which allows complex graphics images to be created with a minimum of coding. The turtle is a triangular-shaped cursor, which is moved on screen with commands that activate the turtle as if you were driving it, for example, go forward 100 units, turn right 45 degrees, turn left 20 degrees. Stemming from a National Science Foundation project, Logo was created by Seymour Papert in the mid 1960s along with colleagues at MIT and members of Bolt Beranek & Newman. Originally developed on large computers, it has been adapted to most personal computers. The following Object Logo example converts Fahrenheit to Celsius:  convert  local [fahr]  print "|Enter Fahrenheit |  make "fahr ReadWord  print "|Celsius is |  print (:fahr - 32) * 5 / 9  end  logoff To quit, or sign off, a computer system. logon To gain access, or sign in, to a computer system. If restricted, it requires users to identify themselves by entering an ID number and/or password. Service bureaus base their charges for the time between logon and logoff. logout Same as logoff. long In programming, an integer variable. In C, a long is four bytes and can be signed (-2G to +2G) or unsigned (4G). Contrast with short. long card In PCs, a full-length controller board that plugs into an expansion slot. Contrast with short card. long-haul In communications, modems or communications devices that are capable of transmitting over long distances. long lines In communications, circuits that are capable of handling transmissions over long distances. longitudinal redundancy check See LRC. LONWORKS Control network from Echelon Corp., Palo Alto, CA, that uses Echelon's NEURON CHIP (made by Motorola and Toshiba) and LONTALK protocol. Each NEURON CHIP uses a 48-bit number for identification. Control modules that contain the NEURON CHIP and transceivers for transmitting via RS-485, twisted pair, coax and AC power lines are available on credit card-sized boards. The LONBUILDER development system is used to create applications, which are written into PROM chips. LONWORKS software, as well as programming interfaces for DOS and Windows, provide node installation and network management. lookup Data search performed within a predefined table of values (array, matrix, etc.) or within a data file. loop In programming, a repetition within a program. Whenever a process must be repeated, a loop is set up to handle it. A program has a main loop and a series of minor loops, which are nested within the main loop. Learning how to set up loops is what programming technique is all about. The following example prints an invoice. The main loop reads the order record and prints the invoice until there are no more orders to read. After printing date and name and addresses, the program prints a variable number of line items. The code that prints the line items is contained in a loop and repeated as many times as required.  main敖陳陳陳陳陳陳朕  loop Get next order   Print date   Print bill to  Print ship to  line敖陳陳調  item   loop Print line item    青陳陳調   Print totals  青陳陳陳陳陳陳陳  Loops are accomplished by various programming structures that have a beginning, body and end. The beginning generally tests the condition that keeps the loop going. The body comprises the repeating statements, and the end is a GOTO that points back to the beginning. In assembly language, the programmer writes the GOTO, as in the following example that counts to 10.  MOVE "0" TO COUNTER  LOOP ADD "1" TO COUNTER  COMPARE COUNTER TO "10"  GOTO LOOP IF UNEQUAL  STOP  In high-level languages, the GOTO is generated by the interpreter or compiler; for example, the same routine as above using a WHILE loop.  COUNTER = 0  DO WHILE COUNTER <> 10  COUNTER = COUNTER + 1  ENDDO  STOP  loop carrier In telephone communications, a system that concentrates a number of analog or digital lines from a remote termination station into the central office. It normally converts analog voice into digital at the remote station; however, it can be adapted to provide ISDN service to a customer. loopback plug Diagnostic connector that directs the sending line back into the receiving line for test purposes. loosely coupled Refers to stand-alone computers connected via a network. Loosely coupled computers process on their own and exchange data on demand. Contrast with tightly coupled. lossless compression Compression techniques that decompress data 100% back to original. Contrast with lossy compression. lossy compression Compression techniques that do not decompress data 100% back to original. Images and audio samples may be able to afford small losses of resolution in order to increase compression. Contrast with lossless compression. lost cluster Disk records that have lost their identification with a file name. This can happen if a file is not closed properly, which can sometimes occur if the computer is turned off without formally quitting an application. See DOS Chkdsk. Lotus (Lotus Development Corp., Cambridge, MA) Software company founded in 1981 by Mitch Kapor. It achieved outstanding success by introducing the first spreadsheet for the IBM PC (see Lotus 1-2-3). Over the years, it has developed a variety of applications and has helped set industry standards. In 1990, it acquired Samna Corp., makers of the popular, Windows-based Ami word processors. Lotus 1-2-3 Spreadsheet for DOS, Windows, Macintosh, Sun, VAX, OS/2 and IBM mainframe platforms from Lotus. Introduced in 1982, it was the first, new and innovative spreadsheet for the PC. It included graphics, file management and limited word processing along with spreadsheet capabilities. Its ability to instantly convert numeric data into a graph was a dazzling feature for its time. The program's user interface was also easy to use (see Lotus menu). Over 20 million copies of Lotus are in use today. In 1989, Lotus upgraded Version 2.01 for DOS into two versions: 2.2 and 3.0. Version 2.2 and succeeding 2.x versions run in a 640K PC. They include macro recording, an undo and a dynamic link from one spreadsheet to another. Version 3.0 and succeeding 3.x versions take advantage of extended and expanded memory and can build very large spreadsheets. They include 3-D and dynamic linking capabilities as well as more sophisticated graphing. Lotus Add-in Toolkit Pascal-like programming language from Lotus that allows automated processes to be created and executed in Lotus 1-2-3 Version 3.x. Lotus menu Menu introduced with Lotus 1-2-3 that became a de facto standard. It is a row of words, each of which is an option that can be selected by highlighting it and pressing Enter or by pressing the first letter of the word. When the word is highlighted, an explanation line is displayed above or below it. Contrast with pull-down menu. Lotus Notes Distributed document database system from Lotus that runs in a client/server environment under Windows, OS/2 and various UNIX platforms. Designed for workgroups that need to exchange information, all types of files can be attached to a Notes document. It includes e-mail and outbound fax and keeps distributed documents in sync in an enterprise-wide environment. As of Release 3, it allows a Windows PC to act as a server and will run with any VIM-compliant e-mail system such as cc:Mail. low density Refers to an earlier version of a storage device with less bits per inch than today's version. See DD and double density. low entry networking See LEN. low frequency Electromagnetic wave that vibrates in the range from 30 to 300,000 Hertz. low-level format Sector identification on a disk that the drive uses to locate sectors for reading and writing. See format program. low-level language Programming language that is very close to machine language. All assembly languages are low-level languages. Contrast with high-level language. low radiation Refers to video terminals that emit less VLF (Very Low Frequency) and ELF (Extremely Low Frequency) radiation. This level of radiation cannot be shielded by office partitions. It must be cancelled out from the CRT. Health studies on this are not conclusive and are very controversial. See MPR II. low resolution Low-grade display or printing quality due to a lower number of dots or lines per inch. lower CASE See back-end CASE. lpi (Lines Per Inch) The number of lines printed in a vertical inch. lpm (Lines Per Minute) Number of lines a printer can print or a scanner can scan in a minute. LPT1 Logical name assigned to parallel port #1 in DOS and OS/2 (usually connected to a printer). A second parallel device is assigned LPT2. Contrast with COM1. LQ See letter quality. LRC (Longitudinal Redundancy Check) Error checking method that generates a parity bit from a specified string of bits on a longitudinal track. In a row and column format, such as on magnetic tape, LRC is often used with VRC, which creates a parity bit for each character. LSAPI (Licensing Service API) Programming interface from Microsoft that allows a licensing server to track applications in use for managing multiuser software licenses. LSI (Large Scale Integration) Between 3,000 and 100,000 transistors on a chip. See SSI, MSI, VLSI and ULSI. LSI-11 Family of board-level computers from Digital that uses the micro version of the PDP-11. Introduced in 1974, it was the first to use the Q-bus. LT (Less Than) See relational operator. LU (Logical Unit) In SNA, one end of a communications session. The complete LU to LU session is defined by session type. Common types are: 1 Host to 3770 RJE terminal 2 Host to 3270 mainframe terminal 3 Host to 3270 printer 6.2 Program-to-program 7 Host to 5250 midrange terminal LU 6.2 SNA protocol that establishes a session between two programs. It allows peer-to-peer communications as well as interaction between programs running in the host with PCs and other midrange computers. Before LU 6.2, processing was done only in the mainframe. LU 6.2 allows processing to take place at both ends of the communications, necessary for today's distributed computing and client/server environment. See APPC and CPI-C. lumen Unit of measurement of the flow (rate of emission) of light. A wax candle generates 13 lumens; a 100 watt bulb generates 1,200. See candela. Lumena PC paint program from Time Arts, Inc., Santa Rosa, CA, that provides sophisticated, special effects. It accepts and generates NTSC video output and requires a video graphics board. luminance In computer graphics, the amount of brightness, measured in lumens, that is given off by a pixel or area on a screen. LZW (Lempel-Ziv-Welch) Widely-used dictionary compression method that stems from two techniques introduced by Jacob Ziv and Abraham Lempel. LZ77 scans a fixed length block of data and creates pointers back to data when it repeats. LZ78 scans the data and creates a dictionary of repeating phrases. Pointers are created to those phrases. M See mega. M-byte See megabyte. M Technology Assn. See MUMPS. Mac (1) See Macintosh. (2) (MAC) (Media Access Control) Sublayer that controls the access method in an IEEE 802 LAN. See "LANs" under data link protocol. Mac to midrange Using the Macintosh as the terminal to IBM S/3x and AS/400 computers. Apple and third party connectivity products add local processing and a friendly interface to IBM midrange computers. MacAPPC LU 6.2-compliant software from Apple Computer that allows a Macintosh to be a peer to an IBM APPC application. MacDFT Software that provides 3270 emulation for the Macintosh from Apple. It accompanies Apple's TwinAx/Coax board and supports CUT and DFT modes and DFT multiple sessions under SNA. MacDraw Pro Macintosh drawing program from Claris Corp. that is an enhanced version of the original MacDraw from Apple and includes full on-screen slide presentation capability. It is used for illustrations and elementary CAD work. MacDraw files are a subset of the Claris CAD file format. Mach UNIX-like operating system developed at Carnegie- Mellon Univ. machine Any electronic or electromechanical unit of equipment. A machine is always hardware; however, "engine" refers to hardware or software. machine address Same as absolute address. machine code Same as machine language. machine cycle Shortest interval in which an elementary operation can take place within the processor. It is made up of some number of clock cycles. machine dependent Refers to software that accesses specific hardware features and runs in only one kind of computer. Contrast with machine independent. See device dependent. machine independent Refers to software that runs in a variety of computers. The hardware-specific instructions are in some other program (operating system, DBMS, etc.). Contrast with machine dependent. See device independent. machine instruction Instruction in machine language. Its anatomy is a verb followed by one or more nouns: OP CODE OPERANDS (one or more) (verb) (nouns) The op code is the operation to be performed (add, copy, etc.), while the operands are the data to be acted upon (add a to b). There are always machine instructions to INPUT and OUTPUT, to process data by CALCULATING, COMPARING and COPYING it, and to go to some other part of the program with a GOTO instruction. See computer. machine language Native language of the computer. In order for a program to run, it must be in the machine language of the computer that is executing it. Although programmers are sometimes able to modify machine language in order to fix a running program, they do not create it. It is created by programs called assemblers, compilers and interpreters, which convert programming language into machine language. Machine language tells the computer what to do and where to do it. When a programmer writes: total = total + subtotal, that statement is converted into a machine instruction that tells the computer to add the contents of two areas of memory (where TOTAL and SUBTOTAL are stored). A programmer deals with data logically, "add this, subtract that," but the computer must be told precisely where this and that are located. Machine languages differ substantially. What may take one instruction in one machine can take 10 instructions in another. See assembly language. machine readable Data in a form that can be read by the computer, which includes disks, tapes and punched cards. Printed fonts that can be scanned and recognized by the computer are also machine readable. Macintosh Series of 32-bit personal computers from Apple introduced in 1984. It uses the Motorola 68000 CPU family and an operating system that simulates a user's desktop on screen. The Mac's graphics-based user interface has provided a measure of consistency and ease of use that is unmatched. The Macintosh family is the largest non-IBM compatible personal computer series in use. Introduced in 1984 as a floppy-based computer with 128K of memory, its "high-rise" cabinet and built-in 9" monochrome screen were unique. This design is retained in the Classic models, while the rest of the line is now clothed in traditional cabinetry.  MACINTOSH SPECIFICATIONS  3.5"  Clock Bus Floppy Hard Screen  68xxx Speed Size RAM Disk Disk Res. Model CPU Mhz Bits(--Bytes--)(Mbytes) 陳陳陳陳陳陳陳堕陳堕陳堕陳陳堕陳陳堕陳陳陳堕陳陳陳 128* 000 8 16128K 400K 20 512x342 512* 000 8 16512K 400K 団陳陳陳 9" Mono Plus* 000 8 161-4M 800K Black on 団陳陳 White SE* 000 8 161-4M 3.5" 20-160 SE30* 030 16 321-8M Super Classic* 000 8 161-4M Drive Classic II 030 16 162-10M 40-80 Color Classic 団陳陳陳 256 cols 030 16 164-10M 40-16010" diag II* 020 16 321-8M 団陳陳陳 IIx* 030 16 321-8M 640x480 IIcx* 030 16 321-8M 14" B/W IIci 030 25 325-32M 80-230or 256 IIfx* 030 40 324-32M 80+ cols. IIsi 030 20 323-17M 40-80 IIvi 030 16 324-20M 40-400640x870 IIvx 030 32 324-20M 40-40015" B/W LC* 020 16 161-10M 40-80 LC II 030 16 162-10M 40-80 1152x870 LC III 030 25 324-36M 40-1601152x870 Quadra 700*040 25 324-20M 80-40021" B/W Quadra 800 040 33 328-136 230-1G Quadra 900*040 25 324-64M 160-400 Quadra 950 040 33 328-256 230-1G ** Centris610 040 20 324-68M 80-500 Centris650 040 25 324-132 80-500 団陳陳陳 Portable* 000 16 321-9M 40 am Performa (consumer product line) 200 030 16 164-10M 80-160640x480 400 030 16 164-10M 80-16014" 600 030 32 164-68M 80-160256 cols PowerBook Portables 100* 000 16 162-8M 20 pm 140* 030 16 162-8M 20-40 pm 145 030 25 164-8M 40-80 pm 160 030 25 164-14M 40-120 pm 165c color 030 33 164-14M 80-160 pm 170* 030 25 164-8M 40 am 180 030 33 164-14M 80-120 am 210 Duo 030 25 164-24M 80 pm 230 Duo 030 33 164-24M 80-120 pm 陳陳陳陳陳陳陳祖陳祖陳祖陳陳祖陳陳祖陳陳陳祖陳陳陳 * No longer made as of 2/93 ** Built-in 24-bit color pm passive matrix LCD am active matrix LCD Macintosh user interface Method of operating a Macintosh, originally developed by Xerox and introduced on the Xerox Star in 1981. It uses a graphics-based screen that places familiar objects on a two-dimensional desktop. Programs, files, folders and disks are represented by small pictures (icons). An object is selected by moving a mouse over the real desktop, which correspondingly moves a pointer on the screen desktop. When the pointer touches an icon, the object is selected by clicking the mouse button. A hierarchical file system is provided that lets a user "drag" a document icon into and out of a folder icon. Folders can also contain other folders. To delete a document, its icon is literally dragged into a trash can icon. The Macintosh always displays a row of menu titles at the top of the screen. The full menu appears as if it were pulled down from the top of the screen when selected. With the mouse button held down, the option within the menu is selected by pointing to it and releasing the button. Unlike the PC world, which, before Windows, left the design of the user interface up to the software developer, Macintosh developers always conform to the Mac interface. As a result, users feel more comfortable with new programs from the start. In operation, the operating system and applications are almost indistinguishable, and Apple keeps technical jargon to a minimum. Early Mac applications had little regard for experienced typists, forcing them to use the mouse instead of well-designed keyboard commands. Subsequent versions offer both methods and have greatly improved. The Macintosh style has been adapted to many environments, including Windows, Presentation Manager, GEM and OSF/Motif. MacIRMA Micro to mainframe communications board for the Macintosh from DCA, Inc., Alpharetta, GA. It a 3270 terminal. MacLink Plus Macintosh file transfer program from DataViz Corp., Trumbull, CT, that provides document conversion for over 45 Mac and PC formats. Versions are available for NeXt and Sun workstations and Wang OIS and VS systems. MacPaint II Full-featured Macintosh paint program from Claris that was originally developed by Apple and bundled with every Mac up until the Mac Plus. MacPaint's PICT file format is used for printing the screen. By pressing Command-shift-3, the current screen is stored in a PICT file for printing either in MacPaint or other program. macro (1) Series of menu selections, keystrokes and/or commands that have been recorded and assigned a name or key combination. When the name is called or the key is pressed, the macro is executed from beginning to end. It is used to shorten long menu sequences into one keystroke as well as to create miniature programs within an application. Macro languages often include programming controls (IF THEN, GOTO, WHILE, etc.) that automate sequences like any programming language. See macro recorder, batch file and shell script. (2) In assembly language, a prewritten subroutine that is called for throughout the program. At assembly time, the macro calls are substituted with the actual subroutine or instructions that branch to it. The high-level language equivalent is a function. (3) In dBASE programming, a variable which references another variable that actually contains the data. At runtime, the macro variable is substituted with the data variable. macro assembler Assembler program that lets the programmer create and use macros. macro call Same as macro instruction. macro generator See macro recorder. macro instruction Instruction that defines a macro. In assembly language, MACRO and ENDM are examples that define the beginning and end of a macro. In C, the #DEFINE statement is used. macro language (1) Commands used by a macro processor. Same as script. (2) Assembly language that uses macros. macro processor (1) Software that creates and executes macros from the keyboard. (2) The part of an assembler that substitutes the macro subroutines for the macro calls. macro recorder Program routine that converts menu selections and keystrokes into a macro. A user turns on the recorder, calls up a menu, selects a variety of options, turns the recorder off and assigns a key command to the macro. When the key command is pressed, the selections are executed. MacTerminal Macintosh terminal emulation software from Apple that allows a Mac to function as an IBM 3278 Model 2 (when used with an AppleLine Protocol Converter) or Digital VT 52 or VT 100 terminal. MacTwin Mac to IBM midrange connectivity from Andrew/KMW, which includes a card for the Mac that connects to the twinax cabling from the S/3x or AS/400. Software for the Mac provides 5250, 3196 and 3197 emulation. MacWrite II Full-featured Macintosh word processing program from Claris Corp., that was originally packaged with every Mac 128 and 512. mag Abbreviation for "magnetic." Magellan Disk management utility for PCs from Lotus that searches for file names and contents. It popularized the file viewer, which lets you look into various data files as if you were using the applications that created them. Magic Cap (Magic Communicating Applications Platform) Object-oriented control program from General Magic for personal intelligent communicating devices (PDAs, hand-held units, etc.) that includes the Telescript language. magnetic card (1) See magnetic stripe. (2) Magnetic tape strips used in early data storage devices and word processors. See CRAM, RACE and Data Cell. magnetic coercivity Amount of energy required to alter the state of a magnet. The higher a magnetic disk's coercivity index, the more data it can store. magnetic disk Primary computer storage device. Like tape, it is magnetically recorded and can be re-recorded over and over. Disks are rotating platters with a mechanical arm that moves a read/write head between the outer and inner edges of the platter's surface. It can take as long as one second to find a location on a floppy disk to as short as one millisecond on an ultra-fast hard disk. See floppy disk and hard disk. Tracks and Sectors The disk surface is divided into concentric tracks (circles within circles). The thinner the tracks, the more storage. The data bits are recorded as tiny spots on the tracks. The tinier the spot, the more bits per inch and the greater the storage. Most disks hold the same number of bits on each track, even though the outer tracks are physically longer than the inner ones. Some disks pack the bits as tightly as possible within each track. Tracks are further divided into sectors, which hold the least amount of data that can be read or written at one time; for example, READ TRACK 7 SECTOR 24. In order to update the disk, one or more sectors are read into the computer, changed and written back to disk. The operating system figures out how to fit data into these fixed spaces. See hard disk and floppy disk. magnetic disk & tape Primary computer storage media. The choice depends on accessing requirements. Disk is direct access; tape is sequential access. Locating a program or data on disk can take a fraction of a second. On tape, it can take seconds or minutes. On minis and mainframes, disks are used for daily transaction processing, and tapes are used for backup and history. Tapes have traditionally been more economical for archival storage and easier to transport than disk packs. For personal computers, hard disks are used for all interactive processing, and both floppy disks and tapes are used for backup. Bernoulli disks and removable hard disks are increasingly becoming backup alternatives. In time, magnetic disks will be as obsolete as punched cards. Optical disks are getting faster and cheaper, and optical technologies that employ no moving parts will undoubtedly supersede them all. Compared to the magical technology within the chip, whirling chunks of metal around is rather old fashioned, don't you think? magnetic drum Early high-speed, direct access storage device that used a magnetic-coated cylinder with tracks around its circumference. Each track had its own read/write head. magnetic field Invisible energy emitted by a magnet. Same as flux. magnetic ink Magnetically detectable ink used to print the MICR characters that encode account numbers on bank checks. magnetic oxide See ferric oxide. magnetic recording With regard to computers, the technique used to record, or write, digital data in the form of tiny spots (bits) of negative or positive polarity on tapes and disks. A read/write head discharges electrical impulses onto the moving ferromagnetic surface. Reading is accomplished by sensing the polarity of the bit with the read/write head. magnetic stripe Small length of magnetic tape adhered to ledger cards, badges and credit cards. It is read by specialized readers that may be incorporated into accounting machines and terminals. Due to heavy wear, the data on the stripe is in a low-density format that may be duplicated several times. magnetic tape Sequential storage medium used for data collection, backup and historical purposes. Like videotape, computer tape is made of flexible plastic with one side coated with a ferromagnetic material. Tapes come in reels, cartridges and cassettes of many sizes and shapes. As with any tape, locating a specific item requires reading everything in front of it. There is no way to fast forward. In order to add and delete records, the current tape is input to the computer and a blank tape is used for output. If data on tape is only changed and the physical number of records is not altered, some tape drives can update in place by reading a block of data and writing back over the same area. Except for tape cartridges that use the serpentine or helical scan methods (see QIC and DAT), data bits are recorded on parallel tracks that run the length of the tape. For example, 9- track tape holds one byte of data across the tape's width (8 bits plus parity). Data is recorded in blocks of contiguous bytes, separated by a space called an interrecord or interblock gap. There are a variety of formats used in data cartridges and data cassettes; however, open-reel 1/2" tape is a common standard among minis and mainframes. See tape backup. Tape is more economical than disks for historical data. When tapes are used for archival storage, they must be periodically recopied or the tightly coiled magnetic surfaces may contaminate each other. Storage capacity is measured in bits per inch (bpi). With tape formatted in parallel tracks, bpi is equivalent to bytes per inch. Common 1/2" recording densities are 1650 and 6250 bpi; early densities were 200, 556 and 800 bpi. Tape drive speed is measured in inches per second (ips), thus, transfer rate = ips X bpi. magneto-optic High-density, erasable recording method. Data is recorded magnetically like disks and tapes, but the bits are much smaller, because a laser is used to pinpoint the bit. The laser heats the bit to 150 Celsius, at which temperature the bit is realigned when subjected to a magnetic field. In order to record new data, existing bits must first be set to zero. See Curie point, Kerr effect and optical disk. magnetographic Non-impact printer technology from Groupe Bull that prints up to 90 ppm. A magnetic image is created by a set of recording heads across a magnetic drum. Monocomponent toner is applied to the drum to develop the image, which is transferred to paper by light pressure and an electrostatic field. The toner is then fused by heat. The print quality is not as good as a laser printer, but the machines require less maintenance. mail box Computer storage assigned to a user for electronically transmitted mail. mail merge Printing customized form letters. A common feature of a word processor, it uses a letter and a name and address list. In the letter, Dear A: Thank you for ordering B from our C store..., A, B and C are merge points into which data is inserted from the list. See field squeeze and line squeeze. main line See main loop. main loop Primary logic in a program. It contains the instructions that are repeated after each event or transaction has been processed. See loop. main memory Same as memory. main storage Same as memory. mainframe Large computer. In the "ancient" mid 1960s, all computers were called mainframes, since the term referred to the main CPU cabinet. Today, it refers to a large computer system. There are small, medium and large-scale mainframes, handling from a handful to several thousand online terminals. Large-scale mainframes can have hundreds of megabytes of main memory and terabytes of disk storage. Large mainframes use smaller computers as front end processors that connect to the communications networks. The original mainframe vendors were Burroughs, Control Data, GE, Honeywell, IBM, NCR, RCA and Univac, otherwise known as "IBM and the Seven Dwarfs." After GE and RCA's computer divisions were absorbed by Honeywell and Univac respectively, the mainframers were known as "IBM and the BUNCH." maintenance (1) Hardware maintenance is the testing and cleaning of equipment. (2) Information system maintenance is the routine updating of master files, such as adding and deleting employees and customers and changing credit limits and product prices. (3) Software or program maintenance is the updating of application programs in order to meet changing information requirements. (4) Disk or file maintenance is the periodic reorganizing of online disk files that have undergone fragmentation due to continuous updating. maintenance credits Monetary credits issued to a customer by the vendor for qualified periods during which the vendor's products are not functioning properly. maintenance service Service provided to keep a product in good operating condition. major key Primary key used to identify a record, such as account number or name. make To compile a multi-module program. The make utility recompiles only those modules that have been updated since the last compilation. male connector Plug that is designed to fit into a particular socket. Maltron keyboard Keyboard that uses independent left- and right-hand modules shaped to conform to the natural position of the hands, designed to prevent strain (RSI). MAN (Metropolitan Area Network) Communications network that covers a geographic area such as a city or suburb. See LAN and WAN. management science Study of statistical methods, such as linear programming and simulation, in order to analyze and solve organizational problems. Same as operations research. management support See DSS and EIS. management system Leadership and control within an organization. It is made up of people interacting with other people and machines that, together, set the goals and objectives, outline the strategies and tactics, and develop the plans, schedules and necessary controls to run an organization. Manchester Code Self-clocking data encoding method that divides the time required to define the bit into two cycles. The first cycle is the data value (0 or 1) and the second cylce provides the timing by shifting to the opposite state. MANTIS Application development language from Cincom Systems, Inc., Cincinnati, OH, that runs on IBM mainframes, VAXs and other mainframes. It provides procedural and non-procedural languages for developing prototypes and applications and works with Cincom's SUPRA database, DB2 and IMS. mantissa Numeric value in a floating point number. See floating point. MAP (Manufacturing Automation Protocol) Communications protocol introduced by General Motors in 1982. MAP's goal is to provide common standards for the interconnection of computers and programmable machine tools used in factory automation. At the lowest physical level, it uses the IEEE 802.3 token bus protocol. Although MAP has provided vitally needed consolidation of standards, it continues to be in a constant state of revision. MAP is often used in conjunction with TOP, an office protocol developed by Boeing Computer Services. TOP is used in the front office and MAP is used on the factory floor. map (1) Set of data that has a corresponding relationship to another set of data. (2) List of data or objects as they are currently stored in memory or disk. (3) To transfer a set of objects from one place to another. For example, program modules on disk are mapped into memory. A graphic image in memory is mapped onto the video screen. An address is mapped to another address. (4) To relate one set of objects with another. For example, a logical database structure is mapped to the physical database. A vendor's protocol stack is mapped to the OSI model. MAPI (Mail API) Microsoft e-mail and messaging protcol. See OMI and VIM. MAPPER (MAintaining, Preparing and Processing Executive Reports) Unisys mainframe fourth-generation language. In 1980, it was introduced as a high- level report writer and was later turned into a full-featured development system used successfully by non-technical users. mapping See map and digital mapping. marginal test System test that introduces values far above and far below the expected values. mark (1) Small blip printed on or notched into various storage media used for timing or counting purposes. (2) To identify a block of text in order to perform some task on it such as deletion, copying and moving. (3) To identify an item for future reference. (4) In digital electronics, a 1 bit. Contrast with space. (5) On magnetic disk, a recorded character used to identify the beginning of a track. (6) In optical recognition and mark sensing, a pencil line in a preprinted box. (7) On magnetic tape, a tape mark is a special character that is recorded after the last character of data. Mark I Electromechanical calculator designed by professor Howard Aiken, built by IBM and installed at Harvard in 1944. It strung 78 adding machines together to perform three calculations per second. It was 51 feet long, weighed five tons and used punched cards and typewriters for I/O. Made of 765,000 parts, it sounded like a thousand knitting needles according to Admiral Grace Hopper. The experience helped IBM develop its own computers a few years later. MARK IV See Crosstalk and MARK IX. MARK IX Application generator from Sterling Software's Answer Systems Div., Woodland Hills, CA, that runs on IBM mainframes and personal computers. It stems from MARK IV, the first report writer to use fill- in-the-blanks forms. MARK V was a subsequent online version. mark sensing Detecting pencil lines in predefined boxes on paper forms. The form is designed with boundaries for each pencil stroke that represents a yes, no, single digit or letter, providing all possible answers to each question. A mark sense reader detects the marks and converts them into digital code. mask (1) Pattern used to transfer a design onto an object. See photomask. (2) Pattern of bits used to accept or reject bit patterns in another set of data. For example, the Boolean AND operation can be used to match a mask of 0s and 1s with a string of data bits. When a 1 occurs in both the mask and the data, the resulting bit will contain a 1 in that position. Hardware interrupts are often enabled and disabled in this manner with each interrupt assigned a bit position in a mask register. mask bit 1 bit in a mask used to control the corresponding bit found in data. maskable interrupts Hardware interrupts that can be enabled and disabled by software. masked State of being disabled or cut off. MASM (Macro ASeMbler) Assembly language that allows macros to be defined and used. mass storage High-capacity, external storage such as disk or tape. massage To process data. massively parallel Parallel processing architecture that uses hundreds or thousands of processors. master Primary, controlling. See master-slave communications and master file. master card Master record in punched card format. master clock Clock that provides the primary source of internal timing for a processor or stand-alone control unit. master console Main terminal used by the computer operator or systems programmer to command the computer. master control program See operating system. master file Collection of records pertaining to one of the main subjects of an information system, such as customers, employees, products and vendors. Master files contain descriptive data, such as name and address, as well as summary information, such as amount due and year-to-date sales. Contrast with transaction file. master record Set of data for an individual subject, such as a customer, employee or vendor. See master file. master-slave communications Communications in which one side, called the master, initiates and controls the session. The other side (slave) responds to the master's commands. math coprocessor Mathematical circuit that performs high-speed floating point operations. It increases the performance of CAD applications, but the CAD program must activate its use. See array processor and vector processor. mathematical expression Group of characters or symbols representing a quantity or an operation. See arithmetic expression. mathematical function Rule for creating a set of new values from an existing set; for example, the function f(x) = 2x creates a set of even numbers (if x is a whole number). matrix Array of elements in row and column form. See x-y matrix. matrix printer See dot matrix and printer. MAU (Multi-station Access Unit) Central hub in a token ring local area network. maximize In a graphical environment, to enlarge a window to full size. Contrast with minimize. MB, Mb See megabyte and megabit. Mbit See megabit. Mbits/sec (MegaBITS per SECond) Million bits per second. MBps, Mbps (MegaBytes Per Second, MegaBits Per Second) Million bytes per second. Million bits per second. Mbyte See megabyte. Mbytes/sec (MegaBYTES per SECond) Million bytes per second. MC68000 See 68000. MCA See Micro Channel. MCB (Memory Control Block) Identifier (16-bytes) that DOS places in front of each block of memory it allocates. MCGA (Multi Color Graphics Array) IBM video display standard built into low-end PS/2 models. It is not well supported by software vendors. See PC display modes. MCI (Media Control Interface) High-level programming interface from IBM/Microsoft for controlling multimedia devices. It includes text commands such as open, play and close for languages such as Visual BASIC, as well as functions for languages such as C. See RIFF and AVI. MCI decision FCC decree in 1969 that granted MCI the right to compete with the Bell System by providing private, intercity telecommunications services. MCU (1) (MicroController Unit) Control unit on a single chip. (2) (Multipoint Control Unit) Device that connects multiple sites for audio and video conferencing. MDA (Monochrome Display Adapter) First IBM PC monochrome video display standard for text only. Due to its lack of graphics, MDA cards were often replaced with Hercules cards, which provided both text and graphics. See PC display modes. MDI (Multiple Document Interface) In Windows, multiple windows that are minimized or maximized as a group. Contrast with SDI. mechanical mouse Mouse that uses a rubber ball that rolls against wheels inside the unit. Contrast with optical mouse. media Material that stores or transmits data, for example, floppy disks, magnetic tape, coaxial cable and twisted wire pair. media access method See "LANs" under data link protocol. media conversion Converting data from one storage medium to another, such as from disk to tape or from one type of disk pack to another. media failure Condition of not being able to read from or write to a storage device, such as a disk or tape, due to a defect in the recording surface. medium frequency Electromagnetic wave that oscillates in the range from 300,000 to 3,000,000 Hz. See electromagnetic spectrum. meg Same as mega. mega (1) Million. Abreviated "M." It often refers to the precise value 1,048,576 since computer specifications are usually binary numbers. See binary values and space/time. (2) (MEGA) Personal computer series from Atari that is Motorola 68000 based, runs under GEM and the TOS operating system and includes a MIDI interface. It is ST compatible. Mega VGA 1024x768, 256 color Super VGA mode that requires one megabyte of video RAM. megabit One million bits. Also Mb, Mbit and M-bit. See mega and space/time. megabyte One million bytes. Also MB, Mbyte and M-byte. See mega and space/time. megaflops (mega FLoating point OPerations per Second) One million floating point operations per second. megahertz One million cycles per second. See MHz. megapel display In computer graphics, a display system that handles a million or more pixels. A resolution of 1,000 lines by 1,000 dots requires a million pixels for the full screen image. membrane keyboard Dust and dirtproof keyboard constructed of two thin plastic sheets (membranes) that contain flexible printed circuits made of electrically conductive ink. The top membrane is the printed keyboard and a spacer sheet with holes is in the middle. When a user presses a simulated key, the top membrane is pushed through the spacer hole and makes contact with the bottom membrane, completing the circuit. memo field Data field that holds a variable amount of text. The text may be stored in a companion file, but it is treated as if it were part of the data record. For example, in the dBASE command list name, biography, name is in the data file (DBF file) and biography could be a memo field in the text file (DBT file). memory The computer's workspace (physically, a collection of RAM chips). It is an important resource, since it determines the size and number of programs that can be run at the same time, as well as the amount of data that can be processed instantly. All program execution and data processing takes place in memory. The program's instructions are copied into memory from a disk or tape and are then extracted from memory into an electronic circuit for analysis and execution. The instructions direct the computer to input data into memory from a keyboard, disk, tape or communications channel. As data is entered into memory, the previous contents of that space is lost. Once the data is in memory, it can be processed (calculated, compared and copied). The results are sent to a screen, printer, disk, tape or communications channel. Memory is like an electronic checkerboard, with each square holding one byte of data or instruction. Each square has a separate address like a post office box and can be manipulated independently. As a result, the computer can break apart programs into instructions for execution and data records into fields for processing. Memory Doesn't Usually Remember Oddly enough, the computer's memory doesn't remember anything when the power is turned off. That's why you have to save your files before you quit your program. Although there are memory chips that do hold their content permanently (ROMs, PROMs, EPROMs, etc.), they're used for internal control purposes and not for the user's data. "Remembering" memory in a computer system is its disks and tapes, and although they are also called memory devices, many prefer to call them storage devices (as we do) in order to differentiate them from internal memory. Perhaps in time, memory will refer to disks exclusively and RAM will refer to working memory. Until then, its usage for both RAM and disk only adds confusion to the most confusing industry on earth. Other terms for memory are RAM, main memory, main storage, primary storage, read/write memory, core and core storage. memory allocation Reserving memory for specific purposes. Operating systems generally reserve all the memory they need at startup. Application programs use memory when loaded and may allocate more after being loaded. If there is not enough free memory, they cannot run. On a personal computer, memory can be allocated for a disk cache, which retains large chunks of data from the disk in faster RAM. However, a large disk cache that speeds up one application may slow down another because there is less normal memory available. Memory can be allocated for a RAM disk, which simulates a disk drive in memory. Disk files are copied to the RAM disk and all accesses take place in faster memory. RAM disks may dramatically speed up one program and have little effect on others. Like the disk cache, it takes away from the total available memory. On DOS PCs, allocating a mix of extended memory and EMS memory is often requried. Windows 3.x and DOS-extended applications use extended memory, while other applications may use EMS memory. On 286s, allocation requires changing parameters in the CONFIG.SYS file and rebooting. Older 286s may require changing switches on the EMS boards. On 386s and up, using advanced memory managers such as QEMM386 and 386MAX, allocation can be done on demand automatically. See DOS memory manager. memory bank (1) Physical section of memory. See memory interleaving. (2) Refers generically to a computer system that holds data. memory based Programs that hold all data in memory for processing. Almost all spreadsheets are memory based so that a change in data at one end of the spreadsheet can be instantly reflected at the other end. memory cache See cache. memory card (1) Credit-card-sized memory module used as a disk alternative in portable computers. Called IC cards, ROM cards and RAM cards, they use a variety of chip types, including RAM, ROM, EEPROM and flash memory. RAM cards use a battery to keep the cells charged. See PC card and PCMCIA. (2) Printed circuit board that contains memory. memory cell One bit of memory. In dynamic RAM memory, a cell is made up of one transistor and one capacitor. In static RAM memory, a cell is made up of about five transistors. memory chip Chip that holds programs and data either temporarily (RAM), permanently (ROM, PROM) or permanently until changed (EPROM, EEPROM). memory cycle Series of operations that take place to read or write a byte of memory. For destructive memories, it includes the regeneration of the bits. memory cycle time Time it takes to perform one memory cycle. memory dump Display or printout of the contents of memory. When a program abends, a memory dump can be taken in order to examine the status of the program at the time of the crash. The programmer looks into the buffers to see which data items were being worked on when it failed. Counters, variables, switches and flags are also inspected. memory effect See NiCad and nickel hydride. memory interleaving Category of techniques for increasing memory speed. For example, with separate memory banks for odd and even addresses, the next byte of memory can be accessed while the current byte is being refreshed. memory management Method used to control memory, which includes memory protection, virtual memory and bank switching techniques. See virtual memory, EMS, EMM and DOS memory manager. memory map Location of instructions and data in memory. memory mapped I/O Peripheral device that assigns specific memory locations to input and output. For example, in a memory mapped display, each pixel or text character derives its data from a specific memory byte or bytes. The instant this memory is updated by software, the screen is displaying the new data. memory protection Technique that prohibits one program from accidentally clobbering another active program. Using various different techniques, a protective boundary is created around the program, and instructions within the program are prohibited from referencing data outside of that boundary. memory resident Program that remains in memory at all times. See TSR. memory sniffing Coined by Data General, a diagnostic routine that tests memory during normal processing. The processor uses cycle stealing techniques that allow it to test memory during unused machine cycles. A memory bank can be "sniffed" every few minutes. memory typewriter Typewriter that holds a few pages of text in its memory and provides limited word processing functions. With a display screen of only one or two lines, editing is tedious. menu (1) List of available options on screen. Selection is accomplished by highlighting the option with a mouse or cursor keys and clicking the mouse or pressing Enter. See Lotus menu and pull-down menu. (2) (Menu) Software subsidiary of Black Box Corp., Pittsburgh, PA, that offers the world's most complete listing of software information for LANs and personal computers. menu bar Row of on-screen menu options. menu-driven Using menus to command the computer. Contrast with command-driven. menuing software Software that provides a menu for launching applications and running operating system commands. merge See mail merge and concatenate. merge purge To merge two or more lists together and eliminate unwanted items. For example, a new name and address list can be added to an old list while deleting duplicate names or names that meet certain criteria. mesa Semiconductor process used in the 1960s for creating the sublayers in a transistor. Its deep etching gave way to the planar process. mesh network Net-like communications network in which there are at least two pathways to each node. Since the term network means net-like as well as communications network, the term mesh is used to avoid saying network communications network. message (1) In communications, a set of data that is transmitted over a communications line. Just as a program becomes a job when it's running in the computer, data becomes a message when it's transmitted over a network. (2) In object-oriented programming, communicating between objects, similar to a function call in traditional programming. message handling (1) In communications, a system of electronic mail that handles text (memos, letters) in document form. (2) In communications, the lower level protocols that transfer data over a network, which assemble and disassemble the data into the appropriate codes for transmission. message queue Storage space in memory or on disk that holds incoming transmissions until the computer can process them. message switch Computer used to switch data from one point to another. Computers have always been ideal message switches due to their input/output and compare capabilities. It inputs the message, compares its destination with a set of stored destinations and routes it accordingly. metafile File that can define and store more than one type of information. For example, a Windows Metafile (WMF) can hold pictures in vector graphics and raster graphics formats as well as text. metalanguage Language used to describe another language. meter Basic unit of the metric system (39.37 inches). A yard is about 9/10ths of a meter (0.9144 meter). method In object-oriented programming, an algorithm that governs an object's behavior and performance. When a message is sent to an object, a method is implemented and data may or may not be returned. methodology Specific way of performing an operation that implies precise deliverables at the end of each stage. Mflops See megaflops. MFM (Modified Frequency Modulation) Magnetic disk encoding method used on most floppy disks and most hard disks under 40MB. It has twice the capacity of the earlier FM method, transfers data at 625 Kbytes per second and uses the ST506 interface. See hard disk. MGA (Monochrome Graphics Adapter) Display adapter that employs Hercules Graphics, combining graphics and text on a monochrome monitor. MGP (Monochrome Graphics Printer port) Display adapter that employs Hercules Graphics and a parallel printer port on the same expansion board. MHS (1) (Message Handling Service) E-mail software from Action Technologies, Inc., Alameda, CA, licensed by Novell for its NetWare operating systems. It provides message routing and store and forward capabilities. It also provides gateways into PROFS, All-in-1 and X.400 message systems. (2) (Message Handling System) Often refers to e-mail systems that conform to the OSI model, which is based on the X.400 protocol. MHz (MegaHertZ) One million cycles per second. Often references a computer's clock rate, the raw measure of internal speed. For example, a 12MHz 286 computer processes data internally (calculates, compares, etc.) twice as fast as a 6MHz 286. However, disk speed and caching play a major role in the computer's actual performance. MIB See SNMP. mickey Unit of mouse movement typically set at 1/200th of an inch. MICR (Magnetic Ink Character Recognition) Machine recognition of magnetically-charged characters typically found on bank checks and deposit slips. MICR readers detect the characters and convert them into digital data. micro (1) Microcomputer or personal computer. (2) One millionth. See space/time. (3) Microscopic or tiny. Micro Channel Also known as MCA (Micro Channel Architecture), it is an IBM 32-bit bus used in most PS/2s, the RS/6000 series and certain ES/9370 models. MCA boards can be designed for bus mastering and also contain built-in identification that eliminates manual settings often required with ISA boards. MCA transfers data at 20MBytes/sec and has modes for increasing speeds to 40 and 80MB. Future enhancements may take it to 64 bits and 160MB. MCA boards are not interchangeable with ISA and EISA boards. micro manager Person who manages personal computer operations within an organization and is responsible for the analysis, selection, installation, training and maintenance of personal computer hardware and software. See information center and MMA. Micro PDP-11 Microcomputer version of the PDP-11 from Digital introduced in 1975. Uses the Q-bus and serves as a stand-alone computer or is built into other equipment. micro to mainframe Interconnection of personal computers to mainframes. See 3270 emulator. microchip Same as chip. microcircuit Miniaturized, electronic circuit, such as is found on an integrated circuit. See chip. microcode Permanent memory that holds the elementary circuit operations a computer must perform for each instruction in its instruction set. It acts as a translation layer between the instruction and the electronic level of the computer and enables the computer architect to more easily add new types of machine instructions without having to design electronic circuits. See microprogramming. Microcom Protocol See MNP. microcomputer Same as personal computer. microcontroller See MCU. microelectronics Miniaturization of electronic circuits. See chip. microfiche Pronounced "micro-feesh." A 4x6" sheet of film that holds several hundred miniaturized document pages. See micrographics. microfilm Continuous film strip that holds several thousand miniaturized document pages. See micrographics. microfloppy disk Floppy disk encased in a 3.5" wide, rigid plastic shell. Developed by Sony, it has become the medium of choice as it holds more data and is easier to handle than its 5.25" counterpart. microform In micrographics, a medium that contains microminiaturized images such as microfiche and microfilm. micrographics Production, handling and use of microfilm and microfiche. Images are created by cameras or by COM units that accept computer output directly. The documents are magnified for human viewing by readers, some of which can automatically locate a page using indexing techniques. Microfiche and microfilm have always been an economical alternative for high-volume data and picture storage. However, optical disks are competing with film-based systems and may become the preferred storage medium. microimage In micrographics, any photographic image of information that is too small to be read without magnification. microinstruction Microcode instruction. It is the most elementary computer operation that can take place; for example, moving a bit from one register to another. It takes several microinstructions to carry out one machine instruction. microjacket In micrographics, two sheets of transparent plastic that are bonded together to create channels into which strips of microfilm are inserted and stored. micromainframe Personal computer with mainframe or near mainframe speed. micromechanics Microminiaturization of mechanical devices (gears, motors, rotors, etc.) using similar photomasking techniques as in chip making. micromini Personal computer with minicomputer or near minicomputer speed. micron One millionth of a meter. Approx. 1/25,000 of an inch. The tiny elements that make up a transistor on a chip are measured in microns. Measurements below the micron level are made in Angstroms, in which 10,000 Angstroms equals one micron. microprocessor CPU on a single chip. In order to function as a computer, it requires a power supply, clock and memory. First-generation microprocessors were Intel's 8080, Zilog's Z80, Motorola's 6800 and Rockwell's 6502. The first microprocessor was created by Intel. microprogram Same as microcode. microprogramming Programming microcode. micropublishing In micrographics, the issuing of new or reformatted information on microfilm for sale or distribution. microrepublishing In micrographics, the issuing of microfilm that has been previously or is simultaneously published in hardcopy for sale or distribution. microsecond One millionth of a second. See space/time. Microsoft (Microsoft Corp., Redmond, WA) Leading software company founded in 1975 by Paul Allen and Bill Gates, two college students who wrote the first BASIC interpreter for the Intel 8080 microprocessor (Allen now runs Asymetrix Corp.). MBASIC was licensed to Micro Instrumentation and Telemetry Systems to accompany its Altair 8800 kit. By the end of 1976, more than 10,000 Altairs were sold with MBASIC. Versions were licensed to Radio Shack, Apple and many other vendors. Later, a version called GW-BASIC (Gee Whiz BASIC) was developed for 16-bit personal computers. Although Microsoft became a leader in microcomputer programming languages, its outstanding success is due to supplying IBM with DOS and the compatible companies with MS-DOS. Extending into graphical interfaces with Windows is also proving highly successful, ever since Version 3.0 was introduced in 1990. Microsoft does very well in the applications market with products such as Excel, Microsoft Word and Word for Windows. However, Microsoft's position as the supplier of the major operating system to the world's largest computer base gives it considerable influence over this industry. Microsoft C C compiler from Microsoft used to create a wide variety of commercial products. Windows programming also requires the Microsoft Windows Software Development Kit. Microsoft C and Borland's Turbo C are the most widely used C languages for PC application development. Microsoft Word Full-featured word processing program for PCs and the Macintosh from Microsoft. The DOS version provides both graphics-based and text-based interfaces for working with a document. Microsoft Word for Windows (WinWord) is a separate and distinct Windows product with sophisticated capabilities. Microsoft Works Integrated software package for PCs and the Macintosh from Microsoft. It provides file management with relational-like capabilities, word processing, spreadsheet, business graphics and communications capabilities in one package. microspacing Positioning characters for printing by making very small horizontal and vertical movements. Many dot matrix printers and all laser printers have this ability. MicroStation Full-featured 2-D and 3-D CADD program from Intergraph Corp., Huntsville, AL, for PCs, Macs and Intergraph, Sun and HP workstations. MicroVAX Series of entry-level VAXs introduced in 1983 that run under VMS or ULTRIX. Some models use the Q-bus architecture. microwave Electromagnetic wave that vibrates at 1GHz and above. Microwaves are the transmission frequencies used in communications satellites as well as in line-of-sight systems on earth. middleware Software that sits between the application and the control program (operating system, network control program, DBMS). Similar in purpose to a pseudo language, it provides a single programming interface for an application, which will run in as many different computer environments as the middleware runs in. MIDI (Musical Instrument Digital Interface) Standard protocol for the interchange of musical information between musical instruments, synthesizers and computers. It defines the codes for a musical event, which includes the start of a note, its pitch, length, volume and musical attributes, such as vibrato. It also defines codes for various button, dial and pedal adjustments used on synthesizers. MIDI is commonly used to synchronize notes produced on several synthesizers. Its control messages can orchestrate a series of synthesizers, each playing a part of the musical score. A computer with a MIDI interface can be used to record a musical session, but instead of recording the analog sound waves as in a tape recorder, the computer stores the music as keystroke and control codes. The recording can be edited in an entirely different manner than with conventional recording; for example, the rhythm can be changed by editing the timing codes in the MIDI messages. In addition, the computer can easily transpose a performance from B major into D major. MIDI files also take up much less disk space than sound files that contain the actual digitized music. The objective of MIDI was to allow the keyboard of one synthesizer to play notes generated by another. However, since Version 1.0 in 1983, MIDI has brought electronic control of music to virtually everybody, benefiting musicians and teachers alike. midicomputer Computer with performance and capacity between a minicomputer and a mainframe. midrange computer Same as minicomputer, but excludes single-user minicomputer workstations. mill Very old term for processor (number crunching!). millimeter One thousandth of a meter, or 1/25th of an inch. million One thousand times one thousand. See mega and microsecond. millisecond One thousandth of a second. See space/time. MIMD (Multiple Instruction stream Multiple Data stream) Computer architecture that uses multiple processors, each processing its own set of instructions simultaneously and independently of the others. Contrast with SIMD. mini See minicomputer. mini-supercomputer Computer that is 25% to 100% as fast as a supercomputer, but costs less. Note: A mini- supercomputer is not the same as a supermini. minicomputer Medium-scale computer that functions as a single workstation, or as a multiuser system with up to several hundred terminals. A minicomputer system costs roughly from $20,000 to $250,000. In 1959, Digital launched the minicomputer industry with its PDP-1. Soon after, Data General and HP introduced minis, and eventually Wang, Tandem, Datapoint and Prime joined them. IBM has introduced several minicomputer series (see IBM minicomputers). Today, the term "midrange" is becoming popular for medium-sized computer. High-end microcomputers and low-end mainframes overlap in minicomputer price and performance. minifloppy Floppy disk encased in a 5.25" wide, stiff plastic jacket. Introduced by Shugart in 1978, it superseded IBM's 8" floppy and has been used extensively ever since. minimize In graphical environments, to reduce a window to an icon. MINIX Version of UNIX for the PC, Mac, Amiga and Atari ST developed by Andrew Tannenbaum and published by Prentice-Hall. It comes with complete source code. minor key Secondary key used to identify a record. For example, if transactions are sorted by account number and date, account number is the major key and date is the minor key. MIPS (1) (Million Instructions Per Second) Execution speed of a computer. For example, .5 MIPS is 500,000 instructions per second. High-speed personal computer and workstation CPUs perform in the 20-50 MIPS range. Digital's Alpha chip has a peak rate of 400 MIPS. Inexpensive microprocessors used in toys and games may be in the .05-.1 MIPS range. MIPS rates are not uniform. Some are best-case mixes while others are averages. In addition, it takes more instructions in one machine to do the same thing as another (RISC vs CISC, mainframe vs micro). As a result, MIPS has been called "MisInformation to Promote Sales." MIPS rate is just one factor in overall performance. Bus and channel speed and bandwidth, memory speed, memory management techniques and system software also determine total throughput. (2) (MIPS Computer Systems, Inc., Sunnyvale, CA.) Micro and minicomputer manufacturer. See ACE. Mirror II PC communications program from Softklone Distributing Corp., Tallahassee, FL, that supports a variety of terminals and protocols and provides a learn mode for recording common sequences. mirroring See disk mirroring. Mirrors Software from Micrografx, Inc., Richardson, TX, that allows Windows programs to be converted to OS/2 with minimal modification. MIS (1) (Management Information System) Information system that integrates data from all the departments it serves and provides operations and management with the information they require. It was "the" buzzword of the mid to late 1970s, when online systems were implemented in all large organizations. See DSS. (2) (Management Information Services) See Information Systems. mission critical Vital to the operation of an organization. mixed object Same as compound document. ML Symbolic programming language developed in the 1970s at Univ. of Edinburgh, Scotland. Similar to LISP, its commands and structures are like Pascal. MM See Multiple Master. MMA (Microcomputer Manager's Assn., Inc.) Membership organization with chapters throughout the U.S. devoted to educating personnel responsible for personal computers. Provides seminars, conferences, trade show events, job bank and newsletters. Address: P.O.Box 4615, Warren, NJ, 908/580-9091. MME See Multimedia Extensions. MMF (Multiple Mode Fiber) Class of optical fiber used in FDDI that transmits through multiple paths at 200MBits/sec up to 10 miles. See SMF. MMI (Man Machine Interface) Same as user interface. MMU (Memory Management Unit) Virtual memory circuit that translates logical addresses into physical addresses. mnemonic Pronounced "nuh-monic." Means memory aid. A name assigned to a machine function. For example, in DOS, COM1 is the mnemonic assigned to serial port #1. Programming languages are almost entirely mnemonics. MNP (Microcom Networking Protocol) Family of communications protocols from Microcom, Inc., Norwood, MA, that have become de facto standards for error correction (classes 2 though 4) and data compression (class 5). Class Features 1 Half-duplex asynchronous transmission. (Early mode, no longer used.) 2 Full-duplex asynchronous transmission. 3 Full-duplex synchronous transmission using HDLC framing techniques using 64-byte blocks. Start/stop bits stripped. 4 Increased throughput. Shorter headers, frames up to 256 bytes. Some vendors adjust frame size based on line quality. 5 Compresses data up to two times. 6 Starts at V.22bis modulation and switches to V.29 if possible. Uses pseudo- duplexing ping-pong method for faster turnaround of V.29 transmission. 7 Compresses data up to three times. 8 Not in use. 9 Adds Piggy-back Acknowledgement** and selective retransmission for more efficient transport of data. Provides better performance over variety of links. 10 Adds Adverse Channel Enhancements** for efficient operation on noisy lines (rural, cellular, international, etc.). ** Proprietary Microcom techniques. MO See magneto-optic. MO:DCA (Mixed Object:Document Content Architecure) IBM compound document format for text and graphics elements in a document. It supports Revisable Documents, which are editable like revisable-form DCA, Presentation Documents, which provide specific output formatting similar to DCA final-form, and Resource Documents, which hold control information such as fonts. Formats for specific objects are specified in OCAs (Object Content Architectures): PTOCA for Presentation and Text that has been formatted for output, GOCA for vector Graphics objects, IOCA for bitmapped Images and FOCA for Fonts. Mobiltex Packet radio service from RAM Mobile Data (joint venture of RAM Broadcasting and BellSouth). By the end of 1993, over 800 8Kbps base stations will serve over 100 areas in the U.S. mod See modulo. modal Mode oriented. A modal operation switches from one mode to another. Contrast with non-modal. modal dispersion Signal distortion in an optical fiber in which the light pulses spread out, and the receiving device cannot detect the beginnings and ends of pulses. mode Operational state that a system has been switched to. It implies at least two possible conditions. There are countless modes for hardware and software. See Real Mode, Protected Mode, burst mode, insert mode, supervisor state and program state. model (1) Style or type of hardware device. (2) Mathematical representation of a device or process used for analysis and planning. See data model, data administration, financial planning system and scientific applications. model-based expert system Expert system based on fundamental knowledge of the design and function of an object. Such systems are used to diagnose equipment problems, for example. Contrast with rule-based expert system. modeling Simulating a condition or activity by performing a set of equations on a set of data. See data modeling, data administration, financial planning system and scientific applications. modem (MOdulator-DEModulator) Device that adapts a terminal or computer to a telephone line. It converts the computer's digital pulses into audio frequencies and converts them back into pulses at the receiving side. For hookup, an internal modem needs a free expansion slot, while an external modem requires a free serial port. A communications program provides the user interface and the software protocols (Xmodem, Kermit, etc.). The modem handles the dialing and answering of the call and controls transmission speed, which ranges from 300 to 14,400 bps and higher. The common dial-up modem speed is 2,400 bps with 9,600 becoming popular. See the V dot standards (V.32, V.42). Private lines allow for faster transmission speeds. Very-high-speed modems are used to connect to broadband LANs, which use frequencies like the telephone. At 2,400 bps, it takes about seven seconds to fill up a text-based screen of 2,000 characters, but most interactive sessions display less than a full screen. The character rate is 10% of the bit rate; thus, 2,400 bps is equivalent to 240 cps. Features to look for in a modem are high speed (V.32, V.32bis), error checking (V.42, MNP 2-4) and data compression (V.42bis, MNP 5). New modems have automatic feature negotiation, which adjusts to the other modem's speed and hardware protocols. The term is also used as a verb; for example, "I'll modem you later." modem eliminator Device that allows two close computers to be connected without modems. For personal computers, it is the same as a null modem cable. In synchronous systems, it provides active intelligence for synchronization. modify structure Database command that changes a file's structure. Field lengths and field names can be changed, and fields can be added or deleted. It may convert the old data file into the new structure without data loss, unless fields have been truncated or deleted. Modula-2 (MODUlar LAnguage-2) Enhanced version of Pascal introduced in 1979 by Swiss professor Nicklaus Wirth, creator of Pascal. It supports separate compilation of modules. The following example changes Fahrenheit to Celsius:   MODULE FahrToCent;  FROM InOut IMPORT ReadReal,WriteReal,  WriteString,WriteLn;  VAR Fahr:REAL;  BEGIN  WriteString("Enter Fahrenheit ");  ReadReal(Fahr);  WriteLn;  WriteString("Celsius is ");  WriteReal((Fahr - 32) * 5 / 9);  END FahrToCent  modular programming Breaking down the design of a program into individual components (modules) that can be programmed and tested independently. It is a requirement for effective development and maintenance of large programs and projects. Modular Windows Subset of Windows for TV-based consumer electronics. It does not use Program Manager, scroll bars and overlapping windows. The application is the window. modulate To vary a carrier wave. Modulation blends a data signal (text, voice, etc.) into a carrier for transmission over a network. Major methods are AM (amplitude modulation) - modulate the height of the carrier wave, FM (frequency modulation) - modulate the frequency of the wave, and PM (phase modulation) - modulate the polarity of the wave. Contrast with demodulate. See carrier. module Self-contained hardware or software component that interacts with a larger system. Hardware modules are often made to plug into a main system. Program modules are designed to handle a specific task within a larger program. modulo Mathematical operation (modulus arithmetic) in which the result is the remainder of the division. For example, 20 MOD 3 results in 2 (20/3 = 6 with a remainder of 2. moire Pronounced "mor-ray." Objectionable pattern that sometimes results from scanning halftones or scaling halftones that have already been scanned. molecular beam epitaxy Technique that "grows" atomic-sized layers on a chip rather than creating layers by diffusion. monadic One. Single item or operation that deals with one item or operand. monitor (1) Display screen used to present output from a computer, camera, VCR or other video generator. A monitor's clarity is based on video bandwidth, dot pitch, refresh rate and convergence. See analog monitor, digital monitor and interlaced. (2) Software that provides utility and control functions such as setting communications parameters. It typically resides in a ROM chip and contains startup and diagnostic routines. (3) Software that monitors the progress of activities within a computer system. (4) Device that gathers performance statistics of a running system via direct attachment to the CPU's circuit boards. monochrome Also called "mono." Display of one foreground color and one background color; for example, black on white, white on black and green on black. Non-color laptop PCs commonly use "monochrome VGA" screens, which are actually gray-scale screens. This is like black and white TV and is not the same as the monochrome screens widely used over the years on mini and mainframe terminals and PCs using the MDA adapter, which display a solid color and no shades in between. monolithic integrated circuit Common form of chip design, in which the base material (substrate) contains the pathways as well as the active elements that take part in its operation. monophonic Sound reproduction using a single channel. Contrast with stereophonic. monospacing Uniform horizontal spacing, such as 10 characters per inch. Contrast with proportional spacing. Monte Carlo method Technique that provides approximate solutions to problems expressed mathematically. Using random numbers and trial and error, it repeatedly calculates the equations to arrive at a solution. MORE II Macintosh desktop presentation program and outline processor from Symantec Corp., Cupertino, CA, that includes writing, spell checking, presentation- quality text and graphics and 35mm slide output. morphing Transforming one image into another; for example, a car into a tiger. From metamorphosis. See tweening. morray See moire. Morse code Data code represented by dots and dashes, developed by Samuel Morse in the mid-19th century. A dot can be a voltage, carrier wave or light beam of one duration, while a dash is a longer duration. It was used to send telegraph messages before the telephone and was used in World War II for signalling by light. MOS (Metal Oxide Semiconductor) Pronounced "moss." One of two major categories of chip design (the other is bipolar). It derives its name from its use of metal, oxide and semiconductor layers. There are several varieties of MOS technologies, including PMOS, NMOS and CMOS. MOSFET (Metal Oxide Semiconductor Field Effect Transistor) Common type of transistor fabricated as a discrete component or into MOS integrated circuits. most significant digit Leftmost, non-zero digit in a number. It is the digit with the greatest value in the number. motherboard Main printed circuit board in an electronic device, which contains sockets that accept additional boards. In a personal computer, the motherboard contains the bus, CPU and coprocessor sockets, memory sockets, keyboard controller and supporting chips. Chips that control the video display, serial and parallel ports, mouse and disk drives may or may not be present on the motherboard. If not, they are independent controllers that are plugged into an expansion slot on the motherboard. Motif Graphical user interface endorsed by the Open Software Foundation. It is widely used in the UNIX world. See OSF. motion path In computer graphics, the path to be followed by an animated object. Motorola (Motorola, Inc., Schaumburg, IL) Leading manufacturer of semiconductor devices founded in Chicago in 1928 by Paul V. Galvin as the Galvin Manufacturing Corp. Its first product allowed radios to operate from household current instead of batteries. In the 1930s, the company commercialized car radios under the Motorola brand suggesting "sound in motion," and in 1947, changed the company name. By the 1960s, it was a leader in communications and consumer electronics and had built its first semiconductor facility. It eventually moved from the consumer side, selling its color TV business in the mid-1970s. Although Motorola is known in computers for its 68000 microprocessor family, it is also involved in radio and data communications systems and automotive and industrial products, among others. mouse Puck-like object used as a pointing and drawing device. As it is rolled across the desktop, the screen cursor (pointer) moves correspondingly. It is similar to the tablet cursor on a digitizer tablet; however, the tablet cursor makes contact with the tablet with absolute reference. Placing it on the upper left part of the tablet moves the screen cursor to that same location on screen. With a mouse, movement is relative; the screen cursor moves from its existing location. The mouse could be moved across your arm, and the screen cursor would move as well. See mechanical mouse, optical mouse, serial mouse, bus mouse and mickey. mouse pad Fabric-covered rubber pad roughly 9" square that provides a smooth surface for rolling a mouse. mouse port Socket in the computer into which a mouse is plugged. MOV (1) (Metal Oxide Varister) Electronic component that diverts excessive voltage to ground. (2) Assembly language instruction that moves (copies) data from one location to another. move (1) In programming, to copy data from one place in memory to another. At the end of the move, source and destination data are identical. (2) In word processing and graphics, to relocate text and images to another part of the document or drawing. MPC (Multimedia PC) Microsoft minimum requirements for a multimedia PC: 10Mhz 286 CPU, VGA display 2MB RAM, 30MB hard disk Two-button mouse CD ROM with CD ROM extensions 2.2 Audio board with 8-bit Linear PCM sampling, music synthesizer and analog mixing capabilities Serial, parallel, MIDI and joystick ports DOS 3.1, Windows 3.0 with multimedia extensions MPE (MultiProgramming Executive) Multitasking operating system that runs on the HP 3000 series. MPEG (Moving Pictures Experts Group) ISO/CCITT standard for compressing full-motion video. See JPEG. MPR II Swedish government standard for maximum video terminal radiation. The earlier MPR I is less stringent. See TCO. MPU (MicroProcessor Unit) Same as microprocessor. MRCI (Microsoft Realtime Compression Interface) Programming interface for Microsoft's DoubleSpace technology used in DOS 6. ms (1) (MilliSecond) See space/time. (2) (MS) See Microsoft. MS-DOS (MicroSoft-Disk Operating System) Single user operating system for PCs from Microsoft. It is almost identical to IBM's DOS version, and both versions are called DOS generically. See PC (Operating Environment). MS-Net (MicroSoft Network) Microsoft's version of PC- Network introduced in 1985. MS-Windows (MicroSoft Windows) See Windows. MSI (Medium Scale Integration) Between 100 and 3,000 transistors on a chip. See SSI, LSI, VLSI and ULSI. MSP (1) Microsoft Paint graphics file format. (2) (Multiprocessing Server Pack) Utility that enables LAN Manager to utilize a computer's multiprocessing capabilities. (3) Operating system used in Fujitsu IBM-compatible mainframes. MTBF (Mean Time Between Failure) Average time a component works without failure. It is the number of failures divided by the hours under observation. MTS (Modular TV System) Stereo channel added to the NTSC standard, which includes the SAP audio channel for special use. MTTR (Mean Time To Repair) Average time it takes to repair a failed component. MUG (Macintosh User Group) There are many Mac user groups throughout the world. One organization that disseminates press releases and product ads to over 1,300 MUGs is Pawtuckaway Graphics, 53 Lakeview Dr., Raymond, NH 03077, 603/895-6227. multi mode fiber Optical fiber with a core diameter of from 50 to 100 microns. It is most commonly used, but light rays tend to bounce around within the core causing some distortion of the signal. Contrast with single mode fiber. MULTIBUS Advanced bus architecture from Intel used in industrial, military and aerospace applications. It includes message passing, auto configuration and software interrupts. MULTIBUS I is 16-bits; MULTIBUS II is 32-bits. multicomputer See parallel computing. MULTICS (MULTiplexed Information and Computing Service) Bull HN operating system. Developed at MIT and Bell Labs in the mid 1960s, it was the first timesharing operating system. It was used on GE's mainframes, which were later absorbed into the Honeywell product line. multidrop line See multipoint line. MultiFinder See Finder. multifrequency monitor Monitor that adjusts to all frequencies within a range (multiscan) or to a set of specific frequencies, such as VGA and Super VGA. multiline Cable, channel or bus that contains two or more transmission paths (wires or optical fibers). multimastering See bus mastering. MultiMate PC word processing program from Ashton-Tate that was originally noted for its similarity to the Wang word processors of the 1970s. Version 4.0 (1989) introduced a number of advanced features. multimedia Disseminating information in more than one form. Includes the use of text, audio, graphics, animated graphics and full-motion video. See MPC. Multimedia Extensions Windows routines that support audio recording and playback, animation playback, joysticks, MIDI, the MCI interface for CD ROM, videodiscs, videotapes, etc., and the RIFF file format. See MPC. MultiPlan Early spreadsheet for CP/M machines and PCs from Microsoft. It was one of the first spreadsheets. Multiple Master Font technology from Adobe Systems, Mountain View, CA, that allows a typeface to be generated in different styles, from condensed to expanded and from light to heavy. multiplexing Transmitting multiple signals over a single communications line or computer channel. The two common multiplexing techniques are FDM, which separates signals by modulating the data onto different carrier frequencies, and TDM, which separates signals by interleaving bits one after the other. multiplexor In communications, a device that merges several low-speed transmissions into one high-speed transmission and vice versa. multiplexor channel Computer channel that transfers data between the CPU and several low-speed peripherals (terminals, printers, etc.) simultaneously. It may have an optional burst mode that allows a high-speed transfer to only one peripheral at a time. multiplier-accumulator General-purpose floating point processor that multiplies and accumulates the results of the multiplication. Newer versions also perform division and square roots. multipoint line In communications, a single line that interconnects three or more devices. multiported memory Memory that provides more than one access path to its contents. It allows the same bank of memory to be read and written simultaneously. multiprocessing Simultaneous processing with two or more processors in one computer, or two or more computers processing together. When two or more computers are used, they are tied together with a high-speed channel and share the general workload between them. If one fails, the other takes over. It is also accomplished in special-purpose computers, such as array processors, which provide concurrent processing on sets of data. Although computers are built with various overlapping features, such as executing instructions while inputting and outputting data, multiprocessing refers specifically to concurrent instruction executions. See parallel processing, bus mastering and fault tolerant. multiprogramming Same as multitasking. multiscan monitor Monitor that adjusts to all frequencies within a range. See multifrequency monitor. MultiSync monitor Family of multiscan monitors from NEC Technologies, Inc. NEC popularized the multiscan monitor. multitasking Running two or more programs in one computer at the same time. It is controlled by the operating system. The number of programs that can be effectively multitasked depends on the amount of memory available, CPU speed, hard disk capacity and speed, as well as the efficiency of the operating system. Multitasking is accomplished due to the differences in I/O and processing speed. While one program is waiting for input, instructions in another program are executed. In interactive programs, the delay between keystrokes is used to execute instructions in other programs. In batch processing systems, the milliseconds of delay transferring data to and from a disk are used to execute instructions in other programs. Before the early 1980s, multiprogramming meant multitasking, and multitasking meant multithreading! multithreading Multitasking within a single program. It is used to process multiple transactions or messages concurrently. It is also required for creating synchronized audio and video applications. Multithreading functions are often written in reentrant code. multiuser Computer shared by two or more users. multiuser DOS (1) DOS-compatible operating system that runs multiple terminals from a single PC. (2) (Multiuser DOS) Multiuser DOS-compatible operating system from Novell that runs multiple terminals from a single 386 or higher PC. Supersedes Concurrent DOS. multivariate Use of multiple variables in a forecasting model. MUMPS Advanced, high-level programming language and integrated database used for business applications. It has extensive string handling making it suitable for databases with vast amounts of free text. MUMPS has unique features including the ability to store both data and program statements in its database. In addition, formulas written in a program can be stored and used by other programs. Developed in 1966 at Massachusetts General Hospital (Mass. Utility MultiProgramming System), it has been used extensively in health-care. The following example converts Fahrenheit to Celsius:  READ "Enter Fahrenheit ",FAHR  SET CENT=(FAHR-32)*5/9  WRITE "Celsius is", CENT  The M Technology Association (formerly MUMPS Users Group) is an organization that supports the MUMPS community through training, meetings and distribution of publications and software. Address: 1738 Elton Rd., Suite 205, Silver Spring, MD 20903, 301/431-4070. MUX (MUltipleXor) See multiplexor. MVGA (Monochrome VGA) Non-color VGA (gray scale). MVS (Multiple Virtual Storage) Introduced in 1974, the primary operating system used on IBM mainframes (the others are VM and DOS/VSE). MVS is a batch processing-oriented operating system that manages large amounts of memory and disk space. Online operations are provided with CICS, TSO and other system software. MVS/XA (MVS/eXtended Architecture) manages the enhancements, including 2GB of virtual memory, introduced in 1981 with IBM's 370/XA architecture. MVS/ESA (MVS/Enterprise Systems Architecture) manages the enhancements made to large scale mainframes, including 16TB of virtual memory, introduced in 1988 with IBM's ESA/370 architecture. MVS/ESA runs on all models of the System/390 ES/9000 product line introduced in 1990. MVS/ESA See MVS. MVS/XA See MVS. n-dimensional Some number of dimensions. N-key rollover Keyboard circuit design for fast typing. To test this, press four adjacent keys in sequence without removing any finger from any of the keys. If all four letters appear on screen, it has this feature. NACCB (National Assn. of Computer Consultant Businesses) Organization representing companies that provide professional help in information and engineering fields. Founded in 1987, it is concerned with legislation that affects computer consultants. Address: 1250 Connecticut Ave. N.W., Suite 700, Washington, DC 20036, 202/637-9134. NACOMEX (NAtional COMputer EXchange) See computer exchange. NAEC See NetWare. NAK (Negative AcKnowledgement) Communications code used to indicate that a message was not received, or that a terminal does not wish to transmit. Contrast with ACK. name service See naming service. Named Pipes IPC facility in LAN Manager that allows data to be exchanged from one application to another either over a network or running within the same computer. The use of the term pipes for interprocess communication was coined in UNIX. naming service Software that converts a name into a physical address on a network, providing logical to physical conversion. Names can be user names, computers, printers, services or files. The transmitting station sends a name to the server containing the naming service software, which sends back the actual address of the user or resource. It serves as a Yellow Pages for the network, which is precisely what Sun's NIS system was originally called. NAND (Not AND) Boolean logic operation that is true if any single input is false. Two-input NAND gates are often used as the sole logic element on gate array chips, because all Boolean operations can be created from NAND gates.  Inputs Output  敖陳陳陳堕陳陳  0 0 1  0 1 1  1 0 1  1 1 0  青陳陳陳祖陳陳  nanometer One billionth of a meter. nanosecond One billionth of a second. Used to measure the speed of logic and memory chips, a nanosecond can be visualized by converting it to distance. In one nanosecond, electricity travels about six inches in a wire. Even at 186,000 miles per second, electricity is never fast enough for the hardware designer who worries over a few inches of circuit path. The slightest delay is multiplied millions of times, since millions of pulses are sent through a wire in a single second. See space/time. NAPLPS (North American Presentation-Level Protocol Syntax) ANSI-standard protocol for videotex and teletext. It compresses data for transmission over narrow- bandwidth lines and requires decompression on the receiving end. narrowband In communications, a voice grade transmission of 2,400 bps or less, or a sub-voice grade transmission from 50 to 150 bps. NAS (Network Application Support) Digital's implementation of open systems, which provides standards-based software that allows a variety of workstations (VMS, ULTRIX, Sun, DOS, Windows, OS/2, Mac, etc.) to interface via VAX and ULTRIX servers. Connectivity to non-Digital server platforms is planned for 1992 and beyond. NASI (National Assn. of Systems Integrators) Organization of more than 5,000 members founded in 1991, dedicated to exchanging up-to-date information on members' products and services. Its annual Computer Suppliers & Services Directory, in print and on disk, is organized by zipcode. Address: 412 High Plain Street, Unit #1, Walpole, MA 02081, 508/668-8900. National Computer Exchange See computer exchange. native language Same as machine language. See native mode. native mode (1) Normal running mode of a computer, executing programs from its built-in instruction set. Contrast with emulation mode. (2) Highest-performance state of a computer, such as the 386 running in Protected Mode. NATURAL Fourth-generation language from Software AG, Reston, VA, that runs on a variety of computers from micro to mainframe. natural language English, Spanish, French, German, Japanese, Russian, etc. NAU (1) (Network Access Unit) Interface card that adapts a computer to a local area network. (2) (Network Addressable Unit) SNA component that can be referenced by name and address, which includes the SSCP, LU and PU. NB card (NuBus card) See NuBus. NC See numerical control. NCB (Network Control Block) Packet structure used by the NetBIOS transport protocol. NCF (National Cristina Foundation) Not-for-profit organization, founded by Bruce McMahan and named after his daughter, that channels used and surplus computers to the disadvantaged. Address: 42 Hillcrest Dr., Pelham Manor, NY 10803, 800/CRISTINA. NCGA (National Computer Graphics Assn.) Organization dedicated to developing and promoting the computer graphics industry. It maintains a clearinghouse for industry information and strives to encourage communication among computer graphics users, consultants, educators and vendors. Address: 2722 Merrilee Dr., Suite 200, Fairfax, VA 22031, 800/225-NCGA. NCP (1) (Network Control Program) IBM's SNA network control program. See SNA and network control program. (2) (NetWare Core Protocol) Internal NetWare language used to communicate between workstation and server. (3) (Not Copy Protected) Software that can be easily copied. NCR (NCR Corp., Dayton, OH) Major manufacturer of computers and financial terminals. In 1884, John Henry Patterson purchased National Manufacturing Company of Dayton, Ohio, and renamed it National Cash Register. It became the leading cash register company and, by 1911, had sold its one millionth machine. Starting in the 1930s, NCR made accounting machines that posted customer accounts and became successful in the banking and retail industries, in which it has remained ever since. In 1957, it introduced the "304" transistorized computer. It accepted data from NCR cash registers and banking terminals via paper tape. The 304 was very reliabile and widely accepted. NCR computer lines have included the Century series (1960s), Criterion series (1970s) and the V and I series (1980s). Starting in 1982 with the UNIX- and Motorola 68000-based Tower series, NCR embraced open systems and industry standards. In 1990, the x86-based System 3000 series was introduced, a complete line from laptops to massively parallel machines running DOS and OS/2 at the low end and UNIX at the high end. In 1991, NCR was acquired by AT&T and operates as a wholly-owned subsidiary. NCR paper (No Carbon Required paper) Multiple-part paper form that does not use carbon paper. The ink is adhered to the reverse side of the previous sheet. NCSC (National Computer Security Center) Arm of the U.S. National Security Agency that defines criteria for trusted computer products. Following are the Trusted Computer Systems Evaluation Criteria (TCSEC), DOD Standard 5200.28 (also known as the Orange Book) and the European equivalent. Level D is a non-secure system. Level C provides discretionary control. The owner of the data can determine who has access to it. C1 Requires user log-on, but allows group ID. C2 Requires individual user log-on with password and an audit mechanism. Levels B and A provide mandatory control. Access is based on standard DOD clearances. B1 DOD clearance levels. B2 Guarantees path between user and the security system. Provides assurances that system can be tested and clearances cannot be downgraded. B3 System is characterized by a mathematical model that must be viable. A1 System is characterized by a mathematical model that can be proven. Highest security. European Ratings The European Information Technology Security Evaluation Criteria (ITSEC) is similar to TCSEC, but rates functionality (F) and effectiveness (E) separately. Orange Book TCSEC ITSEC D E0 C1 F-C1, E1 C2 F-C2, E2 B1 F-B1, E3 B2 F-B2, E4 B3 F-B3, E5 A1 F-B3, E6 NDIS (Network Driver Interface Spec) Microsoft specification for hardware-independent drivers at the data link (media access control) layer. When transport protocols are written to NDIS, network adapters with NDIS-compliant MAC drivers can be freely interchanged. See "LANs" under data link protocol. NE (Not Equal to) See relational operator. near pointer In an x86 segmented address, a memory address within a single segment (the offset). Contrast with far pointer. NEAT chipset (New Enhanced AT chipset) Set of chips used to build an AT-class machine from Chips and Technologies, Inc. EMS capability is included. The CPU, BIOS and NEAT chipset are the primary logic chips on a 286-based PC. negative logic Use of high voltage for a 0 bit and low voltage for a 1 bit. Contrast with positive logic. nematic Stage between a crystal and a liquid that has a threadlike nature; for example, a liquid crystal. nemonic See mnemonic. neper Unit of measurement based on Napierian logarithms that represents the ratio between two values, such as current or voltage. nerd Person typically thought of as dull socially. Nerds often like technical work and are generally introspective. Contrast with hacker, a technical person that may or may not be a nerd. nesting In programming, the positioning of a loop within a loop. The number of loops that can be nested may be limited by the programming language. See loop. NetBEUI (NetBIOS Extended User Interface) Pronounced "net- booey." Implementation of the NetBIOS transport protocol within LAN Manager and LAN Server. It communicates to the network adapter via NDIS. NetBIOS Commonly used transport protocol for PC local area networks introduced with IBM's PC Network and implemented in Microsoft's MS-Net and LAN Manager. Application programs use NetBIOS for client/server or peer-to-peer communications. There are two NetBIOS modes for communicating. The Datagram is the fastest method, but does not guarantee delivery of a message. It is a self- contained packet with sender and receiver name, usually limited to 512 bytes. If the recipient device is not listening for messages, the datagram is lost. The Session mode establishes a connection until broken. It guarantees delivery of messages up to 64K bytes long. NetBIOS-compliant protocols refer to layers 3, 4 and 5 on the OSI model. NETROOM DOS memory manager from Helix Software Co., Long Island City, NY, noted for squeezing large network drivers into high DOS memory. Its DISCOVER utility reports the system's current configuration. NetView IBM SNA network management software that provides centralized monitoring and control for SNA, non-SNA and non-IBM devices. NetView/PC interconnects NetView with Token Ring LANs, Rolm CBXs and non-IBM modems, while maintaining control in the host. NetWare Family of network operating systems from Novell, Inc., Provo, UT, that runs on 286s and up and supports DOS, OS/2 and Mac workstations and a variety of LAN access methods, including Token Ring, Ethernet and ARCNET. It is the most widely- used LAN control program. See IPX, SPX, NGM and MHS. NetWare Lite is a peer-to-peer system, which allows any workstation to be a server. It provides upward migration to larger NetWare systems. A starter kit connects two PCs. NetWare Lite supersedes ELS NetWare (Entry Level System), Novell's first peer-to-peer network. NetWare 2.x (formerly Advanced NetWare 286) runs in a dedicated file server and supports up to 100 users. It is the sole control program in the server. NetWare 3.x (formerly NetWare 386) runs on 386 servers and up and takes advantage of the 32- bit architecture. Versions of 3.x are available from 10 to 4,000 nodes. NetWare 4.0, due in 1993, is backward compatible with 2.x and 3.x and includes the NDS (NetWare Directory Service) naming service that provides X.500 compatibility. SFT NetWare (System Fault Tolerant) provides automatic recovery from network malfunctions. NetWare for VMS provides NetWare connectivity to VAX networks. Portable NetWare provides NetWare source code for conversion to other platforms. NetWare Certification Novell provides certification for technical competence with self-study tests and courses given at National Authorized Education Centers (NAECs). Certificates include CNE (Certified NetWare Engineer), CNI (Certified NetWare Instructor) and ECNE (Enterprise CNE), which includes wide area network (WAN) expertise. NetWare NFS Software from Novell that implements the NFS distributed file system on NetWare 3.11 servers. It allows UNIX and other NFS client machines to access files on the NetWare server. See LAN Workplace and UnixWare. network (1) Arrangement of objects that are interconnected. See LAN and network database. (2) In communications, the transmission channels and supporting hardware and software. network adapter Printed circuit board that plugs into a workstation or server and controls the exchange of data over a network. It performs the electronic functions of the access method (data link protocol), such as Ethernet, Token Ring and LocalTalk. The transmission medium (twisted pair, coax or fiber optic cable) interconnects all adapters in the network. network administrator Person who manages a communications network and is responsible for its efficient operation. Tasks include installing new applications and monitoring network activity. network architecture (1) Design of a communications system, which includes the hardware, software, access methods and protocols used. It also defines the method of control: whether computers can act independently or are controlled by other computers monitoring the network. It determines future flexibility and connectability to foreign networks. (2) Access method in a LAN, such as Ethernet, Token Ring and LocalTalk. network card See network adapter. network control program Software that manages the traffic between terminals and the host mini or mainframe. It resides in the communications controller or front end processor. In a personal computer LAN, it is called a network operating system and resides in the server and manages requests from the workstations. IBM's SNA network control program is called NCP. network database (1) Database that runs in a network. It implies that the DBMS was designed with a client/server architecture. (2) Database that holds addresses of other users in the network. (3) Database organization method that allows for data relationships in a net-like form. A single data element can point to multiple data elements and can itself be pointed to by other data elements. Contrast with relational database. network management Monitoring an active network in order to diagnose problems and gather statistics for administration and fine tuning. network modem Modem shared by all users in a network. See ACS. network operating system Control program that resides in a file server in a LAN. It handles the requests for data from the workstations in the network. network ready Software designed to run in a network. It implies that multiple users can share the databases without conflict. network server See file server. neural network Modeling technique based on the observed behavior of biological neurons and used to mimic the performance of a system. It consists of a set of elements that start out connected in a random pattern, and, based upon operational feedback, are molded into the pattern required to generate the required results. It is used in applications such as robotics, diagnosing, forecasting, image processing and pattern recognition. newline End of line code. See CR/LF. NeWS (Network Extensible Windowing Support) Networked windowing system (similar to X Windows) from SunSoft that renders PostScript fonts on screen the way they print on a PostScript printer. Newton Family of PDAs from Apple. First model is a hand- held personal organizer that recognizes hand printing. It can add an appointment to a calendar and dial a phone or send a fax. NewWave PC operating environment from HP that runs between DOS and Windows. It integrates data and activates tasks within the system. Its object-management facility allows data from different applications to be merged to create a compound document. Hot links automatically update the document if data in one of the source files is updated. It allows for the creation of agents (automatic procedures) that can be activated based on time or events. For example, at month end, an agent could extract data from the corporate mainframe and prepare a report using several application programs. Programs must be modified to run under NewWave. NeXT Inc. (Redwood City, CA) Founded in 1985 by Steven Jobs, co-founder of Apple, NeXT created a family of high- resolution, UNIX-based workstations running its NeXTstep environment. The first machine was introduced in 1988. Manufacturing of the hardware ceased Feb. 1993, but NeXT is continuing with its NeXTstep software for the x86. NeXTstep UNIX-based, object-oriented development environment from NeXT Computer, Redwood City, CA. It runs on NeXT computers and 386s and up providing an advanced, integrated environment for creating applications with a graphical user interface. NFS (Network File System) Distributed file system from SunSoft that allows data to be shared across a network regardless of machine, operating system, network architecture or protocol. This de facto UNIX standard lets remote files appear as if they were local on a user's machine. NGM (NetWare Global Messaging) E-mail software from Novell for NetWare 3.x that includes directory synchronization across distributed servers and provides optional interfaces to X.400, SMTP and SNADS. See SMF. nibble Half a byte (four bits). nibble mode memory Type of dynamic RAM that outputs four consecutive bits (nibble) at one time. NIC (Network Interface Card) Same as network adapter. NiCad (Nickel CADmium) Rechargeable battery technology that has been widely used in portable applications, including portable computers. It provides more charge per pound than lead acid batteries, but less than nickel hydride or zinc air. Its major problem is a so-called "memory effect," in which the battery seems to remember how full it was when you last charged it, and it doesn't go past that point the next time. NiCads should be completely drained periodically to maintain the longest charge. It uses a nickel and cadmium plate and potassium hydroxide as the electrolyte. See lead acid, nickel hydride and zinc air. nickel hydride Rechargeable battery technology that provides more charge per pound than lead acid and NiCad, but less than zinc air. It does not suffer from the NiCad memory effect. It uses nickel and metal hydride plates with potassium hydroxide as the electrolyte. See lead acid, NiCad and zinc air. NIS (Network Information Services) Naming service from SunSoft that allows resources to be easily added, deleted or relocated. Formerly called Yellow Pages, NIS is a de facto UNIX standard. NIS+ is a redesigned NIS for Solaris 2.0 products. NIST (National Institute of Standards & Technology) Standards-defining agency of the U.S. government, formerly called the National Bureau of Standards. NLM (NetWare Loadable Module) Software that enhances or provides additional server functions in a server running NetWare 3.x. Support for different kinds of workstations, database engines, fax and print servers are examples. The NetWare 2.x counterpart is a VAP. NLQ (Near Letter Quality) Print quality that is almost as sharp as an electric typewriter. The slowest speed of a dot matrix printer often provides NLQ. NMI (NonMaskable Interrupt) High-priority interrupt that cannot be disabled by another interrupt. It is used to report malfunctions such as parity, bus and math coprocessor errors. NMOS (N-Channel MOS) Pronounced "N moss." Type of microelectronic circuit used for logic and memory chips. NMOS transistors are faster than their PMOS counterpart and more of them can be put on a single chip. It is also used in CMOS design. no-op (NO OPeration) Instruction that does nothing but hold the place for a future machine instruction. no wait state memory Memory fast enough to meet the demands of the CPU. Idle wait states do not have to be introduced. node (1) In communications, a network junction or connection point (terminal or computer). (2) In database management, an item of data that can be accessed by two or more routes. (3) In computer graphics, an endpoint of a graphical element. noise Extraneous signal that invades an electrical transmission. It can come from strong electrical or magnetic signals in nearby lines, from poorly fitting electrical contacts, and from power line spikes. NOMAD Relational DBMS from Must Software Int'l., Norwalk, CT, that runs on IBM mainframes, PCs and VAXs. Introduced in the mid 1970s, it was one of the first database systems to provide a non-procedural language for data manipulation. non-blocking Ability of a signal to reach its destination without interference or delay. non-breaking space See hard space. non-document mode Word processing mode used for creating source language programs, batch files and other text files that contain only text and no proprietary headers and format codes. All text editors, as well as XyWrite III Plus, automatically output this format. non-impact printer Printer that prints without banging a ribbon onto paper, such as a thermal or ink jet printer. See printer. non-interlaced Illuminating a CRT by displaying lines sequentially from top to bottom. Non-interlaced monitors eliminate annoying flicker found in interlaced monitors, which illuminate half the lines in the screen in the first cycle and the remaining half in the second cycle. Contrast with and see interlaced for a diagram. non-modal Not mode oriented. A non-modal operation moves from one situation to another without apparent mode switching. non-numeric programming Programming that deals with objects, such as words, board game pieces and people, rather than numbers. Same as list processing. non-preemptive multitasking Environment in which an application is able to give up control of the CPU to another application only at specific points in its running; for example, when it's ready to accept user input. One program can dominate a machine with this method. Contrast with preemptive multitasking. non-procedural language Computer language that does not require traditional programming logic to be stated. For example, a command, such as LIST, might display all the records in a file on screen, separating fields with a blank space. In a procedural language, such as COBOL, all the logic for inputting each record, testing for end of file and formatting the screen has to be explicitly programmed. Query languages, report writers, interactive database programs, spreadsheets and application generators provide non-procedural languages for user operation. Contrast with and see procedural language for an example. non-return-to-zero See NRZ. non trivial Favorite word among programmers for a difficult task. non-volatile memory Memory that holds its content without power. Firmware chips (ROMs, PROMs, EPROMs, etc.) are examples. Disks and tapes may be called non- volatile memory, but they are usually considered storage devices. nonlinear System in which the output is not a uniform relationship to the input. nonpreemptive multitasking See non-preemptive multitasking. NonStop Family of fault tolerant computer systems from Tandem. NOR (Not OR) Boolean logical operation that is true if all inputs are false, and false if any input is true. An exclusive NOR is true if both inputs are the same.  NOR EXCLUSIVE NOR  Inputs Output Inputs Output  敖陳陳陳堕陳陳 敖陳陳陳堕陳陳  0 0 1 0 0 1  0 1 0 0 1 0  1 0 0 1 0 0  1 1 0 1 1 1  青陳陳陳祖陳陳 青陳陳陳祖陳陳  normal wear Deterioration due to natural forces that act upon a product under average, everyday use. normalization In relational database management, a process which breaks down data into record groups for efficient processing. There are six stages. By the third stage (third normal form), data is identified only by the key field in the record. For example, ordering information is identified by order number, customer information, by customer number. Norton SI (Norton System Information) Norton utility that measures computer performance. It provides a computing index (CI) for CPU speed, a disk index (DI) for disk speed and a performance index (PI) that blends CI and DI. The IBM XT is used as a reference of 1.0. Norton Utilities Disk management utility programs for the PC and Macintosh from Symantec Corp., Cupertino, CA. Includes programs to search and edit files, undelete files and restore damaged files among others. Originally from Peter Norton Computing, these programs were among the first to popularize disk utilities for the PC. NOS (Network Operating System) Software that controls the transmission in a network. NOS/VE (Network Operating System/Virtual Environment) Multitasking, virtual memory operating system from Control Data that runs on its medium to large-scale mainframes. NOT Boolean logic operation that reverses the input. If a 0 is input, a 1 is output, and vice versa. See AND, OR & NOT. Nota Bene See XyWrite III Plus. notation How a system of numbers, phrases, words or quantities is written or expressed. Positional notation is the location and value of digits in a numbering system, such as the decimal or binary system. notebook computer Portable computer that typically weighs less than six pounds (heavier than a pocket computer; lighter than a laptop). Nova Minicomputer series from Data General. When introduced in 1969, it was the first 16-bit mini to use four CPU accumulators, quite advanced for its time. Novas and its RDOS operating system were used extensively in the OEM marketplace. NovaNET Satellite-based network for educational services created by the Education Research Lab of the Univ. of Illinois. It includes over 10,000 hours of lesson material from third grade to post graduate work in over a hundred subject areas. Novell network LAN controlled by one of Novell's NetWare operating systems. See NetWare. nroff (Nontypesetting RunOFF) UNIX utility that formats documents for terminals and dot matrix printers. Using a text editor, troff codes are embedded into the text and the nroff command converts the document into the required output. Complex troff codes are ignored. See troff. NRZ (Non-Return-To-Zero) Signalling method used in magnetic recording and communications that does not automatically return to a neutral state after each bit is transmitted. ns (NanoSecond) See nanosecond. NSTL (National Software Testing Lab, Philadelphia) Independent organization that evaluates computer hardware and software. It adheres to controlled testing methods to ensure objective results and publishes its findings in Software Digest Ratings Report and PC Digest. NT See Windows NT. NTSC (National TV Standards Committee) U.S. TV standard administered by the FCC that is currently 525 lines transmitted at 60 half frames/sec (interlaced). It is a composite of red, green and blue signals for color and includes an FM frequency for audio and an MTS signal for stereo. NTSC reconvenes to change TV standards. NuBus Bus architecture (32-bits) originally developed at MIT and defined as a Eurocard (9U). Apple has changed its electrical and physical specs for its Macintosh series. Many Macs have one or more NuBus slots for peripheral expansion. NUI (1) (Notebook User Interface) Term coined by Go Corp. for its PenPoint pen-based interface. (2) (NetWare Users International) NetWare operating systems user group. (3) (Network User Identifier) Code used to gain access into local European packed-switched networks. NUL See null. null First character in ASCII and EBCDIC. In hex, it prints as 00; in decimal, it prints as a blank. It is naturally found in binary numbers when a byte contains no 1 bits. It is also used to pad fields and act as a delimiter; for example, in C, it specifies the end of a character string. null modem cable RS-232 cable used to connect two personal computers in close proximity. It connects to both serial ports and crosses the sending wire on one end to the receiving wire on the other. null pointer In programming, a reference to zero. May be the response of an unsuccessful search function. null string In programming, a character string that contains no data. Num Lock (NUMeric Lock) Key used to switch a combination number/cursor keypad into number key mode. Number 9 board Family of high-resolution display boards for PCs from Number Nine Computer Corp., Lexington, MA, noted for its features (virtual screen, built-in zoom) and speed. Products begin with #9, such as #9GXi and #9GXe. number crunching Refers to computers running mathematical, scientific or CAD applications, which perform large amounts of calculations. numbers In a computer, numbers can be stored in several forms. Although they are all coded as binary digits (bits), BCD and packed decimal numbers retain the decimal relationship of a number, whereas fixed and floating point do not. Binary Coded Decimal (BCD) BCD encodes each decimal digit in a single byte. The number 6508 would take four bytes. A variation, called packed decimal, encodes two digits in one byte. 6508 would take two bytes. Decimal Packed Decimal 敖賃陳堕賃陳 敖賃陳 6 5 0 8 6508 青珍陳祖珍陳 青珍陳 敖賃陳堕賃陳 敖賃陳堕賃陳堕朕 6508 650800 青珍陳祖珍陳 青珍陳祖珍陳祖潰 Fixed Point Floating Point Binary Fixed Point This method converts the entire decimal number into a binary number, placing it in a fixed unit of storage. The number 6508 would require at least two bytes. Binary numbers are calculated faster than decimal (BCD) numbers. Bytes Bits Values 1 8 0 to 255 2 16 0 to 65,535 4 32 0 to 4,294,967,295 Binary Floating Point Floating point allows very small fractions and very large numbers to be maintained and calculated quickly. Both the mantissa (significant digits) and the exponent (power to which the base is raised) are converted into binary numbers. See floating point. numeric data Refers to quantities and money amounts used in calculations. Contrast with string or character data. numeric field Data field that holds only numbers to be calculated. Contrast with character field. numeric keypad Four-row keyboard.  Calculator Telephone  789 123 456 456 123 789 0 0 numerical control Category of automated machine tools, such as drills and lathes, that operate from instructions in a program. Numerical control (NC) machines are used in manufacturing tasks, such as milling, turning, punching and drilling. First-generation machines were hardwired to perform specific tasks or programmed in a very low- level machine language. Today, they are controlled by their own microcomputers and programmed in high- level languages, such as APT and COMPACT II, which automatically generate the tool path (physical motions required to perform the operation). The term was coined in the 1950s when the instructions to the tool were numeric codes. Just like the computer industry, symbolic languages were soon developed, but the original term remained. NZ (Non Zero) Value greater or less than 0. OA See office automation. OADG (Open Architecture Development Group) Organization founded by IBM Japan in 1991 to promote PC standards in Japan. See DOS/V. OAI (Open Application Interface) Computer to telephone interface that lets a computer control and customize PBX and ACD operations. object (1) In object-oriented programming, a self- contained module of data and its associated processing. (2) In a compound document, an independent block of data, text or graphics that was created by a separate application. object code Same as machine language. object computer Same as target computer. object language (1) Language defined by a metalanguage. (2) Same as target language. (3) Object-oriented programming language. object module Output of an assembler or compiler, which must be linked with other modules before it can be executed. object-oriented analysis Examination of a problem by modeling it as a group of interacting objects. An object is defined by its class, data elements and behavior. For example; in an order processing system, an invoice is a class, and printing, viewing and totalling are examples of its behavior. Objects (individual invoices) inherit this behavior and combine it with their own data elements. object-oriented database Database that holds abstract data types (objects). It can store objects directly from an object- oriented programming language. Because any type of data can be stored (the rules for processing the data are part of an object), the object database promises fully integrated databases that will hold data, text, pictures and voice; essentially an endless variety of ever-changing formats. object-oriented DBMS DBMS that manages an object-oriented database. It is capable of handling complex queries about objects that would be difficult in relational database programs. object-oriented design Transforming an object-oriented model into the specifications required to create the system. Moving from object-oriented analysis to object- oriented design is accomplished by expanding the model into more and more detail. object-oriented graphics Same as vector graphics. object-oriented interface Graphical interface that uses icons and a mouse, such as the Macintosh, Windows and GEM environments. object-oriented programming Abbreviated "OOP," a programming technology that is more flexible than standard programming. It is an evolutionary form of modular programming with more formal rules that allow pieces of software to be reused and interchanged between programs. Major concepts are (1) encapsulation, (2) inheritance, and (3) polymorphism. Encapsulation is the creation of self-sufficient modules that contain the data and the processing (data structure and functions that manipulate that data). These user-defined, or abstract, data types are called classes. One instance of a class is called an object. Classes are created in hierarchies, and inheritance allows the knowledge in one class to be passed down the hierarchy. New objects can be created by inheriting characteristics from existing classes. For example, the object MACINTOSH could be one instance of the class PERSONAL COMPUTER, which could inherit properties from the class COMPUTER SYSTEMS. Adding a new computer requires entering only what makes it different from other computers, while the general characteristics of personal computers can be inherited. Object-oriented programming allows procedures about objects to be created whose exact type is not known until runtime. For example, a screen cursor may change its shape from an arrow to a line depending on the program mode. The routine to move the cursor on screen in response to mouse movement would be written for "cursor," and polymorphism would allow that cursor to be whatever shape is required at runtime. It would also allow a new shape to be easily integrated into the program. Xerox's Smalltalk was the first OOP language and was used to create the graphical user interface whose derivations are so popular today. C++ is becoming the mainstay OOP language, because it combines traditional C programming with object- oriented features. Following is a terminology comparison:  Object-oriented Traditional  programming programming  class data type + characteristics instance variable instantiate declare a variable method processing code message call object data type + processing object-oriented technology Variety of disciplines that support object-oriented programming, including object-oriented analysis and object-oriented design. object program Machine language program ready to run in a particular operating environment. It has been assembled, or compiled, and link edited. Objective-C Object-oriented C programming language from The Stepstone Corp. that runs on PCs and popular workstations. It was the first commercial object- oriented extension of the C language. ObjectVision Application development system from Borland for creating Windows and OS/2 2.0 applications. Uses visual techniques for user interface design as well as for programming logic. It also provides links to spreadsheets and databases. ObjectWindows Class library of Windows objects from Borland that helps developers create Windows applications. It is an open standard available from Borland and the Object Management Group. occam Parallel processing language designed to handle concurrent operations. The INMOS Transputer executes occam almost directly. In the following statements, two items of data are read and incremented at the same time. PAR specifies that following statements are to be executed concurrently, and SEQ indicates that the following statements are executed sequentially.  PAR  SEQ  chan1 ? item1  item1 := item1 + 1  SEQ  chan2 ? item2  item2 := item2 + 1  OCE (Open Collaboration Environment) Extension to System 7 from Apple that provides e-mail and document sharing across multiple platforms in an enterprise. OCR (Optical Character Recognition) Machine recognition of printed characters. OCR systems can recognize many different OCR fonts, as well as typewriter and computer-printed characters. Advanced OCR systems can recognize hand printing. octal Numbering system that uses eight digits. It is used as a shorthand method for representing binary numbers that use six-bit characters. Each three bits (half a character) is converted into a single octal digit. Okta is Greek for 8.  Decimal Binary Octal 0 000 0 1 001 1 2 010 2 3 011 3 4 100 4 5 101 5 6 110 6 7 111 7 ODBC (Open DataBase Connectivity) Microsoft programming interface for accessing databases on a network. It supports SQL and is part of WOSA. odd parity See parity checking. ODI (Open Data link Interface) Novell driver specification that allows multiple transport protocols to be run on one network adapter. For example, a PC can connect to a NetWare network running SPX/IPX and a UNIX network running TCP/IP. ODT See SCO Open Desktop. Oe See Oersted. OEM (Original Equipment Manufacturer) Manufacturer that sells equipment to a reseller. Also refers to the reseller itself. OEM customers either add value to the product before reselling it, private label it, or bundle it with their own products. See VAR. Oersted Pronounced "ers-ted," the measurement of magnetic resistance. The higher the "Oe," the more current required to magnetize it. off-hook State of a telephone line that allows dialing and transmission but prohibits incoming calls from being answered. The term stems from the days when a telephone handset was lifted off of a hook. Contrast with on-hook. off-the-shelf Refers to products that are packaged and available for sale. office automation Integration of office information functions, including word processing, data processing, graphics, desktop publishing and e-mail. The backbone of office automation is a LAN, which allows users to transmit data, mail and even voice across the network. All office functions, including dictation, typing, filing, copying, fax, Telex, microfilm and records management, telephone and telephone switchboard operations, are candidates for integration. Office Vision Integrated office automation applications from IBM that run in all IBM computer families. It was the first major implementation of SAA and incorporates the Presentation Manager interface across OS/2 networks, AS/400s and mainframes. Introduced in 1989, it includes e-mail, scheduling, document creation and distribution as well as decision support and graphics capabilities among all users. offline Not connected to or not installed in the computer. If a terminal, printer or other device is physically connected to the computer, but is not turned on or in ready mode, it is still considered offline. Disks and tapes that have been demounted and stored in the data library are considered offline. Contrast with online. offline storage Disks and tapes that are kept in a data library. offload To remove work from one computer and do it on another. See cooperative processing. offset (1) Distance from a starting point, either the start of a file or the start of a memory address. Its value is added to a base value to derive the actual value. An offset into a file is simply the character location within that file, usually starting with 0; thus "offset 240" is actually the 241st byte of the file. See relative address. (2) In word processing, the amount of space a document is printed from the left margin. ohm Unit of measurement for electrical resistance. One ohm is the resistance in a circuit when one volt maintains a current of one amp. OLCP (OnLine Complex Processing) Processing complex queries, long transactions and simultaneous reads and writes to the same record. Contrast with OLTP, in which records are updated in a more predictable manner. OLE (Object Linking and Embedding) Windows compound document protocol. The "client" application creates the document; the "server" application creates an object within the document. When a user double clicks on an embedded object in a client app, the server app is loaded and the appropriate data file is retrieved. OLTP (OnLine Transaction Processing) See transaction processing and OLCP. OMG (Object Management Group) International organization founded in 1989 to endorse technologies as open standards for object-oriented applications. Address: 492 Old Connecticut Path, Framingham, MA 01701, 508/820-4300. OMI (Open Messaging Interface) E-mail protocol developed by Lotus, now included in VIM. omnidirectional In all directions. For example, an omnidirectional antenna can pick up signals in all directions. OmniPage Character recognition software for PCs and the Macintosh from Caere Corp., Los Gatos, CA. It was the first personal computer software that could distinguish text from graphics and convert a wide variety of fonts into text. on-hook State of a telephone line that can receive an incoming call. Contrast with off-hook. on-line See online. on the fly As needed. Implies little or no degradation in performance to accomplish the task. See realtime and realtime compression. ONA (Open Network Architecture) FCC plan that allows users and competing enhanced service providers (ESPs) equal access to unbundled, basic telephone services. The Open Network Provision (ONP) is the European counterpart. ONC (Open Network Computing) Family of networking products from SunSoft for implementing distributed computing in a multivendor environment. Includes TCP/IP and OSI protocols, NFS distributed file system, NIS naming service and TI-RPC remote procedure call library. ONC+ adds Federated Services, which is an interface for third-parties to connect network services into the Solaris environment. one-chip computer See computer on a chip. onion diagram Graphical representation of a system that is made up of concentric circles. The innermost circle is the core, and all outer layers are dependent on the core. online (1) Peripheral device (terminal, printer, etc.) that is ready to operate. A printer can be attached and turned on, yet still not online, if the ONLINE or SEL light is out. Pressing the ONLINE button will usually turn it back online. (2) An online computer system refers to a system with terminals, but does not imply how the system functions. All the following are online systems. Data collection systems accept data from terminals, but do not update master files. Interactive systems imply data entry and updating. Transaction processing systems update necessary files as transactions arrive (orders, financial quotes, etc.). Realtime systems provide an immediate response to a question. 敖Want to impress your friends?陳陳陳陳陳陳陳陳朕 Although complete overkill, it is not incorrect to say that one has an online, realtime, interactive, transaction processing system. However, don't say this to an experienced systems analyst! 青陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳 online help On-screen instruction that is immediately available. online industry Collection of service organizations that provide dial-up access to databases, shopping, news, weather, sports, e-mail, etc. See online services. online services Following are major online information service organizations, including the types of databases provided. "Wide variety" generally includes news, weather and shopping as well as information on a host of topics. Many services provide e-mail.  America Online, Inc.  Databases: wide variety, personal computer  technical  8619 Westwood Center Dr. Vienna, VA 22182 800/827-6364 703/448-8700  BIX  Databases: personal computer technical  Byte Information Exchange General Videotex Corp. 1030 Massachusetts Ave. Cambridge, MA 02138 800/695-4775 617/491-3393  CompuServe Information Service, Inc.  Databases: wide variety, personal computer  technical P.O. Box 20212 Columbus, OH 43220 800/848-8199 (Ohio) 800/848-8990 614/457-8650  DataTimes Corporation  Databases: newspapers, magazines, financial  14000 Quail Springs Pkwy., Suite 450 Oklahoma City, OK 73134 800/642-2525 405/751-6400  DELPHI  Databases: wide variety, access to DIALOG  General Videotex Corp. 1030 Massachusetts Ave. Cambridge, MA 02138 800/544-4005 617/491-3393  DIALOG Information Services, Inc.  Databases: over 400 (largest) 3460 Hillview Avenue Palo Alto, CA 94304 800/334-2564 415/858-2700  Dow Jones News/Retrieval Service  Databases: financial plus shopping  airline reservations, etc.  P.O. Box 300 Princeton, NJ 08543 800/522-3567 609/520-4000  EasyLink  Services: e-mail, Telex, EDI  Databases: access to major providers (DIALOG,  CompuServe, etc.)  AT&T EasyLink Services 400 Interpace Pkwy. Parsippany, NJ 07054 800/242-6005 201/331-4000  GEnie  Databases: wide variety  General Electric Information Services Co. 401 N. Washington St. Rockville, MD 20850 800/638-9636 301/340-4000  Mead Data Central  Databases: news (NEXIS), legal (LEXIS)  P.O. Box 933 Dayton, OH 45401 800/227-4908 513/865-6800  Maxwell Online  Databases: medical (BRS),  patent, trademark (ORBIT)  8000 Westpark Dr. McClean, VA 22102 ORBIT 800/456-7248 BRS 800/289-4277  MEDLARS  Databases: medical  National Library of Medicine 8600 Rockville Pike Bethesda, MD 20894 800/638-8480 301/496-6193  MCI Mail  Services: e-mail, Telex, fax  Databases: access to Dow Jones  1133 19th St., NW Washington, DC 20036 800/444-6245 202/833-8484  National Videotex Network  Databases: wide variety  5555 San Felipe, Suite 1200 Houston, TX 77056 800/336-9096 713/877-4444  NewsNet, Inc.  Databases: newsletters  945 Haverford Rd. Bryn Mawr, PA 19010 800/952-0122 215/527-8030  PRODIGY  Databases: wide variety, shopping 445 Hamilton Ave. White Plains, NY 10601 800/776-3449 914/993-8848  VU/TEXT Information Services, Inc.  Databases: newspapers 325 Chestnut St., Suite 1300 Philadelphia, PA 19106 800/323-2940 215/574-4400  WESTLAW  Databases: legal (plus access to  DIALOG and Dow Jones)  West Publishing Co. 610 Opperman Dr. St. Paul, MN 55123 800/WESTLAW 612/687-7000  ZiffNet  Databases: personal computer (technical,  news, shopping)  25 First St. Cambridge, MA 02141 800/666-0330 617/252-5000 OO Object oriented. OOA See object-oriented analysis. OOD See object-oriented design. OODB See object-oriented database. OODBMS See object-oriented DBMS. OOP See object-oriented programming. OOPL (OOP Language) See object-oriented programming. OOPS (Object Oriented Programming System) See object- oriented programming. op amp (Operational Amplifier) Device that amplifies analog signals. It uses two inputs; one for power and one for data. It is used in myriads of applications from communications to stereo. op code See operation code. open (1) To identify a disk or tape file for reading and writing. The open procedure "locks on" to an existing file or creates a new one. (2) With regard to a switch, open is "off." open architecture System in which the specifications are made public in order to encourage third-party vendors to develop add-on products. Much of Apple's early success was due to the Apple II's open architecture. The PC is open architecture. Open Desktop See SCO Open Desktop. Open Look X Window-based graphical user interface for UNIX developed by Sun and defined and distributed by AT&T. It conforms to POSIX, ANSI C and XPG standards. open pipe Continuous path from sender to receiver, such as found in a circuit-switching network or leased line. Transmitted data is not broken up into packets. open shop Computing environment that allows users to program and run their own programs. Contrast with closed shop. open system Vendor-independent system that is designed to interconnect with a variety of products. It implies that standards are determined from a consensus of interested parties rather than one or two vendors. Contrast with closed system. See OSI. "Open systems" often refers to UNIX-based computer systems, since UNIX runs on more different kinds of hardware than any other operating environment. See OSF and X/Open. OpenOSF UNIX-based OSF/1 from Digital that runs on its Alpha systems. OpenView Network management software from HP. It supports SNMP and CMIP protocols, and third-party products that run under OpenView support SNA and DECnet network management protocols. OpenView is an enterprise-wide network management solution. OpenVMS VMS operating system from Digital that is POSIX and XPG3-compliant and runs on VAX and Alpha systems. operand The part of a machine instruction that references data or a peripheral device. In the instruction, ADD A to B, A and B are the operands (nouns), and ADD is the operation code (verb). In the instruction READ TRACK 9, SECTOR 32, track and sector are the operands. operating system Master control program that runs the computer. It is the first program loaded when the computer is turned on, and its main part, called the kernel, resides in memory at all times. It may be developed by the vendor of the computer it's running in or by a third party. It is an important component of the computer system, because it sets the standards for the application programs that run in it. All programs must "talk to" the operating system. Also called an executive or supervisor, it performs the following functions. Job Management In small computers, it responds to commands from the user and loads the requested application program into memory for execution. In large computers, the operating system carries out its job control instructions (JCL), which describe the programs that must be run for an entire shift. Task Management In single tasking computers, the operating system has virtually no task management to do, but in multitasking computers, it is responsible for the concurrent operation of one or more programs (jobs). Advanced operating systems have the ability to prioritize programs so that one job gets done before the other. In order to provide users at terminals with the fastest response time, batch programs can be put on lowest priority and interactive programs can be given highest priority. Advanced operating systems can be fine-tuned by the computer operator so that a specific job can be speeded up or slowed down. Multitasking is accomplished by executing instructions for one function while data is coming into or going out of the computer for another. Large computers are designed to overlap these operations, and data can move simultaneously in and out of the computer through separate channels with the operating system governing these actions. In small computers, the operating system can monitor idle time when a user is interactively working with a program to execute another program in the background. Even the milliseconds between keystrokes can be used for something else. A user, pausing at the keyboard for just a couple of seconds, is light years to the computer, which can use that time to execute hundreds of thousands of instructions. Data Management A major operating system function is to keep track of data on disk; hence the term DOS, or disk operating system. The application program does not know where the data is actually stored or how to get it. That knowledge is contained in the operating system's access method, or device driver, routines. When a program is ready to accept data, it signals the operating system with a message. The operating system finds the data and delivers it to the program. Conversely, when the program is ready to output, the operating system transfers the data from the program onto the available space on disk. Device Management In theory, the operating system is supposed to manage all devices, not just disk drives. It is supposed to handle the input and output to the display screen as well as the printer. By keeping the details of the peripheral device within the operating system, a device can be replaced with a newer model, and only the routine in the operating system that deals with that device needs to be replaced. In the PC world running DOS, software developers often bypass the operating system, because DOS either doesn't support the device or adds too much performance overhead. For example, developers with graphics, word processing and desktop publishing applications have become responsible for providing drivers (routines) for all the popular displays and printers, adding an enormous burden to their development efforts. Security Multiuser operating systems maintain a list of authorized users and provide password protection to unauthorized users who may try to gain access to the system. Large operating systems also maintain activity logs and accounting of the user's time for billing purposes. They also provide backup and recovery routines to start over again in the event of a system failure. History The earliest operating systems were developed in the late 1950s to manage tape storage, but programmers mostly wrote their own I/O routines. In the mid 1960s, operating systems became essential to manage disks, complex timesharing and multitasking systems. Today, all multi-purpose computers from micro to mainframe use an operating system. Special-purpose devices (appliances, games, toys, etc.) do not. They usually employ a single program that performs all the required I/O and processing tasks. Common Operating Systems PCs use DOS, OS/2, SCO XENIX and AIX. Apple II's use ProDOS. Macintoshes use the System along with Finder and Multifinder, as well as A/UX. Digital uses VMS and ULTRIX. IBM mainframes use MVS, VM and VSE. In the past, when a vendor introduced a new operating system, users had little understanding of this behind-the-glass-enclosed-datacenter phenomenon. Today, it is squarely in their hands. Perhaps the Japanese have the right idea with their TRON operating system. It is intended to be a common interface across all applications from a microwave oven to the largest supercomputer! operation code The part of a machine instruction that tells the computer what to do, such as input, add or branch. The operation code is the verb; the operands are the nouns. operations See datacenter. operations research See management science. operator Person who operates the computer and performs such activities as commanding the operating system, mounting disks and tapes and placing paper in the printer. Operators may also write the job control language (JCL), which schedules the daily work for the computer. OPI (Open Prepress Interface) Extension to PostScript by Aldus Corp. to provide a format for color separations. optical disk Direct access disk written and read by light. CDs, CD ROMs and videodiscs are optical disks that are recorded at the time of manufacture and cannot be erased. WORM disks are recorded in the user's environment, but cannot be erased. Erasable optical disks function like magnetic disks and can be rewritten over and over. In the late 1980s, a variety of erasable optical disks were introduced that use magneto-optic, dye polymer and phase change recording technologies. Throughout the 1990s, erasable optical disks may become a viable alternative to magnetic disks. Optical disks have greater storage capacity per square inch than their magnetic counterparts, and optical technology will eventually replace magnetic media. Lasers can be moved electronically and, in time, will be built into a new breed of non- spinning storage device that will dramatically impact future computers. optical fiber Thin glass wire designed for light transmission, capable of transmitting billions of bits per second. Unlike electrical pulses, light pulses are not affected by random radiation in the environment. When the telephone companies eventually replace the copper wire from their central stations into everyone's home with optical fiber, all varieties of information services will be interactively available to the consumer. See FDDI, multi mode fiber and single mode fiber. optical isolator Device used with current loop transmission that uses an LED and photoresistor to detect current in the line. optical mouse Mouse that uses light to get its bearings. It is rolled over a small desktop pad that contains a reflective grid. The mouse emits a light and senses its reflection as it is moved. Contrast with mechanical mouse. optical reader Input device that recognizes typewritten or printed characters and bar codes and converts them into their corresponding digital codes. optical recognition See OCR. optical scanner See scanner. optimizer Hardware or software that improves performance. See disk management. optoelectronics Merging light and electronics technologies, such as in optical fiber communications systems. OR Boolean logic operation that is true if any of the inputs is true. An exclusive OR is true if only one of the inputs is true, but not both.  OR EXCLUSIVE OR  Inputs Output Inputs Output  敖陳陳陳堕陳陳 敖陳陳陳堕陳陳  0 0 0 0 0 0  0 1 1 0 1 1  1 0 1 1 0 1  1 1 1 1 1 0  青陳陳陳祖陳陳 青陳陳陳祖陳陳  ORACLE (1) Relational DBMS from Oracle Corp., Redwood Shores, CA, that runs on a wide variety of computers from micro to mainframe. It was the first DBMS to incorporate the SQL language. Database applications can be created on a PC and easily moved to other hardware platforms. (2) (Oracle) European broadcast television text- message service. Orange Book See NCSC. Order Info DOS and Windows versions are available. If you're in Windows ALL THE TIME, order the Windows version. It looks the same, but is a full Windows application with scroll bars and buttons. To order, contact Gary Smith at  OEC SYSTEMS  4646 North Shallowford Road Atlanta, GA 30338 BBS (404) 804-7889 FAX (404) 394-1006 Voice (404) 394-1000 (800) 444-2424 Checks, M/C and Visa accepted.  BE SURE TO MENTION THE NAME OF THIS BBS  TO RECEIVE YOUR 20% DISCOUNT. Regular OEC/BBS Format Price price DOS 5.25" $30 24 DOS 3.5" $30 24 Windows 5.25" $30 24 Windows 3.5" $30 24  All disks are high-density!!  GA residents, please add sales tax Shipping & handling, add: U.S. 4.00 Canada 5.00 To other countries 10.00 COD, add $7  FUTURE UPGRADES ARE ONLY $12.95   敖陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳  OTHER GLOSSARY PRODUCTS...  **SITE LICENSES**  Make everyone in your department "Computer Literate." You can also add your own information to the Glossary and distribute it via the world's easiest-to-use dictionary software.   **BUNDLES**  The Glossary is the perfect bundle or premium every PC user can enjoy. The Glossary can be customized with "Compliments of..." on screen AT ALL TIMES. The Glossary helps users learn about the computers they just purchased. It also adds value to software packages and membership promotions. Some of the organizations that use the Glossary as a bundle or premium are... Acma Computer AICPA Information Technology Membership The Boston Computer Society Circuit Specialists ComputerWorld FM Computer HardFacts JM Computers Landmark Research Int'l. Personal Computing Tools Simply Better Computers ZiffNet 青陳end of ordering information陳陳陳陳陳陳陳潰 ordinal number Number that identifies the sequence of an item, for example, record #34. Contrast with cardinal number. orientation In typography, the direction of print across a page. See portrait. orphan See widow & orphan. OS See operating system. OS/2 Single user, multitasking operating system for PCs. It is an advanced operating system that is not confined to DOS' infamous 1MB limit. Although new commands have been added, many OS/2 commands are the same as in DOS. The first versions of OS/2 (Version 1.x) were written for 286s and were developed jointly by IBM and Microsoft. The current OS/2 (Version 2.x) is written for 32-bit 386s and up and is solely the product of IBM. OS/2's graphical interface, called Presentation Manager in Versions 1.x and the Workplace Shell in Versions 2.x, is similar to Windows and the Macintosh. It is compliant with IBM's SAA and CUA specfications. OS/2 16-bit Version 1.x The first OS/2 versions (1.0, 1.1, etc.) are written for the 16-bit 286. Only one DOS application of about 500K ran in compatibility mode. Version 1.3, called OS/2 Lite, requires 2MB RAM instead of 4MB and includes Adobe Type Manager. IBM's Extended Edition version includes Communications Manager and Database Manager. OS/2 32-bit Version 2.x - IBM Introduced in April 1992, this 32-bit version for 386s and up from IBM multitasks DOS, Windows and OS/2 applications. Data can be shared between applications using the clipboard and between Windows and PM apps using the DDE protocol. Version 2.x provides each application with a 512MB virtual address space, which allows huge and complicated tasks to be easily managed. Version 2.1 supports Windows' Enhanced Mode and applications that take full advantage of Windows 3.1. It also provides support for more video standards and CD ROM drives. IBM's Extended Services option adds Communications Manager and Database Manager. Windows NT - Microsoft Originally OS/2 Version 3.0, this 32-bit version from Microsoft (to be released in 1993) was renamed Windows NT. OS/2 compatibility was dropped, then reannounced. Stay tuned! See Windows NT. OS/2 PM (OS/2 Presentation Manager) See OS/2. OS/8 Single user, multitasking operating system from Digital for its PDP-8 computers. Variants run on DECstation and DECmate systems. OS/9 UNIX-like, realtime operating system from Microware Systems Corp. for Motorola 68000 CPUs. Originally developed for the 6809 chip, a version was created for CD-I players. oscillate To swing back and forth between the minimum and maximum values. An oscillation is one cycle, typically one complete wave in an alternating frequency. oscillator Electronic circuit used to generate high-frequency pulses. See clock. oscilloscope Test instrument that displays electronic signals (waves and pulses) on a screen. It creates its own time base against which signals can be measured, and display frames can be frozen for visual inspection. OSF (Open Software Foundation) Non-profit organization dedicated to delivering an open computing environment based on standards. Formed in 1988, it solicits technologies from industry, invites member participation to set technical direction and licenses software to members. Address: 11 Cambridge Center, Cambridge, MA 02142, 617/621- 8700. Following are the major OSF standards: OSF/1 is the operating system that uses Carnegie Mellon's Mach kernel. It is a B1-secure, symmetric multiprocessing operating system that can run on multiple processors within the same machine. Compliant with POSIX, XPG3 and SVID base and kernel extensions. Motif is a graphical user interface for applications running on any system with X Window Version 11. Compliant with POSIX, ANSI C and XPG. Distributed Computing Environment (DCE) is a set of integrated programs that provides an environment for creating, using and maintaining client/server applications on a network. It includes security, directory naming, time synchronization, file sharing, RPCs and multithreading services. Distributed Management Environment (DME) is a set of integrated programs that provides coherent management of systems and networks. Architecture Neutral Distribution Format (ANDF) supports developing portable applications. The developer generates an intermediate ANDF language that can be shrink-wrapped. The ANDF language is compiled into machine language at install time in the target machine. OSI (Open System Interconnection) ISO standard for worldwide communications that defines a framework for implementing protocols in seven layers. Control is passed from one layer to the next, starting at the application layer in one station, proceeding to the bottom layer, over the channel to the next station and back up the hierarchy. Similar functionality exists in all communications networks; however, existing non-OSI systems often incorporate two or three layers of functionality into one. Most vendors have agreed to support OSI in one form or another; however OSI serves more as a model than a universal standard. Many OSI components are too loosely defined, and proprietary standards are entrenched. One exception is the OSI-compliant X.400 e-mail protocol that is widely implemented. See OSI model. OSI model User Meaningful information. 敖陳陳祖陳陳朕 The purpose for communicating. 7Application E-mail, file transfers, 青陳陳堕陳陳潰 transactions. 敖陳陳祖陳陳朕 6Presentation Transfer syntax. 青陳陳堕陳陳潰 敖陳陳祖陳陳朕 Coordinates 5 Session overall 青陳陳堕陳陳潰 communications. 敖陳陳祖陳陳朕 4 Transport End to end control. 青陳陳堕陳陳潰 敖陳陳祖陳陳朕 Routes data from sending 3 Network to receiving station. 青陳陳堕陳陳潰 敖陳陳祖陳陳朕 Node to node control. 2 Data Link (Token Ring, Ethernet, SDLC 青陳陳堕陳陳潰 X.25, Xmodem, Zmodem) 敖陳陳祖陳陳朕 Transmission type, 1 Physical encoding method, speeds, cable, plugs. 青陳陳楪陳陳潰 (RS-232, TDM, FDM) Transmission medium (twisted pair, coax, optical fiber) 敖陳陳瀋陳陳朕 1 Physical 青陳陳陳陳陳潰 Application - Layer 7 Defines the rules for gaining entrance into the communications system. Programs communicate with other programs through this layer. Presentation - Layer 6 Negotiates and manages the way data is represented and encoded. Provides a common denominator for transferring data from different systems, ASCII, EBCDIC, binary, etc. Session - Layer 5 Provides coordination of the communications in an orderly manner. For example, it marks significant parts of the transmitted data to ensure that the entire message is received properly. Transport - Layer 4 Responsible for end to end validity and integrity of the transmission. "OSI transport services" include layers 1-4, collectively responsible for getting the bits from the sending station to the receiving station. Network - Layer 3 Establishes the route between the sending and receiving stations. For example, this layer is the switching function of the dial-up telephone system. Data Link - Layer 2 Responsible for node to node validity and integrity of the transmission. See data link protocol. Physical - Layer 1 Defines functional characteristics for passing data bits onto and receiving them from the connecting medium. For example, it includes the RTS (request to send) and CTS (clear to send) signals in an RS- 232 environment, as well as the TDM (time division multiplexing) in an ISDN environment. Note: Electrical and mechanical characteristics define the interface between the OSI environment and the connecting transmission medium. OTPROM (One Time PROM) PROM chip that can be programmed only once. out of band See signaling out of band. outdent Same as hanging indent and hanging paragraph. outline font Type of font made from basic outlines of each character. The outlines are scaled into actual characters (bitmaps) before printing. See scalable font. outline processor Software that allows the user to type in thoughts and organize them into an outline form. output (1) Any computer-generated information displayed on screen, printed on paper or in machine readable form, such as disk and tape. (2) To transfer or transmit from the computer to a peripheral device or communications line. output area Reserved segment of memory used to collect data to be transferred out of the computer. Same as buffer. output bound Excessive slowness due to output functions, typically slow-speed communications lines or printers. See print buffer. output device Any peripheral that presents output from the computer, such as a screen or printer. Although disks and tapes receive output, they are called storage devices. outsourcing Contracting with outside consultants, software houses or service bureaus to perform systems analysis, programming and datacenter operations. See facilities management. OverDrive Intel's 486 upgrade CPUs. See 486. overflow error Error that occurs when calculated data cannot fit within the designated field. The result field is usually left blank or is filled with some symbol to flag the error condition. overhead (1) Amount of processing time used by system software, such as the operating system, TP monitor or database manager. (2) In communications, the additional codes transmitted for control and error checking. overlay (1) Preprinted, precut form placed over a screen, key or tablet for indentification purposes. See keyboard template. (2) Program segment called into memory when required. When a program is larger than the memory capacity of the machine, the parts of the program that are not in constant use can be set up as overlays. When called in, the contents of the previous overlay is lost. Virtual memory is a system of automatic overlays. overlay card Controller that digitizes NTSC signals from a video source for display in the computer. overloading In programming, the ability to use the same name for more than one variable or procedure, requiring the compiler to differentiate them based on context. overscan Area outside of the normal rectangular viewing area on a display screen. Contrast with underscan. overstrike (1) To type over an existing character. (2) Character with a line through it. overwrite (1) Data entry mode that writes over existing characters on screen when new characters are typed in. Contrast with insert mode. (2) To record new data on top of existing data such as when a disk record or file is updated. p-code See pseudo language and UCSD p-System. p-System See UCSD p-System. P24T See Pentium. P5 See Pentium. PA See HP Precision Architecture. PABX (Private Automatic Branch eXchange) Same as PBX. PACBASE Integrated CASE software for IBM, Bull HN and Unisys mainframes from CGI Systems, Pearl River, NY. It supports a wide variety of databases including DB2 and Oracle. PACLAN is the version for PCs running on LANs. pack (1) To compress data in order to save space. Unpack refers to decompressing data. See data compression. (2) Instruction that converts a decimal number into a packed decimal format. Unpack converts a packed decimal number into decimal. (3) In database programs, a command that removes records that have been marked for deletion. package See software package. packaged software See software package. packed decimal Storage mode that places two decimal digits into one byte, each digit occupying four bits. The sign occupies four bits in the least significant byte. packet Frame or block of data used for transmission in packet switching and other communications methods. packet cellular Transmission of data over the cellular network. Data is divided into packets, or frames, for error checking. Contrast with circuit cellular. See CDPD and wireless. packet radio Wireless transmission of data, which is divided into packets, or frames, for error checking. See Ardis, Mobiltex and wireless. packet switching Technique for handling high-volume traffic in a network by breaking apart messages into fixed length packets that are transmitted to their destination through the most expedient route. All packets in a single message may not travel the same route (dynamic routing). The destination computer reassembles the packets into their proper sequence. This method efficiently handles messages of different lengths and priorities in large networks, such as Telenet, Tymnet and AT&T's Accunet. X.25 is the international standard for such a network. Packet switching networks also provide value added services, such as protocol conversion and electronic mail. packetized voice Transmission of realtime voice in a packet switching network. packing density Number of bits or tracks per inch of recording surface. Also refers to the number of memory bits or other electronic components on a chip. pad (1) To fill a data structure with padding characters. (2) (PAD) (Packet Assembler Dissassembler) Communications device that formats outgoing data into packets of the required length for transmission in a packet switching network. It also strips the data out of incoming packets. padding Characters used to fill up unused portions of a data structure, such as a field or communications message. A field may be padded with blanks, zeros or nulls. paddle Input device that moves the screen cursor in a back-and-forth motion. It has a dial and one or more buttons and is typically used in games to hit balls and steer objects. See joy stick. page (1) In virtual memory systems, a segment of the program that is transferred into memory. (2) In videotex systems, a transmitted frame. (3) In word processing, a printed page. page break In printing, a code that marks the end of a page. A "hard" page break, inserted by the user, breaks the page at that location. "Soft" page breaks are created by word processing and report programs based on the current page length setting. page description language Device-independent, high-level language for defining printer output. If an application generates output in a page description language, such as PostScript, the output can be printed on any printer that supports it. Much of the character and graphics shaping is done within the printer rather than in the user's computer. Instead of downloading an entire font from the computer to the printer, which includes the design of each character, a command to build a particular font is sent, and the printer creates the characters from font outlines. Likewise, a command to draw a circle is sent to the printer rather than sending the actual bits of the circle image. page fault Virtual memory interrupt that reads the required page from disk when the next instruction or item of data is not in memory. page frame See EMS. page header Common text that is printed at the top of every page. It generally includes the page number and headings above each column. page makeup Formatting a printed page, which includes the layout of headers, footers, columns, page numbers, graphics, rules and borders. page mode memory Common dynamic RAM chip design. Memory bits are accessed by row and column coordinates. Without page mode, each bit is accessed by pulsing the row and column select lines. With page mode, the row (page) is selected only once for all bits (columns) within the row, resulting in faster access. page printer Type of printer that prints a page at a time. See laser printer and ion deposition. page recognition Software that recognizes the content of a printed page which has been scanned into the computer. It uses OCR to convert the printed words into computer text and should be able to differentiate text from other elements on the page, such as pictures and captions. PageMaker Full-featured desktop publishing program for the PC and Macintosh from Aldus Corp., Seattle, WA. Originally introduced for the Mac in 1985, it set the standard for desktop publishing. In fact, Paul Brainerd, president of Aldus, coined the term desktop publishing. The PC version was introduced in 1987. pagination (1) Page numbering. (2) Laying out printed pages, which includes setting up and printing columns, rules and borders. Although pagination is used synonymously with page makeup, the term often refers to the printing of long manuscripts rather than ads and brochures. paging In virtual memory, the transfer of program segments (pages) into and out of memory. paint (1) In computer graphics, to "paint" the screen using a tablet stylus or mouse to simulate a paintbrush. (2) To transfer a dot matrix image as in the phrase "the laser printer paints the image onto a photosensitive drum." (3) To create a screen form by typing anywhere on screen. To "paint" the screen with text. paint program Graphics program that allows the user to simulate painting on screen with the use of a graphics tablet or mouse. Paint programs create raster graphics images. PAL (1) (Paradox Application Language) Paradox's programming language. (2) (Programmable Array Logic) Programmable logic chip (PLD) technology from Advanced Micro Devices. (3) (Phase Alternating Line) European TV standard that uses 625 lines of resolution (100 more than NTSC). palette (1) In computer graphics, the total range of colors that can be used for display, although typically only a subset of them can be used at one time. May also refer to the collection of painting tools available to the user. (2) Set of functions or modes. palmtop Computer small enough to hold in one hand and operate with the other. Palmtops may have specialized keyboards or keypads for data entry applications or have small qwerty keyboards. pan (1) In computer graphics, to move (while viewing) to a different part of an image without changing magnification. (2) To move (while viewing) horizontally across a text record. paper tape (1) Slow, low-capacity, sequential storage medium used in the first half of the 20th century to hold data as patterns of punched holes. (2) Paper roll printed by a calculator or cash register. paperless office Long predicted, the paperless office is still a myth. Although paper usage has been reduced in some organizations, it has increased in others. Today's PCs make it easy to churn out documents. In time, laptop computers with immense storage and high-resolution screens will serve to replace paper when travelling. Optical fiber networks will make it easy to send data, pictures, voice and video quickly. As color laser printers become commonplace, it will be easy to reproduce any document, no matter how complex. People will eventually get used to the idea that a paper document is no better proof of a transaction than its electronic form. When this occurs, the paperless office will arrive. paradigm Pronounced "para-dime." A model, example or pattern. Paradise Video display boards from the Paradise subsidiary of Western Digital Corp., Irvine, CA. Paradox Network-ready relational DBMS for PCs from Borland known for its ease of use and query by example method for asking questions. Its PAL programming language is unique. Many PAL statements are interactive Paradox commands, so that a Paradox user can adjust to programming more easily. Version 4.0 supports memo fields and BLObs. The Paradox engine (available separately) lets C applications access Paradox databases. paragraph In DOS programming, a 16 byte block. Memory addresses are generated as "segment:offset," where the segment is expressed in paragraphs. To compute an address, the segment register is shifted left four bits (multiplying it by 16). For example, the address A000:0100 = 655,616: Segment A000 655,360 (40,960 X 16) Offset 0100 256 Result A0100 655,616 This means there are 4,096 possibilities for expressing each memory byte, a situation that has helped generate confusion and bugs. paragraph tag In desktop publishing, a style sheet assigned to a text paragraph. It defines font, tab, spacing and other settings. parallel computing Solving a single problem with multiple computers or computers made up of multiple processors. See array processor and hypercube. parallel interface Multiline channel that transfers one or more bytes simultaneously. For example, personal computers often connect printers via a Centronics 36-wire parallel interface, which transfers one byte at a time over eight wires, the remaining wires used for control signals. Large computer parallel interfaces transfer more than one byte at a time. Contrast with serial interface. See Centronics. parallel port I/O attachment used to hook up a printer or other parallel interface device. On a PC, it is a 25-pin female DB-25 connector. See printer cable. parallel processing (1) Architecture within a single computer that performs more than one operation at the same time. See pipeline processing and vector processor. (2) Multiprocessing architecture made up of multiple CPUs or computer systems. Either one operation is performed on many sets of data (SIMD), or different parts of the job are worked on simultaneously (MIMD). See hypercube and multiprocessing. parallel transmission Transmitting data one or more bytes at a time. Contrast with serial transmission. parallelizing To generate instructions for a parallel processing computer. parameter (1) Any value that customizes a program. Parameters include such information as file names, coordinates, ranges of values and specific codes. They are often entered along with the program name when the program is loaded. See DOS switch. (2) In programming, a value passed to a subroutine or function for processing. parameter-driven Software that requires external values. It solves a problem that is partially or entirely described by the values (parameters) that are entered. PARC (Palo Alto Research Center) Xerox's research and development center where the Smalltalk programming language and GUI interface were developed. Established in 1970, it is located in the Stanford Univ. Industrial Park, Palo Alto, CA. parent-child In database management, a relationship between two files. The parent file contains required data about a subject, such as employees and customers. The child is the offspring; for example, the child of a customer file may be the order file. parent program Main, or primary, program or first program loaded into memory. See child program. parity bit Extra bit attached to the byte, character or word used to detect errors in transmission. parity checking Error detection technique that tests the integrity of digital data within the computer system or over a network. Parity checking uses an extra ninth bit that holds a 0 or 1 depending on the data content of the byte. Each time a byte is transferred or transmitted, the parity bit is tested. Even parity systems make the parity bit 1 when there is an even number of 1 bits in the byte. Odd parity systems make it 1 when there is an odd number of 1 bits. parity drive Separate disk drive that holds parity bits in a disk array. See RAID. parity error Error condition that occurs when the parity bit of a character is found to be incorrect. park To retract the read/write head on a hard disk to its home location before the unit is physically moved in order to prevent damage. Most modern drives park themselves when the power is turned off. parse To analyze a sentence or language statement. Parsing breaks down words into functional units that can be converted into machine language. For example, to parse the dBASE expression  sum salary for title = "MANAGER" SUM must be identified as the primary command, FOR as a conditional search, TITLE as a field name and MANAGER as the data to be searched. Parsing breaks down a natural language request, such as "What's the total of all the managers' salaries" into the commands required by a high- level language, such as in the example above. parser Routine that performs parsing operations on a computer or natural language. partition Reserved part of disk or memory that is set aside for some purpose. Pascal High-level programming language developed by Swiss professor Niklaus Wirth in the early 1970s and named after the French mathematician, Blaise Pascal. It is noted for its structured programming, which caused it to achieve popularity initially in academic circles. Pascal has had strong influence on subsequent languages, such as Ada, dBASE and PAL. See Turbo Pascal. Pascal is available in both interpreter and compiler form and has unique ways of defining variables. For example, a set of values can be stated for a variable, and if any other value is stored in it, the program generates an error at runtime. A Pascal set is an array-like structure that can hold a varying number of predefined values. Sets can be matched and manipulated providing powerful non-numeric programming capabilities. The following Turbo Pascal example converts Fahrenheit to Celsius:  program convert;  var  fahr, cent : integer;  begin  write('Enter Fahrenheit ');  readln(fahr);  cent := (fahr - 32) * 5 / 9;  writeln('Celsius is ',cent)  end.  Pascaline Calculating machine developed in 1642 by French mathematician Blaise Pascal. It could only add and subtract, but gained attention because 50 units were placed in prominent locations throughout Europe. Accountants expressed grave concern that they might be replaced by technology! passive matrix Common LCD technology used in laptops. See LCD. passive star Network topology that joins wires from several nodes without providing any additional processing. Contrast with active star. See hub. password Word or code used to serve as a security measure against unauthorized access to data. It is normally managed by the operating system or DBMS. However, the computer can only verify the legitimacy of the password, not the legitimacy of the user. See NCSC. paste See cut & paste. patch Temporary or quick fix to a program. Too many patches in a program make it difficult to maintain. It may also refer to changing the actual machine code when it is inconvenient to recompile the source program. path (1) In communications, the route between any two nodes. Same as line, channel, link or circuit. (2) In database management, the route from one set of data to another, for example, from customers to orders. (3) The route to a file on a disk. In DOS and OS/2, the path for file MYLIFE located in subdirectory STORIES within directory JOE on drive C: looks like:  c:\joe\stories\mylife  The equivalent UNIX path is (UNIX knows which drive is used):  /joe/stories/mylife  The Macintosh also uses a path in certain command sequences; for example, with "hard disk" as the drive, path is:  hard disk:joe:stories:mylife  See DOS Path and DOS abc's. PATHWORKS Family of network software from Digital that lets a VAX function as a file and print server for DOS and OS/2 workstations. DOS and OS/2 servers may also use PATHWORKS services. Protocols such as DECnet, TCP/IP, AppleTalk and NetWare, are supported. PAX (1) (Private Automatic Exchange) Inhouse intercom system. (2) (Parallel Architecture Extended) Parallel processing environment standard based on Intel's i860 RISC chip, UNIX System V and Alliant Computer's parallel and 3-D graphics technologies. PAX-1 Software from VXM Technologies, Boston, MA, that allows a network of computers to function as a single parallel processing system. It runs in an Ethernet network under TCP/IP and supports personal computers, minis and mainframes. payware Software distributed for money. Contrast with freeware. PBX (Private Branch eXchange) Inhouse telephone switching system that interconnects telephone extensions to each other, as well as to the outside telephone network. It may include functions such as least cost routing for outside calls, call forwarding, conference calling and call accounting. Modern PBXs use all-digital methods for switching and can often handle digital terminals and telephones along with analog telephones. PC (1) (Personal Computer) Machines that conform to the PC standard, originally developed by IBM and subsequently governed by Intel, Microsoft and major PC vendors collectively. The PC is the world's largest computer base; 1992 estimates are from 50 to 80 million units. A rather wide range, one wonders who's keeping count. (2) (Personal Computer) Any personal computer. (3) Sometimes refers to first-generation IBM models PC, XT and AT in contrast with second-generation PS/2s. (4) See printed circuit board. THE PC In this Glossary, PC refers to definition #1 above. PCs are used as stand-alone personal computers or as workstations and file servers in a local area network. They are predominantly used as single- user systems under DOS; however, they are also used as a central computer in a multiuser environment under UNIX and other operating systems. IBM's first PCs used acronyms and names: XT, AT, Convertible, etc. The PS/2 series use numbers: Model 30, 55, 80, etc. (see IBM PC). Compatibles often use the CPU designation in the name, such as "386 Turbo." Although there are literally thousands of PC vendors, from mom and pop shops to large mail order houses to the major computer companies (Compaq, HP, Digital, etc.), and IBM, the world's largest, all PCs fit into the following categories: THE CPU The brains of the PC is a CPU, or processor, from the Intel 8086 family (x86) of microprocessors. Increasingly, Intel-compatible CPUs from Advanced Micro Devices and Cyrix Corp. are being used. XT CLASS - 8086, 8088 The original PC launched by IBM in 1981 used the 16-bit 8088 CPU. This architecture was chosen by IBM because it was similar to the major personal computer base of that time (Z80 CPU running the CP/M operating system). It allowed vendors to easily migrate their applications from CP/M to the IBM PC, which they did rather quickly. Unfortunately, the design of the Intel 8088 was not only limited to one megabyte of memory, but was limited in scope and flexibility for the future (who knew this would become the world's greatest hardware standard). This architecture has caused enormous confusion and problems for software developers and users alike. Although more advanced CPUs (286, 386, etc.) came later, they had to build in operating modes that conformed to the original standard in order to run all PC applications on the market. Even today, all DOS applications are still written to the original limitations of the first PC. Today, these first PCs, known as XT-class machines, survive in a second-hand market. They are used for many data processing functions, but are too slow for intensive graphics or Windows applications. Memory can be increased beyond one megabyte using expanded memory (EMS). AT CLASS - 286 First used in the IBM AT in 1984, the 286's 16-bit CPU is capable of addressing up to 16 megabytes of memory. However, until DOS extenders and Windows 3.0 (see "Operating Environment" below), this "extended memory" was not widely used. AT-class machines are fast enough for many applications, but are still sluggish under Windows and are not geared for future 32-bit applications and operating systems, such as Windows NT. 386, 486, Pentium First used by Compaq in 1986, the 386, or 386DX, is a 32-bit machine that runs faster than the 286 and can address an unbelievable four gigabytes of memory, although motherboards generally only have slots for up to 16, 32 or 64 megabytes. Its flexible architecture allows both extended and expanded (EMS) memory to be allocated on demand (see memory allocation). 386s will also run Windows NT and other future 32-bit applications and operating systems. The 386SX is slower than the 386, but retains its same advanced features. The 386SL is designed for battery conservation in laptops. With initial models introduced in late 1989, the 486, or 486DX, is about twice as fast as the 386 and has a built-in math coprocessor, which is typically required by CAD programs. The 486 is suited for today's demanding applications. The 486SX runs at slower speeds than the 486DX and makes the coprocessor an optional item. Introduced in 1993, the Pentium is the successor to the 486 and is currently the fastest CPU in the Intel x86 family. It will linitially be used as a server and high-end CAD workstation.   Extended  Memory  1MB and  up  敖陳陳朕- - -団陳陳陳調- - - - - - -  8088 286 Conventional  8086 386 Memory  (XT) 486 Up to 1MB  Pentium  青陳潰 青陳陳陳   敖陳陳陳陳陳陳陳陳陳陳陳陳陳陳  Expanded memory (EMS)  青陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳   CPUs AND MEMORY TYPES  敖陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳 For more details on Intel CPUs, look up x86 in this Glossary. Also look up the invidivual CPUs: 286, 386, 486, etc. 青陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳 OPERATING ENVIRONMENT Almost all PCs use Microsoft's DOS operating system, which was developed for the 8088 CPU that could only address one megabyte of RAM. The PC was also designed so that the first 640K of the one megabyte is used for applications, while the next 384K (upper memory area, UMA) is used by the operating system to control peripheral devices (see PC memory map). Since some of the 640K is also used by DOS, only about 570K to 600K is available to user programs. As users became comfortable with PCs, they wanted more than one application open and active at the same time. In order to get around DOS' single task nature and the PC's 640K limit, a variety of add-ons, techniques and remedies have been created to solve this dilemma. Following is a synopsis. TSRs In 1984, Borland introduced Sidekick and popularized the TSR, or popup, program. Sidekick stayed in memory but swapped in and out of view by pressing a hotkey, and users could instantly switch to a handy phone directory or notepad. However, keeping many TSRs in memory may not leave room for important, big applications, and TSRs are known to cause conflicts. EXPANDED MEMORY In 1984, expanded memory (EMS) was created to break the one megabyte barrier. An EMS board with multiple megabytes of RAM could be plugged in, and its memory used directly by EMS applications. Lotus 1-2-3 quickly took advantage of it and hundreds of other applications have been written to use it. EMS can be installed in all PCs from XTs on up, a major advantage when XTs were purchased widely. See EMS for details. TASK SWITCHERS AND MULTITASKERS Programs such as Software Carousel extend DOS's capabilities by allowing the user to keep a variety of programs open at the same time and switch back and forth between them. These "task switchers" use EMS memory, extended memory and/or the hard disk to swap applications in and out of conventional memory. Combining multitasking with task switching, Quarterdeck's popular DESQview was the first control program to use expanded (EMS) memory to allow programs to run in, not just reside in, the background. MEMORY MANAGERS Memory managers were developed to store TSRs and other memory-resident software (drivers) in the 384K upper memory area (UMA), thus freeing more precious "conventional memory" in the 640K region. Memory managers manage both extended and EMS memory, and products, such as QEMM-386, 386MAX and DOS 6's EMM386.EXE, can allocate both types on demand on 386s and up. See DOS memory manager and memory allocation. EXTENDED MEMORY AND WINDOWS 3.X By the late 1980s, the DOS extender was introduced, which is software that allows DOS applications to run in, not just reside in, extended memory in 286s and up. Paradox 386 and Lotus 1-2-3 Version 3.0 were some of the first programs to use it. Windows 3.x uses its own DOS extender to manage up to 16MB of memory, which lets users launch, keep active and switch between several Windows and DOS applications. Windows is making the PC more cohesive, and its Macintosh-like desktop environment is very popular. See Windows. DOS 5 DOS 5 added a task switching capability that runs multiple DOS applications and swaps inactive ones to disk. It has improved memory management and can load part of itself into the 1024-1088K HMA region. It can also load TSRs and drivers into the upper memory area (UMA). DOS 6 DOS 6 has improved memory management and realtime compression (doubles disk capacity). New utility programs are designed to make running DOS easier. DR DOS DR DOS is a DOS-compatible operating system with advanced features that has always inspired Microsoft to include similar functionality in subsequent DOS releases. DR DOS stores TSRs and drivers in upper memory, and Version 6.0 includes realtime compression that doubles hard disk capacity. THE NEXT GENERATION: OS/2 AND WINDOWS NT The OS/2 operating system, initially developed by IBM and Microsoft, was originally written for 286s and up. Joint development was disbanded, and in 1992, IBM introduced its own Version 2.0, which runs on 386s and up and manages large amounts of memory (see OS/2). Its Workplace Shell graphical user interface is similar to Windows, and this version of OS/2 is highly regarded. Microsoft turned its development of OS/2 into Windows NT (scheduled for 1993), a redesigned operating system for 386s and up. It runs current- day DOS and Windows software as well as Windows NT applications. OS/2 compatibility is unclear. THE BAD NEWS The transition from DOS to Windows NT and OS/2 may take years, just like it did to convert from the old mainframe DOS to OS in the 1960s and 1970s. In the meantime, TSRs, EMS, memory managers, task switchers, Windows, DESQview, DR DOS, DOS extenders, DOS 5 and DOS 6 all compete to make the PC more usable. It's a nightmare for the micro manager! THE GOOD NEWS If somebody already set up your PC, you may not have to deal with any of the bad news! Also, DOS and Windows are entrenched. You should be able to buy DOS and Windows software packages for years to come. Any operating environment that runs on the desktop must run these programs. People are demanding Windows. While this environment is complicated to develop for, it offers more consistency across all applications than straight DOS programs. Windows' multimedia capabilities also bring a new level of enjoyment to using computers. INPUT AND OUTPUT There are three ways of getting data into and out of the PC. The first is via the keyboard, which plugs into a keyboard connector always built onto the motherboard. The keyboard plugs directly into the 5-pin DIN receptacle. The PS/2 uses a 6-pin mini-DIN connector. The second is via the data bus, or expansion bus, which is a set of slots on the motherboard. Expansion boards, or cards, are plugged into the slots and contain cables to their respective devices. These cards are control circuits for disk drives, the video display, CD ROM reader and network adapter for example. See PC conflicts. The third way is through serial and parallel ports which are input/output pathways built into the motherboard or contained on a separate expansion board. On the back of the PC, there are typically two serial ports (one 9-pin male and one 25-pin male). In DOS, the first port is named COM1, and the second is COM2. Both ports provide the same capability. The parallel port (LPT1) uses a 25-pin female connector on the PC. The serial ports are typically used for modems, mice, scanners and digitizer tablets, and the parallel port is used for the printer, although some printers use a serial port. Both serial and parallel ports can be used for file transfer between two computers cabled together. Mice can be purchased for either the serial port (serial mouse) or for connection via an expansion board (bus mouse). Some scanners and printers require an expansion board, which accompanies the product when you buy it and must be plugged into the PC. DATA BUS (EXPANSION SLOTS) The original PC used an 8-bit bus (transfers 8 bits simultaneously) known as the PC or XT bus. With the 286-based AT model, the bus was extended to 16- bits. Machines come with a mix of 8-bit and 16-bit slots. 8-bit cards fit in both slots, but 16-bit cards require 16-bit slots. When IBM introduced the PS/2 line, it switched from the AT bus to the high-speed 32-bit Micro Channel (MCA) bus. The MCA also provides bus mastering, which has yet to be exploited. Later, IBM introduced PS/2 models with the original AT- bus, now known as the ISA ("i-suh") bus. ISA and MCA cards are not interchangeable. To counter the Micro Channel and extend the life of the original bus, EISA ("e-suh") was conceived by the compatible vendors in late 1988. EISA accepts new 32-bit EISA boards as well as the original 8-bit and 16-bit boards. See ISA, EISA and Micro Channel. VIDEO DISPLAY Since 1981, IBM has introduced several display standards, implemented by plugging a graphics adapter into an expansion slot and connecting the appropriate monitor to it. Each new standard incorporates the previous ones for compatibility; however, vendors have to modify their programs to handle the higher resolution graphics each time. Unlike the graphics-based Macintosh, PCs operate in two software-selectable modes: text mode (character mode) and graphics mode. Prior to Windows 3.x applications, which are graphics based like the Mac, most business applications were text based and text scrolled quickly on the earliest PCs. The graphics computations required to display Windows applications on screen take longer than text-based programs. As a result, specialized display adapters, known as graphics accelerators, perform common graphics functions within their own chips and improve on-screen Windows performance dramatically, even on slow PCs. For demanding desktop publishing and CAD requirements, there are many very-high-resolution graphics systems (display adapter and monitor) from third parties. To use them, the user plugs in a graphics adapter into the PC and installs driver software that works with popular software packages, such as AutoCAD and Windows. However, once a display system becomes widely used, it may be supported by the software vendors. The following list shows the highest-resolution for each display type. For details, see PC display modes. COMMON PC DISPLAY STANDARDS IBM STANDARDS MDA 720x350 text only, monochrome Hercules 720x348 text/graphics (mono/non-IBM) CGA 320x200 text/graphics (4 cols)* EGA 640x350 text/graphics (16 cols)* MCGA 640x400 text-320x200 graphics (256 cols) VGA 720x400 text-640x480 graphics (16 cols)* 8514 1024x768 text/graphics (256 cols) XGA 1024x768 text/graphics (256 cols) * More colors available from 3rd-party vendors. VESA STANDARDS (Super VGA) 640x480 800x600 text/graphics in 16, 256, 1024x768 32K, 64K and 16M colors 1280x1024 Note: High-end graphics systems provide resolutions up to 2000x2000 pixels. PRINTERS There are hundreds of printer models that work with PCs from dot matrix to ink jet to laser printers and most of them plug into the PC's parallel port. Printing text files directly from DOS works with all printers, but in order to select fonts, boldface, underline and other print attributes, the application must support the printer. Word processing, desktop publishing, CAD and any other package that offers full-featured printing, provides drivers for the popular printers. These drivers are selected by the user when installing the program, and fonts installed for one application are often not sharable by another. One of the significant advantages of Windows is that once the printer installation has been performed for Windows, every Windows application can use all the installed fonts. All Windows applications use the print services in Windows to do their printing. Once products such as LaserMaster's WinJet system, which extends Windows' printing capabilities, is hooked into Windows, then all applications use it. In either case, Windows provides a single, central facility for managing all the installed fonts and doing the printing. KEYBOARDS The original PC keyboard used an awkward return and left shift key placement. Finally corrected on the AT keyboard, the backspace key was made harder to reach. Then came the Enhanced keyboard with a host of relocated keys, making it impossible to assign function keys intelligently. What was easy to reach on one is hard to reach on the other. Only a few keyboards, such as Northgate's Omnikey 102, dare to be different and incorporate the best features of both. Some laptop keyboards are worse than the first PC keyboards, placing often-used Ctrl and Alt keys in hard to reach locations and forcing users to press the Fn key for commonly-used functions. Touch typists beware! FLOPPY DISKS The most common floppy is the 360KB, 5.25" disk introduced soon after the first IBM PC. Later, the AT model introduced the 1.2 megabyte floppy. The 1.2MB drives can read and write the 360KB disks, but earlier models of the drive cannot be used to format 360KB disks. IBM introduced the 720KB, 3.5" microfloppy on its Convertible laptop, then doubled the capacity to 1.44MB with the PS/2 line. Due to their greater capacity and convenience, the 3.5" floppies have been retrofitted to many machines and have become the medium of choice. 1.44MB drives can read, write and format 720KB disks. Newer IBM models include the extra-high density 2.88MB floppy drives, compatible with the 1.44MB disks. FLOPPY DISK FORMATS 360KB 5.25" Low density (Double Density) 1.2MB 5.25" High density 720KB 3.5" Low density (Double Density) 1.44MB 3.5" High density 2.88MB 3.5" Extra-high density HARD DISKS Non-removable, hard disks for PCs are available with storage capacities from 40MB to 2GB and above, although buying a system with less than an 80MB hard disk may be shortsighted, considering the low cost of today's drives. Applications are getting larger and are using more and more of the hard disk all the time. There have been several hard disk interface standards used for PCs, including MFM, RLL, ESDI, IDE and SCSI (see hard disk). Today, most hard drives sold with PCs are IDE and SCSI. It depends on the controller (expansion board) whether or not another hard disk interface type can co-exist in the PC. In some cases, IDE and SCSI drives can co- exist, in others they cannot. The IDE host adapter (expansion board) that plugs into a PC can generally control two IDE hard disks. Installing the second IDE hard disk on a reasonably-new PC is not complicated (see IDE~). Since most hard disks are not removable, the low-level physical format of one drive has no bearing on that of another in a different machine. For example, two computers can be cabled together and files can be transferred from the IDE hard disk of one PC to the SCSI disk of another. The hard disk controllers are reading and writing their disks according to their own technology. Removable disk drives and Bernoulli disks provide the convenience of transportability and unlimited amounts of storage, although each drive holds only one disk module at a time. Cartridges come in 40MB and higher capacities, and optical disks hold up to 600MB and more. Each cartridge is of a proprietary design and can be inserted only into the drive it is designed for. As storage capacity grows, so does performance. Disk access times run from 9 milliseconds (fast) to 100 ms (slow). SUMMARY First attempts at cloning the IBM PC were not all successful. From 1982 to 1985, there were a lot of "almost compatible" PCs. However, as soon as the part of the operation system known as the ROM BIOS was successfully cloned and made commercially available, true compatibles appeared in abundance. Today, you can replace floppies, hard disks and video displays, add a scanner, CD ROM or other device without too much difficulty. In general, PC components are interchangeable, especially if you have a newer PC. Expansion cards are easily taken out and plugged in, and an entire motherboard can be replaced with a faster one (from a different vendor) in about a half hour. The problems come when you add a second or third device and run into a conflict with an existing one (see PC conflicts). In addition, having to modify DOS's infamous AUTOEXEC.BAT and CONFIG.SYS configuration files causes every novice to flinch in the beginning. Conflicts aside, the PC has become a commodity item, winding its way onto the shelves of a wide variety of retail outlets. This is a testimonial to the power of a standard. Today, most PCs run most software and work with most plug-in boards, but there are always exceptions. With the myriads of adapters and applications available for the PC, one device, application, TSR or utility can always conflict with another. The way to guarantee that something works is to try it. However, this has been true since day one in the computer business. Nevertheless, if all this hasn't confused the life out of you... Good Luck and Happy Computing! PC-8 Symbol set that contains the extended ASCII characters of the IBM PC. PC board See printed circuit board. PC bus Bus architecture used in first-generation IBM PCs and XTs. It refers to the original 8-bit bus, which accepted only 8-bit expansion boards. In 286s and up, it was superseded by the 16-bit AT bus, later known as the ISA bus. Contrast with ISA, EISA and Micro Channel. PC card (1) Memory card, I/O card or memory and I/O card. The "PC Card" logo refers to PCMCIA Version 2.0 and JEIDA Version 4.1, compatible standards as of late 1991. (2) Expansion board for a PC. PC color codes Following are the color numbers for the 16 foreground and eight background colors in text mode. Foreground and background numbers are added together; for example, white text on a red background is 79. To blink the text, add 128.  Number陳陳陳陳  Color  BACKGROUND FOREGROUND 0 Black 0 16 Blue 1 32 Green 2 48 Cyan 3 64 Red 4 80 Magenta 5 96 Brown 6 112 Light gray 7 FOREGROUND ONLY 8 Dark gray 9 Light blue 10 Light green 11 Light cyan 12 Light red 13 Light magenta 14 Yellow 15 White 128 Blinking PC conflicts When adding new peripherals, such as a scanner, CD ROM, sound card, etc., to your ISA-bus PC, the new plug-in board may conflict with a setting of an existing board. If you're adding your first or even second device to a basic system, you may have no conflicts, but as you add more, the chances are greater. The reason for conflicts is that PCs use the three following ways to transfer signals to a peripheral device, and the settings associated with these methods are not entirely standardized. 1. IRQ 2. I/O address (port address) 3. memory address Most peripherals use an IRQ and an I/O address. Many use a memory address. When you install a new board in your PC, you MUST read the installation manual in order to find out what the initial settings are and how to change them if necessary. If a new board uses the same setting as an existing board, it won't work properly or at all. Or, it will work and the old one won't, or both won't work. 敖陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳 Note: PCs that use the EISA and Micro Channel buses avoid many of these conflicts, because the boards are self configuring. A setup program is run when installing an EISA or Micro Channel expansion board. 青陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳 Keep a List If you plan on installing several peripherals, it's a good idea to write down the status of each board you install. Utility programs, such as MSD.EXE, which comes with Windows, and Quarterdeck's Manifest, which comes with QEMM, will help you identify most current settings, but not all of them. Make a chart like the one below and keep it handy: Device IRQ I/O Memory address 敖陳陳陳陳陳賃陳賃陳陳賃陳陳陳陳陳陳 COM1 COM2 LPT1 scanner CD ROM etc. IRQ (Interrupt Request) An interrupt is a method of signalling the computer for attention. There are 16 IRQ lines in a PC. Older XTs have only eight. If the device uses an interrupt, it must use a unique IRQ line. IRQ settings are changed by setting DIP switches or changing jumpers on the board itself or by running a setup program. Following are common IRQ settings as reported by Microsoft's MSD.EXE utility: 0 - System timer 1 - Keyboard 2 - Connects to IRQ 9 3 - COM2, COM4 4 - COM1, COM3 5 - LPT2 6 - Floppy disk 7 - LPT1 8 - Realtime clock 9 - Redirected IRQ2 10 - 11 - 12 - 13 - Math coprocessor 14 - Hard disk 15 - I/O Address The I/O address, or port address, is one way a peripheral device is identified, or addressed, from another. The addresses are numbered in hex; for example: 280h 290h 2A0h Like IRQs, they are set with DIP switches or jumpers on the board, or possibly by running a setup program. If you change settings, you may have to identify that change elsewhere, such as by changing a parameter in a device= line in the CONFIG.SYS file. Read the manual for your new device. There is no other source for that kind of information. If you change I/O addresses and still have a problem, try an address that is one or two numbers apart on the list. For example, if one board is set to 280h and another at 290h, change 280h to 270h or 260h and try again. For details on this technology, see PC I/O addressing. Memory Address A peripheral device often requires a block of upper memory (between 640K-1M) for transferring data, which must be reserved for its exclusive use. Some common devices, such as VGA video, use fixed areas in upper memory that are automatically reserved. With other devices, you have to find an unused block in this area (for a diagram, see PC memory map). That's why you'll find a number of memory addresses to select, typically in the C800h to F000h range (800-960K) so that you can hopefully find an unused block. Addresses are usually given as beginning and ending address in hex; for example: C800-CFFF D000-D7FF D800-DFFF When a block is chosen, it is also necessary to inform your memory manager not to load other drivers or TSRs into it. This may be done by a setup program or you may have to do it yourself by adding an "exclude" to the line in CONFIG.SYS that loads the memory manager. For example, EMM386.EXE is the memory manager in DOS 5 and Windows. To exclude the E800-EFFF block, the x= parameter is added to the device= line as follows: device=emm386.exe noems x=e800-efff See DOS EMM386.EXE for more on the above syntax. For other memory managers, such as QEMM and 386MAX, a similar "exclude" parameter is also used. If you use Windows, an "exclude" line is also added to the [386Enh] section in the SYSTEM.INI file; for example: EMMExclude=e800-efff If you later change the board to another memory area, both CONFIG.SYS and SYSTEM.INI must be updated. Summary You MUST read the installation manual that comes with your peripheral. Each type of board is configured differently. The first time you install a new board, fill out the chart suggested above. It will save you headaches later! PC display modes Following are the resolutions and mode numbers for the IBM, VESA and Hercules display standards. 敖 Mode number  colsXrows text Colors or  Resolution or graphics gray scale (gray) 青  CGA 0 320x200 40x25 txt 16 gray 1 320x200 40x25 txt 16 2 640x200 80x25 txt 16 gray 3 640x200 80x24 txt 16 4 320x200 graphics 4 5 320x200 graphics 4 gray 6 640x200 graphics 2 EGA 0 320x350 40x25 txt 16 gray 1 320x350 40x25 txt 16 2 640x350 80x25 txt 16 gray 3 640x350 80x25 txt 16 7 720x350 80x25 txt mono 13 320x200 graphics 16 14 640x200 graphics 16 15 640x350 graphics 2 16 640x350 graphics 16 MCGA 0 320x400 40x25 txt 16 gray 1 320x400 40x25 txt 16 2 640x400 80x25 txt 16 gray 3 640x400 80x25 txt 16 17 640x480 graphics mono 19 320x200 graphics 256 VGA 0 360x400 40x25 txt 16 gray 1 360x400 40x25 txt 16 2 720x400 80x25 txt 16 gray 3 720x400 80x25 txt 16 7 720x400 80x25 txt mono 18 640x480 graphics 16  VESA VBE Standards (Super VGA)  Video Colors RAM used 256 640x400 256 250K 257 640x480 256 300K 258 800x600 16 234K 259 800x600 256 469K 260 1024x768 16 384K 261 1024x768 256 768K 262 1280x1024 16 640K 263 1280x1024 256 1280K 264 80x60 text 9.3K 265 132x25 text 6.4K 266 132x43 text 11.1K 267 132x50 text 12.9K 268 132x60 text 15.5K 269 320x200 32K 125K 270 320x200 64K 125K 271 320x200 16M 188K 272 640x480 32K 600K 273 640x480 64K 600K 274 640x480 16M 900K 275 800x600 32K 938K 276 800x600 64K 938K 277 800x600 16M 1406K 278 1024x768 32K 1536K 279 1024x768 64K 1536K 280 1024x768 16M 2304K 281 1280x1024 32K 2560K 282 1280x1024 64K 2560K 283 1280x1024 16M 3840K Number Pixel Bits of colors R G B 32K 5 5 5 64K 5 6 5 16M 8 8 8 XGA 640x480 graphics 256 cols 640x480 graphics 64K cols 1024x768 graphics 256 cols Hercules 720x348 txt/graphics mono PC-DOS DOS operating system from Microsoft supplied by IBM for its PCs. Almost identical to MS-DOS for non- IBM PCs, both versions are called DOS. PC EXPO Trade show for resellers and corporate PC buyers held in the summer (New York) and fall (Chicago). It started in New York in 1983 with 120 exhibitors and drew 9,600 attendees. In 1991, it had 728 exhibitors and 75,000 attendees. Sponsored by Bruno Blenheim Inc., 385 Sylvan Ave., Englewood Cliffs, NJ 07632, 800/829-3976. 1993 schedule is 6/29-7/1 and 10/19-21. PC I/O addressing I/O addresses, or port addresses, on x86 architecture is a common method used to address the controller boards of peripheral devices. The other method is memory-mapped peripherals, in which a block of memory in the UMA is reserved for a device, such as a video card. There is 64K of address space for I/O addresses, although typically less than 1K is used. Each board that uses an I/O address contains a few bytes of memory (16, 32, etc.) that have a default address range and one or more alternate addresses to resolve conflicts with other boards. This physically winds up as a bunch of tiny memory banks scattered over different devices. As long as each one is set to a different address, the CPU can signal one device from another. An I/O address operation takes place as follows. If a program needs to send a byte to the serial port, it issues an OUT instruction to the CPU with the address of that serial port. The CPU notifies the address bus to activate the I/O space, not regular memory, and the address bus signals the appropriate byte location on the board. The CPU then sends the data character over the data bus to that memory location. I/O and memory addressing are often used in conjunction in which control instructions are passed via the I/O space and the data is passed and buffered via memory. PC keyboard Keyboard introduced with the IBM PC that provides a dual-function keypad for numeric entry and cursor movement. It was severely criticized for its non- standard shift key placement, which was corrected with the AT keyboard. Regardless of key placement, users often praise the feel of IBM keyboards. PC LAN (1) Network of IBM or IBM-compatible PCs. (2) Network of any variety of personal computers. PC memory card See memory card. PC memory map The following chart shows how the first megabyte of RAM is used in a PC: Address 11000:0000 1088K団陳陳陳陳陳陳陳陳陳陳 Extended HMA(high memory area) Memory 10000:0000 1024K団陳陳陳陳陳堕陳陳陳陳------------ PC ROM BIOSPS/2 F000:0000 960K団陳陳陳陳陳ROM BIOS & VGA ROM E000:0000 896K Available 青陳陳陳陳 Top 384K for drivers and of the D000:0000 832K EMS page frame first C800:0000 800K団陳陳陳陳陳陳陳陳陳陳 megabyte EGA, VGA ROM BIOS of RAM is C000:0000 768K団陳陳陳陳陳堕陳陳陳陳 called the Free UMA (upper BC00:0000 752K団陳陳陳陳陳 memory area CGA made up Graphics Hercules of UMBs CGA, EGA, Graphics (upper VGA Text memory B800:0000 736K団陳陳陳陳陳 blocks) Free B400:0000 720K団陳陳陳陳陳 MDA RAM B000:0000 704K団陳陳陳陳陳祖陳陳陳陳 EGA, VGA Graphics RAM A000:0000 640K団陳陳陳陳陳陳陳陳陳陳------------ Conventional Memory Lower 640K is used by DOS and user programs. DOS and COMMAND.COM Interrupt vectors 0K青陳陳陳陳陳陳陳陳陳陳 PC-MOS/386 Mmultiuser PC operating system from The Software Link, Inc., Norcross, GA. It runs most standard DOS applications as well as applications written for the 386's Protected Mode. PC network (1) Network of IBM and/or IBM-compatible PCs. (2) Network of any variety of personal computers. (3) (PC Network) First PC LAN from IBM introduced in 1984. It inaugurated the NetBIOS interface and uses the CSMA/CD access method. Token Ring support was added later. See MS-Net. PC Paintbrush PC paint program from ZSoft Corp., Marietta, GA, that is widely used and has set an industry standard graphics format. Its PCX raster graphics format is generated and accepted by many graphics, word processing and desktop publishing programs. PC Tools Comprehensive package of PC utilities from Central Point Software, Beaverton, OR, that includes a DOS shell (PC Tools Desktop) as well as antivirus, file management, communications, disk caching, backup, data compression and data recovery utilities. PCB See printed circuit board. PCI (Peripheral Component Interconnect) PC local bus from Intel that connects up to 10 peripherals, supports 32- and 64-bit data paths and allows bus mastering. Final specs are due in 1993. PCjr (PC junior) IBM's first home computer introduced in 1983. Its original keyboard was unsuitable for typing, but adequate keyboards were later added. It was discontinued in 1985. PCL (Printer Control Language) Command language for the HP LaserJet printers. It has become a de facto standard used in many printers and typesetters. PCL Level 5, introduced with the LaserJet III in 1990, also supports Compugraphic's Intellifont scalable fonts. PCM (1) (Pulse Code Modulation) Technique for digitizing speech by sampling the sound waves and converting each sample into a binary number. It uses waveform coding that samples a 4KHz bandwidth 8,000 times a second. Each sample is an 8 bit number, resulting in 64K bits of data per second. See ADPCM. (2) (Plug Compatible Manufacturer) Organization that makes a computer or electronic device that is compatible with an existing machine. PCMCIA (Personal Computer Memory Card International Association) Organization of U.S. and Japanese companies set up to standardize memory cards. See PC card. PCradio IBM laptop designed for mobile use. It is a ruggedized machine that provides cellular, wireless data radio (Ardis) and modem communications. PCTE (Portable Common Tool Environment) ECMA standard for exchanging data between CASE tools. See CDIF. PCX Widely-used raster graphics file format developed by Zsoft Corp., Marietta, GA, that handles monochrome, 2-bit, 4-bit, 8-bit and 24-bit color and uses RLE to achieve compression ratios of approximately 1.1:1 to 1.5:1. Images with large blocks of solid colors compress best under the RLE method. PD software See public domain software. PDA (Personal Digital Assistant) Handheld computer that serves an an organizer, electronic book or note taker and includes features such as pen-based entry and wireless transmission to a cellular service or desktop system. PDES (Product Data Exchange Specification) Standard format for exchanging data between advanced CAD and CAM programs. It describes a complete product, including the geometric aspects of the images as well as manufacturing features, tolerance specifications, material properties and finish specifications. See IGES. PDIP (Plastic DIP) Common type of DIP made of plastic. PDL See page description language. PDP (Programmed Data Processor) Minicomputer family from Digital that started with the 18-bit PDP-1 in 1959. Its $120,000 price was much less than the million dollar machines of the time and 50 units were built. In 1965, Digital legitimized the minicomputer industry with the PDP-8, which sold for about $20,000. By the late 1970s, the PDP-8 processor was put on a single chip and used in DECmate workstations. Other PDPs were built, including 12-, 18- and 36-bit machines, the larger ones evolving into DECsystem models. In 1970, Digital introduced the 16-bit PDP-11, which became the most widely used minicomputer with over 50,000 systems sold. The PDP series was followed by the VAX series in 1977; however, PDP- 11s are still made. PE (1) (Phase Encoding) Early magnetic encoding method used on 1600bpi tapes in which a 1 is an up transition and a 0 is a down transition in the center of the bit cell. (2) (Processing Element) One of multiple CPUs in a parallel processing system. (3) (Professional Engineer) Engineering degree. PE format (Portable Executable format) Win32 file format for executable programs (EXEs and DLLs) supported under Windows 3.1 Enhanced Mode (Win32s) and Windows NT. peek/poke Instructions that view and alter a byte of memory by referencing a specific memory address. Peek displays the contents; poke changes it. peer In communications, a functional unit that is on the same protocol layer as another. peer-to-peer communications Communications in which both sides have equal responsibility for initiating, maintaining and terminating the session. Contrast with master- slave communications, in which the host controls everything and determines which users can initiate which sessions. If the host were programmed to allow all users to initiate all sessions, it would look like a peer-to-peer system to the user. peer-to-peer network Network that allows users access to data on all workstations or computers in the network. Dedicated file servers may be used, but are not required. In today's environments, a peer-to-peer network often implies peer-to-peer communications, but peer-to-peer communications does not imply a peer-to-peer network. Downright confusing. pel Same as pixel. pen-based computing Using a stylus to enter hand writing and marks into a computer. See gesture recognition. pen plotter See plotter. Pen Windows Extension to Windows that allows pen-based computing. PenPoint Operating system from Go Corp., Foster City, CA, that provides a stylus (pen) interface for hand- written input. It uses a DOS-compatible file system, but does not run DOS applications. The direction, speed and order of the user's pen strokes is analyzed for recognition. See NUI. Pentium Successor to the 486 from Intel. Originally to be called the 586 and code named P5, it refers to the Pentium CPU chip or the PC that uses it. It runs about twice as fast as a 66MHz 486, and its floating point operations are up to four times as fast as a 486. Although its integer performance rivals major RISC-based CPUs (Alpha, HP-PA, MIPS, SPARC, etc.), its floating point performance is generally slower. Pentium PCs will be initially used as servers, CAD workstations and for process-intensive applications. However, today's leading edge technology always becomes tomorrow's entry level machine. The P24T is the code name for a scaled-down Pentium that will be used as a 486 upgrade on motherboards that have the required socket. Pentium CPU Technical Specs 32-bit multitasking microprocessor in a 273-pin PGA package. Same registers and operational modes as the 386 (see 386). Uses RISC design techniques and obtains its speed from a dual pipeline architecture that executes several instructions in one clock cycle. It uses a 64-bit internal bus compared to 32-bits on the 486. It contains 3.1 million transistors. PEP High-speed modem protocol from Telebit Corp., Sunnyvale, CA, suited for cellular phone use. PEPPER board Family of high-resolution graphics display boards for PCs from Number Nine Computer Corp., Lexington, MA. peripheral Any hardware device connected to a computer, such as a monitor, keyboard, printer, plotter, disk or tape drive, graphics tablet, scanner, joy stick, paddle and mouse. peripheral controller See control unit (2). permanent font (1) A soft font that is kept in the printer's memory until the printer is turned off. (2) Same as internal font. permanent memory Same as non-volatile memory. permutation One possible combination of items out of a larger set of items. For example, with the set of numbers 1, 2 and 3, there are six possible permutations: 12, 21, 13, 31, 23 and 32. perpendicular recording See vertical recording. persistence In a CRT, the time a phosphor dot remains illuminated after being energized. Long- persistence phosphors reduce flicker, but generate ghost-like images that linger on screen for a fraction of a second. persistent link See hot link. personal computer Synonymous with microcomputer, a computer that serves one user. It is used at home and in the office for almost all applications traditionally performed on larger computers. With the addition of a modem, it becomes a terminal, capable of retrieving information from other computers and online services worldwide. There are a variety of personal computers on the market, priced from $300 to over $10,000. Size is based on its memory and disk capacity. Speed is based on the CPU that runs it, and output quality is based on the resolution of its display screen and printer. MAJOR SUPPLIERS OF PERSONAL COMPUTERS The personal computer world is overwhelmingly dominated by IBM PCs and IBM-compatible PCs. There are hundreds of vendors and thousands of models, although all models fall into a handful of categories (see PC). The next largest supplier is Apple Computer, with its Macintosh family and Apple IIe. The Apple II has been widely used in schools, but is rapidly giving way to the Macs. Macintoshes are popular with individuals and are increasingly being purchased by large corporations. Both Atari and Commodore continue to carve out a niche and are popular as home and small business computers. Each of them has support from software vendors providing a rounded supply of applications. THE HISTORY OF PERSONAL COMPUTERS The industry began in 1977, when Apple, Radio Shack and Commodore introduced the first off-the-shelf computers as consumer products. The first machines used an 8-bit microprocessor with a maximum of 64K of memory and floppy disks for storage. The Apple II, Atari 500, and Commodore 64 became popular home computers, and Apple was successful in companies after the VisiCalc spreadsheet was introduced. However, the business world was soon dominated by the Z80 processor and CP/M operating system, used by countless vendors in the early 1980s, such as Vector Graphic, NorthStar, Osborne and Kaypro. By 1983, hard disks began to show up on these machines, but CP/M was soon to be history. In 1981, IBM introduced the PC, an Intel 8088- based machine, slightly faster than the genre, but with 10 times the memory. It was floppy-based, and its DOS operating system from Microsoft was also available for the clone makers (MS-DOS). The 8088 was cleverly chosen so that CP/M software vendors could convert to it easily. They did! dBASE II was introduced in 1981 bringing mainframe database functions to the personal computer level and launching an entire industry of compatible products and add-ons. Lotus 1-2-3 was introduced in 1982, and its refined interface and combined graphics helped spur sales of the new standard. The IBM PC was successfully cloned by Compaq and unsuccessfully by others. However, by the time IBM announced the AT in 1984, vendors were effectively cloning the PC and, as a group, eventually grabbed the majority of the PC market. In 1983, Apple introduced the Lisa, a graphics- based machine that simulated the user's desktop. Although ahead of its time, Lisa was abandoned for the Macintosh in 1984. The graphics-based desktop environment caught on with the Mac, especially in desktop publishing, and the graphical interface, or "gooey," (GUI) worked its way to the PC world with Microsoft Windows, and, eventually Ventura Publisher with its GEM interface. In 1986, the Compaq 386 ushered in the first Intel 386-based machine. In 1987, IBM introduced the PS/2, its next generation of personal computers, which added improved graphics, 3.5" floppy disks and an incompatible bus to help fend off the cloners. OS/2, jointly developed by IBM and Microsoft, was also introduced to handle the new machines, but the early versions didn't catch on. In the same year, more powerful Macintoshes were introduced, including the Mac SE and Mac II, which opened new doors for Apple. In 1989, the PC makers introduced 486-based computers, and Apple gave us faster Macs, which it has continued to do each year since. In 1990, Microsoft's introduced Windows 3.0, which is rapidly catching on as the graphical environment for PCs. Software publishers are developing Windows versions of all their products. In 1991, Microsoft and IBM decided to go it alone each working on their own version of the future PC operating system (IBM's OS/2 2.0 and Microsoft's Windows NT). OS/2 2.0 has been moderately successful and Windows NT is still to be delivered. 1992 was the year of PC price cuts with all major suppliers slashing prices to keep in line with mail-order vendors. Prices keep getting lower, machines keep getting faster. In 1993, Intel will introduce its Pentium CPU, successor to the 486, with nearly 3,000,000 transistors. Inspired by Radio Shack's Model 100 in 1984 and ignited by Toshiba and Zenith, the laptop market provides a fascinating growth area in personal computing. More circuits are being stuffed into less space, providing computing power on the go that few would have imagined back in 1977. THE FUTURE The personal computer industry sprang up without any planning. All of a sudden, it was there. Machines were bought to solve individual problems, such as automating a budget or typing a letter. However, in large organizations, the real data exists in the mainframe, and it doesn't make sense to have an employee retype the mainframe reports into the micro in order to analyze and manipulate it. Personal computers can serve as invaluable tools for the user when they are designed into the fabric of the organization. The major issue of the 1990s is to tie them together in LANs and interconnect them with the company's minis and mainframes. Fast personal computers are changing the marketplace. Not only do they begin to compete with minicomputer workstations, but, networks of these machines are now being installed for applications that were previously relegated to minis and mainframes. These high-powered desktop computers will encourage the development of more artificial intelligence applications that are the backbone of the next computing generation. By the turn of the century, you should be able to talk to your computer as easily as typing on it. As stand-alone machines, personal computers have placed creative capacity into the hands of an individual that would have cost millions of dollars less than 20 years ago. It slowly but surely is shifting the balance of power from the large company to the small, from the elite to the masses, from the wealthy to individuals of modest means. The personal computer has truly revolutionized the computer industry and the world. personal workstation Same as personal computer or workstation. PET computer (Personal Electronic Transaction computer) CP/M and floppy disk-based personal computer introduced in 1977 by Commodore. It was one of the three first personal computers. PFS:First Choice Integrated software package for PCs from Spinnaker Software Corp., Cambridge, MA, that provides word processing, database, spreadsheet, graphics and communications capabilities. PFS:Write See Professional Write. PGA (1) (Pin Grid Array) Chip housing with high density of pins (200 pins can fit in 1.5" square). Used for large amounts of I/O, its underside looks like a "bed of nails." (2) (Programmable Gate Array) Type of gate array that is programmed by the customer. (3) (Professional Graphics Adapter) Early high-res PC display standard (640x480, 256 cols.) with 3-D processor that had minimal support. PgUp/PgDn keys Page Up and Page Down keys are typically used to move text up and down one screenful, but they can be programmed to do anything. phase change recording Optical recording technique that uses a laser to create a bit by altering the crystalline structure of a metallic surface. The bit either reflects or absorbs light when read. phase encoding See PE. phase locked Technique for maintaining synchronization in an electronic circuit. The circuit receives its timing from input signals, but also provides a feedback circuit for synchronization. phase modulation Transmission technique that blends a data signal into a carrier by varying (modulating) the phase of the carrier. See modulate. phase-shift keying See DPSK. PHIGS (Programmer's Hierarchical Interactive Graphics Standard) Graphics system and language used to create 2-D and 3-D images. Like the GKS standard, PHIGS is a device independent interface between the application program and the graphics subsystem. It manages graphics objects in a hierarchical manner so that a complete assembly can be specified with all of its subassemblies. It is a very comprehensive standard requiring high-performance workstations and host processing. Phoenix BIOS PC-compatible ROM BIOS from Phoenix Technolgies, Ltd., Norwood, MA. Phoenix was the first company to successfully mass produce the ROM BIOS for the PC. phone connector (1) Plug and socket for a two or three-wire coaxial cable used to plug microphones and headphones into amplifiers. The plug is a single, nail-like " thick prong about 1" in length. See phono connector. (2) Plug and socket for a telephone line, typically the RJ-11 modular connector. phone hawk Slang for a person who calls up a computer via modem and either copies or destroys data. phoneme Speech utterance, such as "k," "ch," and "sh," that is used in synthetic speech systems to compose words for audio output. PhoneNET Communications products from Farallon Computing, Inc., Emeryville, CA, that extend LocalTalk distances to 3,000 feet and use unshielded twisted phone lines instead of shielded twisted pair. Configurations include daisy chain, passive star as well as active star topologies for both EtherTalk and LocalTalk. Optional Traffic Watch software provides network management and administration. Phong shading In computer graphics, a technique developed by Phong Bui Tuong that computes a shaded surface based on the color and illumination at each pixel. It is more accurate than Gouraud shading, but requires much more extensive computation. phono connector Also called an RCA connector, a plug and socket for a two-wire coaxial cable used to connect audio and video components. The Apple II has a video out phono connector for a TV. The plug is a 1/8" thick prong that sticks out 5/16" from the middle of a cylinder. See phone connector. phosphor Rare earth material used to coat the inside face of a CRT. When struck by an electron beam, the phosphor emits a visible light for a few milliseconds. In color displays, red, green and blue phosphor dots are grouped as a cluster. Photo CD CD system from Kodak that records 35mm film images on a CD. Each image takes up 4.5MB of storage and includes five resolutions, the highest known as Base/16: 2048x3072x24. The Photo CD is created by photo finishers that have a Kodak Picture Imaging Workstation. Additional formats include the Pro Photo CD Master, which stores images from professional format film (120, 4x5, etc.), the Photo CD Portfolio, which holds up to 800 TV-quality images, the Photo CD Catalog for use in catalog distribution and the Photo CD Medical disk for storing film-based images photocomposition Laying out a printed page using electrophotographic machines, such as phototypesetters and laser printers. See page makeup and pagination. photolithography Lithographic technique used to transfer the design of the circuit paths and electronic elements on a chip onto a wafer's surface. A photomask is created with the design for each layer of the chip. The wafer is coated with a light-sensitive film (photoresist) and is exposed to light shining through the photomask. The light hardens the film, and when the wafer is exposed to an acid bath (wet processing) or hot ions (dry processing), the unhardened areas are etched away. photomask Opaque image on a transluscent plate that is used as a light filter to transfer an image from one device to another. See chip. photomicrography Photographing microscopic images. photon Unit of energy. Elementary particle of electromagnetic radiation (light, radio waves, X- rays, etc.). photonics Science of building machine circuits that use light instead of electricity. photooptic memory Storage device that uses a laser beam to record data onto a photosensitive film. photorealistic Having the image quality of a photograph. photorealistic image synthesis In computer graphics, a format for describing a picture that depicts the realism of the actual image. It includes such attributes as surface texture, light sources, motion blur and reflectivity. photoresist Film used in photolithography that temporarily holds the pattern of a circuit path or microscopic element of a chip. When exposed to light, it hardens and is resistant to the acid bath that washes away the unexposed areas. photosensor Light-sensitive device that is used in optical scanning machinery. phototypesetter Device that generates high-resolution text directly onto a photo-sensitive material. Input comes from the keyboard, or via disk, tape or modem. The output is a paper-like or transparent film that is processed into a camera-ready master for printing. Phototypesetters employ various light technologies. Older machines pass light through a spinning font photomask, then through lenses that create the point size and onto film. Others create images on CRTs and expose the film. Modern imagesetters use lasers to generate the image directly onto the film. The phototypesetter was originally the only machine that could handle multiple fonts and text composition such as kerning. Today, desktop laser printers are used for many typesetting jobs and are quickly advancing in resolution, although the 1270 and 2540 dpi resolutions of the phototypesetter still provide the highest quality. Phototypesetters that handle both text and graphics are called imagesetters. physical Refers to devices at the electronic, or machine, level. Contrast with logical. See logical vs physical. physical address Actual, machine address of an item or device. physical format See record layout and low-level format. physical link (1) Electronic connection between two devices. (2) In data management, a pointer in an index or record that refers to the physical location of data in another file. physical lock Prevention of user access to data provided by a locking on/off switch or file protection mechanism such as on a floppy disk. Contrast with logical lock. PIC (1) (PICture) File extension used for graphics formats. Lotus PIC is a vector format for 1-2-3 charts and graphs. Videoshow PIC is a vector format that is a subset of the NAPLPS standard. (2) (Personal Intelligent Communicator) Hand-held computer that uses 3" CD ROMs and has a HyperCard- like interface from General Magic, Inc. (Apple and Sony) scheduled for 1992. It will have cellular phone capability. Wireless communications for networks, radio and TV is planned. (3) (Programmable Interrupt Controller) Intel 8259 chip that controls interrupts in PCs. pica (1) In word processing, a monospaced font that prints 10 characters per inch. (2) In typography, about 1/6th of an inch (0.166") or 12 points. Pick System Multiuser operating environment from Pick Systems, Inc., Irvine, CA, that runs in a variety of computers and includes a virtual memory operating system and relational database. It is highly praised for its ease of use and flexibility. It was originally developed by Richard Pick, who created a system for the U.S. Army while working at TRW Corp. He later transformed it into the Reality operating system for Microdata and then obtained the right to license it to other vendors. picosecond One trillionth of a second. Pronounced "pee-co- second." PICT (PICTure) Macintosh graphics file format that stores images in the QuickDraw vector format. When PICT files are converted to the PC, they use the .PCT file extension. picture In programming, a pattern that describes the type of data allowed in a field or how it will print. The pattern is made up of a character code for each character in the field; for example, 9999 is a picture for four numeric digits. A picture for a telephone number could be (999) 999-9999. XXX999 represents three alphanumerics followed by three numerics. Pictures are similar but not identical in all programming languages. picture element See pixel. Picturephone Proposed video/telephone introduced by AT&T at the 1964 World's Fair (New York). Many thought it would flourish by the end of the 1980s. PID (1) (Process IDentifier) Temporary number assigned by the operating system to a process or service. (2) (Proportional Integral Derivative) Controller used to regulate a continuous process such as grinding or cooking. pie chart Graphical representation of information in which each unit of data is represented as a pie-shaped piece of a circle. See business graphics. piezoelectric Generation of electricity from a crystal subjected to pressure. Certain crystal oscillators and microphones are piezoelectric devices. PIF (Program Information File) Windows data file used to hold requirements for DOS applications running under Windows. Windows comes with a variety of PIFs, but users can edit them and new ones can be created with the PIF editor if a DOS application doesn't work properly. An application can be launched by clicking on its PIF. piggyback board Small printed circuit board that plugs into another circuit board in order to enhance its capabilities. It does not plug into the motherboard, but would plug into the boards that plug into the motherboard. PIL (Publishing Interchange Language) Standard for document interchange that defines the placement of text and graphics objects on the page. It does not address the content of the objects. PILOT (Programmed Inquiry Learning Or Teaching) High- level programming language used to generate question-and-answer courseware. A version that incorporates turtle graphics runs on Atari personal computers. PIM (Personal Information Manager) Combination word processor, database and desktop accessory program that organizes a variety of information. It allows the user to tie together more loosely structured information than traditional programs. PIMs vary widely, but all of them attempt to provide methods for managing information the way people use it in their jobs. pin (1) Male lead on a connecting plug (serial port, monitor cable, keyboard connector, etc.) or the spiderlike foot on a chip. Each pin is plugged into a socket to complete the circuit. (2) (PIN) (Personal Identification Number) Personal password used for identification purposes. pin compatible All connecting signal lines are compatible. pin feed Method for moving continuous paper forms. Pins at both ends of a rotating platen or tractor engage the forms through pre-punched holes at both sides. pinch roller Small, freely-turning wheel in a tape drive that pushes the tape against a motor-driven wheel in order to move it. pincushioning Screen distortion in which the sides bow in. Contrast with barrel distortion. ping pong (1) Half-duplex communications method in which data is transmitted in one direction and acknowledgement is returned at the same speed in the other. The line is alternately switched from transmit to receive in each direction. Contrast with asymmetric modem. (2) To go in one direction and then in the other. ping-pong buffer See double buffering. Pink Code name for Taligent's portable, object-oriented operating system that will run on a variety of computers. Expected in 1994. See Apple. pinouts Description and purpose of each pin in a multiline connector. PIP (Peripheral Interchange Program) CP/M utility program used to copy files. pipe Shared space that accepts the output of one program for input into another. In DOS and OS/2, the pipe command is a vertical line (|). The statement, dir | sort directs the output of the directory list to the sort utility. See DOS filters & pipes and DOS redirection. pipeline processing Category of techniques that provide simultaneous, or parallel, processing within the computer It refers to overlapping operations by moving data or instructions into a conceptual pipe with all stages of the pipe processing simultaneously. For example, while one instruction is being executed, the computer is decoding the next instruction. In vector processors, several steps in a floating point operation can be processed simultaneously. piracy Illegal copying of software for personal or commercial use. pitch Number of printed characters per inch. With proportionally spaced characters, the pitch is variable and must be measured as an average. See dot pitch. pixel (PIX [picture] ELement) Smallest element on a video display screen. A screen is broken up into thousands of tiny dots, and a pixel is one or more dots that are treated as a unit. A pixel can be one dot on a monochrome screen, three dots (red, green and blue) on color screens, or clusters of these dots. For monochrome screens, the pixel, normally dark, is energized to different light intensities, creating a range from dark to light. For color, each red, green and blue dot is energized to different intensities, creating a range of colors perceived as the mixture of these dots. Black is all three dots off, white is all three dots on, and grays are even intensities of each color. The number of bits assigned to each pixel in its associated digital memory determines the number of shades and colors that can be represented. The most economical system is monochrome in which one bit is used per pixel (on or off). In the most elaborate color displays, which use up to four full bytes for each of the red, green and blue dots, each pixel can display billions of different shades. Considering that a high-resolution screen may use a million pixels, many megabytes of memory would have to be reserved to hold such an image. pixel graphics Same as raster graphics. PixelPaint Macintosh drawing program from SuperMac Technology, Sunnyvale, CA, that is known for its extensive paint palette and color mixing schemes. PK software Popular PC shareware compression programs from PKWARE Inc., Brown Deer, WI (PK stands for Phil Katz). PKZIP compresses files into a ZIP file and PKUNZIP decompresses them. PKSFX compresses files into a self-extracting EXE file that decompresses when loaded and doesn't require the PKUNZIP program. ZIP2EXE creates the self-extracting file from an existing ZIP file. PKLITE compresses only EXE and COM program files. Unlike ZIP'd files, which are compressed for archiving or distribution and decompressed upon installation, PKLITE'd files stay compressed all the time and decompress automatically when loaded. PKARC and PKXARC were previous compression programs no longer supported. PL/I (Programming Language 1) High-level IBM programming language introduced in 1964 with the System/360 series. It was designed to combine features of and eventually supplant COBOL and FORTRAN, which never happened. A PL/I program is made up of procedures (modules) that can be compiled independently. There is always a main procedure and zero or more additional ones. Functions, which pass arguments back and forth, are also provided. PL/M (Programming Language for Microprocessors) Dialect of PL/I developed by Intel as a high-level language for its microprocessors. PL/M+ is an extended version of PL/M, developed by National Semiconductor for its microprocessors. PLA (Programmable Logic Array) Programmable logic chip (PLD) technology from Philips/Signetics. plaintext Normal text that has not been encrypted and is readable by text editors and word processors. Contrast with ciphertext. planar Technique developed by Fairchild Instruments that creates transistor sublayers by forcing chemicals under pressure into exposed areas. Planar superseded the mesa process and was a major step toward creating the chip. planar area In computer graphics, an object that has boundaries, such as a square or polygon. planning system See spreadsheet and financial planning system. plasma display Also called gas discharge, a flat-screen technology that contains an inert ionized gas sandwiched between x- and y-axis panels. A pixel is selected by charging one x- and one y-wire, causing the gas in that vicinity to glow a bright orange. platen Long, thin cylinder in a typewriter or printer that guides the paper through it and serves as a backstop for the printing mechanism to bang into. platform Hardware architecture of a particular model or computer family. It is the standard to which software developers write their programs. The term may also include the operating system. See environment. PLATO (Programmed Logic for Automatic Teaching Operations) Developed by Donald Bitzer and originally marketed by CDC, it was the first CBT system to combine graphics and touch-sensitive screens for interactive training. platter One of the disks in a disk pack or hard disk drive. Each platter provides a top and bottom recording surface. See magnetic disk. PLB (Picture Level Benchmark) Graphics Performance Characterization (GPC) committee's benchmark, available through NCGA, for measuring graphics workstation performance. The Benchmark Interface Format (BIF) defines the PLB format, the Benchmark Timing Methodology (BTM) performs the test and the Benchmark Reporting Format (BRF) generates results in GPCmarks. Image quality is not rated. PLC (Programmable Logic Controller) Computer used in process control applications. PLC microprocessors are typically RISC-based and are designed for high- speed, realtime and rugged industrial environments. PLCC (Plastic LCC) Widely-used type of leaded chip carrier. See LCC. PLD (Programmable Logic Device) Logic chip that is programmed at the customer's site. There are a wide variety of PLD techniques; however, most PLDs are compatible with the PAL method from Advanced Micro Devices. The PLD is not a storage chip like a PROM or EPROM, although fuse-blowing techniques are used. It contains different configurations of AND, OR and NOR gates that are "blown" together. Contrast with gate array, which requires a manufacturing process to complete the programming. plot To create an image by drawing a series of lines. In programming, a plot statement creates a single vector (line) or a complete circle or box that is made up of several vectors. plotter Graphics printer that draws images with ink pens. It requires data in vector graphics format, which makes up an image as a series of point-to-point lines. See flatbed plotter and drum plotter. Plotter in a Cartridge HPGL emulation in a cartridge for laser printers from Pacific Data Products, San Diego, CA. PLP (Presentation Level Protocol) North American standard protocol for videotex. plug compatible Hardware that is designed to perform exactly like another vendor's product. A plug compatible CPU runs the same software as the machine it's compatible with. A plug compatible peripheral works the same as the device it's replacing. plugboard Socket board with used to program early tabulating machines and computers. A wire is inserted into one output and one input socket, closing a circuit and activating a function. Complicated programs looked like "mounds of spaghetti." plugs & sockets Physical connectors used to link together all variety of electronic devices. See DB-9, RS-232, and Centronics. PM See preventive maintenance, Presentation Manager and phase modulation. PMMU (Paged Memory Management Unit) Virtual memory chip for the 68020 processor (it is built in on the 68030), which is required to run A/UX on the Mac or any 68020 platform running hardware virtual memory. PMOS (Positive channel MOS) Pronounced "P moss." Type of microelectronic circuit in which the base material is positively charged. PMOS transistors were used in the first microprocessors and are still used in CMOS. They are also used in low-cost products (calculators, watches, etc.). PMS (Pantone Matching System) Color matching system that has assigned a number to over 500 different colors. pocket computer Hand-held, calculator-sized computer that runs on batteries. It can be plugged into a personal computer for data transfer. point (1) To move the cursor onto a line or image on screen by rolling a mouse across the desk or by pressing the arrow keys. (2) In typography, a unit equal to 1/72nd of an inch, used to measure the vertical height of a printed character. point and shoot To select a menu option or activate a function by moving the cursor onto a line or object and pressing the return key or mouse button. point of sale Capturing data at the time and place of sale. Point of sale systems use personal computers or specialized terminals that are combined with cash registers, optical scanners for reading product tags, and/or magnetic stripe readers for reading credit cards. Point of sale systems may be online to a central computer for credit checking and inventory updating, or they may be stand-alone machines that store the daily transactions until they can be delivered or transmitted to the main computer for processing. pointer (1) In database management, an address embedded within the data that specifies the location of data in another record or file. (2) In programming, a variable that is used as a reference to the current item in a table (array) or to some other object, such as the current row or column on screen. (3) On-screen symbol used to identify menu selections or the current screen location. It is moved by a mouse or other pointing device. pointing device Input device, such as a mouse or graphics tablet, used to move the cursor on screen or to draw an image. Poisson distribution Statistical method developed by the 18th century French mathematician S. D. Poisson, which is used for predicting the probable distribution of a series of events. For example, when the average transaction volume in a communications system can be estimated, Poisson distribution is used to determine the probable minimum and maximum number of transactions that can occur within a given time period. poke See peek/poke. polarity (1) Direction of charged particles, which may determine the binary status of a bit. (2) In micrographics, the change in the light to dark relationship of an image when copies are made. Positive polarity is dark characters on a light background; negative polarity is light characters on a dark background. polarized One-way direction of a signal or the molecules within a material pointing in one direction. Polish notation Method for expressing a sequence of calculations developed by the Polish logician Jan Lukasiewicz in 1929. For example, A(B+C) would be expressed as * A + B C. In reverse Polish notation, it would be A B C + *. polling Communications technique that determines when a terminal is ready to send data. The computer continually interrogates its connected terminals in a round robin sequence. If a terminal has data to send, it sends back an acknowledgement and the transmission begins. Contrast with interrupt- driven, in which the terminal generates a signal when it has data to send. polling cycle One round in which each and every terminal connected to the computer or controller has been polled once. polygon In computer graphics, a multi-sided object that can be filled with color or moved around as a single entity. polyhedron Six- or more-sided object. A group of connected polygons. polyline In computer graphics, a single entity that is made up of a series of connected lines. polymorphic tweening See tweening. polymorphism Meaning many shapes. In object-oriented programming, the ability of a generalized request (message) to produce different results based on the object that it is sent to. Polyvision Flat panel display from Alpine Polyvision Inc. that uses a plastic film of metal ions sandwiched between horizontal and vertical electrodes. Where current intersects, the metal ions turn black. pop See push/pop. POP-11 (Package for Online Programming) General-purpose programming language with list processing and compiler writing functionality from SD-Scicon PLC. pop-down menu See pull-down menu. populate To plug in chips or components into a printed circuit board. A fully populated board is one that contains all the devices it can hold. popup (1) Type of menu called for and displayed on top of the existing text or image. When the item is selected, the menu disappears and the screen is restored. (2) Same as TSR. port (1) Pathway into and out of the computer. The serial and parallel ports on a personal computer are external sockets for plugging in communications lines, modems and printers. On a front end processor, serial ports connect to communications lines and modems. (2) To convert software to run in a different computer environment. port address Physical identification of an I/O port. See PC conflicts. port expander Device that connects several lines to one port in the computer. A line is given access to the port either by a hardware switch or through software selection. portability See portable. portable Refers to software that can be easily moved from one type of machine to another. It implies a product that has a version for several hardware platforms or has built-in capabilities for switching between them. However, a program that can be easily converted from one machine type to another is also considered portable. portable computer Personal computer that can be easily transported. Compared to desktop models, it has limited expansion slots and disk capacity. The first portable was the Osborne I, a CP/M machine that was soon followed by many others, such as the Kaypro and Otrona's Attache. In late 1982, Compaq introduced the first MS-DOS portable. See laptop computer, notebook computer and pocket computer. Portable NetWare OEM version (C source code) of Novell's NetWare operating system that can be compiled for a specific vendor's machine. porting See port. portrait Orientation in which the data is printed across the narrow side of the form.  敖陳陳陳朕  敖陳陳陳陳陳朕  Portrait Landscape   青陳陳陳陳陳潰  青陳陳陳潰  POS See point of sale. positive logic Use of low voltage for a 0 bit and high voltage for a 1 bit. Contrast with negative logic. POSIX (Portable Operating System Interface for UNIX) IEEE standard that defines the language interface between application programs and the UNIX operating system. Adherence to the standard ensures compatibility when programs are moved from one UNIX computer to another. POST (Power On Self Test) Series of built-in diagnostics that are performed when the computer is first started. Proprietary codes are generated (POST codes) that indicate test results. See diagnostic board. postfix notation See reverse Polish notation. postprocessor Software that provides some final processing to data, such as formatting it for display or printing. PostScript Page description language from Adobe Systems, Inc., Mountain View, CA, used in a wide variety of printers, imagesetters and display systems. PostScript commands do not drive the printer directly. They are language statements (ASCII text) that are translated into the printer's machine language by a PostScript interpreter built into the printer. Fonts are scaled to size by the interpreter, thus eliminating the need to store a variety of font sizes on disk. PostScript Level 2, downward compatible with original PostScript, adds data compression and enhancements, especially for color printing. PostScript fonts come in Type 1 and Type 3 formats, and Adobe makes only Type 1. Type 1 fonts are widely used and are made by other companies as Adobe later made the format public. Type 1 fonts are encrypted and compressed and also allow for hints, which improve the appearance of text, especially at desktop laser printer resolutions. Type 1 fonts use a simpler, more efficient command language than Type 3. With Adobe Type Manager, Type 1 fonts can also be used on non- PostScript printers. Type 3 fonts do not use encryption or hints, but can use the entire PostScript language to create complex designs that include fills and patterns. Type 3 fonts can also be bitmaps. In order to speed up printing small fonts on PostScript printers, Windows 3.1 creates Type 3 bitmaps from its TrueType outlines. Originally developed as a device-independent imaging language, PostScript is used extensively on Macs and PCs. It has also migrated to workstations, minis and mainframes. pot See potentiometer. potentiometer Device that controls the amount of current that flows through a circuit, such as a volume switch on a radio. POTS (Plain Old Telephone Service) Traditional analog telephone network. power See computer power. power down To turn off the computer in an orderly manner by making sure all applications have been closed normally and then shutting the power. Power Platform IBM 486 replacement processor boards for PS/2 models. power supply Electrical system that converts AC current from the wall outlet into the DC currents required by the computer circuitry. power up To turn the computer on in an orderly manner. power user Person who is very proficient with personal computers. It implies knowledge of a variety of software packages. PowerBook Family of Macintosh portable computers from Apple that include a trackball centered in a wrist rest. See Macintosh for specifications. PowerBuilder Application generator for developing Windows client/server applications from PowerSoft Corp., Burlington, MA. Its programming language is a superset of Visual BASIC. Supports SQL and a variety of databases including DB2 and Oracle. PowerOpen Version of UNIX from IBM/Apple's joint venture that runs AIX and Mac applications on the PowerPC. PowerPC RISC chip from Motorola for IBM/Apple's joint venture. PowerPoint Macintosh desktop presentation program from Microsoft. It was the first desktop presentation program for the Mac and provides the ability to create output for overheads, handouts, speaker notes and film recorder. Color palettes for Genigraphics slides accompany the product. PowerSCSI! Software from Future Domain Corp. that accompanies its SCSI host adapters for PCs allowing them to control all SCSI peripherals. It translates the popular methods for accessing SCSI devices, including DOS' int 13, Windows FastDisk, ASPI and various CD ROM methods into industry standard CAM, supported on its host adapter. See CorelSCSI. PPGA (Plastic PGA) See PGA. pph (Pages Per Hour) Measures printing speed. ppi (Pixels Per Inch) Measures display or print elements. (2) (Points Per Inch, Pulses Per Inch) Measures mouse movement. ppm (Pages Per Minute) Measures printing speed. PQFP (Plastic Quad FlatPack) Surface mount chip housing with flat leads on all four sides. PR/SM (Processor Resource/Systems Manager) IBM mainframe feature that allows the CPU to run as multiple logical processors, each capable of running a different operating system and set of applications. Standard on ES/9000 models, it is an upgrade to 3090 processors. PRAM (Parameter RAM) Pronounced "P RAM." Battery- backed part of the Macintosh's memory that holds Control Panel settings and the settings for the hidden desktop file. If the command and option keys are held down at startup, the desktop settings are cleared and a dialog to rebuild the desktop is initiated. precedence Order in which an expression is processed. Mathematical precedence is normally: 1. unary + and - signs 2. exponentiation 3. multiplication and division 4. addition and subtraction In the following two examples: fahrenheit-32*5/9 and (fahrenheit-32)*5/9 the first one is incorrect, because multiplication is evaluated before subtraction. Logical precedence is normally: 1. NOT 2. AND 3. OR In the dbase query: list for item = "TIE" .and. color = "GRAY"  .or. color = "RED" all gray ties and anything red will be selected, since ANDs are evaluated before ORs. Grouping the colors in parentheses: (color="GRAY" .or. color="RED") yields only gray and red ties. precision Number of digits used to express the fractional part of a number. The more digits, the more precision. See single precision and double precision. predicate In programming, a statement that evaluates an expression and provides a true or false answer based on the condition of the data. preemptive multitasking Multitasking that shares processing time with all running programs. For example, background programs can be given recurrent CPU time no matter how heavy the foreground load. Contrast with nonpreemtive multitasking. prefix notation See Polish notation. prepress In typography and printing, the preparation of camera-ready materials up to the actual printing stage, which includes typesetting and page makeup. preprocessor Software that performs some preliminary processing on the input before it is processed by the main program. presentation graphics Business graphics, such as bar charts and graphs, that are used as presentation material in meetings and lectures. It implies the ability to create stylized graphics such as 3-D charts. Presentation Manager Graphical user interface included with OS/2, which provides a desktop and windows environment similar to Windows. Prestel Commercial videotex service of British Telecom (formerly part of the British Post Office). preventive maintenance Routine checking of hardware that is performed by a field engineer on a regularly scheduled basis. See remedial maintenance. PRI See ISDN. primary index The index that controls the current processing order of a file. See secondary index. primary storage The computer's internal memory (RAM). Contrast with secondary storage. primitive (1) In computer graphics, a graphics element that is used as a building block for creating images, such as a point, line, arc, cone or sphere. (2) In programming, a fundamental instruction, statement or operation. (3) In microprogramming, a microinstruction, or elementary machine operation. print buffer See printer buffer. print column Column of data on a printed report that may be subtotalled or totalled. Print columns are the heart of a report writer's description. print engine See printer engine. print head Mechanism that deposits ink onto paper in a character printer. print image Text or graphics document that has been prepared for the printer. Format codes for the required printer have been embedded in the document at the appropriate places. With text files, headers, footers and page numbers have been created and inserted in every page. print image format See print image. print queue Disk space that holds output designated for the printer until the printer can receive it. print screen Ability to print the current on-screen image. See screen dump. print server Computer in a network that controls one or more printers. It stores the print-image output from all users of the system and feeds it to the printer one job at a time. This function may be part of the network operating system or an add-on utility. print spooler Software that manages printing in the background. When an application is made to print, it quickly generates the output on disk and the spooler feeds the print images to the printer at slower printing speeds. This second step can be run in the background without appreciably interfering with user interaction in the foreground. See spooling. print to disk To redirect output from the printer to the disk. The resulting file contains text and graphics with all the codes required to direct the printer to print it. The file can be printed later or at a remote location without requiring the word processor, DTP or drawing program that was originally used to create it. This is actually the first stage of a print spooling operation. See print spooler. printed circuit board Flat board that holds chips and other electronic components. The board is made of reinforced fiberglass or plastic and interconnects components via copper pathways. The main printed circuit board in a system is called a system board or motherboard, while smaller ones that plug into the slots in the main board are called boards or cards. The printed circuit board of the 1960s connected discrete components together. The circuit board of the 1990s interconnects chips, each containing hundreds of thousands and millions of elementary components. The "printed" circuit is really an etched circuit. A copper foil is placed over the glass or plastic base and covered with a photoresist. Light is shined through a negative image of the circuit paths onto the photoresist, hardening the areas that will remain after etching. When passed through an acid bath, the unhardened areas are washed away. A similar process creates the microminiaturized circuits on a chip (see chip). printer Device that converts computer output into printed images. Following is an overview of printer types. Serial Printers Serial printers print a character at a time from approximately 10 to 400 cps (about 6 to 240 lpm). Serial printers use dot matrix and character printer technologies. Serial printers are referred to as character printers regardless of the printing technology employed. Line Printers Line printers print a line at a time from approximately 100 to 5,000 lpm and are the standard impact printers found in datacenters. They employ drum, chain, train, band, dot matrix and dot band technologies. Page Printers Page printers, also called laser printers, print a page at time from approximately 4 to 215 ppm (400 to 14,000 lpm), and generally use the copy machine electrophotographic technique. High-speed page printers are used in large datacenters, and desktop laser printers are now commonplace for personal computers. Graphics Printers Graphics printers use impact serial dot matrix, impact line dot matrix, impact line dot band and all non-impact technologies. Color Printers Color printers use impact dot matrix with multiple color ribbons, electrophotographic with multiple color toners, electrostatic plotters with multiple color toners, printers using Cycolor technology, ink jet with multiple color inks and thermal- transfer with multiple colors. IMPACT PRINTERS  Band, Chain & Train Printers A continuous loop of several character sets connected together spins horizontally around a set of hammers. When the desired character is in front of the selected print location, that particular hammer hits the paper forcing the shaped character image on the band, chain, or train into the ribbon and onto the paper. Since the chain, band, or train moves so fast, it appears to print a line at a time. A band is a solid loop, while the chain is individual character images (type slugs) chained together. The train is individual character images (type slugs) revolving in a track, one pushing the other. See band printer and chain printer. Drum Printer A rotating drum (cylinder) contains the character set carved around it for each print location, like an odometer. When the desired character for the selected print location has rotated around to the hammer line, the appropriate hammer hits the paper from behind, forcing it against the ribbon that is between the paper and the drum. Since the drum rotates so fast, it appears to print a line at a time. See drum printer. Character Printers Character printers are similar to Selectric typewriters, printing one character at a time. A daisy wheel or similar mechanism is moved serially across the paper. At the selected print location, a hammer hits the shaped character image on the wheel into the ribbon and onto the paper. Serial Dot Matrix A vertical set of printing wires moves serially across the paper, formulating characters by impacting a ribbon and transferring dots of ink onto the paper. The clarity of the character is determined by how close the dots print together. Line Dot Matrix A stationary or oscillating line of printing wires generates images by impacting a ribbon and transferring dots of ink onto the paper a line at a time. Dot Band Matrix A combination band and dot matrix configuration. A steel band is etched to create fingers (petals). At the tip of each finger is an anvil with a steel dot attached. Print hammers impact the anvils, which are larger than the dots, allowing the dots to be printed in areas between the hammer faces. Different size dots may be used on different bands to change the speed of printing and the print resolution. NON-IMPACT PRINTERS  Electrophotographic A drum is charged with a high voltage and an image source paints a negative light copy of the image to be printed onto the drum. Where the light falls onto the drum, the drum is discharged. A toner (ink) is allowed to adhere to the charged portion of the drum. The drum then fuses the image onto the paper by pressure and heat. See electrophotographic. Electrosensitive Dots are charged onto specially coated silver- colored paper, usually in a serial fashion. The charge removes the aluminum coating, leaving a black image. Electrostatic Dots are charged onto specially coated paper, usually a line at a time. An ink adheres to the charges that become embedded into the paper by pressure or by heat. Ink Jet Continuous streams of ink are sprayed onto paper, or droplets of ink generate a dot matrix image, usually in a serial fashion. Another technique uses ink in a solid form, which is melted just before it is ejected. Ionographic A technology that uses ion deposition and is similar to direct electrostatic, except that in this type of indirect electrostatic, the image is formed on a dielectric surface and then transferred to plain paper. Magnetographic A magnetic image is created by a set of recording heads across a magnetic drum. Monocomponent toner is applied to the drum to develop the image. It is transferred to paper by light pressure and an electrostatic field. The toner is then fused by heat. Thermal Dots are burned onto specially coated paper that turns black or blue when heat is applied to it. A line of heat elements forms a dot matrix image as the paper is passed across it, or a serial head with heating elements is passed across the paper. Thermal Wax Transfer Dots of ink are transferred from a mylar ribbon onto paper by passing the ribbon and the paper across a line of heat elements, or by passing a serial head with heating element across the paper. See thermal wax transfer. printer buffer Memory device that accepts printer output from one or more computers and transmits it to the printer. It lets the computer dispose of its printer output at full speed without waiting for each page to print. Printer buffers with automatic switching are connected to two or more computers and accept their output on a first-come, first-served basis. printer cable Wire that connects a printer to a computer. On a PC, the cable has a 25-pin DB-25 male connector for the computer and a 36-pin Centronics male connector for the printer. printer driver Software routine that converts an application program's printing request into the language the printer understands. printer engine Unit within the printer that does the actual printing. For example, in a laser printer, it is the "copy machine" unit, which transfers and fuses the toner onto the paper. It is specified by its resolution and speed. printer file (1) Document in print image format ready to be printed. See print to disk. (2) Same as printer driver. printer font Font used for printing. Printer and screen resolutions are not the same, thus fonts generated for the printer will not display accurately on screen. Contrast with screen font. printout (PRINTer OUTput) Same as hard copy. privacy Authorized distribution of information (who has a right to know?). Contrast with security, which deals with unauthorized access to data. Private Eye Headband-mounted LED display system from Reflection Technology, Waltham, MA, that plugs into a PC. Its 1x1" screen gives the appearance of a 12" monitor floating in space in front of the viewer. private file File made available only to the user that created it. Contrast with public file. private line (1) Dedicated line leased from a common carrier. (2) Line owned and installed by the user. PRMD (PRivate Management Domain) Inhouse e-mail service. See X.400. PRN (PRiNter) DOS name for the first connected parallel port. See DOS device names. problem-oriented language Computer language designed to handle a particular class of problem. For example, COBOL was designed for business, FORTRAN for scientific and GPSS for simulation. procedural language Programming language that requires programming discipline, such as COBOL, FORTRAN, BASIC, C, Pascal and dBASE. Programmers writing in such languages must develop a proper order of actions in order to solve the problem, based on a knowledge of data processing and programming. Contrast with non-procedural language. The following dBASE example shows procedural and non-procedural language to list a file.  Procedural Non-procedural (interactive) USE FILEX USE FILEX DO WHILE .NOT. EOF LIST NAME, AMOUNTDUE ? NAME, AMOUNTDUE SKIP ENDDO procedure (1) Manual procedures are human tasks. (2) Machine procedures are lists of routines or programs to be executed, such as described by the job control language (JCL) in a mini or mainframe, or the batch processing language in a personal computer. (3) In programming, another term for a subroutine or function. procedure oriented Application that forces the user to follow a predefined path from step A to step B. Data entry programs are typical examples. Contrast with event driven. process To manipulate data in the computer. The computer is said to be processing no matter what action is taken upon the data. It may be updated or simply displayed on screen. In order to evaluate a computer system's performance, the time it takes to process data internally is analyzed separately from the time it takes to get it in and out of the computer. I/O is usually more time consuming than processing. See computer (The 3 C's). process bound Excessive amount of processing causing an imbalance between I/O and processing. Process-bound applications may slow down other users in a multiuser system. A personal computer is process bound when it is recalculating a spreadsheet, for example. process control Automated control of a process, such as a manufacturing process or assembly line. It is used extensively in industrial operations, such as oil refining, chemical processing and electrical generation. It uses analog devices to monitor real-world signals and digital computers to do the analysis and controlling. It makes extensive use of analog/digital, digital/analog conversion. processing Manipulating data within the computer. The term is used to define a variety of computer functions and methods. See centralized processing, distributed processing, batch processing, transaction processing, multiprocessing and computer (The 3 C's). processor (1) Same as CPU. (2) May refer to software. See language processor and word processor. processor unit Same as computer. Procomm Popular PC shareware communications program from Datastorm Technologies, Inc., Columbia, MO, that supports a wide number of protocols and terminals. Procomm Plus is the commercial version with more features. PRODIGY Online information service (partnership of IBM and Sears) that includes weather and stock market reports, airline scheduling and at-home shopping. Users receive a communications program that must be installed in their personal computer, which provides full-screen displays and simplifies the logon. See online services. ProDOS (PROfessional Disk Operating System) Operating system for the Apple II family that superseded Apple's DOS 3.3. It provides a hierarchical file system with file names up to 15 characters in length. production database Central database containing an organization's master files and daily transaction files. production system Computer system used to process an organization's daily work. Contrast with a system used only for development and testing or for ad hoc inquiries and analysis. Professional Write Word processing program for DOS and Windows from Software Publishing Corp., Mountain View, CA. It is easy to use and meets the needs of many who write uncomplicated letters and memos. Originally called PFS:Write, it was one of the earliest PC word processors. Professional YAM (Professional Yet Another Modem) PC communications program from Omen Technology, Inc., Portland, OR, for the serious communications user. It is a flexible, full-featured program that supports a wide variety of terminals and protocols. PROFS (PRofessional OFfice System) IBM office automation software for the VM mainframe environment. It provides an e-mail facility for text and graphics, a library service for centrally storing text, electronic calendars and appointment scheduling, and it allows document interchange with DISOSS users. ProgMan See Program Manager. program Collection of instructions that tell the computer what to do. A program is called software; hence, program, software and instructions are synonymous. A program is written in a programming language and is converted into the computer's machine language by software called assemblers, compilers and interpreters. A program is made up of instructions, buffers and constants. Instructions are the directions that the computer will follow (the program's logic). Buffers are reserved space in the program that will accept and hold the data while it's being processed. Constants are fixed values within the program used for processing. See computer (The 3 C's). The program calls for data in an input-process- output sequence. After data has been input into one of the program's buffers from a peripheral device (keyboard, disk, etc.), it is processed. The results are then output to a peripheral device (screen, printer, etc.). If data has been updated, it is output back onto the disk. The application program, which does the actual data processing, does not instruct the computer to do everything. When it is ready for input or needs to output data, it sends a request to the operating system, which performs those services and then turns control back to the application program. program generator See application generator. program logic Sequence of instructions in a program. There are many logical solutions to a problem. If you give a specification to ten programmers, each one may create program logic that is slightly different than all the rest, but the results can be the same. The solution that runs the fastest is usually the most desired, however. Program logic is written using three classes of instructions: sequential processing, selection and iteration. 1. Sequential processing is the series of steps that do the actual data processing. Input, output, calculate and move (copy) instructions are used in sequential processing. 2. Selection is the decision making within the program and is performed by comparing two sets of data and branching to a different part of the program based on the results. In assembly languages, the compare and branch instructions are used. In high-level languages, IF THEN ELSE and CASE statements are used. 3. Iteration is the repetition of a series of steps and is accomplished with DO LOOPS and FOR LOOPS in high-level languages and GOTOs in assembly languages. See loop. program maintenance Updating programs to reflect changes in the organization's business or to adapt to new operating environments. Program Manager Control center for Windows 3.x operation. It provides the means to launch applications and manage the desktop. program state Operating mode of the computer that executes instructions in the application program. Contrast with supervisor state. program statement Phrase in a high-level programming language. One program statement may result in several machine instructions when the program is compiled. program step Elementary instruction, such as a machine language instruction or an assembly language instruction. Contrast with program statement. program-to-program communications Communications between two programs. Often confused with peer-to-peer communications, it is a set of protocols a program uses to interact with another program. Peer-to-peer establishment is the network's responsibility. You can have program-to- program communications in a master-slave environment without peer-to-peer capability. programmable Capable of following instructions. What sets the computer apart from all other electronic devices is its programmability. programmable calculator Limited-function computer capable of working with only numbers and not alphanumeric data. programmatic interface Same as API. programmer Person who designs the logic for and writes the lines of codes of a computer program. See application programmer and systems programmer. programmer analyst Person who analyzes and designs information systems and designs and writes the application programs for the system. A programmer analyst is both systems analyst and applications programmer. Programmer's Switch Physical buttons included with the Macintosh (fkey on the LC) that include a System Reset button and a Debugging button that will invoke MacsBug if present or switch to the built in monitor in ROM. programming Creating a computer program. The steps are: 1. Developing the program logic to solve the particular problem. 2. Writing the program logic in a specific programming language (coding the program). 3. Assembling or compiling the program to turn it into machine language. 4. Testing and debugging the program. 5. Preparing the necessary documentation. The logic is the most difficult part of programming. Writing the language statements is comparatively easy once the solution has been developed. However, regardless of how difficult the program may be, documenting it is considered the most annoying activity by most programmers. programming interface See API. programming language Language used to write instructions for the computer. It lets the programmer express data processing in a symbolic manner without regard to machine-specific details. The statements that are written by the programmer are called source language, and they are translated into the computer's machine language by programs called assemblers, compilers and interpreters. For example, when a programmer writes MULTIPLY HOURS TIMES RATE, MULTIPLY must be turned into a code that means multiply, and HOURS and RATE must be turned into memory locations where those items of data are actually located. Like human languages, each programming language has its own grammar and syntax. There are many dialects of the same language, and each dialect requires its own translating system. Standards have been set by ANSI for many programming languages, and ANSI-standard languages are dialect free. However, it can take years for new features to be included in ANSI standards, and new dialects inevitably spring up as a result. Programming languages fall into two categories: low-level assembly languages and high-level languages. Assembly languages are available for each CPU family, and each assembly instruction is translated into one machine instruction by the assembler program. With high-level languages, a programming statement may be translated into one or several machine instructions by the compiler. Following is a synopsis of the major high-level languages. Look up each one for more details. Ada Comprehensive, Pascal-based language used by the Dept. of Defense. ALGOL International language for expressing algorithms. APL Used for statistics and mathematical matrices. Requires special keyboard symbols. BASIC Developed as a timesharing language in the 1960s. Widely used in microcomputer programming. C Developed in the 1980s at AT&T. Widely used to develop commercial applications. UNIX is written in C. C++ Object-oriented version of C that is becoming very popular. COBOL Developed in the 1960s. Widely used for mini and mainframe programming. Also available for personal computers. dBASE Widely used in business applications. Offshoots of dBASE ("Xbase" languages) are Clipper, Quicksilver, FoxBase and FoxPro. FORTH Developed in the 1960s. Used in process control and game applications. FORTRAN Developed in 1954 by IBM. First major scientific programming language. Some commercial applications have been developed in it. LISP Developed in 1960. Used for AI applications. Its syntax is very different than other languages. Logo Developed in the 1960s. Noted for its ease of use, it includes "turtle graphics" drawing functions. Modula-2 Enhanced version of Pascal introduced in 1979. MUMPS Originally Massachusetts Utility MultiProgramming System, it includes its own database. Widely used in medical applications. Pascal Originally an academic language developed in the 1970s. Borland commercialized it with its Turbo Pascal. Prolog Developed in France in 1973. Used throughout Europe and Japan for AI applications. REXX Runs on IBM mainframes. Used as a general purpose macro language. progressive scan Same as non-interlaced. project manager Software used to monitor the time and materials on a project. All tasks to complete the project are entered into the database, and the program computes the critical path, the series of tasks with the least amount of slack time. Any change in the critical path slows down the entire project. Prokey Keyboard macro processor for PCs from RoseSoft, Inc., Bellevue, WA, that allows users to eliminate repetitive typing by setting up an occurrence of text or a series of commands as a macro. Prolog (PROgramming in LOGic) Programming language used for developing AI applications (natural language translation, expert systems, abstract problem solving, etc.). Developed in France in 1973, it is used throughout Europe and Japan and is gaining popularity in the U.S. Similar to LISP, it deals with symbolic representations of objects. The following example, written in Univ. of Edinburgh Prolog, converts Fahrenheit to Celsius:  convert:- write('Enter Fahrenheit'),  read(Fahr),  write('Celsius is '),  Cent is (5 * (Fahr - 32)) / 9,  write(Cent),nl.  PROM (Programmable Read Only Memory) Permanent memory chip that is programmed, or filled, by the customer rather than by the chip manufacturer. Contrast with ROM, which is programmed at the time of manufacture. See PROM programmer. PROM blower Same as PROM programmer. PROM programmer Device that writes instructions and data into PROM and/or EPROM chips. The bits in a new PROM are all 1s (continuous lines). The PROM programmer only creates 0s, by "blowing" the middle out of the 1s. The bits in EPROMs, which are not permanently altered, can be erased under ultraviolet light and reprogrammed. prompt Software message that requests action by the user; for example, "Enter employee name." Command-driven systems issue a cryptic symbol when ready to accept a command; for example, in dBASE it is simply a dot (.), in UNIX, a $, and in DOS, the venerable C:\>. propagation Transmission (spreading) from one place to another. propagation delay Time it takes to transmit a signal from one place to another. property list In a list processing language, an object that is assigned a descriptive attribute (property) and a value. For example, in Logo, PUTPROP "KAREN "LANGUAGE "PARADOX assigns the value PARADOX to the property LANGUAGE for the person named KAREN. To find out what language Karen speaks, the Logo statement PRINT GETPROP "KAREN "LANGUAGE will generate PARADOX as the answer. proportional spacing Character spacing based on the width of each character. For example, an I takes up less space than an M. In monospacing (fixed), the I and M each take up the same space. See kerning. proprietary software Software owned by an organization or individual. Contrast with public domain software. Protected Mode In Intel 286s and up, an operational state that allows the computer to address all of memory. It also prevents an errant program from entering into the memory boundary of another. See Real Mode, Virtual 8086 Mode and memory protection. protocol Rules governing transmitting and receiving of data. See communications protocol and OSI. protocol stack Hierarchy of protocols used in a communications network. See OSI. protocol suite Same as protocol stack. prototyping Creating a demo of a new system. Prototyping is essential for clarifying information requirements. The design of a system (functional specs) must be finalized before the system can be built. While analytically-oriented people may have a clear picture of requirements, others may not. Using fourth-generation languages, systems analysts and users can develop the new system together. Databases can be created and manipulated while the user monitors the progress. Once users see tangible output on screen or on paper, they can figure out what's missing or what the next question might be if this were a production system. If prototyping is carefully done, the end result can be a working system. Even if the final system must be reprogrammed in other languages for standardization or machine efficiency, prototyping has served to provide specifications for a working system rather than a theoretical one. Prt Sc See print screen. PS (Personal Services) IBM office automation software for PCs, minis and mainframes, which includes word processing, electronic mail and library services. PS/1 IBM home computer series introduced in 1990 that features an integrated monitor and easy-to-open case. Original models use the 286 CPU and PC bus. See PC. PS/2 IBM personal computer series introduced in 1987 that supersedes the original PC line. It features the 3.5" microfloppy disk, VGA graphics and Micro Channel bus. The 3.5" disks and VGA are now common in all PCs and Micro Channel PCs are offered by some non-IBM vendors. Smaller PS/2 models use the original PC bus. See PC. PS/2 bus Same as Micro Channel. pseudo compiler Compiler that generates a pseudo language, or intermediate language, which must be further compiled or interpreted for execution. pseudo-duplexing Communications technique that simulates full-duplex transmission in a half-duplex line by turning the line around very quickly. pseudo language Intermediate language generated from a source language, but not directly executable by a CPU. It must be interpreted or compiled into machine language for execution. It facilitates the use of one source language for different types of computers. See "ANDF" in OSF definition. PSK See DPSK. PSN (1) (Packet-Switched Network) Communications network that uses packet switching technology. (2) See Personal Server Network. PSS See EPSS. PSTN (Public Switched Telephone Network) Worldwide voice telephone network. PSW (Program Status Word) Hardware register that maintains the status of the program being executed. PTOCA (Presentation Text Object Content Architecture) See MO:DCA. PTT (Postal, Telegraph & Telephone) Governmental agency responsible for combined postal, telegraph and telephone services in many European countries. PU (Physical Unit) In SNA, software responsible for managing the resources of a node, such as data links. A PU supports a connection to the host (SSCP) for gathering network management statistics. PU 2.1 (Physical Unit 2.1) In SNA, the original term for Node Type 2.1, which is software that provides peer-to-peer communications between intelligent devices (PCs, workstations, minicomputers). Only LU 6.2 sessions are supported between Type 2.1 nodes (PU 2.1). public domain software Software in which ownership has been relinquished to the public at large. See freeware and shareware. public file File made available to all other users connected to the system or network. Contrast with private file. Publish and Subscribe Macintosh System 7 capability that provides hot links between files. All or part of a file can be published into an "edition file," which is imported into a subscriber file. When any of the published files are updated, the subscriber file is also updated. puck Puck-like tablet cursor used on a digitizer tablet. pull-down menu Also called a pop-down menu, a menu that is displayed from the top of the screen downward when its title is selected. The menu remains displayed while the mouse button is depressed. To select a menu option, the highlight bar is moved (with the mouse) to the appropriate line and the mouse button is let go. The drop-down menu is a variation that keeps the menu open after its title is selected. To select a menu option, the highlight bar is moved to the line and the mouse button is clicked. Key commands may also activate drop-down menus. pulse code modulation See PCM. pulse level device Disk drive or other device that inputs and outputs raw voltages. Data coding/decoding is in the controller the device. Contrast with bit level device. PUMA (Programmable Universal Micro Accelerator) Chips and Technolgies' chip set that accelerates graphics operations for the screen and printer. punch block Also called a quick-connect block, a device that interconnects telephone lines from remote points. The wires are pushed, or punched, down into metal teeth that strip the insulation and make a tight connection. punched card Early storage medium made of thin cardboard stock that holds data as patterns of punched holes. Each of the 80 or 96 columns holds one character. The holes are punched by a keypunch machine or card punch peripheral and are fed into the computer by a card reader. Although still used as turnaround documents, punched cards are practically obsolete. However, from 1890 until the 1970s, they were synonymous with data processing. Concepts were simple: the database was the file cabinet; a record was a card. Processing was performed on separate machines called sorters, collators, reproducers, calculators and accounting machines. push/pop Instructions that store and retrieve an item on a stack. Push enters an item on the stack, and pop retrieves an item, moving the rest of the items in the stack up one level. See stack. push/pull tractor Printer tractor that can be switched from pushing paper onto the platen to pulling it from the platen. Single-sheet continuous forms can be pushed, but most multipart forms and labels must be pulled to prevent jamming. put In programming, a request to store the current record in an output file. Contrast with get. PVGA (Paradise VGA) VGA display board or VGA chips from Paradise Division of Western Digital. Px64 CCITT standard for transmitting audio and video in 64 Kbits/sec ISDN channels (P represents number of channels used). Although video conferencing can be done in only one or two channels, more are required for quality viewing of motion. Q-bus Bus architecture used in Digital's PDP-11 and MicroVAX series. Q&A Integrated PC file manager and word processor from Symantec Corp., Cupertino, CA, that includes mail merge capability as well as a programming language for customizing data entry forms and reports. Its Intelligent Assistant feature provides a query language that can learn new words from the user. QAM (1) (Quadrature Amplitude Modulation) Modulation technique that generates four bits out of one baud. For example, a 600 baud line (600 shifts in the signal per second) can effectively transmit 2,400 bps using this method. Both phase and amplitude are shaped with each baud, resulting in four possible patterns. (2) (Quality Assessment Measurement) System used to measure and analyze voice transmission. QBasic BASIC interpreter from Microsoft that comes with DOS starting with DOS 5. It supersedes Microsoft's GW-BASIC and includes REMLINE.BAS, a program that helps convert GW-BASIC programs to QBasic. QBE (Query By Example) Method for describing a query originally developed by IBM for mainframes. A replica of an empty record is displayed and the search conditions are typed in under their respective columns. The following query selects all Pennsylvania records that have a balance due of $5000 or more. City State Balance due 敖陳陳陳陳陳賃陳陳賃陳陳陳陳陳陳朕 PA >=5000 A query by example QCIF (Quarter CIF) Video format that transmits 9.115 Mbits/sec at 30 frames/sec, one quarter the speed of CIF. See H.261. QEMM-386 (Quarterdeck EMM-386) Popular DOS memory manager for 386s and up from Quarterdeck Office Systems, Santa Monica, CA. Its Stealth feature in Version 6.0 remaps ROM BIOS routines into EMS to free up high DOS memory. It is also part of DESQview 386. QEMM-50/60 is a version for PS/2 Models 50 and 60 (286s). QIC (Quarter Inch Cartridge Drive Standards, Inc.) International trade association that develops standards for 1/4" (6.35mm) magnetic tape drives and cartridges. QIC-compatible products use a serpentine recording method.  Recording Media Storage  Format Type (MB) Interfaces  MINICARTRIDGE QIC-40 DC2000 40 QIC-107, 115, 117 QIC-80 DC2080 80 QIC-107, 115, 117 DC2080 120 QIC-100 DC2000 20/40 QIC-103, 108 QIC-128 DC2110 86 QIC-103, 108 DC2165 128 QIC-385M QIC-143 385 Floppy, IDE QIC-410M QIC-143 410 SCSI-2 QIC-6GB(M) QIC-138 6GB* SCSI-2 CARTRIDGE QIC-24 DC600A 60 QIC-02, 36, SCSI QIC-120 DC6150 125 QIC-02, SCSI QIC-150 DC6150 150 QIC-02, SCSI DC6250 250 SCSI, SCSI-2 QIC-525 DC6320 320 QIC-02, SCSI, SCSI-2 DC6525 525 QIC-1000C QIC-136 1GB SCSI, SCSI-2 QIC-1350 QIC-137 1.35GB SCSI-2 QIC-2100C QIC-137 2.1GB SCSI-2 QIC-20GB(C) QIC-139 20GB* SCSI-2 *With QIC-122 or QIC-130 built-in data compression. QMF (Query Management Facility) IBM fourth-generation language for end-user interaction with DB2. QNX Multiuser, multitasking, realtime operating system for PCs from Quantum Software Systems, Kanata, Ontario, noted for its low-memory requirement and rapid response. Similar to UNIX, it has been in use since the early 1980s. quadbit Group of four bits used in QAM modulation. quadrillion One thousand times one billion. See femtosecond. quantize To break into discrete values for sampling purposes. QuarkXpress Desktop publishing program for the Macintosh and Windows from Quark, Inc., Denver, CO. Originally developed for the Mac, it is noted for its precise typographic control and advanced text and graphics manipulation. quartz crystal Slice of quartz ground to a prescribed thickness that vibrates at a steady frequency when stimulated by electricity. The tiny crystal, about 1/20th by 1/5th of an inch, creates the computer's heartbeat. Quattro Pro PC spreadsheet from Borland that provides advanced graphics and presentation capabilities. It has an optional interface that is keystroke, macro and file compatible with Lotus 1-2-3. Version 2.0 adds goal seeking, 3-D graphing and the ability to create multi-layered slide shows. query To interrogate a database (count, sum and list selected records). Contrast with report, which is usually a more elaborate printout with headings and page numbers. The report may also be a selective list of items; hence, the two terms may refer to programs that produce the same results. query by example See QBE. query language Generalized language that allows a user to select records from a database. It uses a command language, menu-driven method or a query by example (QBE) format for expressing the matching condition. Query languages are usually included in DBMSs, and stand-alone packages are available for interrogating files in non-DBMS applications. See query program. query program Software that counts, sums and retrieves selected records from a database. It may be part of a large application and be limited to one or two kinds of retrieval, such as pulling up a customer account on screen, or it may refer to a query language that allows any condition to be searched and selected. queue Pronounced "Q." Temporary holding place for data. See message queue and print queue. Quick B CompuServe's communications protocol for downloading files. QuickBASIC Popular BASIC compiler from Microsoft that adds advanced features to the BASIC language. QuickC C compiler from Microsoft that is compatible with its larger C compiler and is used by the beginner or occasional programmer. QuickC for Windows is a version that works entirely within Windows environment for developing Windows applications. It includes the QuickWin library. Quickdraw Graphics display system built into the Macintosh. It accepts commands from the application and draws the corresponding objects on the screen. It provides a consistent interface that software developers can work with. Quicken Popular personal financial management program for PCs and Macs from Intuit, Menlo Park, CA. It writes checks, organizes investments and produces a variety of financial reports. QuickPascal Pascal compiler from Microsoft that is compatible with Turbo Pascal and provides object oriented capabilities. Quicksilver Family of dBASE III PLUS compilers originally developed by WordTech Systems, Inc. In 1992, the technology was acquired by Borland. See Arago. QuickTime Multimedia extensions to Macintosh's System 7 that add sound and video capabilities. QuickWin Library of C and FORTRAN routines from Microsoft that allows quick porting of DOS applications to the Windows environment. Character-based apps run in resizable windows. quit To exit the current program. It's a good habit to quit a program before turning the computer off. Some programs don't close all files properly until quit is activated. To quit the DOS version of this Glossary, hold down the Ctrl key and press Q. qwerty keyboard Standard English language typewriter keyboard. Q, w, e, r, t and y are the letters on the top left, alphabetic row. It was originally designed to slow typing to prevent the keys from jamming. See Dvorak keyboard. R3000, R4000 Families of 32-bit and 64-bit RISC processors from MIPS. MIPS licenses the design to other companies. R:BASE Relational DBMS for PCs from Microrim, Inc., Bellevue, WA, that provides interactive data processing, a complete programming language and an application generator. It was the first DBMS to compete with dBASE II in the early 1980s. RACE (Random Access Card Equipment) Early RCA mass storage device. Magnetic cards were released from a cartridge, passed down a raceway and wrapped around a read/write head. It often jammed! RACF (Resource Access Control Facility) IBM mainframe security software introduced in 1976 that verifies user ID and password and controls access to authorized files and resources. rack Frame or cabinet into which components are mounted. rack mounted Components that are built to fit in a metal frame. Electronic devices, such as testing equipment and tape drives, are often rack mounted units. RAD (Rapid Application Development) Approach to systems development that includes automated design and development tools (CASE) and joint application development (JAD). Developed by industry guru, James Martin, it focuses on human management and user involvement as much as on technology. radio Transmission of electromagnetic energy (radiation) over the air or through a hollow tube called a waveguide. Although radio is often thought of as only AM or FM, all airborne transmission is radio, including satellite and line-of-sight microwave. radio buttons Series of on-screen buttons that allow only one selection. If a button is currently selected, it will de-select when another button is selected. radio frequency See RF. radix Base value in a numbering system. For example, in the decimal numbering system, the radix is 10. radix point Location in a number that separates the integral part from the fractional part. For example, in the decimal system, it is the decimal point. ragged right In typography, non-uniform text at the right margin, such as the text you're reading. RAID (Redundant Arrays of Inexpensive Disks) Category of disk arrays (two or more drives working together) that provide increased performance and various levels of error recovery and fault tolerance. The disk controller is designed to perform these techniques. In some cases, RAID can be implemented in software using standard drives and controllers. Level Configuration 0 Single disk only or multiple disks using disk striping only (essentially non-RAID). 1 Uses disk mirroring to provide 100% duplication of data. 2 Highest performance. Uses extra drives to detect 2-bit errors and correct 1-bit errors on the fly. Interleaves by bit or block. 3 Highest performance. Does parity checking but cannot guarantee on-the-fly recovery. Interleaves data by bit or block. 4 Uses dedicated drive for parity. Can be used with only two drives. Interleaves data by sector and can handle multiple I/Os from sophisticated operating systems. 5 Most popular RAID method. Works with two or more drives. Does not require dedicated parity drive. Can be made fault tolerant. RAM (Random Access Memory) Computer's primary workspace. Also true of most memory chips (ROMs, PROMs, etc.), "random" means that the contents of each byte can be directly accessed without regard to the bytes before or after it. RAM chips require power to maintain their content. See dynamic RAM, static RAM and memory. RAM cache See cache. RAM card (1) Printed circuit board containing memory chips that is plugged into a socket within the computer. (2) Credit-card-sized module that contains memory chips and battery. See memory card. RAM chip (Random Access Memory chip) Memory chip. See dynamic RAM, static RAM, RAM and memory. RAM cram Insufficient memory to run applications, especially in DOS PCs with its 1MB memory limit. RAM disk Disk drive simulated in memory. To use it, files are copied from magnetic disk into the RAM disk. Processing is faster, because there's no mechanical disk action, only memory transfers. Updated data files must be copied back to disk before the power is turned off, otherwise the updates are lost. Same as E-disk and virtual disk. RAM refresh Recharging dynamic RAM chips many times per second in order to keep the bit patterns valid. RAM resident Refers to programs that remain in memory in order to interact with other programs or to be instantly popped up when required by the user. See TSR. RAMAC (Random Access Method of Accounting and Control) First hard disk computer introduced by IBM in 1956. All 50 of its 24" platters held a total of five million characters! It was half computer, half tabulator. It had a drum memory for program storage, but I/O was wired by plugboard. RAMDAC (Random Access Memory Digital to Analog Converter) The VGA controller chip that maintains the color palette and converts data from memory into analog signals for the monitor. Ramdrive See DOS RAM disks. RAMIS II IBM mainframe DMBS and DSS from On-Line Software Int'l., Inc., Ft. Lee, NJ. The earlier version of RAMIS II was one of the first database packages with a non-procedural language. random access Same as direct access. random noise Same as Gaussian noise. random number generator Program routine that produces a random number. Random numbers are created easily in a computer, since there are many random events that take place; for example, the duration between keystrokes. Only a few milliseconds' difference is enough to seed a random number generation routine with a different number each time. Once seeded, an algorithm computes different numbers throughout the session. range (1) In data entry validation, a group of values from a minimum to a maximum. (2) In spreadsheets, a series of cells that are worked on as a group. It may refer to a row, column or rectangular block defined by one corner and its diagonally opposite corner. RARP See ARP. RAS (Reliability Availability Serviceability) Originally an IBM term, it refers to a product's quality, availability of optional features and ease of diagnosis and repair. raster display Display terminal that generates dots line by line on the screen. TVs and almost all computer screens use the raster method. Contrast with vector display. raster graphics In computer graphics, a technique for representing a picture image as a matrix of dots. It is the digital counterpart of the analog method used in TV. However, unlike TV, which uses one standard, there are many raster graphics standards. See graphics. Contrast with vector graphics. raster image processor See RIP. Remember... use the acronym first! raster scan Displaying or recording a video image line by line. rasterize To perform the conversion of vector graphics images, vector fonts or outline fonts into bitmaps for display or printing. Unless output is printed on a plotter, which uses vectors directly, all non- bitmapped images must be rasterized into bitmaps for display or printing. See font scaler. raw data Data that has not been processed. ray tracing In computer graphics, the creation of reflections, refractions and shadows on a graphics image. It follows a series of rays from a specific light source and computes each pixel in the image to determine the effect of the light. It is a very process-intensive operation. RBASE See R:BASE. RBHC (Regional Bell Holding Company) Same as RBOC. RBOC (Regional Bell Operating Company) One seven regional telephone companies created by divestiture: Nynex, Bell Atlantic, BellSouth, Southwestern Bell, US West, Pacific Telesis and Ameritech. RCA connector Same as phono connector. RCS (1) (Remote Computer Service) Remote timesharing service. (2) (Revision Control System) UNIX utility that provides version control. Rdb (Relational DataBase/VMS) Relational DBMS from Digital for its VAX series. RDBMS (Relational DataBase Management System) See relational database. RDRAM (Rambus DRAM) Dynamic RAM chip from Rambus, Inc., that transfers data at 500MBytes/sec (3-10 times faster than DRAM and VRAM chips). It requires modified motherboards, but eliminates the need for memory caches. read To input into the computer from a peripheral device (disk, tape, etc.). Like reading a book or playing an audio tape, reading does not destroy what is read. A read is both an input and an output (I/O), since data is being output from the peripheral device and input into the computer. Memory is also said to be read when it is accessed to transfer data out to a peripheral device or to somewhere else in memory. Every peripheral or internal transfer of data is a read from somewhere and a write to somewhere else. read error Failure to read the data on a storage or memory device. Although it is not a routine phenomenon, magnetic and optical recording surfaces can become contaminated with dust or dirt or be physically damaged, and cells in memory chips can malfunction. When a read error occurs, the program will allow you to bypass it and move on to the next set of data, or it will end, depending on the operating system. However, if the damaged part of a disk contains control information, the rest of the file may be unreadable. In such cases, a recovery program must be used to retrieve the remaining data if there is no backup. read only (1) Refers to storage media that permanently hold their content; for example, ROM and CD ROM. (2) File which can be read, but not updated or erased. See file attribute. read-only attribute File attribute that, when turned on, indicates that a file can only be read, but not updated or erased. read/write (1) Refers to a device that can both input and output or transmit and receive. (2) Refers to a file that can be updated and erased. read/write channel Same as I/O channel. read/write head Device that reads (senses) and writes (records) data on a magnetic disk or tape. For writing, the surface of the disk or tape is moved past the read/write head. By discharging electrical impulses at the appropriate times, bits are recorded as tiny, magnetized spots of positive or negative polarity. For reading, the surface is moved past the read/write head, and the bits that are present induce an electrical current across the gap. read/write memory Same as RAM. reader Machine that captures data for the computer, such as an optical character reader, magnetic card reader and punched card reader. A microfiche or microfilm reader is a self-contained machine that reads film and displays its contents. readme file Text file copied onto software distribution disks that contains last-minute updates or errata that have not been printed in the documentation manual. readout (1) Small display device that typically shows only a few digits or a couple of lines of data. (2) Any display screen or panel. real address Same as absolute address. Real Mode Operational state in Intel 286s and up in which the computer functions as an 8086/8088. It is limited to one megabyte of memory. See Protected Mode and Virtual 86 Mode. real storage Real physical memory in a virtual memory system. Realizer Windows development software from Computer Associates that uses a structured superset of BASIC, has its own forms design utilities and includes a runtime module. realtime Immediate response. It refers to process control and embedded systems; for example, space flight computers must respond instantly to changing conditions. It also refers to fast transaction processing systems as well as any electronic operation fast enough to keep up with its real- world counterpart (animating complex images, transmitting live video, etc.). realtime clock Electronic circuit that maintains the time of day. It may also provide timing signals for timesharing operations. realtime compression Quickly compressing and decompressing data. PC products such as Stacker and SuperStor let you create a separate compressed drive on your hard disk. All data written to that drive is compressed and decompressed when read back. Realtime compression is included with DOS 6 (see DOS DoubleSpace). See JPEG. realtime conferencing See teleconferencing (3). realtime image In computer graphics, a graphics image that can be animated on screen in the same time frame as in real life. realtime information system Computer system that responds to transactions by immediately updating the appropriate master files and/or generating a response in a time frame fast enough to keep an operation moving at its required speed. See transaction processing. realtime operating system Master control program that can provide immediate response to input signals and transactions. realtime system Computer system that responds to input signals fast enough to keep an operation moving at its required speed. reasonable test Type of test that determines if a value falls within a range considered normal or logical. It can be made on electronic signals to detect extraneous noise as well as on data to determine possible input errors. reboot To reload the operating system and restart the computer. See boot. receiver Device that accepts signals. Contrast with transmitter. record (1) Group of related fields that store data about a subject (master record) or activity (transaction record). A collection of records make up a file. Master records contain permanent data, such as account number, and variable data, such as balance due. Transaction records contain only permanent data, such as quantity and product code. (2) In certain disk organization methods, a record is a block of data read and written at one time without any relationship to records in a file. record format Same as record layout. record head Device that writes a signal on tape. Some tape drives and all disk drives use a combination read/write head. record layout Format of a data record, which includes the name, type and size of each field in the record. record locking See file and record locking. record mark Symbol used to identify the end of a record. record number Sequential number assigned to each physical record in a file. Record numbers change when the file is sorted or records are added and deleted. records management Creation, retention and scheduled destruction of an organization's paper and film documents. Computer- generated reports and documents fall into the records management domain, but traditional data processing files do not. recovery See backup & recovery, checkpoint/restart and tape backup. rectifier Electrical circuit that converts AC into DC current with the use of diodes that act as one-way valves. Contrast with inverter. recursion In programming, the ability of a subroutine or program module to call itself. It is helpful for writing routines that solve problems by repeatedly processing the output of the same process. redirection Diverting data from its normal destination to another; for example, to a disk file instead of the printer, or to a server's disk instead of the local disk. See DOS redirection and redirector. redirector In a LAN, software that routes workstation requests for data to the server. redundancy check In communications, a method for detecting transmission errors by appending a calculated number onto the end of each segment of data. See CRC. reentrant code Programming routine that can be used by multiple programs simultaneously. It is used in operating systems and other system software as well as in multithreading, where concurrent events are taking place. It is written so that none of its code is modifiable (no values are changed) and it does not keep track of anything. The calling programs keep track of their own progress (variables, flags, etc.), thus one copy of the reentrant routine can be shared by an any number of users or processes. It is analogous to several people baking their own cake by looking at a single recipe on the wall. Everyone keeps track of their own progress on the master recipe by jotting down the step number they're at on their own sheet of paper so they can pick up where they left off. referential integrity Database management safeguard that ensures every foreign key matches a primary key. For example, customer numbers in a customer file are the primary keys, and customer numbers in the order file are the foreign keys. If a customer record is deleted, the order records must also be deleted otherwise they are left without a primary reference. If the DBMS doesn't test for this, it must be programmed into the applications. reflection mapping In computer graphics, a technique for simulating reflections on an object. reflective spot Metallic foil placed on each end of a magnetic tape. It reflects light to a photosensor to signal the end of tape. reflective VGA LCD screen that needs bright ambient light for viewing. Backlit and sidelit screens are much easier to see. reformat (1) To change the record layout of a file or database. (2) To initialize a disk over again. refraction Bending of light, heat or sound as it passes through different materials. refresh To continously charge a device that cannot hold its content. CRTs must be refreshed, because the phosphors hold their glow for only a few milliseconds. Dynamic RAM chips require refreshing to maintain their charged bit patterns. refresh rate (1) Number of times per second that a device is re- energized, such as a CRT or dynamic RAM chip. See vertical scan frequency. (2) In computer graphics, the time it takes to redraw or redisplay an image on screen. regenerator (1) In communications, the same as a repeater. (2) In electronics, a circuit that repeatedly supplies current to a memory or display device that continuously loses its charges or content. ReGIS (REmote Graphics InStruction) Graphics language from Digital used on graphics terminals and first introduced on the PDP-11. register Small, high-speed computer circuit that holds values of internal operations, such as the address of the instruction being executed and the data being processed. When a program is debugged, register contents may be analyzed to determine the computer's status at the time of failure. In microcomputer assembly language programming, programmers reference registers routinely. Assembly languages in larger computers are often at a higher level. register level compatibility Hardware component that is 100% compatible with another device. It implies that the same type, size and names of registers are used. regression analysis Statistical technique for detecting relationships among multiple properties of observations in a sample. related files Two or more data files that can be matched on some common condition, such as account number or name. relational algebra (1) Branch of mathematics that deals with relations; for example, AND, OR, NOT, IS and CONTAINS. (2) In relational database, a collection of rules for dealing with tables; for example, JOIN, UNION and INTERSECT. relational calculus Rules for combining and manipulating relations; for example De Morgan's law, "the complement of a union is equal to the union of the complements." relational database Database organization method that links files together as required. In non-relational systems (hierarchical, network), records in one file point to the locations of records in another, such as customers to orders and vendors to purchases. These are fixed links set up ahead of time to speed up daily processing. In a relational database, relationships between files are created by comparing data, such as account numbers and names. A relational system has the flexibility to take any two or more files and generate a new file from the records that meet the matching criteria. Routine queries often involve more than one data file. For example, a customer file and an order file can be linked in order to ask a question that relates to information in both files, such as the names of the customers that purchased a particular product. In practice, a pure relational query can be very slow. In order to speed up the process, indexes are built and maintained on the key fields used for matching. Sometimes, indexes are created "on the fly" when the data is requested. The term was coined in 1970 by Edgar Codd, whose objective was to easily accomodate a user's ad hoc request for selected data.  Relational terms Common terms table or relation file tuple record attribute field relational operator A symbol that specifies a comparison between two values.  Relational Operator Symbol EQ Equal to = NE Not equal to <> or # or != GT Greater than > GE Greater than or equal to >= LT Less than < LE Less than or equal to <= relational spreadsheet See spreadsheet. relative address Memory address that represents some distance from a starting point (base address), such as the first byte of a program or table. The absolute address is derived by adding it to the base address. relative vector In computer graphics, a vector with end points designated in coordinates relative to a base address. Contrast with absolute vector. relay Electrical switch that allows a low power to control a higher one. A small current energizes the relay, which closes a gate, allowing a large current to flow through. Relay Gold PC communications program from Microcom, Inc., Norwood, MA, that provides standard asynchronous transmission as well as mainframe file transfer and LAN support. relocatable code Machine language that can be run from any memory location. See base/displacement. REM (REMarks) Programming language statement used to document the program and contains no executable code. remedial maintenance Repair service that is required due to a malfunction of the product. Contrast with preventive maintenance. remote access software See remote control software. remote batch See RJE. remote communications (1) Communicating via long distances. (2) See remote control software. remote control software Software, installed in both machines, that allows a user at a local computer to have control of a remote computer via modem. Both users run the remote computer. It is used to teach remote students as well as provide technical support. See door. remote job entry See RJE. removable disk Disk unit that is inserted into a disk drive for reading and writing and removed when not required; for example, floppy disks, disk cartridges and disk packs. render To draw a real-world object as it actually appears. rendering In computer graphics, creating a 3-D image that incorporates the simulation of lighting effects, such as shadows and reflection. Renderman interface Graphics format from Pixar, Point Richmond, CA, that uses photorealistic image synthesis. Developer's Renderman (PCs and UNIX) and Mac Renderman (Macintosh) are Pixar programs that apply photorealistic looks and surfaces to 3-D objects. repeater In communications, a device that amplifies or regenerates the data signal in order to extend the transmission distance. Available for both analog and digital signals, it is used extensively in long distance transmission. It is also used to tie two LANs of the same type together. See bridge and router. report Printed or microfilmed collection of facts and figures with page numbers and page headings. See report writer and query. report file File that describes how a report is printed. report format Layout of a report showing page and column headers, page numbers and totals. report generator Same as report writer. report writer Software that prints a report based on a description of its layout. As a stand-alone program or part of a DBMS or file manager, it can sort selected records into a new sequence for printing. It may also print standard mailing labels. A report is described by entering text for the page header and stating the position of the print columns (data fields) and which ones are totalled or subtotalled. Once created, the description is stored in a report file for future use. Developed in the early 1970s, report writers (report generators) were the precursor to query languages and were the first programs to generate computer output without having to be programmed. repository Database of information about applications software that includes author, data elements, inputs, processes, outputs and interrelationships. It may be the central core of a CASE system; for example, Repository Manager in IBM's AD/Cycle is designed to integrate third-party CASE products. reproducer Early tabulating machine that duplicated punched cards. reprographics Duplicating printed materials using various kinds of printing presses and high-speed copiers. ResEdit (Resource Editor) Macintosh system utility used to edit the resource fork. reserved word Verb or noun in a programming or command language that is part of the native language. reset button Computer button or key that reboots the computer. All current activities are stopped cold, and any data in memory is lost. On a printer, the reset button clears the printer's memory and readies it to accept new data. resident module The part of a program that must remain in memory at all times. Instructions and data that stay in memory can be accessed instantly. resident program Program that remains in memory at all times. See TSR. resistor Electronic component that resists the flow of current in an electronic circuit. resolution Degree of sharpness of a displayed or printed character or image. On screen, resolution is expressed as a matrix of dots. VGA resolution of 640x480 means 640 dots across each of 480 lines. Sometimes the number of colors are added to the spec; for example, 640x480x16 or 640x480x256. The same resolution looks sharper on a small screen than a large one. For printers, resolution is expressed as the number of dots per linear inch. 300 dpi means 90,000 dots per square inch (300x300). Laser printers and plotters have resolutions from 300 to 1000 dpi and more, whereas most display screens provide less than 100 dpi. That means jagged lines on screen may smooth out when they print. resolve To change, transform or solve a problem. The phrase "external references are resolved" refers to determining the addresses that link modules together; that is, solving the unknown links. resource compiler In a graphical interface (GUI), software that converts and links a resource (menu, dialog box, icon, font, etc.) into the executable program. resource fork Resource part of a Macintosh file. For example, in a text document, it contains format codes with offsets into the text in the data fork. In a program, it contains executable code, menus, windows, dialog boxes, buttons, fonts and icons. response time Time it takes for the computer to comply with a user's request, such as looking up a customer record. restart To resume computer opertion after a planned or unplanned termination. See boot, warm boot and checkpoint/restart. restricted function Computer or operating system function that cannot be used by an application program. retrieve To call up data that has been stored in a computer system. When a user queries a database, the data is retrieved into the computer first and then transmitted to the screen. return key Also called the enter key, the keyboard key used to signal the end of a line of data or the end of a command. In word processing, return is pressed at the end of a paragraph, and a return code is inserted into the text at that point. See CR.  敖陳 敖陳 敖陳陳朕  { [ } ]  青陳 青陳  敖陳 敖陳  " ' 潰 Enter  青陳 青陳陳陳陳潰  Standard Return Key Placement reusability Ability to use all or the greater part of the same programming code or system design in another application. reverse engineer To isolate the components of a completed system. When a chip is reverse engineered, all the separate circuits that make up the chip are identified. reverse polish notation Mathematical expression in which the numbers precede the operation. For example, 2 + 2 would be expressed as 2 2 +, and 10 - 3 * 4 would be 10 3 4 * -. See FORTH. reverse video Display mode used to highlight characters on screen. For example, if the normal display mode is black on white, reverse video would be white on black. revision level See version number. REXX (REstructured EXtended eXecutor) IBM mainframe structured programming language that runs under VM/CMS and MVS/TSO. It can be used as a general- purpose macro language that sends commands to application programs and to the operating systems. REXX is also included in OS/2 Version 2.0. The following REXX example converts Fahrenheit to Celsius: Say "Enter Fahrenheit "  Pull FAHR  Say "Celsius is " (FAHR - 32) * (5 / 9) RF (Radio Frequency) Range of electromagnetic frequencies above the audio range and below visible light. All broadcast transmission, from AM radio to satellites, falls into this range, which is between 30KHz and 300GHz. See RF modulation. RF/ID (Radio Frequency/IDentification) Identification system that uses tags that transmit a wireless message. The tag gets its power from a hand-held gun/reading unit. RF modulation Transmission of a signal through a carrier frequency. In order to connect to a TV's antenna input, some home computers and all VCRs provide RF modulation of a TV channel, usually Channel 3 or 4. See FCC class. RF shielding Material that prohibits electromagnetic radiation from penetrating it. Personal computers and electronic devices used in the home must meet U.S. government standards for electromagnetic interference. RFI (Radio Frequency Interference) High-frequency electromagnetic waves that eminate from electronic devices such as chips. RFP (Request For Proposal) Document that invites a vendor to submit a bid for hardware, software and/or services. It may provide a general or very detailed specification of the system. RFT See DCA. RGB (Red Green Blue) Video color generation method that displays colors as varying intensities of red, green and blue dots. When all three are turned on high, white is produced. As intensities are equally lowered, shades of gray are derived. The base color of the screen appears when all dots are off. See colors. RGB monitor (1) Video display screen that requires separate red, green and blue signals from the computer. It generates a better image than composite signals (TV) which merge the three colors together. It comes in both analog and digital varieties. (2) Sometimes refers to a CGA monitor that accepts digital RGB signals. ribbon cable Thin, flat, multiconductor cable that is widely used in electronic systems; for example, to interconnect peripheral devices to the computer internally. rich e-mail E-mail annotated with voice messages. RIFF (Resource Interchange File Format) Multimedia data format jointly introduced by IBM and Microsoft. See MCI. right justify Same as flush right. rightsizing Selecting a computer system, whether micro, mini or mainframe, that best meets the needs of the application. rigid disk Same as hard disk. ring One stage or level in a set of prioritized stages or levels, typically involved with security and password protection. ring network Communications network that connects terminals and computers in a continuous loop. RIP (1) (Raster Image Processor) In computer graphics, the component (hardware, software or both) that prepares data for a raster output device (screen or printer). RIPs are designed for a specific type of input, such as vectors, PostScript as well as different raster data. (2) (Routing Information Protocol) Early BSD UNIX routing protocol used within a small network. RISC (Reduced Instruction Set Computer) Computer architecture that reduces chip complexity by using simpler instructions. RISC compilers have to generate software routines to perform complex instructions that were previously done in hardware by CISC computers. In RISC, the microcode layer and associated overhead is eliminated. RISC keeps instruction size constant, bans the indirect addressing mode and retains only those instructions that can be overlapped and made to execute in one machine cycle or less. The RISC chip is faster than its CISC counterpart and is designed and built more economically. RISC System/6000 See RS/6000. RJ-11 Four or six-wire telephone connector. The four- wire plug and socket is the common connector for telephone handsets and for plugging telephones and modems into wall outlets. RJE (Remote Job Entry) Transmitting batches of transactions from a remote terminal or computer. The receiving computer processes the data and may transmit the results back to the RJE site for printing. RJE hardware at remote sites can employ teleprinters with disk or tape storage or complete computer systems. RLE See run length encoding. RLL (Run Length Limited) Magnetic disk encoding method that packs 50% more bits into the same space than the earlier MFM method. It is used with RLL, IDE, ESDI, SCSI, SMD and IPI interfaces. The "run length" is the number of consecutive 0s before a 1 bit is recorded. MFM is actually a run length of 1,3; not less than one or more than three "no pulses" separating adjacent pulses. RLL increases the run length over MFM; for example, RLL 2,7 means not less than two or more than seven 0s before a 1 is recorded. ARLL (Advanced RLL) is RLL 3,9. See hard disk. RLL interface See ST506 RLL. RMS (1) (Record Management Services) File management system used in VAXs. (2) (Root Mean Square) Method used to measure electrical output in volts and watts. RO terminal (Receive Only terminal) Printing device only (no keyboard). RoboCAD PC CAD program from Robo Systems Int'l., Inc., Newtown, PA, that includes a wide variety of features and text functions. It provides up to 256 colors and layers, has two drawing pages and a scratch pad, and can transfer data to its solid modeling program. robot Stand-alone hybrid computer system that performs physical and computational activities. It is a multiple-motion device with one or more arms and joints that is capable of performing many different tasks like a human. It can be designed similar to human form, although most industrial robots don't resemble people at all. It is used extensively in manufacturing for welding, riveting, scraping and painting. Office and consumer applications are also being developed. Robots, designed with AI, can respond to unstructured situations. For example, specialized robots can identify objects in a pile, select the objects in the appropriate sequence and assemble them into a unit. Robots use analog sensors for recognizing real- world objects and digital computers for their direction. Analog to digital converters convert temperature, motion, pressure, sound and images into binary code for the robot's computer. The computer directs the physical actions of the arms and joints by pulsing their motors. robotics Art and science of the creation and use of robots. robust Refers to a solid program that works properly under all normal and most abnormal conditions. roll in/roll out Swapping technique for freeing up memory temporarily in order to perform another task. The current program or program segment is stored (rolled out) on disk, and another program is brought into (rolled in) that memory space. rollback Database management system feature that reverses the current transaction out of the database, returning the database to its former state. This is done when some failure interrupts a half- completed transaction. rollover See n-key rollover. ROM (Read Only Memory) Memory chip that permanently stores instructions and data. Its contents are created at the time of manufacture and cannot be altered. Used extensively to store control routines in personal computers (ROM BIOS) and in peripheral controllers, it is also used in plug-in cartridges for printers, video games and other systems. See PROM, EPROM and EEPROM. ROM BIOS (ROM Basic Input Output System) Instructions contained in a ROM chip that activate peripheral devices in a PC. It includes routines for the keyboard, screen, disk, parallel and serial port and for internal services such as time and date. It accepts requests from the device drivers in the operating system as well as from application programs. It also contains autostart functions that test the system on startup and prepare the computer for operation. It searches for other BIOS's on the plug-in boards and sets up pointers (interrupt vectors) in memory to access BIOS routines. It loads the operating system and passes control to it. BIOSs prior to 1990 may not be compatible with new software and peripherals. In order to use devices such as 3.5" diskettes, 101-key keyboards, IDE drives as well as provide compatibility with Windows, NetWare and other applications, you can upgrade an older PC with a new BIOS. The following firms specialize in ROM BIOS upgrades: UNICORE SOFTWARE 800/800-BIOS 1538 Turnpike St. N. Andover, MA 01845 UPGRADES, ETC. 800/955-3527 2432-A Palma Drive Ventura, CA 93003 ROM BIOS swapping Alternating areas in the UMA (640K-1M) between ROM BIOSs and applications as needed. ROM card Credit-card-sized module that contains permanent software or data. See memory card. ROMable Machine language capable of being programmed into a ROM chip. Being "read only" the chip cannot be updated and ROMable programs must use RAM or disk for holding changing data. root directory In hierarchical file systems, the starting point in the hierarchy. When the computer is first started, the root directory is the current directory. Access to directories in the hierarchy requires naming the directories that are in its path. See path and DOS abc's. rotational delay Amount of time it takes for the disk to rotate until the required location on the disk reaches the read/write head. round robin Continuously repeating sequence, such as the polling of a series of terminals, one after the other, over and over again. router Computer system that routes messages from one LAN (local area network) to another. It is used to internetwork similar and dissimilar networks and can select the most expedient route based on traffic load, line speeds and costs and network failures. Routers maintain address tables for all nodes in the network and work at OSI layer 3. See intermediate node routing. Routers are used to break apart the LAN into smaller LANs for improved security, troubleshooting and performance. Routers with high-speed (gigabit) buses may serve as an internet backbone, connecting all networks in the enterprise. See bridge, brouter, gateway and hub. routine Set of instructions that perform a task. Same as subroutine, module, procedure and function. routing See intermediate node routing and router. row Horizontal set of data or components. In a graph, it is called the x-axis. Contrast with column. RPC (Remote Procedure Call) Type of interface that allows one program to call another in a remote location. Using a standard RPC allows an application to be used in a variety of networks without change. RPG (Report Program Generator) One of the first program generators designed for business reports, introduced in 1964 by IBM. In 1970, RPG II added enhancements that made it a mainstay programming language for business applications on IBM's System/3x midrange computers. RPG III, which added more programming structures, is widely used on the AS/400. RPG statements are written in columnar format. The following RPG III System/38-AS/400 example changes Fahrenheit to Celsius. The A lines are Data Description Specs (DDS) code. They define a display file and are compiled separately. The F line links RPG code (C lines) to the A lines: A R FHEITR A 6 18'Enter Fahrenheit: ' A FRHEIT 3Y 0B 6 42DSPATR(PC) A EDTCDE(J) A 9 18'Celsius is ' A CGRADE 3Y 0B 9 42DSPATR(PC) A EDTCDE(J) FFHEITD CF E WORKSTN C EXFMTFHEITR C Z-ADDO CGRADE C FRHEIT SUB 32 CGRADE C CGRADE MULT 5 CGRADE C CGRADE DIV 9 CGRADE H C EXFMTFHEITR  rpm (Revolutions Per Minute) Used to measure the speed of a disk drive. Floppy disks rotate at 300 rpm, while hard disks rotate at 2,400 to 3,600 rpm. RPN See reverse polish notation. RPQ (Request for Price Quotation) Document that requests a price for hardware, software or services to solve a specific problem. It is created by the customer and delivered to the vendor. RS-170 NTSC standard for composite video signals. RS-232 (Recommended Standard-232) EIA standard for serial transmission between computers and peripheral devices (modem, mouse, etc.). It uses a 25-pin DB- 25 or 9-pin DB-9 connector. Its normal cable limitation of 50 feet can be extended to several hundred feet with high-quality cable. RS-232 defines the purpose and signal timing for each of the 25 lines; however, many applications use less than a dozen. RS-232 transmits positive voltage for a 0 bit, negative voltage for a 1. In 1984, this interface was officially renamed TIA/EIA-232-E standard (E is the current revision, 1991), although most people still call it RS-232.  Pin Settings for Plug  (Reverse order for socket.)  陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳  1 2 3 4 5 6 7 8 9 10 11 12 13  14 15 16 17 18 19 20 21 22 23 24 25  陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳  陳陳陳陳陳陳陳陳  1 2 3 4 5  6 7 8 9  陳陳陳陳  25 pin 9 pin  1 - PG Protective ground  2 - TD Transmitted data 3  3 - RD Received data 2  4 - RTS Request to send 7  5 - CTS Clear to send 8  6 - DSR Data set ready 6  7 - SG Signal ground 5  8 - CD Carrier detect 1  9 - + voltage (testing)  10 - - voltage (testing)  11 -  12 - SCD Secondary CD  13 - SCS Secondary CTS  14 - STD Secondary TD  15 - TC Transmit clock  16 - SRD Secondary RD  17 - RC Receiver clock  18 -  19 - SRS Secondary RTS  20 - DTR Data terminal ready 4  21 - SQD Signal quality detector  22 - RI Ring indicator 9  23 - DRS Data rate select  24 - XTC External clock  25 -  RS-422, 423, 449 EIA standards for serial interfaces that extend distances and speeds beyond RS-232. They often use a DB-37 connector. RS-422 is a balanced system requiring more wire pairs than RS-423 and is intended for use in multipoint lines. RS-449 specifies the pin definitions for 422 and 423. RS-422/423 are subsets of RS-449, each specifying electrical and timing characteristics of the lines. RS-485 EIA standard for multipoint communications lines. It can be implemented with as little as a wire block with four screws or with DB-9 or DB-37 connectors. By using lower-impedance drivers and receivers, RS-485 allows more nodes per line than RS-422. RS/6000 (RISC System/6000) IBM family of RISC-based workstations introduced in 1990. It comes in workstation (POWERstation) and server (POWERserver) models and uses the Micro Channel bus. It introduced Version 3 of AIX and two graphical user interfaces: AIXwindows Environment/6000 (enhanced X Window system) and AIX NeXTStep Environment/6000 from NeXT Computer. RSA (Rivest-Shamir-Adleman) Highly-secure encryption method by RSA Data Security, Inc., Redwood City, CA, that uses a two-part key. The private key is kept by the owner; the public key is published. You encrypt data by using the recipient's public key, which can only be decrypted by the recipient's private key. RSA is very computation intensive, thus it is often used to create a Digital Envelope, which holds an RSA-encrypted DES key and DES- encrypted data. You can create a digital signature as a means of verifying who you are by encrypting with your private key and letting others decrypt your message with your public key. RSCS (Remote Spooling Communications Subsystem) Software that provides batch communications for IBM's VM operating system. It accepts data from remote batch terminals, executes them on a priority basis and transmits the results back to the terminals. The RSCS counterpart in MVS is called JES. Contrast with CMS, which provides interactive communications for VM. RSI (Repetitive Strain Injury) Ailments of the hands, neck, back and eyes due to computer use. The remedy for RSI is frequent breaks which should include stretching or yoga postures. See carpal tunnel syndrome. RSTS/E PDP-11 operating system from Digital. RSX-11 (Resource Sharing eXtension-PDP 11) Multiuser, multitasking operating system from Digital that runs on its PDP-11 series. RT RISC-based workstation from IBM introduced in 1986 that has been superseded by the RS/6000 family. RT-11 Single user, multitasking operating system from Digital that runs on its PDP-11 series. RTF (Rich Text Format) Microsoft standard for encoding formatted text and graphics. It was adapted from IBM's DCA format and supports ANSI, IBM PC and Macintosh character sets. RTFM (Read The Flaming Manual) Last resort when having a hardware or software problem! RTS (Request To Send) RS-232 signal sent from the transmitting station to the receiving station requesting permission to transmit. Contrast with CTS. rubber banding In computer graphics, the moving of a line or object where one end stays fixed in position. rubout key Keyboard key on a terminal that deletes the last character that was entered. rule-based expert system Expert system based on a set of rules that a human expert would follow in diagnosing a problem. Contrast with model-based expert system. ruler line Graphic representation of a ruler on screen that is used for laying out text and graphics. rules (1) Set of conditions or standards which have been agreed upon. (2) In printing, horizontal and vertical lines between columns or at the top and bottom of a page in order to enhance the appearance of the page. run (1) To execute a program. (2) Single or multiple programs scheduled for execution. run around In desktop publishing, the flowing of text around a graphic image. run length encoding Simple data compression method that converts a run of identical symbols as a symbol followed by a count. A rough example might be []36* where [] is a code and 36* means 36 *'s follow. run length limited See RLL. run on top of To run as the control program to some other program, which is subordinate to it. Contrast with run under. run time See runtime. run under To run within the control of a higher-level program. Contrast with run on top of. runtime Refers to the actual execution of a program. runtime version Software that enables another program to execute on its own or with enhanced capabilities. For example, a runtime version of GEM comes with the DOS version of Ventura Publisher. It lets Ventura use GEM's graphical interface, but won't run other GEM programs. A DBMS often includes an interpreted programming language for developing applications. When running the programs, the DBMS must be used to execute each line of the program. A runtime version of a DBMS allows the programs to be run on computers that don't have the DBMS installed. S-100 bus IEEE 696, 100-pin bus standard used extensively in first-generation personal computers (8080, Z80, 6800, etc.). It is still used in various systems. S/360 See System/360. S/370 See System/370. S/3x See System/3x. S-RAM See static RAM. S3 chip Refers to one of the graphics accelerator chips (86C911, 86C928, etc.) from S3, Inc., San Jose, CA, used in a variety of graphics accelerator boards. SAA (System Application Architecture) Introduced in 1987, a set of IBM standards (user interfaces, programming interfaces and communications protocols) that provide consistency across all IBM platforms. Categories are Common User Access (CUA), Common Programming Interface for Communications (CPI-C) and Common Communications Support (CCS). See CUA, CPI-C and CCS. sabermetrician Slang for a statistician who uses computers to predict future performance of sports teams and players. sag Momentary drop in voltage from the power source. Contrast with spike. SAM (1) (Symantec AntiVirus for Macintosh) Popular Macintosh antivirus program from Symantec Corp., Cupertino, CA. (2) See sequential access method. Samna One of the first full-featured word processors for PCs (1983) from Samna Corp., now part of Lotus. sampling (1) In statistics, the analysis of a group by determining the characteristics of a significant percentage of its members chosen at random. (2) In digitizing operations, the conversion of real-world signals or movements at regular intervals into digital code. sampling rate In digitizing operations, the frequency with which samples are taken and converted. The higher the sample rate, the closer real-world objects are represented in digital form. sans-serif Typeface style without serifs, which are the short horizontal lines added at the tops and bottoms of the vertical member of the letter. Helvetica is a common sans-serif font. SAP (Secondary Audio Program) NTSC audio channel used for auxiliary transmission, such as foreign language broadcasting or teletext. SAS (Statistical Analysis System) Integrated software from SAS Institute Inc., Cary, NC, that runs on IBM mainframes, VAXs and other machines. It includes data management, spreadsheets, CBT, presentation graphics, project management, operations research, scheduling, linear programming, statistical quality control, econometric and time series analysis, mathematical, engineering and statistical applications and full application development. SASI (Shugart Associates Systems Interface) Peripheral interface developed by Shugart and NCR in 1981 that evolved into the ANSI SCSI standard in 1986. satellite See communications satellite satellite channel Carrier frequency used for satellite transmission. satellite computer Computer located remotely from the host computer or under the control of the host. It can function as a slave to the master computer or perform offline tasks. satellite link Signal that travels from the earth to a communications satellite and back down again. Contrast with terrestrial link. saturation (1) On magnetic media, occurs when the magnetizable particles are completely aligned and a more powerful writing signal will not improve the reading back. (2) In a bipolar transistor, occurs when the current on the gate (the trigger) is equal to or greater than what is necessary to close the switch. (3) In a diode, occurs when the diode is fully conducting. save To write the contents of memory to disk or tape. Some applications save data automatically, others do not. Memory-based word processors, and most all spreadsheets require that the user saves the data before exiting the program. SBS (Satellite Business Systems) Organization developed to offer satellite communications services to business, currently part of MCI. Sbus Originally a proprietary bus from Sun, it has been released into the public domain. The IEEE is standardizing on a 64-bit version in 1993. SCAI (Switch-to-Computer Applications Interface) Standard for integrating computers to a PBX. See switch-to-computer. scalability Ability to expand. Implies minimal change in current procedures in order to accomodate growth. scalable Capable of being changed in size and configuration. scalable font Font that is created in the required point size as needed to display or print a document. The dot patterns (bitmaps) are generated from a set of outline fonts, or base fonts, which contain a mathematical representation of the typeface. Although a bitmapped font designed from scratch for a particular font size will always look the best, scalable fonts eliminate storing dozens of different font sizes on disk. Contrast with bitmapped font. The major scalable fonts are Adobe's Type 1 PostScript, Apple/Microsoft's TrueType, Agfa's Intellifont and Bitstream's Speedo. There are more Type 1 typefaces available, although TrueType faces are quickly appearing. scalar Single item or value. Contrast with vector and array, which are made up of multiple values. scalar processor Computer that performs arithmetic computations on one number at a time. Contrast with vector processor. scalar variable In programming, a variable that contains only one value. scale (1) In computer graphics and printing, to resize an object, making it smaller or larger. (2) To change the representation of a quantity in order to bring it into prescribed limits of another range. For example, values such as 1249, 876, 523, -101 and -234 might need to be scaled into a range from -5 to +5. (3) To designate the position of the decimal point in a fixed or floating point number. scan (1) In optical technologies, to view a printed form a line at a time in order to convert images into bitmapped representations, or to convert characters into ASCII text or some other data code. (2) In video, to move across a picture frame a line at a time, either to detect the image in an analog or digital camera, or to refresh a CRT display. (3) To sequentially search a file. scan head Optical sensing device in an scanner or fax machine that is moved across the image to be scanned. scan line One of many horizontal lines in a graphics frame. scan rate Number of times per second a scanning device samples its field of vision. See horizontal scan frequency. ScanJet Family of popular desktop scanners from HP. Monochrome and color models are available. scanner Device that reads text, images and bar codes. Text and bar code scanners recognize printed fonts and bar codes and convert them into a digital code (ASCII or EBCDIC). Graphics scanners convert a printed image into a video image (raster graphics) without recognizing the actual content of the text or pictures. scatter diagram Graph plotted with dots or some other symbol at each data point. Also called a scatter plot or dot chart. scatter plot Same as scatter diagram. scatter read Capability that allows data to be input into two or more noncontiguous locations of memory with one read operation. See gather write. SCERT II (Systems and Computers Evaluation and Review Technique) Pronounced "skirt." Software from Pinnacle Software Corp., Washington, DC, that measures the performance of a system by modeling the computer environment and applications. scheduler The part of the operating system that initiates and terminates jobs (programs) in the computer. Also called a dispatcher, it maintains a list of jobs to be run and allocates computer resources as required. scheduling algorithm Method used to schedule jobs for execution. Priority, length of time in the job queue and available resources are examples of criteria used. schema Definition of an entire database. See subschema. Scheme LISP dialect developed at MIT and Indiana University. TI has a personal computer version of Scheme called PC Scheme. Schottky Category of bipolar transistor known for its fast switching speeds in the three-nanosecond range. Schottky II devices have switching speeds in the range of a single nanosecond. scientific applications Applications that simulate real-world activities using mathematics. Real-world objects are turned into mathematical models and their actions are simulated by executing the formulas. For example, some of an airplane's flight characteristics can be simulated in the computer. Rivers, lakes and mountains can be simulated. Virtually any objects with known characteristics can be modeled and simulated. Simulations use enormous calculations and often require supercomputer speed. As personal computers become more powerful, more laboratory experiments will be converted into computer models that can be interactively examined by students without the risk and cost of the actual experiments. scientific computer Computer specialized for high-speed mathematic processing. See array processor and floating point processor. scientific language Programming language designed for mathematical formulas and matrices, such as ALGOL, FORTRAN and APL. Although all programming languages allow for this kind of processing, statements in a scientific language make it easier to express these actions. scientific notation Display of numbers in floating point form. The number (mantissa) is always equal to or greater than one and less than 10, and the base is 10. For example, 2.345E6 is equivalent to 2,345,000. The number following E (exponent) represents the power to which the base should be raised (number of zeros following the decimal point). scissoring In computer graphics, the deleting of any parts of an image which fall outside of a window that has been sized and laid over the original image. Also called clipping. SCL (1) (Switch-to-Computer Link) Refers to applications that integrate the computer through the PBX. See switch-to-computer. (2) Extension used for ColoRIX raster graphics file format (640x400 256 colors). SCO (The Santa Cruz Operation, Inc., Santa Cruz, CA) System software company noted for its UNIX operating systems. SCO Open Desktop Multiuser, virtual memory graphical operating system for 386s and up from SCO that runs UNIX, XENIX, DOS and X Window applications. It includes TCP/IP and NFS networking and database services based on INGRES 6.2. SCO UNIX System V AT&T-licensed implementation of UNIX System V/386 3.2 for 386s and up from SCO. It is a multiuser, multitasking environment that runs both XENIX and UNIX applications. It has more security, networking features and standards conformance than SCO XENIX. When used with SCO VP/ix or SCO Open Desktop, it can also run DOS applications. SCO VP/ix System program for 386s and up from SCO that allows DOS applications to run concurrently with SCO UNIX or SCO XENIX in a virtual memory environment. Each application runs in its own secure virtual address space. SCO XENIX System V AT&T-licensed, SVID-conforming implementation of UNIX System V for 286 PCs and up from SCO. Developed by Microsoft, it was the original UNIX system for personal computers. Faster and smaller than SCO UNIX, it includes improved documentation and easier installation. scope (1) CRT type of screen, such as used on an oscilloscope or common display terminal. (2) In programming, the visibility of variables within a program; for example, whether one function can use a variable created in another function. (3) In dBASE, a range of records, such as the "next 50" or "current record to end of file." scrambler Device or software program that encodes data for encryption. scrambling Encoding data to make it indecipherable. See encryption and DES. Scrapbook Macintosh disk file that holds frequently-used text and graphics objects, such as a company letterhead. Contrast with Clipboard, which holds data only for the current session. scratch tape Magnetic tape that can be erased and reused. scratchpad Special register or a reserved section of memory or disk used for temporary storage. screen Display area of a video terminal or monitor. It is either a CRT or one of the flat panel technologies. screen angle The angle at which a halftone screen is placed over an image, typically 45. screen capture Transfering the current on-screen image to a text or graphics file. screen dump Printing the current on-screen image. In PCs, pressing Shift-PrtSc prints the screen. If the screen contains graphics, the DOS Graphics utility must be loaded. Third party screen capture programs also dump graphic screens to the printer or to disk. In the Macintosh, pressing Command-shift-3 creates a MacPaint file of the current screen. screen font Font used for on-screen display. For true WYSIWYG systems, screen fonts must be matched as close as possible to the printer fonts. Contrast with printer font. screen frequency Resolution of a halftone. It is the density of dots (how far they're spaced apart from each other) measured in lines per inch. screen overlay (1) Clear, fine-mesh screen that reduces the glare on a video screen. (2) Clear touch panel that allows the user to command the computer by touching displayed buttons on screen. (3) Temporary data window displayed on screen. The part of the screen that was overlaid is saved and restored when the screen overlay is removed. screen saver Utility that prevents a CRT from being etched by an unchanging image. After a specified duration without keyboard or mouse input, it blanks the screen or displays moving objects. Pressing a key or moving the mouse restores the screen. It would actually take many hours to burn in an image on today's color monitors. However, the entertainment provided by these utilities (swimming fish, flying toasters, etc.) has made them very popular. screen scraper See frontware. script (1) Typeface that looks like handwriting or calligraphy. (2) Program written in a special-purpose programming language such as used in a communications program or word processor. Same as macro. ScriptX Multimedia technology from Kaleida Labs, Inc. that includes data formats, a scripting language and a runtime environment. It is designed for creating applications that can be played on a variety of personal computers and consumer electronic devices. scroll To continuously move forward, backward or sideways through the images on screen or within a window. Scrolling implies continuous and smooth movement, a line, character or pixel at a time, as if the data were on a paper scroll being rolled behind the screen. scroll arrow On-screen arrow that is clicked in order to scroll the screen in the corresponding direction. The screen moves one line, or increment, with each mouse click. scroll back buffer Reserved memory that holds a block of transmitted data, allowing the user to browse back through it. scroll bar Horizontal or vertical bar that contains a box that looks like an elevator in a shaft. The bar is clicked to scroll the screen in the corresponding direction, or the box (elevator, thumb) is clicked and then dragged to the desired direction. scrollable See scroll. scrollable field Short line on screen that can be scrolled to allow editing or display of larger amounts of data in a small display space. SCSI (Small Computer System Interface) Pronounced "scuzzy." SCSI is a hardware interface that allows for the connection of up to seven peripheral devices, such as a disk, tape or CD ROM, to a single SCSI expansion board, called a SCSI host adapter (also called a SCSI controller), that plugs into the computer. The advantage of SCSI is that seven different devices use up only one expansion slot in the computer. However, the Macintosh, Sun and Digital operating systems have supported SCSI directly, but DOS has not, allowing various implementations of SCSI drivers and host adapters to be developed for the PC. The SCSI host adapter and driver that comes with a SCSI peripheral often works with only that device or similar devices. Thus when several SCSI devices are used in a PC, multiple host adapters are required, each taking up an expansion slot. Attempts at standardizing SCSI have resulted in Microsoft's LADDR, Adaptec's ASPI and ANSI's CAM specifications (see CorelSCSI and PowerSCSI!). SCSI is a bus structure itself and functions like a mini-LAN connecting eight devices, but the host adapter counts as one device. SCSI allows any two devices to communicate at one time (host to peripheral, peripheral to peripheral). Each SCSI device can actually be broken up into eight logical units as logical unit numbers (LUNs) 0 to 7, theoretically allowing up to 56 peripherals to connect to one SCSI host adapter. For example, a jukebox for five disks could be LUN 0 to 4. SCSI devices can be built to take advantage of this capability, but to date, most function only as a single device (LUN 0). SCSI, or SCSI-1, is an 8-bit interface that provides up to five MBytes/sec data transfer and uses a 50-pin ribbon cable for interconnection. SCSI-2 provides command queuing and a "fast SCSI" option that provides 10MB data transfer. With a secondary cable for 16- and 32-bit data, "wide SCSI" provides up to 40MB transfer. A new 68-conductor "P" cable is a single-cable solution for 16 bits. SCSI-3 proposes enhanced features and the ability to handle more than eight devices. It also supports serial transmission for small computers such as palmtops. See hard disk. Parallel to SCSI There are adapters that allow SCSI peripherals to be connected via the parallel port. Although the parallel port's transfer rate is considerably less than the SCSI host adapter, it does provide a means to hook up SCSI devices that might be otherwise impossible, such as to a laptop with no expansion slots. scuzzy See SCSI. SDBN (Software-Defined Broadband Network) Future high- bandwidth service from AT&T for data, voice and video. It uses ATM cell relay technology with speeds up to 600 Mbits/sec. SDF (Standard Data Format) Simple file format that uses fixed length fields. It is commonly used to transfer data between different programs.  SDF Pat Smith 5 E. 12 St. Rye NY Robert Jones 200 W. Main St. Palo Alto CA  Comma delimited "Pat Smith","5 E. 12 St.","Rye","NY" "Robert Jones","200 W. Main St.","Palo Alto","CA" SDI (1) (Switched Digital Int'l.) AT&T dial-up service providing 54/64 Kbits/sec digital transmission to international locations. (2) (Standard Drive Interface) Hard disk interface for VAXs. (3) (Single Document Interface) In Windows, a single window that is minimized or maximized independently. Contrast with MDI. (4) (Serial Data Interface) See serial interface. (5) (Strategic Defense Initiative) Proposed U.S. high-tech defense system. SDK (Software Developer's Kit) See developer's toolkit. SDLC (Synchronous Data Link Control) Primary data link protocol used in IBM's SNA networks. It is a bit- oriented synchronous protocol that is a subset of the HDLC protocol. SDP (Streaming Data Procedure) Micro Channel mode that increases data transfer from 20MB per second to 40MB per second. SDRAM (Synchronous DRAM) New high-speed memory being specified by JEDEC that can transfer bursts of non- contiguous data at 100MBytes/sec. SE See systems engineer and Macintosh. Seagate (Seagate Technology, Inc., Scotts Valley, CA) Largest independent manufacturer of disk drives. Founded in 1979 by Alan Shugart, Tom Mitchell and Doug Mahon, it was the first to offer a 5MByte drive using 5.25" platters making it ideal for the burgeoning desktop computer industry. Seagate became the first company to ship 10 million drives. In 1989, it aquired Imprimis Technology, a CDC subsidiary making workstation and mainframe drives, nearly doubling Seagate's revenue to $2.5 billion. SEAlink Version of Xmodem that uses a sliding window protocol, transmits file name, date and size and provides batch file transfer. Good for delay- introduced transmissions (packet switching, satellites). seamless integration Addition of a new application, routine or device that works smoothly with the existing system. It implies that the new feature can be activated and used without problems. Contrast with transparent, which implies that there is no discernible change after installation. search and replace To look for an occurrence of data or text and replace it with another set of data or text. search key In a search routine, the data entered and used to match other data in the database. second-generation computer Computer made of discrete electronic components. In the early 1960s, the IBM 1401 and Honeywell 400 were examples. second source Alternative supplier of an identical or compatible product. A second source manufacturer is one that holds a license to produce a copy of the original product from another manufacturer. secondary channel In communications, a subchannel that is derived from the main channel. It is used for diagnostic or supervisory purposes, but does not carry data messages. secondary index Index maintained for a data file, but is not used to control the current processing order of the file. See primary index. secondary storage External storage, such as disk and tape. sector Smallest unit of storage read or written on a disk. See magnetic disk. sector interleave Sector numbering on a hard disk. A one to one interleave (1:1) is sequential: 0,1,2,3, etc. A 2:1 interleave staggers sectors every other one: 0,4,1,5,2,6,3,7. In 1:1, after data in sector 1 is read, the disk controller must be fast enough to read sector 2, otherwise the beginning of sector 2 will pass the read/write head and must rotate around to come under the head again. If it isn't fast enough, a 2:1 or 3:1 interleave gives it time to read all sectors in a single rotation, eliminating wasted rotations. The best interleave depends on the disk and disk controller. It can be changed with a low-level format program. sector map See sector interleave. sector sparing Maintaining a spare sector per track to be used if another sector becomes defective. security Protection of data against unauthorized access. Programs and data can be secured by issuing identification numbers and passwords to authorized users of a computer. However, systems programmers, or other technically competent individuals, will ultimately have access to these codes. Passwords can be checked by the operating system to prevent users from logging onto the system in the first place, or they can be checked in software, such as DBMSs, where each user can be assigned an individual view (subschema) of the database. Any application program running in the computer can also be designed to check for passwords. Data transmitted over communications networks can be secured by encryption to prevent eavesdropping. Although precautions can be taken to detect an unauthorized user, it is extremely difficult to determine if a valid user is performing unauthorized tasks. Effective security measures are a balance of technology and personnel management. See NCSC. security kernel The part of the operating system that grants access to users of the computer system. security levels See NCSC. sed (Stream EDitor) UNIX editing command that makes changes a line at a time and is used to edit large files that exceed buffer limitations of other editors. seed (1) Starting value used by a random number generation routine to create random numbers. (2) (SEED) (Self-Electro-optic-Effect Device) Optical transistor developed by David Miller at Bell Labs in 1986. seek (1) To move the access arm to the requested track on a disk. (2) Assembly language instruction that activates a seek operation on disk. (3) High-level programming language command used to select a record by key field. seek time Time it takes to move the read/write head to a particular track on a disk. segment (1) Any partition, reserved area, partial component or piece of a larger structure. (2) One of the bars that make up a single character in an LED or LCD display. (3) For DOS segment addressing, see paragraph. segmented address space Memory addressing in which each byte is referenced by a segment, or base, number and an offset that is added to it. Contrast with flat address space. Sel (SELect) Printer switch that takes the printer alternately online and offline. selection sort Search for specific data starting at the beginning of a file or list. It copies each matching item to a new file so that the selected items are in the same sequence as the original data. selective calling In communications, the ability of the transmitting station to indicate which station in the network is to receive the message. selector channel High-speed computer channel that connects a peripheral device (disk, tape, etc.) to the computer's memory. selector pen Same as light pen. Selectric typewriter Introduced in 1961 by IBM, the first typewriter to use a golf-ball-like print head that moved across the paper, rather than moving the paper carriage across the print mechanism. It rapidly became one of the world's most popular typewriters. IBM has always excelled in electromechanical devices. self-booting Refers to automatically loading the operating system upon startup. self-checking digit See check digit. self-clocking Recording of digital data on a magnetic medium such that the clock pulses are intrinsically part of the recorded signal. A separate timer clock is not required. Phase encoding is a commonly-used self- clocking recording technique. self-documenting code Programming statements that can be easily understood by the author or another programmer. COBOL provides more self-documenting code than does C, for example. self-extracting file One or more compressed files that have been converted into an executable program which decompresses its contents when run. semantic error In programming, writing a valid programming structure with invalid logic. semantic gap Difference between a data or language structure and the real world. For example, in order processing, a company can be both customer and supplier. Since there is no way to model this in a hierarchical database, the semantic gap is said to be large. A network database could handle this condition, resulting in a smaller semantic gap. semantics Study of the meaning of words. Contrast with syntax, which governs the structure of a language. semaphore (1) Hardware or software flag used to indicate the status of some activity. (2) Shared space for interprocess communications (IPC) controlled by "wake up" and "sleep" commands. The source process fills a queue and goes to sleep until the destination process uses the data and tells the source process to wake up. semiconductor Solid state substance that can be electrically altered. Certain elements in nature, such as silicon, perform like semiconductors when chemically combined with other elements. A semiconductor is halfway between a conductor and an insulator. When charged with electricity or light, semiconductors change their state from nonconductive to conductive or vice versa. The most significant semiconductor is the transistor, which is simply an on/off switch. semiconductor device Elementary component, such as a transistor, or a larger unit of electronic equipment comprised of chips. sensor Device that measures or detects a real world condition, such as motion, heat or light and converts the condition into an analog or digital representation. An optical sensor detects the intensity or brightness of light, or the intensity of red, green and blue for color systems. sequel See SQL. sequence check Testing a list of items or file of records for correct ascending or descending sequence based on the item or key fields in the records. sequential One after the other in some consecutive order such as by name or number. sequential access method Organizing data in a prescribed ascending or descending sequence. Searching sequential data requires reading and comparing each record, starting from the top or bottom of file. serial One after the other. serial computer Single-processor computer that executes one instruction after the other. Contrast with parallel computer. serial interface Data channel that transfers digital data in a serial fashion: one bit after the other. Communications lines are generally serial, thus modems are connected to the computer via a serial port. So are mice and scanners. Serial interfaces have multiple lines, but only one is used for data. Contrast with parallel interface. See RS-232. serial mouse See bus mouse. serial number Unique number assigned by the vendor to each unit of hardware or software. See signature. serial port I/O connector used to attach a modem, mouse, scanner or other serial interface device to the computer. The typical serial port uses a DB-25 or DB-9 connector, which on the back of a PC is a 25- pin male or 9-pin male connector. Contrast with parallel port. See RS-232. serial printer Type of printer that prints one character at a time, in contrast to a line or page at a time. In this context, serial has no relationship to a serial or parallel interface that is used to attach the printer to the computer. See printer. serial transmission Transmitting data one bit at a time. Contrast with parallel transmission. serialize To convert a parallel signal made up of one or more bytes into a serial signal that transmits one bit after the other. Series/1 IBM minicomputer series introduced in 1976. It was used primarily as a communications processor and for data collection in process control. serif Short horizontal lines added to the tops and bottoms of traditional typefaces, such as Times Roman. Contrast with sans-serif. serpentine recording Tape recording format of parallel tracks in which the data "snakes" back and forth from track to track. server Computer in a network shared by multiple users. See file server and print server. server application (1) Application designed to run in a server. See client/server. (2) Any program that is run in the server, whether designed as a client/server application or not. (3) See OLE. service Functionality derived from a particular software program. For example, network services may refer to programs that transmit data or provide conversion of data in a network. Database services provides for the storage and retrieval of data in a database. service bureau Organization that provides data processing and timesharing services. It may offer a variety of software packages, batch processing services (data entry, COM, etc.) as well as custom programming. Customers pay for storage of data on the system and processing time used. Connection is made to a service bureau through dial-up terminals, private lines, or other networks, such as Telenet or Tymnet. servo Electromechanical device that uses feedback to provide precise starts and stops for such functions as the motors on a tape drive or the moving of an access arm on a disk. session (1) In communications, the active connection between a user and a computer or between two computers. (2) Using an application program (period between starting up and quitting). set theory Branch of mathematics or logic that is concerned with sets of objects and rules for their manipulation. UNION, INTERSECT and COMPLEMENT are its three primary operations and they are used in relational database as follows. Given a file of Americans and a file of Barbers, UNION would create a file of all Americans and Barbers. INTERSECT would create a file of American Barbers, and COMPLEMENT would create a file of Barbers who are not Americans, or of Americans who are not Barbers. setup program Software that configures a system for a particular environment. It is used to install a new application and modify it when the hardware changes. When used with expansion boards, it may change the hardware by altering on-board memory chips (flash memory, EEPROMs, etc.). See install program. setup string Group of commands that initialize a device, such as a printer. See escape character. seven dwarfs IBM's early competitors in the mainframe business: Burroughs, CDC, GE, Honeywell, NCR, RCA and Univac. seven-segment display Common display found on digital watches and readouts that looks like a series of 8s. Each digit or letter is formed by selective illumination of up to seven separately addressable bars. sex changer See gender changer. SGML (Standard Generalized Markup Language) ISO- standard metalanguage for defining ways of marking up text content for purposes such as formatting and hypertexting. sh (SHell) UNIX command that invokes a different shell. It can be used like a batch file to execute a series of commands saved as a shell. shadow batch Data collection system that simulates a transaction processing environment. Instead of updating master files (customers, inventory, etc.) when orders or shipments are initiated, the transactions are stored in the computer. When a user makes a query, the master record from the previous update cycle is retrieved; but before it's displayed, it's updated in memory with any transactions that may affect it. The up-to-date master record is then displayed for the user. At the end of the day or period, the transactions are then actually batch processed against the master file. shadow mask Screen full of holes that adheres to the back of a color CRT's viewing glass. The electron beam is aimed through the holes onto the phosphor dots. shadow RAM In a PC, a copy of the operating system's BIOS routines in RAM to improve performance. RAM chips are faster than ROM chips. shared DASD Disk system accessed by two or more computers within a single datacenter. Disks shared in personal computer networks are called file servers or database servers. shared logic Using a single computer to provide processing for two or more terminals. Contrast with shared resource. shared resource Sharing a peripheral device (disk, printer, etc.) among several users. For example, a file server and laser printer in a LAN are shared resources. Contrast with shared logic. shareware Software distributed on a trial basis through BBS's, online services, mail-order vendors and user groups. Shareware is software on the honor system. If you use it regularly, you're required to register and pay for it, for which you will receive technical support and perhaps additional documentation or the next upgrade. Paid licenses are required for commercial distribution. See freeware and public domain software. There are tens of thousands of shareware programs, some fantastic, some awful. Shareware vendors compile catalogs with hundreds and thousands of products and sell them by mail or at shows for a small fee. That fee is not the registration fee, but the fee for distributing the shareware to you. For a catalog of hand-picked shareware from noted shareware expert, Alfred Glossbrenner, who endorses one product from each category, contact: GLOSSBRENNER'S CHOICE 699 River Road Yardley, PA 19067 215/736-1213 sheet feeder Mechanical device that feeds stacks of cut forms (letterheads, legal paper, etc.) into a printer. shelfware Products that remain unsold on a dealer's shelf or unused by the customer. shell Outer layer of a program that provides the user interface, or way of commanding the computer. Shells are typically add-on programs created for command-driven operating systems, such as UNIX and DOS. It provides a menu-driven or graphical icon- oriented interface to the system in order to make it easier to use. DOS 4.0 and 5.0 come with their own shell (DOSshell). shell out To temporarily exit an application, go back to the operating system, perform a function and then return to the application. shell script File of executable UNIX commands created by a text editor and made executable with the chmod command. shift register High-speed circuit that holds some number of bits for the purpose of shifting them left or right. It is used internally within the processor for multiplication and division, serial/parallel conversion and various timing considerations. short In programming, an integer variable. In C, a long is two bytes and can be signed (-32K to +32K) or unsigned (64K). Contrast with long. short card In a PC, a plug-in printed circuit board that is half the length of a full-size board. Contrast with long card. short-haul modem In communications, a device that transmits signals up to about a mile. Similar to a line driver that can transmit up to several miles. shrink-wrapped software Refers to store-bought software, implying a standard platform that is widely supported. SI See systems integration, Norton SI and Macintosh. sideband In communications, the upper or lower half of a wave. Since both sidebands are normally mirror images of each other, one of the halves can be used for a second channel to increase the data-carrying capacity of the line or for diagnostic or control purposes. Sidekick PC desktop utility program from Borland. Introduced in 1984, it was the first popup (TSR) program for the PC. It includes a calculator, WordStar-compatible notepad, appointment calendar, phone dialer and ASCII table. Sidekick Plus (1988) adds more notepad commands, calendar alarms, scientific and programming calculators, limited file management and an outliner. Sieve of Eratosthenes Benchmark program used to test the mathematical speed of a computer. The program calculates prime numbers based on Eratosthenes's algorithm. SIG (Special Interest Group) Group of people that meets and shares information about a particular topic of interest. It is usally a part of a larger group or association. SIGGRAPH Special interest group on computer graphics that is part of the ACM. sign Symbol that identifies a positive or negative number. In digital code, it is either a separate character or part of the byte. In ASCII, the sign is kept in a separate character typically transmitted in front of the number it represents (+ and - is 2B and 2D in hex). In EBCDIC, the minus sign can be stored as a separate byte (hex 60), or, more commonly, as half a byte (+ and - is C and D in hex), which is stored in the high-order bits of the least significant byte. For packed decimal, it is in the low-order bits of the least significant byte. sign on/sign off Same as log-on/log-off. signal Physical form of transmitted data (pulses or frequencies of electricity or light). signal converter Device that changes the electrical or light characteristics of a signal. signal processing See digital signal processing. signal to noise ratio Ratio of the amplitude (power, volume) of a data signal to the amount of noise (interference) in the line. Usually measured in decibels, it measures the clarity or quality of a transmission channel or electronic device. signaling in/out of band In communications, signaling "in band" refers to sending control signals within the same frequency range as the data signal. Signaling "out of band" refers to sending control signals outside of the frequency range of the data signal. signature (1) Unique number built into hardware or software for identification. (2) (Signature) Successor to XyWrite word processor. See XyWrite III Plus. significant digits Those digits in a number that add value to the number. For example, in the number 00006508, 6508 are the significant digits. silica Same as silicon dioxide. silica gel Highly absorbent form of silicon dioxide often wrapped in small bags and packed with equipment to absorb moisture during shipping and storage. silicon (Si) Base material used in chips. Next to oxygen, it is the most abundant element in nature and is found in a natural state in rocks and sand. Its atomic structure and abundance make it an ideal semiconductor material. In chip making, it is mined from rocks and put through a chemical process at high temperatures to purify it. To alter its electrical properties, it is mixed (doped) with other chemicals in a molten state. silicon compiler Software that translates the electronic design of a chip into the actual layout of the components. silicon dioxide (SiO2) Hard, glassy mineral found in such materials as rock, quartz, sand and opal. In MOS chip fabrication, it is used to create the insulation layer between the metal gates of the top layer and the silicon elements below. silicon disk Disk drive permanently simulated in memory. Typically used in laptops for weight reduction, it requires constant power from a battery to maintain its contents. silicon foundry Organization that makes chips for other companies that have only design, but not manufacturing facilities. It is typically a large chip maker that uses excess manufacturing capacity in this manner. silicon nitride (Si3N4) Silicon compound capable of holding a static electric charge and used as a gate element on some MOS transistors. silicon on sapphire See SOS. Silicon Valley Area around San Jose (south of San Francisco) noted for its large number of high-tech companies. SIM (Society for Information Management) Organization of MIS professionals founded as the Society for MIS in 1968. It is an exchange for technical information and offers educational and research programs, competitions and awards to its members. Address: 111 East Wacker Dr., Suite 600, Chicago, IL 60601. SIMD (Single Instruction stream Multiple Data stream) Computer architecture that performs one operation on multiple sets of data, for example, an array processor. One computer or processor is used for the control logic and the remaining processors are used as slaves, each executing the same instruction. Contrast with MIMD. SIMM (Single In-line Memory Module) Narrow printed circuit board about three inches long that holds eight or nine memory chips. It plugs into a SIMM socket on the circuit board.  SIMM specs Capacity/configuration  1x3 1MB, two 4Mb chips, one 1Mb chip 1x9 1MB, nine 1Mb chips 4x9 4MB, nine 4Mb chips 16x9 16MB, nine 16Mb chips 1x8, 4x8, etc., use eight chips (no parity). A number, typically from 50 to 80, following the above designation is chip speed; for example, 1x9-60 means 60 nanosecond 1MB SIMMs. On PCs, SIMMs are installed in multiples of two on 286s and 386SXs (16-bit data bus), and multiples of four on 386DXs and up (32-bit). In order to increase memory in small increments, 256KB SIMMs are used. Adding two 256KB SIMMs on 286s and 386SXs adds 512KB, while four of them adds one megabyte on 386DXs and up. simplex One way transmission. Contrast with half-duplex and full-duplex. SIMSCRIPT Programming language used for discrete simulations. simulation (1) Mathematical representation of the interaction of real-world objects. See scientific applications. (2) Execution of a machine language program designed to run in a foreign computer. sine wave Uniform wave that is generated by a single frequency. single board computer Printed circuit board that contains a complete computer, including processor, memory, I/O and clock. single density disk First-generation floppy disk. single-ended configuration Electrical signal paths that use a common ground, which are more susceptible to noise than differential configuration. single mode fiber Optical fiber with a core diameter of less than 10 microns used for high-speed transmission and long distances. Contrast with multi mode fiber. single precision Use of one computer word to hold a numeric value for calculation. Contrast with double precision. single sided disk Floppy disk that stores data on only one side. single-system image Operational view of multiple networks, distributed databases or multiple computer systems as if they were one system. single threading Processing one transaction to completion before starting the next. sink Device or place that accepts something. See heat sink and data sink. SIP (Single In-line Package) Type of chip module that is similar to a SIMM, but uses pins rather than edge connectors. SIPs are sometimes called SIPPs (Single In-Line Pin Package). SISD (Single Instruction stream Single Data stream) Architecture of a serial computer. Contrast with SIMD and MIMD. site license License to use software within a facility. It provides authorization to make copies and distribute them within a specific jurisdiction. SIXEL Graphics language from Digital that supersedes ReGIS. ReGIS to SIXEL conversion programs are available. skew (1) Misalignment of a document or punched card in the feed tray or hopper that prohibits it from being scanned or read properly. (2) In facsimile, the difference in rectangularity between the received and transmitted page. (3) In communications, a change of timing or phases in a transmission signal. (4) See cylinder skew and head skew. sky wave Radio signal transmitted into the sky and reflected back down to earth from the ionosphere. slave Computer or peripheral device controlled by another computer. For example, a terminal or printer in a remote location that only receives data is a slave. When two personal computers are hooked up via their serial or parallel ports for file exchange, the file transfer program may make one computer the master and the other the slave. slave tube Display monitor connected to another monitor in order to provide an additional viewing station. SLC See 386SLC. SLED (Single Large Expensive Disk) Traditional disk drive. Contrast with RAID. sleep (1) In programming, an inactive state due to an endless loop or programmed delay. A sleep statement in a programming language creates a delay for some specified amount of time. (2) Inactive status of a terminal, device or program that is awakened by sending a code to it. slew rate (1) How fast paper moves through a printer (ips). (2) Speed of changing voltage. sliding window (1) Communications protocol that transmits multiple packets before acknowledgement. Both ends keep track of packets sent and acknowledged (left of window), those which have been sent and not acknowledged (in window) and those not yet sent (right of window). (2) View of memory that can be instantly shifted to another location. slipstream To fix a bug or add enhancements to software without identifying such inclusions by creating a new version number. slot (1) Receptacle for additional printed circuit boards. (2) Receptacle for inserting and removing a disk or tape cartridge. (3) In communications, a narrow band of frequencies. See time slot. (4) May refer to reserved space for temporary or permanent storage of instructions, data or codes. slot mask Sony Trinitron counterpart to the shadow mask. It uses vertical rectangular slots instead of holes. slow scan TV Transmission of still video frames over telephone lines. Not realtime transmission, it takes several seconds to transmit one frame. Also called electronic still photography (ESP). slug Metal bar containing the carved image of a letter or digit that is used in a printing mechanism. SMA (1) (Software Maintenance Assn.) Non-profit professional organization founded in 1985 and dedicated to enhance understanding of software maintenance and to advance those concerned with it. Active chapters are in major cities worldwide. Annual conference is held in the spring. Address: Ms. Robin Gross, Box 12004, Vallejo, CA 94590, 707/643-4423. (2) (Systems Management Architecture) IBM network management repository. (3) Type of fiber optic connector. (4) (Spectrum Manufacturers Assn.) DBMS standard for application compatibility. Smalltalk Operating system and object-oriented programming language that was developed at Xerox Corp.'s Palo Alto Research Center. As an integrated environment, it eliminates the distinction between programming language and operating system. It also allows the programmer to customize the user interface and behavior of the system. Smalltalk was the first object-oriented programming language and was used on Xerox's Alto computer, which was designed for it. It was originally used to create prototypes of simpler programming languages and the graphical interfaces that are so popular today. Smalltalk V Version of Smalltalk for PCs from Digitalk, Inc., Los Angeles. Versions for DOS, OS/2, Windows and the Mac are also available. smart cable Connecting cable between two devices that has a built-in microprocessor. It analyzes incoming signals and converts them from one protocol to another. smart card Credit card with built-in microprocessor and memory used for identification or financial transactions. When inserted into a reader, it transfers data to and from a central computer. It is more secure than a magnetic stripe card and can be programmed to self-destruct if the wrong password is entered too many times. As a financial transaction card, it can store transactions and maintain a bank balance. smart hub See intelligent hub. smart install program Install program that configures itself automatically based on the hardware environment. smart terminal Video terminal with built-in display characteristics (blinking, reverse video, underlines, etc.). It may also contain a communications protocol. Sometimes refers to intelligent terminal. See intelligent terminal and dumb terminal. Smartcom Family of communications programs for PCs and Macs from Hayes Microcomputer Products, Inc., Atlanta, GA. Versions emulate a several terminals and support a variety of protocols, including the Hayes V-series. Smartcom EZ is for the novice. Smartdrive Disk cache program that comes with DOS 4.0 and Windows 3.0. Driver is SMARTDRV.SYS. SmartKey PC keyboard macro processor from No Brainer Software, Midvale, UT. It was one of the first macro processors that let users eliminate repetitive typing by creating a macro for an occurrence of text or a series of commands. SmartWare Integrated software package for PCs and various UNIX-based systems from Informix Software, Inc., Menlo Park, CA, that includes a programming language. SMB (Server Message Block) Message format used in the Microsoft/3Com file sharing protocol for PC Network, MS-Net and LAN Manager. Used to transfer file requests between workstations and servers as well as within the server for internal operations. For network transfer, SMBs are carried within the NetBIOS network control block (NCB) packet. SMD (1) (Storage Module Device) High-performance hard disk interface used with minis and mainframes that transfers data in the 1-4 MBytes/sec range (SMD-E provides highest rate). See hard disk. (2) (Surface Mount Device) Surface mounted chip. SMDS (Switched Multimegabit Data Services) High-speed data services in the 45 Mbits/sec range proposed by local telephone companies that will allow companies to build private MANs. SMF (1) (Standard Messaging Format) E-mail programming interface from Novell. NGM (NetWare Global Messaging) is based on SMF-71, which supports long addresses and synchronized directories. (2) (Single Mode Fiber) Class of optical fiber used in FDDI that transmits through a single path at 2Gbits/sec up to 50 miles. See MMF. smoke test Test of new or repaired equipment by turning it on. If there's smoke, it doesn't work! smoothed data Statistical data that has been averaged or otherwise manipulated so that the curves on its graph are smooth and free of irregularities. smoothing circuit Electronic filtering circuit in a DC power supply that removes the ripples from AC power. SMP See symmetric multiprocessing. SMPTE (Society for Motion Picture and TV Engineers) Organization that prepares standards and documentation for TV production. SMPTE time code records hours, minutes, seconds and frames on audio or videotape for synchronization purposes. Address: 595 W. Hartsdale Ave., White Plains, NY 10607, 914/761-1100. SMT (1) See surface mount. (2) (Station ManagemenT) FDDI network management protocol that provides direct management. Only one node requires the software. SMTP (Simple Mail Transfer Protocol) E-mail protocol used in TCP/IP networks. SNA (Systems Network Architecture) IBM mainframe network standards introduced in 1974. Originally a centralized architecture with a host computer controlling many terminals, enhancements, such as APPN and APPC (LU 6.2), have adapted SNA to today's peer-to-peer communications and distributed computing environment. Following are some of SNA's basic concepts.  Nodes and Data Links In SNA, nodes are end points or junctions, and data links are the pathways between them. Nodes are defined as Type 5 (hosts), Type 4 (communications controllers) and Type 2 (peripheral; terminals, PCs and midrange computers). Type 2.0 nodes can communicate only with the host, and Type 2.1 nodes can communicate with other 2.1 nodes (peer-to-peer) without going to the host. Data links include high-speed local channels, the SDLC data link protocol and Token Ring.  SSCPs, PUs and LUs The heart of a mainframe-based SNA network is the SSCP (System Services Control Point) software that resides in the host. It manages all resources in its domain. Within all nodes of an SNA network, except for Type 2.1, there is PU (Physical Unit) software that manages node resources, such as data links, and controls the transmission of network management information. In Node Type 2.1, Control Point software performs these functions. In order to communicate user data, a session path is created between two end points, or LUs (Logical Units). When a session takes place, an LU-LU session is established between an LU in the host (CICS, TSO, user appliction, etc.) and an LU in the terminal controller or PC. An LU 6.2 session provides peer-to-peer communication and lets either side initiate the session.  VTAM and NCP VTAM (Virtual Telecommunications Access Method) resides in the host and contains the SSCP, the PU for the host, and establishes the LU sessions within the host. NCP (Network Control Program) resides in the communications controller (front end processor) and manages the routing and data link protocols, such as SDLC and Token Ring.  SNA Layers SNA is implemented in functional layers with each layer passing control to the next layer. This layering is called a protocol stack. User 敖陳陳祖陳陳朕 Transaction Program to program communications 7 Services for e-mail, file sharing, etc. (DIA, SNA/DS, DDM, etc.) 団陳陳陳陳陳調 6Presentation Formats data for terminal. Services (3270 screens, APPC, etc.) 団陳陳陳陳陳調 5 Data flow Assigns sequence nos., controls Control direction, groups related data. Provides end user acknowledgment. 団陳陳陳陳陳調 Transmission Logical end-to-end. Checks packet 4 Control sequence, handles encryption and paces transmission. 団陳陳陳陳陳調 Path Path control 陳陳 3 Control Physical end-to-end (routing). 団陳陳陳陳陳調 Data link Error detection and 2 Control correction. (Local channel, SDLC, Token Ring, X.25, etc.) 団陳陳陳陳陳調 1 Physical Wires, signals. Control (RS232, 802.5, etc.) 陳 青陳賃賃陳陳潰 敖陳珍珍陳陳朕 1 Physical  Back up the hierarchy to the other user.  SNA vs OSI SNA had major influence on the international OSI model; however, OSI does not implement every layer exactly the same.  SNA OSI  敖陳陳陳陳陳陳 敖陳陳陳陳陳陳  Transaction Application  団陳陳陳陳陳陳 団陳陳陳陳陳陳  Presentation Presentation  団陳陳陳陳陳陳 団陳陳陳陳陳陳  Data flow Session  団陳陳陳陳陳陳 団陳陳陳陳陳陳  Transmission Transport  団陳陳陳陳陳陳 団陳陳陳陳陳陳  Path control Network  団陳陳陳陳陳陳 団陳陳陳陳陳陳  Data link Data link  団陳陳陳陳陳陳 団陳陳陳陳陳陳  Physical Physical  青陳陳陳陳陳陳 青陳陳陳陳陳陳  SNADS (SNA Distribution Services) IBM e-mail system for SNA networks. It also provides store and forward capabilities if a user's machine is unavailable to receive a transmission. snap to Feature in a drawing program that moves a text or graphic element to the closest grid line. snapshot Storing the contents of memory including all hardware registers and status indicators. It is periodically taken in order to restore the system in the event of failure. snapshot dump Memory dump of selected portions of memory. snapshot program Trace program that provides selected dumps of memory when specific instructions are executed or when certain conditions are met. snd (SouND resource) Macintosh resource fork that contains sound information, including compression ratios if used and sampling rate. sneakernet Carrying floppy disks from one machine to another to exchange information, when you don't have a network. sniffer Software and/or hardware that analyzes traffic and detects bottlenecks and problems in a network. SNMP (Simple Network Management Protocol) Format used for network management data. Data is passed between SNMP agents (processes that monitor activity in hubs, routers, bridges, etc.) and the workstation used to oversee the network. Originating in the UNIX community, it has spread to VMS, DOS and other environments. SNMP uses Management Information Bases (MIBs), which are databases that define what information is obtainable from a networked device and what can be controlled (turned off, on, etc.). SNOBOL (StriNg Oriented symBOlic Language) One of the first list processing languages (Bell Labs; early 1960s). It was used for text processing and compiler development. snow Flickering snow-like spots on a video screen caused by display electronics that are too slow to respond to changing data. socket (1) Receptacle which receives a plug. (2) BSD UNIX function that lets an application access a communications protocol by "opening a socket" and declaring a destination. soft Flexible and changeable. Software can be reprogrammed for different results. The computer's soft nature is its greatest virtue; however, the reason it takes so long to get new systems developed has little to do with the concept. It is based on how systems are developed (file systems vs database management), the programming languages used (assembly vs high-level), combined with the skill level of the technical staff, compounded by the organization's bureaucracy. soft boot Same as warm boot. soft copy Refers to data displayed on a video screen. Contrast with hard copy. soft error Recoverable error, such as a garbled message that can be retransmitted. Contrast with hard error. soft font Set of characters for a particular typeface that is stored on the computer's hard disk, or in some cases the printer's hard disk, and downloaded to the printer before printing. Contrast with internal font and font cartridge. soft hyphen Hyphen that prints if it winds up at the end of the line, but does not print otherwise. Contrast with hard hyphen. See discretionary hyphen. soft key Keyboard key simulated by an icon on screen. soft patch Quick fix to machine language currently in memory that only lasts for the current session. soft return Code inserted by the software into a text document to mark the end of the line. When the document is printed, the soft return is converted into the end- of-line code required by the printer. Soft returns are determined by the right margin and change when the margins are changed. In graphics-based environments, such as in the Macintosh, soft returns are not used as the text must be free to change within movable windows. With PCs, soft return codes differ; for example, WordPerfect uses a return (ASCII 13) and WordStar uses a line feed (ASCII 10). Contrast with hard return. soft sectored Common method of identifying sectors on a disk by initially recording sector information on every track with a format program. Contrast with hard sectored. Soft-Switch E-mail switching software and hardware from Soft- Switch, Inc., Wayne, PA, that provides an e-mail backbone for organizations with diverse e-mail systems. It directly supports X.400, SNADS and SMTP and provides gateways to other e-mail systems. Soft-Switch Central is software for IBM MVS and VM mainframes, and its EMX 88000-based e-mail server connects to Token Ring, Ethernet, X.25 and SDLC. Softstrip Optical scanner from Softstrip, Inc., Waterbury, CT, that reads a unique, encoded pattern of 50 to 600 bytes of data per inch. software Instructions for the computer. A series of instructions that performs a particular task is called a program or software program. The two major categories are system software and application software. System software is made up of control programs, including the operating system, communications software and database manager. Application software is any program that processes data for the user (inventory, payroll, spreadsheet, word processor, etc.). software architecture Design of application or system software that incorporates protocols and interfaces for interacting with other programs and for future flexibility and expandability. A self-contained, stand-alone program would have program logic, but not a software architecture. Software Carousel Task switching program for PCs from SoftLogic Solutions, Inc., Manchester, NH, that allows the user to have up to a dozen applications open at the same time and switch back and forth between them. software engineering Design, development and documentation of software. software failure Inability of a program to continue processing due to erroneous logic. Same as crash, bomb and abend. software house Organization that develops customized software for a customer. Contrast with software publisher, which develops and markets software packages. software IC Object-oriented programming class packaged for sale. Term coined by The Stepstone Corp. software interface Same as API. software interrupt Interrupt caused by an instruction in the program. See interrupt. software package Application program developed for sale to the general public. software program Commonly used to refer to a computer application. All computer software is made up of computer programs. All computer programs are software. software programmer Same as systems programmer. software protection See copy protection. software publisher Organization that develops and markets software. It does market research, production and distribution of software. It may develop its own software, contract for outside development or obtain software that has already been written. software stack Stack implemented in memory. See stack. software tool Program that aids in the development of other software programs. It may assist the programmer in the design, coding, compiling, link editing or debugging phases. software vendors Following is the calendar 1991 worldwide packaged software ranking from the June 1992 Special Issue of Software Magazine. Consulting, custom services and programming revenues are excluded. Hardware manufacturers are not included. See vendors. Reprinted with permission of Sentry Publishing Co., Inc., 1900 West Park Drive, Westborough, MA 01581.  TOP 50 INDEPENDENT SOFTWARE VENDORS (* = privately held) Total number employees朕 1991 Packaged  COMPANY NAME Software revenue HQ city (date founded) ($ millions)  1 MICROSOFT CORP. Redmond, WA (1975) 10000 1801  2 COMPUTER ASSOCIATES INT'L., INC. Islandia, NY (1976) 7700 1438  3 LOTUS DEVELOPMENT CORP. Cambridge, MA (1982) 4324 829  4 ORACLE CORP. Redwood Shores, CA (1977) 7786 661  5 WORDPERFECT CORP.* Orem, UT (1979) 2896 603  6 NOVELL, INC. Provo, UT (1983) 3100 571  7 DUN & BRADSTREET SOFTWARE Atlanta, GA (1990) 3400 549  8 BORLAND INT'L. INC. Scotts Valley, CA (1983) 2000 502  9 SAP AG (SAP AMERICA) Lester, PA (1972) 2685 375  10 THE ASK COMPANIES Mountain View, CA (1972) 2200 315  11 SOFTWARE AG* Reston, VA (1969) 4000 304  12 SAS INSTITUTE, INC.* Cary, NC (1976) 2386 295  13 LEGENT CORP. Vienna, VA (1989) 1300 215  14 SYMANTEC CORP. Cupertino, CA (1982) 770 196  15 INFORMATION BUILDERS INC.* New York, NY (1975) 1650 176  16 BMC SOFTWARE, INC. Sugar Land, TX (1980) 738 170  17 CANDLE CORP. Los Angeles, CA (1977) 950 169  18 ALDUS CORP. Seattle, WA (1984) 952 164  19 CINCOM SYSTEMS, INC.* Cincinnati, OH (1968) 1355 158  20 INFORMIX SOFTWARE, INC. Menlo Park, CA (1980) 941 149  21 SOFTWARE PUBLISHING CORP. Mountain View, CA (1980) 750 141  22 COMPUWARE CORP.* Farmington Hills, MI('73) 1379 137  23 AMERICAN MANAGEMENT SYSTEMS Arlington, VA (1970) 3120 137  24 THE CONTINUUM CO. Austin, TX (1968) 1100 129  25 THE SANTA CRUZ OPERATION Santa Cruz, CA (1979) 1200 125  26 STERLING SOFTWARE, INC. Dallas, TX (1983) 2000 123  27 GOAL SYSTEMS INT'L. INC. Columbus, OH (1975) 900 121  28 SYSTEMS CENTER, INC. Reston, VA (1981) 939 120  29 SYSTEM SOFTWARE ASSOCIATES INC. Chicago, IL (1981) 800 119  30 COMSHARE, INC. Ann Arbor, MI (1966) 1100 117  31 SYBASE, INC. Emeryville, CA (1984) 1100 115  32 COGNOS, INC. Ottawa, Ontario (1969) 1091 108  33 CGI SYSTEMS, INC. Berwyn, PA (1951) 4050 104  34 BOOLE & BABBAGE, INC. Sunnyvale, CA (1967) 640 99  35 MICRO FOCUS GROUP PLC. Palo Alto, CA (1976) 548 98  36 KNOWLEDGEWARE, INC. Atlanta, GA (1979) 775 97  37 J.D. EDWARDS & CO.* Denver, CO (1977) 934 91  38 INTERLEAF, INC. Waltham, MA (1981) 820 81  39 UNIX SYSTEM LABS, INC.* Summit, NJ (1991) 700 80  40 CENTRAL POINT SOFTWARE, INC. Beaverton, OR (1981) 310 75  41 POLICY MANAGEMENT SYSTEMS CORP. Columbia, SC (1974) 4309 73  42 AMERICAN SOFTWARE Atlanta, GA (1970) 854 72  43 SOFTWARE ENGINEERING OF AMERICA, INC.* Lake Success, NY (1982) 250 67  44 INFORMATION RESOURCES, INC. Waltham, MA (1982) 528 66  45 LUCAS MANAGEMENT SYSTEMS Fairfax, VA (1977) 697 66  46 ANDERSEN CONSULTING* Chicago, IL (1954) 25100 65  47 ATTACHMATE CORP. Bellevue, WA (1984) 500 65  48 BANYAN SYSTEMS, INC. Westborough, MA (1983) 625 62  49 SOFTLAB, INC. San Francisco, CA (1971) 800 54  50 INTERSOLV, INC. Rockville, MD (1991) 530 53 SOG (Small Outline Gullwing) Same as SOIC. SOIC (Small Outline IC) Small-dimension, surface mount DIP that uses gullwing-shaped pins extending outward. SOJ (Small Outline J lead) Small-dimension, surface mount DIP that uses J-shaped pins extending inward. Solaris 2.0 Multitasking, multiprocessing distributed computing environment from SunSoft for SPARC computers and 386s and up. Solaris 2.0 for SPARC machines is backward compatible with Solaris 1.0, and includes the SunOS 5.0 operating system (based on UNIX SVR4), Sun's ONC networking products (NFS, NIS, etc.), OpenWindows (Sun's version of X Windows) and Sun's Open Look graphical interface with DeskSet utilities that provide multimedia mail and drag & drop capability. Solaris 2.0 for x86 machines will run applications written for Solaris, Sun's INTERACTIVE UNIX for x86 machines, as well as DOS and Windows applications. solder mask Insulating pattern applied to a printed circuit board that exposes only the areas to be soldered. solenoid Magnetic switch that closes a circuit, often used as a relay. solid logic Same as solid state. solid modeling Mathematical technique for representing solid objects. It is the least abstract form of CAD. Unlike wireframe and surface modeling, solid modeling systems ensure that all surfaces meet properly and that the object is geometrically correct. A solid model can also be sectioned (cut open) to reveal its internal features. Solids allow interference checking, which tests to see if two or more objects occupy the same space. solid state Electronic component or circuit made of solid materials, such as transistors, chips and bubble memory. There is no mechanical action in a solid state device, although an unbelievable amount of electromagnetic action takes place within. For data storage, solid state devices are much faster and more reliable than mechanical disks and tapes, but are more expensive. Although solid state costs continually drop, disks, tapes and optical disks also continue to improve their cost/performance ratio. The first solid state device was the "cat's whisker" of the 1930s. A whisker-like wire was moved around on a solid crystal in order to detect a radio signal. solid state disk Disk drive made of memory chips used for high-speed data access or in adverse environments. Dynamic RAM solid state disks are used in battery-powered, hand-held devices as well as in desktop units with hundreds of megabytes of storage that contain their own UPS systems. solid state memory Any transistorized, semiconductor or thin film memory that contains no mechanical parts. solid state relay Relay that contains no mechanical parts. All switching mechanisms are semiconductor or thin film components. solver Mathematical mechanisms that allow spreadsheets to perform goal seeking. SONET (Synchronous Optical NETetwork) International standard for broadband transmission through fiber optic cables in the 50 megabit to 13 gigabit per second range. It is included in the Broadband ISDN (BISDN) specification. sort To reorder data into a new sequence. The operating system can typically sort file names and text lists. In word processors, sorting allows for all the text in the document or a marked block of text to be resequenced into either an ascending (normal) or descending sequence. In database programs, sorting resequences all the records in the file by one or more fields and often generates an entirely new copy of the file. sort algorithm Formula used to reorder data into a new sequence. Like all complicated problems, there are many solutions that can achieve the same results. One sort algorithm can resequence data faster than another. In the early 1960s, when tape was "the" storage medium, the sale of a computer system may have hinged on the sort algorithm, since without direct access capability, every transaction had to be sorted into the sequence of the master file. sort field Same as sort key. sort key Field or fields in a record that dictate the sequence of the file. For example, the sort keys STATE and NAME arrange the file alphabetically by name within state. STATE is the major sort key, and NAME is the minor key. sorter (1) Sort program. (2) Person who manually puts data into a specific sequence. (3) Early tabulating machine that routed punched cards into separate stackers based on the content of a card column. The complete operation required passing the cards through the machine once for each column sorted. SOS (1) (Silicon On Sapphire) MOS chip-fabrication method that places a thin layer of silicon over a sapphire substrate (base). (2) (Sophisticated Operating System) Operating system used on the Apple III. sound bandwidth Range of sound frequencies. The human ear can perceive approximately from 20 to 20,000Hz, but human voice is confined to within 3,000Hz. sound board Same as sound card. sound card Personal computer expansion board that generates sound and provides outputs for external amplification and speakers. Unshielded speakers located too close to CRT screens will cause visible interference. Shielded speakers are commonly available for computer use. See MPC. source (1) Source of current in a MOS transistor. Same as emitter in a bipolar transistor. (2) (The Source) Online information service in McLean, VA, launched in 1979 and purchased by CompuServe in 1989. source code Program in its original form as written by the programmer. It is not executable by the computer directly. It must be converted into machine language by compilers, assemblers and interpreters. In some cases, source code can be converted into another dialect or a different language by a conversion program. source computer Computer in which a program is being assembled or compiled. Contrast with object computer. source data Original data that is handwritten or printed on a source document or typed into the computer system from a keyboard or terminal. source data acquisition Same as source data capture. source data capture Capturing data electronically when a transaction occurs; for example, at the time of sale. source directory Directory from which data is obtained. source disk Disk from which data is obtained. Contrast with target disk. source document Paper form onto which data is written. Order forms and employment applications are examples. source drive Disk or tape drive from which data is obtained. Contrast with target drive. source language Language used in a source program. source program Program in its original form, as written by the programmer. source routing Communications protocol in which stations are aware of bridges in the network and route messages via the bridges. Contrast with transparent bridging. See SRT. source statement Instructional phrase in a programming language (source language). SPA (Software Publishers Assn.) Trade organization of the personal computer software industry that supports legislation for copyright enforcement. It conducts raids on organizations suspected of illegal copying and files lawsuits against violators. To blow the whistle on a company that has a policy of making illegal copies, call 800/388-PIR8. Address: 1730 M St., N.W., Washington, DC 20036, 202/452-1600. space In digital electronics, a 0 bit. Contrast with mark. space/time The following units of measure are used to define storage and transmission capacities. S P A C E Bits or bytes Kilo (K) Thousand 1,024 Mega (M) Million 1,048,576 Giga (G) Billion 1,073,741,824 Tera (T) Trillion 1,099,511,627,776 Peta (P) Quadrillion 1,125,899,906,842,624 T I M E Fraction of second Millisecond (ms) Thousandth 1/1,000 Microsecond (s) Millionth 1/1,000,000 Nanosecond (ns) Billionth 1/1,000,000,000 Picosecond (ps) Trillionth 1/1,000,000,000,000 Femtosecond (fs) Quadrillionth 1/100,000,000,000,000 Storage/channel capacity measured in: CPU word size Bits Bus size Bits Disk, tape Bytes MEMORY Overall capacity Bytes SIMM or SIP module Bytes Individual chip Bits Transmission speed measured in: Network line/channel Bits per second Disk transfer rate Bits or bytes per second Disk access time Milliseconds Memory access time Nanoseconds Machine cycle Microseconds/Nanoseconds Instruction execution Microseconds/Nanoseconds Transistor switching Nanoseconds, Picoseconds and Femtoseconds spaghetti code Program code written without a coherent structure. The logic moves from routine to routine without returning to a base point, making it hard to follow. It implies excessive use of the GOTO instruction, which directs the computer to branch to another part of the program without a guarantee of returning. In structured programming, functions are used, which are subroutines that guarantee a return to the instruction following the one that called it. SPARC (Scalable Performance ARChitecture) 32-bit RISC CPU developed by Sun and licensed by SPARC Int'l., Menlo Park, CA. spatial data Data represented as 2-D or 3-D images. spawn To launch another program from the current program. The DOS TSR version of this Glossary is called POPGLOSS.EXE. It resides in RAM and "spawns" GLOSS.EXE when the hotkey is pressed. spec See specs and specification. spec sheet Detail listing of the components of a system. special character Non-alpha or non-numeric character, such as @, #, $, %, &, * and +. special-purpose computer Computer designed from scratch to perform a specific function. Contrast with general-purpose computer. special-purpose language Programming language designed to solve a specific problem or class of problems. For example, LISP and Prolog are designed for and used extensively in AI applications. Even more specific are languages such as COGO, for civil engineering problems, and APT for directing machine tools. Contrast with general-purpose language. specification Definition (layout, blueprint, design) of hardware or software. See specs and functional specification. SPECmark (Systems Performance Evaluation Cooperative MARK) Suite of 10 benchmarks that test integer (SPECint) and floating point (SPECfp) performance of a computer. SPEC reporting requires all 10 numbers as users may only need subsets. A VAX-11\780 is a one-SPECmark machine, and SPECmarks closely track VUPs ratings from Digital's internal benchmarks. specs (SPECificationS) Details of the components built into a device. See specification. spectral color In computer graphics, the color of a single wavelength of light, starting with violet at the low end and proceeding through indigo, blue, green, yellow and orange and ending with red. spectral response Variable output of a light-sensitive device that is based on the color of the light it perceives. spectrum Range of electromagnetic frequencies. speech recognition Same as voice recognition. speech synthesis Generating machine voice by arranging phonemes (k, ch, sh, etc.) into words. It is used to turn text input into spoken words for the blind. Speech synthesis performs realtime conversion without a pre-defined vocabulary, but does not create human- sounding speech. Although individual spoken words can be digitized into the computer, digitized voice takes a lot of storage, and resulting phrases still lack inflection. speed buffering Technique that compensates for speed differences between input and output. Data is accepted into the buffer at high speed and transferred out at low speed, or vice versa. Speed Doubler See 486. speed of electricity/light Approximately 186,000 miles per second. Electricity and light travel around the equator over seven times per second. This inherent speed of Mother Nature is why computers are so fast. Within the tiny chip, electricity has to flow only a couple of millimeters, and, within an entire computer, only a few feet. As fast as that is, it's never fast enough. There is resistance in the lines, and even though transistors switch in billionths of a second, CAD, image processing and scientific applications are always exhausting the fastest computers. spelling checker Separate program or word processing function that tests for correctly spelled words. It can test the spelling of a marked block, an entire document or group of documents. Advanced systems check for spelling as the user types and can correct common typos and misspellings on the fly. Spelling checkers simply compare words to a dictionary of words, and the wrong use of a correctly-spelled word cannot be detected. See grammar checker. spherization In computer graphics, turning an image into a sphere. SPI (Service Provider Interface) Programming interface for developing Windows drivers under WOSA. In order to provide common access to services, the application is written to a particular interface, such as ODBC and MAPI, and the developer of the service software (DBMS, e-mail, etc.) writes to the SPI for that class of service. spike Also called a transient, a burst of extra voltage in a power line that lasts only a fraction of a second. Contrast with sag. See surge. spindle Rotating shaft in a disk drive. In a fixed disk, the platters are attached to the spindle. In a removable disk, the spindle remains in the drive. SpinRite Popular low-level formatting program for PCs from Gibson Research, Aliso Viejo, CA, that reformats without erasing data. It rewrites only sector ID, which may have drifted over time. Version 3.0 can low-level format IDE drives, which have typically required proprietary format programs. SPL (1) (Systems Programming Language) HP 3000 assembly language. See assembly language for an SPL program example. (2) (Structured Programming Language) See structured programming. spline In computer graphics, a smooth curve that runs through a series of given points. The term is often used to refer to any curve. See Bezier and B-spline. split screen Display of two or more sets of data on screen at the same time. It implies that one set of data can be manipulated independently of the other. Split screens, or windows, are usually created by the operating system or application software, rather than the hardware. spooling (Simultaneous Peripheral Operations OnLine) Overlapping of low-speed operations with normal processing. It originated with mainframes in order to optimize slow operations such as reading cards and printing. Card input was read onto disk and printer output was stored on disk. In that way, the actual business data processing was done at high speed, since all I/O was on disk. Today, spooling is used to buffer data for the printer as well as remote batch terminals. See print spooler. spread spectrum Radio transmission that continuously changes carrier frequency according to a unique pattern in both sending and receiving devices. It is used for security as well as to allow multiple wireless transmissions in the same space. spreadsheet Software that simulates a paper spreadsheet, or worksheet, in which columns of numbers are summed for budgets and plans. It appears on screen as a matrix of rows and columns, the intersections of which are identified as cells. Spreadsheets can have thousands of cells and can be scrolled horizontally and vertically in order to view them. The cells are filled with: 1. labels 2. numeric values 3. formulas The labels, can be any descriptive text, for example, RENT, PHONE or GROSS SALES. The values are the actual numeric data used in the budget or plan, and the formulas command the spreadsheet to do the calculations; for example, SUM CELLS A5 TO A10. Formulas are easy to create, since spreadsheets allow the user to point to each cell and type in the arithmetic operation that affects it. Roughly speaking, a formula is created by saying "this cell PLUS that cell TIMES that cell." The formulas are the spreadsheet's magic. After numbers are added or changed, the formulas will recalculate the data either automatically or with the press of a key. Since the contents of any cell can be calculated with or copied to any other cell, a total of one column can be used as a detail item in another column. For example, the total from a column of expense items can be carried over to a summary column showing all expenses. If data in the detail column changes, its column total changes, which is then copied to the summary column, and the summary total changes. Done manually, each change would require recalculating, erasing and changing the totals of each column. The automatic ripple effect allows users to create a plan, plug in different assumptions and immediately see the impact on the bottom line. This "what if?" capability makes the spreadsheet indispensable for budgets, plans and other equation-based tasks. The spreadsheet originated with VisiCalc in 1978 for the Apple II, and was followed by SuperCalc, Multiplan, Lotus 1-2-3 and a host of others. CLASSES OF SPREADSHEETS Standard Every spreadsheet creates a two-dimensional matrix of rows and columns. In order to summarize data, totals from various parts of the spreadsheet can be summed to another part of the spreadsheet. Dynamic Linking Allows data in one spreadsheet to automatically update another spreadsheet. Although often referred to as 3-D spreadsheets, dynamic linking creates the effect of a third dimension in a separate file. For example, several detail files can be summarized into one summary file. Excessive linking is difficult to manage, since the relationships span several physical files. 3-Dimensional Each cell in the spreadsheet has an X, Y and Z reference. For example, a spreadsheet of expense items by month uses two dimensions, but expense items by month by department requires three dimensions. While this method is superior for consolidating and summarizing data, it lacks some of the flexibility inherent in the dynamic linking approach, since all pages must have essentially the same structure. In addition, all data must reside in one file as with a standard 2-D spreadsheet. Relational Spreadsheet This method stores the data separate and apart from the formulas. Data is stored in a central database and the formulas are stored in the spreadsheet. When the spreadsheet is called up, the data from the database is copied into it, thus ensuring that everyone's spreadsheet contains current data. Relational spreadsheets reference data by name rather than by row and column number. With name references, data can be used in multiple spreadsheets with greater accuracy, and new spreadsheets can be created more easily. A spreadsheet that analyzes the budget for one department can analyze the budget for any department simply by changing the department name and recalculating. Name references make it possible to analyze data from multiple perspectives. Since data isn't tied to cell references as with 3-D spreadsheets, more than three dimensions can be created. For example, in a corporate budget, numbers are kept for every combination of accounts, time periods and departments in both forecast and actual versions. A view of accounts by department by period can be automatically switched to a view of accounts by period by version. Instead of complicated spreadsheet programming, the relational spreadsheet prepares the views automatically. spreadsheet compiler Software that translates spreadsheets into stand- alone programs that run without the spreadsheet package that created them. sprite Independent graphic object controlled by its own bit plane (area of memory). Commonly used in video games, sprites move freely across the screen, passing by, through and colliding with each other with much less programming. sprocket feed Same as pin feed. SPS (Standby Power System) UPS system that switches to battery backup upon detection of power failure. SPS Association Nonprofit organization dedicated to an open PostScript standard. Address: 7 Stuart Road, Chelmsford, MA 01824. SPSS Statistical package from SPSS, Inc., Chicago, that runs on PCs, most mainframes and minis and is used extensively in marketing research. It provides over 50 statistical processes, including regression analysis, correlation and analysis of variance. Originally named Statistical Package for the Social Sciences, it was written by Norman Nie, a professor at Stanford. In 1976, he formed SPSS, Inc. spt (Sectors Per Track) Number of sectors in one track. SPX (Sequenced Packet EXchange) NetWare communications protocol used for interprocess communications (IPC). It guarantees that an entire message arrives intact and uses the NetWare IPX protocol as its delivery mechanism. SQL (Structured Query Language) Pronounced "SQL" or "see qwill," a language used to interrogate and process data in a relational database. Originally developed by IBM for its mainframes, there have been many implementations created for mini and micro database applications. SQL commands can be used to interactively work with a database or can be embedded within a programming language to interface to a database. The following SQL query selects customers with credit limits of at least $5,000 and puts them into sequence from highest credit limit to lowest. SELECT NAME, CITY, STATE, ZIPCODE FROM CUSTOMER WHERE CREDITLIMIT > 4999 ORDER BY CREDITLIMIT DESC SQL/DS (SQL/Data System) Full-featured relational DBMS from IBM for VSE and VM environments that has integrated query and report writing facilities. SQL engine Program that accepts SQL commands and accesses the database to obtain the requested data. Users' requests in a query language or database language must be translated into an SQL request before the SQL engine can process it. SQL Server Relational DBMS from Sybase, Inc., Emeryville, CA, that runs on OS/2-based PCs, VAXs and UNIX workstations. It is designed for network use and is accessed by applications using SQL or via Sybase's own QBE and decision support utilities. It is also available from Microsoft as Microsoft SQL Server for OS/2. square wave Graphic image of a digital pulse as visualized on an oscilloscope. It appears square because it rises quickly to a particular amplitude, stays constant for the duration of the pulse and drops fast at the end of it. SQUID (Superconducting Quantum Interference Device) Electronic detection system that uses Josephson junctions circuits. It is capable of detecting extremely weak signals. SRAM See static RAM. SRPI (Server Requester Programming Interface) IBM programming interface that allows a PC to interact with a mainframe. See ECF. SRT (Source Routing Transparent) IEEE-standard technology that allows bridging between Ethernet and token ring networks (Token Ring, FDDI). Existing token ring bridges are not compatible with SRT bridges, but Proteon's (Westborough, MA) Adaptive SRT bridges are compatibile with the installed base. See source routing. SS/DD (Single Sided/Double Density) Refers to earlier floppy disk formats that store data on only one side of the disk. SSCP (System Services Control Point) Controlling program in an SNA domain. It resides in the host and is a component within VTAM. SSD See solid state disk. SSE Protected Mode full-screen editor in OS/2. SSI (Small Scale Integration) Up to 100 transistors on a chip. See MSI, LSI, VLSI and ULSI. SSP (System Support Program) Multiuser, multitasking operating system from IBM that is the primary control program for System/34 and System/36. ST (1) Personal computer series from Atari that uses a Motorola 68000 CPU and includes the GEM interface, ROM-based TOS operating system, a MIDI interface and a three-voice sound chip. The 520ST has 512K RAM; the 1040ST has 1MB. Display is 640x200, 16 colors. The current model is the 1040STE. (2) Type of fiber optic connector. ST412 Enhancement to ST506 standard that buffers track- to-track commands for a continuous seek to the required track. All new ST506 drives/controllers incorporate this, thus ST412, ST506/412 and current ST506 units are the same. ST506 Hard disk interface commonly used in drives 40MB and less. It transfers data at 625 KBytes/sec and uses the MFM encoding method. See ST412 and hard disk. ST506 RLL (ST506 Run-Length Limited) Hard disk interface (also called RLL interface) that increases capacity and speed by 50% over ST506 MFM drives and transfers data at 937 KBytes/sec. With MFM drives certified for increased capacity, the ST506 MFM controller can be replaced with an ST506 RLL controller and the drive can be reformatted. See hard disk. stack (1) Set of hardware registers or a reserved amount of memory used for arithmetic calculations or to keep track of internal operations. Stacks keep track of the sequence of routines called in a program. For example, one routine calls another, which calls another and so on. As each routine is completed, the computer returns control to the calling routine all the way back to the first one that started the sequence. Stacks used in this way are LIFO based: the last item, or address, placed (pushed) onto the stack is the first item removed (popped) from the stack. Stacks are also used to hold interrupts until they can be serviced. Used in this manner, they are FIFO stacks, in which the first item onto the stack is the first one out of the stack. See DOS Stacks. An "internal stack failure" is a fatal error which means that the operating system has lost track of its next operation. Restarting the computer usually corrects this, otherwise the operating system may have to be re-installed. (2) See HyperCard. stack overflow Error condition that occurs when there is no room in the stack for a new item. A stack underflow occurs when an item is called for, but the stack is empty. stack pointer Address that identifies the location of the most recent item placed on the stack. stacker (1) Output bin in a document feeding or punched card machine. Contrast with hopper. (2) (Stacker) Realtime compression program from Stac Electronics, Carlsbad, CA, that doubles (approximately) the disk capacity of a PC and is transparent to the user. A coprocessor board is optionally available. stackware HyperCard application that is made up of a HyperCard stack (data) and HyperTalk programming. STAIRS (STorage And Information Retrieval System) IBM text document management system for mainframes. It allows users to search for documents based on key words or word combinations. standard cell Finished design of an electronic function ready for chip fabrication. It can be as small as a clock circuit or as large as a microprocessor. It is used to make custom-designed chips. standard deviation In statistics, the average amount a number varies from the average number in a series of numbers. Standard Mode Windows operation mode. See Windows. standards & compatibility Machine Languages Data Codes Hardware Interfaces Storage Media Operating Systems Communications Standards is the most important issue in the computer field. As an unregulated industry, we have wound up with thousands of data formats and languages, but very few standards that are universally used. This subject is as heated as politics and religion to vendors and industry planners. No matter how much the industry talks about compatibility, new formats and languages appear routinely. The standards makers are always trying to cast a standard in concrete, while the innovators are trying to create a new one. Even when standards are created, they are violated as soon as a new feature is added by the vendor. If a format or language is used extensively and others copy it, it becomes a de facto standard and may become as widely used as official standards from ANSI and IEEE. When de facto standards are sanctioned by these organizations, they become stable, at least, for a while. In order to truly understand this industry, it is essential to understand the categories for which standards are created. MACHINE LANGUAGES Machine language is the fundamental standard for hardware compatibility. Vendors often have several families of computers, each with different machine languages. For example, although all IBM mainframes use the same machine language, IBM's AS/400, RS/6000 and PC series are each different. After a program is written, it must be translated (assembled, compiled or interpreted) into the machine language that the computer understands. In order to run in a different machine, the program must be reassembled or recompiled into a different machine language, providing there are appropriate translators. Since the late 1960s, companies seeking a chunk of the IBM market have designed computers that run the same machine language as the IBM computers. RCA's Spectra 70 was the first IBM-compatible mainframe, and companies, such as Amdahl, Itel, National Advanced Systems, Hitachi and Fujitsu have introduced IBM-compatible mainframes at one time or another. IBM PC machine language compatibility is achieved by using a processor from Intel's 8086 family of microprocessors. Machine language compatibility can also be achieved by simulation or emulation. A simulator is software that translates and executes a program in a foreign machine language. An emulator is hardware that executes the machine language of another computer and is used to encourage customers to buy a new series of computers. For example, in the 1960s, IBM provided an optional emulator in its System/360 series that executed most of its customer's existing 1401 programs. The terms simulator and emulator are used interchangeably. DATA CODES The data code is built into the computer and determines how each character (letter, digit or special character) is represented in binary code. Fortunately, there are only two major data codes in wide use today, EBCDIC and ASCII. That means alphabetic data and numbers stored in one code can easily be converted to the other. IBM mainframes and minicomputers and other mainframes use EBCDIC. ASCII is used by all personal computers, most minicomputers and some mainframes. However, ASCII is only a 7-bit code with 128 character combinations, and the 8th bit (which derives another 128 values) is used differently. In the PC, it is used for foreign language characters and line drawing symbols. In the Macintosh, it can be defined by the programmer. Other codes are used in various different machines, but all data codes can be converted from one to another with one possible exception. If numbers are stored in floating point and the new machine can't handle as many digits as the old machine, a loss of precision may occur. When data is moved to a different computer, data code conversion is often only one small part of the conversion process. Data, text and graphics file formats must also be converted if different programs are going to process them. The following is a sample of ASCII and EBCDIC code. See ASCII chart, hex chart and EBCDIC chart.  Character ASCII EBCDIC space 01000000 00100000 period 01001011 00101110 < sign 01001100 00111100 + sign 01001110 00101011 $ sign 01011011 00100100 A 11000001 01000001 B 11000010 01000010 HARDWARE INTERFACES The hardware interface specifies the plugs, sockets, cables and electrical signals that pass through each line between the CPU and a peripheral device or communications network. Common hardware interfaces for personal computers are the Centronics parallel interface used for printers and the RS-232 interface, typically used for modems, graphics tablets, mice and printers. In addition, the ST506, RLL, ESDI and SCSI interfaces are used for disks and tapes, and the GPIB IEEE 488 standard is used for process control instruments. The bus in a computer's motherboard, into which additional printed circuit boards are inserted, is a hardware interface. For example, the Micro Channel in IBM's PS/2 series accepts a physically different board than the original PC bus. LANs, such as ARCNET and Ethernet, also dictate the hardware interface as part of their specifications. STORAGE MEDIA There are many varieties of disk packs, disk cartridges, floppy disks, reel-to-reel tapes, tape cartridges and tape cassettes. Each one has its own unique shape and size and can be used only in drives designed to accommodate them. With removable media, the physical standard is half the compatibility issue. The other half is the recording pattern, which is invisible to the human eye. Magnetic tapes and disks fresh out of the box are blank. The recording tracks are placed onto the surface by the read/write head of the storage drive. Thus, the same floppy disk that stores 720K bytes in one disk drive, can hold 800K if formatted for another. If the computer reads an incompatible tape or reads and writes and incompatible disk, it will signal a read/write error. For minicomputers and mainframes, the half-inch magnetic tape reel is a common interchangeable medium. For personal computers, the 5.25" minifloppy and the 3.5" microfloppy disks are used. OPERATING SYSTEMS An operating system is a master control program that manages the running of the computer system. In all environments, except for specialized scientific and process control applications, the operating system interacts with the application programs. The application programs must "talk" to the operating system. If application programs are moved to a different computing environment, they have to be converted to interface with a different operating system. If a new operating system is installed that is not compatible with the old one, the application programs have to be converted to the new operating system. COMMUNICATIONS Transmitting between two personal computers or between a personal computer and a timesharing or information service is relatively simple. All that's required is a modem for each computer, a telephone line and a communications program in each computer that uses the same error checking protocol to ensure that data has not been lost. Most communications programs support several protocols. If data is not critical, an ASCII protocol without error checking can be used, which is found in every communications program. Transmitting in a network is another story. Traditional minicomputer and mainframe networks allow multiple users to have access to central databases via terminals. The control is typically in the main, or host, computer. Personal computer LANs have evolved to share information within a small work group. The major problem most large organizations have is to tie independent networks together so that each user's workstation can communicate with any other user's workstation within the company. Since each type of network uses different protocols, conversion from one protocol to another is required. In today's multivendor environment, protocol conversion can be performed by gateways, black boxes, digital PBXs or via interconnection to value added communication services. The OSI is a seven-layer reference model for worldwide communications that has been defined by ISO (Int'l. Standards Organization). Although most vendors have committed to support OSI in one form or another, it will take a long time before universal communications is achieved. Computers were originally developed for computations, not communications. In the early days, nobody realized the implications or computer communications might have been standardized as was the telephone industry. See next definition for more standards. standards (continued) Programming Languages File Management Systems Database Management Systems Text Systems Graphics Systems Standards Organizations PROGRAMMING LANGUAGES Every software program is written in a programming language, and there is at least one programming language for every major CPU series. There is typically an assembly language and a number of high-level languages for each series or family. Assembly languages are machine specific, and the machine language they generate runs on only one CPU family. Unless the machine languages are very similar, it is difficult to translate an assembly language program from one CPU series into another. The high-level programming language was created to eliminate this machine dependency. Programming languages, such as COBOL, FORTRAN and BASIC are supposed to be able to run on many different computers. However, due to many dialects of each language, compatibility is still an issue. Each compiler vendor keeps adding new features to its language thereby making it incompatible with previous or other versions. By the time a new feature becomes a standard, a dozen new features have been already implemented. For example, dBASE has become a de facto standard business programming language. Since 1981, dBASE has spawned competitive products, such as Clipper, QuickSilver, Force III, dbXL and Foxbase, all of which are incomplete versions of dBASE. None of them provides every command in dBASE, and they all provide features not found in dBASE. There's no rule of thumb for translating one dialect of a programming language into another. The job may be difficult or easy. At times, software is written to translate one dialect into another, as well as one programming language into another. If the translation program cannot translate the program entirely, then manual tailoring is necessary. In these cases, it is often easier to rewrite the program from scratch. Compatibility can be achieved when a programming language conforms to the ANSI (American National Standards Institute) standard for that language. If the same version of an ANSI COBOL compiler is available for two different CPUs, a program written in ANSI COBOL will run on both machines. FILE MANAGEMENT SYSTEMS In its simplest form, a data file uses fields of the same length for each item of data, for example, a plain EBCDIC or ASCII file would look like: Chris Smith 34 Main St. Bangor ME18567 Pat Jones 10 W. 45 St. New York NY10002  A common format created by BASIC programming languages is an ASCII comma delimited file; for example, the data above would look as follows: "Chris Smith","34 Main St.","Bangor","ME","18567" "Pat Jones","10 W. 45 St.","New York","NY","10002"  Both file formats above are simple, contain only data (except for quotes and commas) and can be easily manipulated by a word processor. However, data files may also contain special codes that identify the way the data is structured within the file. For example, variable length records require a code in each field indicating the size of the field. Whether fixed or variable length fields, the data in non-DBMS systems is linked directly to the processing. The program must know the layout of the fields in each record that it processes, and it cannot accept records in a different format. In order to process a different file format, the program must be changed. Incompatible file formats often exist within the same organization when developed separately. The following fixed-length records are incompatible even though they contain the same data. The program that processes the first file structure would have to be changed to process the second. 敖陳陳陳陳陳陳堕陳陳陳陳陳陳陳堕陳陳陳陳賃陳堕陳陳  Name Address City StZip 青陳陳陳陳陳陳祖陳陳陳陳陳陳陳祖陳陳陳陳珍陳祖陳陳 敖陳陳陳陳賃陳陳陳陳陳陳賃陳陳陳陳陳堕賃陳陳朕  Name Address City StZip 青陳陳陳陳珍陳陳陳陳陳陳珍陳陳陳陳陳祖珍陳陳潰  DBMSs (DATABASE MANAGEMENT SYSTEMS) DBMSs have their own proprietary formats for storing data. For example, a header record with a unique format that contains identification data is typically placed at the beginning of each file. Codes may also be embedded in each record. Most DBMSs have an import and export capability that converts popular database formats into their proprietary format. If not, the program usually can import and export a plain EBCDIC or ASCII file, which is stripped of all proprietary codes and can be used as a common denominator between both systems. If conversion facilities cannot be found, a custom program can be written to convert one database format into another if documentation describing the old format is available. The application program interface (API), or language used by the application program to "talk" to the database, is typically a proprietary language in every DBMS. SQL has become popular as a standard language and has been implemented in many DBMSs. Theoretically, that means any application program requesting data in the SQL language would work with any DBMS that supports SQL. Like everything else however, there are dialects of SQL. TEXT SYSTEMS Although the basic structure of an English-language text file is standard throughout the world: word, sentence, paragraph, page; every word processing, desktop publishing and typesetting program uses its own codes to set up the layout within a document. For example, the code that turns on boldface in WordPerfect Version 5.0 is [BOLD]; in WordStar, it's ^PB. The codes that define a header, footer, footnote, page number, margin, tab setting, indent and font change are unique to the word processing program in which the document was created or the desktop publishing program into which the text file is converted. Even the codes to end a line or paragraph are not the same. Document conversion is accomplished with special conversion programs or black boxes. Although every word processing program has a search and replace capability, it may not be effective for converting embedded layout codes from one format to another. In some programs, the search & replace simply does not handle layout codes. In addition, while some systems use one code to turn a function on and another code to turn it off, other systems use the same code for on and off, requiring manual verification and tailoring when using the search & replace function. GRAPHICS SYSTEMS There are many formats for storing a picture in a computer; but, unlike text and data files, which are primarily made up of alphanumeric characters, graphics formats are more complex. To begin with, there are the two major categories of graphics: vector graphics (objects made up of lines) and raster graphics (TV-like dots). Images stored in vector format can be moved to another vector system typically without loss of resolution. There are 2-D vector formats as well as 3-D vector formats. In transferring raster images among different devices, resolution is a major concern. Such transfers can occur without loss of resolution as long as the new format has the same or higher resolution as the older one. Standard graphics formats allow graphics data to be moved from machine to machine, while standard graphics languages let graphics programs be moved from machine to machine. For example, GKS and PHIGS are major graphics languages that have been adopted by many high-performance workstation and CAD vendors. Apple's consistent use of its QuickDraw language has helped the Macintosh become very popular in graphics-oriented applications. High-resolution graphics has typically been expensive to implement due to its large storage and fast processing requirements. However, as personal computers become more powerful, graphics are becoming widely used in business applications. The ability to see a person's face or a product's appearance on screen will eventually become as commonplace as text and data. De Facto Standards When a vendor's product is widely used, it becomes a de facto standard. Apple, Digital, HP, IBM, Intel, Lotus, Microsoft, Motorola and many others have set de facto standards. For a list of standards bodies, see Lessons Associations. THE FUTURE The problem of standards and compatibility is a never ending dilemma. However, the fact is that standards could be created that would embrace the future and allow for expandability far more than they currently do. Ironically, the field that is the very forefront of the future, has a very myopic view of it. Some day, a standard for defining the standard will have to be implemented in order that one program can ask another what language it speaks. A program could also interrogate a data file and quickly determine its format. If the program can't understand the other program's language or the file's format, the interfacing problem would still exist. However, as programs become more multi- lingual, a standard identification protocol would go a long way to establishing an AI link between all computers in the future. standards bodies See Lessons Associations. Star Xerox workstation that formally introduced the graphical user interface and desktop metaphor in 1981. Although unsuccessful, it was inspiration for Xerox's subsequent computers and for Apple's Lisa and Macintosh. See Alto. star network Communications network in which all terminals are connected to a central computer or central hub. PBXs are prime examples as well as IBM's Token Ring and AT&T's Starlan LANs. Starlan AT&T LAN that uses twisted pair wire, the CSMA/CD access method, transmits at 1Mbps and uses a star or bus topology. In 1988, Starlan was renamed Starlan 1, and Starlan 10 was introduced, a 10Mbps Ethernet version that uses twisted pair or optical fibers. start bit In asynchronous communications, the bit transmitted before each character. start/stop transmission Same as asynchronous transmission. startup routine Routine that is executed when the computer is booted or when an application is loaded. It is used to customize the environment for its associated software. STARTUP.CMD (STARTUP.CoMmanD) OS/2 file executed immediately upon startup. It contains instructions that can initialize operating system settings and call in a specific application program. The DOS counterpart is AUTOEXEC.BAT. stat mux (STATistical MUltipleXor) See statistical multiplexor. state-of-the-art Most current technique or method applied to designing and developing hardware and software. statement In a high-level programming language, a descriptive phrase that generates one or more machine language instructions in the computer. In a low-level assembly language, programmers write instructions rather than statements, since each source language instruction is translated into one machine language instruction. static binding Same as early binding. static column memory A type of page mode memory that requires less electronic pulsing in order to access the memory bits. static electricity Stationary electrical charge that is the result of intentional charging or of friction in low-humidity environments. static RAM Memory chip that requires power to hold its content. Static RAM chips have access times in the 10 to 30-nanosecond range. Dynamic RAMs are usually above 30, and Bipolar and ECL memories are under 10. A static RAM bit is made up of a pretzel-like flip-flop circuit that lets current flow through one side or the other based on which one of two transistors is activated. Static RAMs do not require refresh circuitry as do dynamic RAMs, but they take up more space and use more power. static SQL See embedded SQL. station Computer, workstation or terminal in a network. Same as node. statistical multiplexor In communications, a device that combines several low-speed channels into a single high-speed channel and vice versa. A standard multiplexor is set to a fixed interleaving pattern, but the statistical multiplexor can analyze the traffic load and dynamically switch to different channel patterns to speed up transmission. status line Information line displayed on screen that shows current activity. STD bus Bus architecture used in medical and industrial equipment due to its small size and rugged design. Originally an 8-bit bus, extensions have increased it to 16 and 32 bits. stepper motor Motor that rotates in small, fixed increments and is used to control the movement of the access arm on a disk drive. Contrast with voice coil. stereophonic Sound reproduction using two or more channels. Contrast with monophonic. stick font Same as vector font. stick model Picture made of lines, or vectors. For example, in biomedical applications, the limbs of a person or animal are converted into lines so that the motion can be visually observed and graphically plotted and analyzed. stiction (STatic frICTION) Type of hard disk failure in which the read/write heads stick to the platters. The lubricant used on certain drives heats up and liquifies. When the disk is turned off, it cools down and can become like a glue. STN See LCD. stop bit In asynchronous communications, a bit transmitted after each character. storage device Hardware unit that holds data. In this Glossary, it refers only to external peripheral equipment, such as disk and tape, in contrast with memory (RAM). storage hierarchy Range of memory and storage devices within the computer system. The following list runs from lowest to highest speed.  Low Punched cards  Speed Punched paper tape  Removable cartridge mass storage  devices (non-disk)  Magnetic tape  Floppy disks  CD ROM and optical disks  Magnetic disks (movable heads)  Magnetic disks (fixed heads)  Bubble memory  Low-speed bulk memory  Main memory   Cache memory  High  Microcode  Speed  Registers storage media Refers to disks, tapes and bubble memory cartridges. store and forward In communications, the temporary storage of a message for transmission to its destination at a later time. Store and forward techniques allow for routing over networks that are not accessible at all times; for example, messages headed for different time zones can be stored and forwarded when daytime arrives at the destination location. Messages can be stored and forwarded at night in order to obtain off-peak rates. stored program concept Fundamental computer architecture in which it acts upon (executes) internally-stored instructions. See von Neumann architecture. STP (Shielded Twisted Pair) Telephone wire wrapped in a metal sheath to eliminate external interference. See twisted pair. Strand88 Parallel processing programming language developed by AI Ltd., England. stream (1) Contiguous group of data. (2) I/O management in the C programming language. A stream is a channel through which data flows to/from a disk, keyboard, printer, etc. stream-oriented file Type of file, such as a text document or digital voice file, that is more openly structured than a data file. Text and voice are continuous streams of characters, whereas database records are repeating structures with a fixed or reasonably uniform format. streaming tape High-speed magnetic tape drive that is frequently used to make a backup copy of an entire hard disk. Streamline Macintosh tracing program from Adobe Systems Inc., Mountain View, CA. It converts scanned or MacPaint images into PostScript files, which can be modified in Illustrator 88. STREAMS Architecture in the UNIX System V operating system used for creating layered communications protocols. Each layer is comprised of a STREAMS module, which passes messages to other modules. AT&T's TLI transport protocol is a STREAMS module. See OSI. string (1) In programming, a contiguous set of alphanumeric characters that does not contain numbers used for calculations. Names, addresses, words and sentences are strings. Contrast with numeric data. (2) Any connected set of structures, such as a string of bits, fields or records. string handling Abilty to manipulate alphanumeric data (names, addresses, text, etc.). Typical functions include the ability to handle arrays of strings, to left and right align and center strings and to search for an occurrence of text within a string. Stringy Floppy Continuous loop cartridge of 1/16" tape from Exatron, Inc., available for early personal computers. striping Interleaving or multiplexing data to increase speed. See disk striping. stroke (1) In printing, the weight, or thickness, of a character. For example, in the LaserJet, one of the specifications of the font description is the stroke weight from -3 to +3. (2) In computer graphics, a pen or brush stroke or to a vector in a vector graphics image. stroke font Same as vector font. stroke weight Thickness of lines in a font character. The HP LaserJet III manual defines stroke weights from Ultra Thin (-7) to Ultra Black (+7), with Medium, or Text, as normal (0). stroke writer Same as vector display. structured analysis Techniques developed in the late 1970s by Yourdon, DeMarco, Gane and Sarson for applying a systematic approach to systems analysis. It included the use of data flow diagrams and data modeling and fostered the use of implementation-independent graphical notation for documentation. structured design Systematic approach to program design developed in the mid 1970s by Constantine, Yourdon, et al, that included the use of graphical notation for effective documentation and communication, design guidelines and recipes to help programmers get started. structured programming Techniques that impose a logical structure on the writing of a program. Large routines are broken down into smaller, modular routines. The use of the GOTO statement is discouraged (see spaghetti code). Certain programming statements are indented in order to make loops and other program logic easier to follow. Structured walkthroughs, which invite criticism from peer programmers, are also used. Structured languages, such as Pascal, Ada and dBASE, force the programmer to write a structured program. However, unstructured languages such as FORTRAN, COBOL and BASIC require discipline on the part of the programmer. Stuffit Macintosh shareware program from Aladdin Systems, Aptos, CA, that compresses files onto multiple floppies. A commercial version adds a scripting language, file viewing and supports multiple compression techniques. It was originally developed by Raymond Lau at age 16. style sheet In word processing and desktop publishing, a file that contains layout settings for a particular category of document. Style sheets include such settings as margins, tabs, headers and footers, columns and fonts. stylus Pen-shaped instrument that is used to "draw" images or point to menus. See light pen and digitizer tablet. sub-notebook Lightweight notebook computer. As computers get lighter, the sub-notebook (if term persists) should weigh two to three pounds, the notebook four to five. subarea node In an SNA network, a system that contains network controlling functions. It refers to a host computer or a communications controller and its associated terminals. subdirectory Disk directory that is subordinate to (below) another directory. In order to gain access to a subdirectory, the path must include all directories above it. submarining Temporary visual loss of the moving cursor on a slow display screen such as found on a laptop computer. See active matrix LCD. submenu Additional list of options within a menu selection. There can many levels of submenus. subroutine Group of instructions that perform a specific task. A large subroutine is usually called a module or procedure; a small one, a function or macro, but all terms are used interchangeably. subschema Pronounced "sub-skeema." In database management, an individual user's partial view of the database. The schema is the entire database. subscript (1) In word processing and mathematical notation, a digit or symbol that appears below the line. Contrast with superscript. (2) In programming, a method for referencing data in a table. For example, in the table PRICETABLE, the statement to reference a specific price in the table might be PRICETABLE (ITEM), ITEM being the subscript variable. In a two-dimensional table that includes price and discount, the statement PRICETABLE (ITEM,DISCOUNT) could reference a discounted price. The relative locations of the current ITEM and DISCOUNT are kept in two index registers. substrate Base material upon which integrated circuits are built. Silicon is the most widely used substrate for chips. substring Subset of an alphanumeric field or variable. A programming language substring function extracts the subset; for example, substr(prodcode,4,3) extracts characters 4, 5 and 6 out of a product code field or variable. subtract In relational database, an operation that generates a third file from all the records in one file that are not in a second file. SUM II (Symantec Utilities for Macintosh) Set of Macintosh utilities from Symantec Corp., Cupertino, CA, that provides hard disk optimization, analysis and repair and security capabilities. Summit Code name for IBM's ES/9000 models. Since water cooled models below the 820 are re-architected 3090 J models, the term may stay in usage to refer to the top-end models (820, 860, 900). Sun (Sun Microsystems, Inc., Mountain View, CA) Manufacturer of network-based, high-performance workstations founded in 1982. Product lines include stand-alone and networked systems, diskless workstations and file servers that feature its SPARC microprocessor architecture. Sun supports an open systems model of computing throughout its product line that allows it to interact in networks of computer systems from other vendors. Its ONC (Open Network Computing) software is supported by over 300 vendors, and its NFS (Network File System) software, which allows data sharing across the network, has become an industry standard. In 1991, Sun split its business into the following wholly-owned subsidiaries: Sun Microsystems - Systems SunSoft - System software SunPro - Programmer productivity tools SunPics - Printing and imaging SunConnect - Network integration SunExpress - Distribution SunSoft See Sun. super floppy (1) PC 3.5" floppy disk that holds 2.88MB and is compatible with the 1.44MB and 720KB formats. (2) Very-high-capacity floppy disk in the 20MB range. See Floptical. Super VGA See VGA and PC display modes. SuperCalc PC spreadsheet from Computer Associates. It was one of the first spreadsheets following in VisiCalc's footsteps in the early 1980s. SuperCalc5 (1988) provides 3-D capability, enhanced graphics and can link up to 256 spreadsheets. supercomputer Fastest computer available. It is typically used for simulations in petroleum exploration and production, structural analysis, computational fluid dynamics, physics and chemistry, electronic design, nuclear energy research and meteorology. It is also used for realtime animated graphics. superconductor Material that has little resistance to the flow of electricity. Traditional superconductors operate at -459 Fahrenheit (absolute zero). Thus far, the major use for superconductors, made of alloys of niobium, is for high-powered magnets in medical imaging machines that use magnetic fields instead of x-rays. Using experimental materials, such as copper oxides, barium, lanthanum and yttrium, IBM's Zurich research lab in 1986 and the Univ. of Houston in 1987 raised the temperature of superconductivity to -59 degrees Fahrenheit. If superconductors can work at reasonable temperatures, they will have a dramatic impact on the future. See Josephson junction. SuperDrive Macintosh floppy disk drive that stores 1.44MB of data in its highest density format. It also reads and writes earlier Mac 400 and 800KB disks, as well as Apple II ProDOS, MS-DOS and OS/2 formats. SuperFloppy Superdrive-compatible floppy disk for older Macintoshes from Peripheral Land, Inc., Fremont, CA. See super floppy. superframe T1 transmission formats made up of 12 T1 frames (superframe) and 24 frames (extended superframe). See D4. SuperKermit See Kermit. SuperKey PC keyboard macro processor from Borland that lets users create keyboard macros, rearrange the keyboard and encrypt data and programs. supermini Large-scale minicomputer that overlaps in processing capability with a small-scale mainframe. The difference in terminology is point of view. If you're a mini maker, your largest machine is "super." If you're a mainframe maker, your smallest machine isn't worth talking about! Note: Supermini is not the same as mini- supercomputer. superscript Any letter, digit or symbol that appears above the line. Contrast with subscript. superserver Network server with very large RAM and disk capacity, multiple processors and high-speed multiprocessing (Micro Channel, EISA, etc.) buses. supertwist LCD technology that twists liquid molecules greater than 90 in order to improve contrast and viewing angle. See LCD. supervisor Same as operating system. supervisor call Instruction in an application program that switches the computer to supervisor state. supervisor control program The part of the operation system that always resides in memory. Same as kernel. supervisor state Typically associated with mainframes, it is a hardware mode in which the operating system executes instructions unavailable to an application program; for example, I/O instructions. Contrast with program state. support (1) Assistance provided by a hardware or software vendor in installing and maintaining its product. (2) Software or hardware designed to work with some other software or hardware product. For example, if a word processor "supports the LaserJet," it can activate special features of that printer. SUPRA Relational DBMS from Cincom Systems, Inc., Cincinnati, OH, that runs on IBM mainframes and VAXs. It includes a query language and a program that automates the database design process. surface (1) In CAD, the external geometry of an object. Surfaces are generally required for NC (numerical control) modeling rather than wireframe or solids. (2) Coined by Wayne Ratliff, creator of dBASE, a language that interfaces to a database engine. surface modeling In CAD, a mathematical technique for representing solid-appearing objects. Surface modeling is a more complex method for representing objects than wireframe modeling, but not as sophisticated as solid modeling. Although surface and solid models can appear the same on screen, they are quite different. Surface models cannot be sliced open as can solid models. In addition, in surface modeling, the object can be geometrically incorrect; whereas, in solid modeling, it must be correct. surface mount Circuit board packaging technique in which the leads (pins) on the chips and components are soldered on top of the board, not through it. Boards can be smaller and built faster. surge Oversupply of voltage from the power company that can last up to several seconds. See spike. surge protector Device that protects a computer from excessive voltage (spikes and surges) in the power line. See voltage regulator and UPS. surge suppressor Same as surge protector. suspend and resume To stop an operation and restart where you left off. In portable computers, the hard disk is turned off, and the CPU is made to idle at its slowest speed. All open applications are retained in memory. SV (Scientific Visualization) See visualization. SVGA (Super VGA) See VGA. SVID (System V Interface Definition) AT&T specification for the UNIX System V operating system. SVID Release 3 specifies the interface for UNIX System V Release 4. SVR4 See System V Release 4.0. swap file Disk file used to temporarily save a program or part of a program running in memory. See Windows swap file. swapping Replacing one segment of a program in memory with another and restoring it back to the original when required. In virtual memory systems, it is called paging. switch (1) Mechanical or electronic device that directs the flow of electrical or optical signals. Remember! Open is "off." Closed is "on." See data switch and transistor. (2) In programming, a bit or byte used to keep track of something. Sometimes refers to a branch in a program. (3) Command modifier. See DOS switch. switch-to-computer To integrate voice telephone and database access. For example, in customer service applications, using telephone services, such as automatic number identification (ANI) and automatic call distribution (ACD), an incoming call can retrieve and route the customer's file to the next available human agent. switched line In communications, a link that was established in a switched network. switched network (1) International dial-up telephone system. (2) Network in which a temporary connection is established from one point to another for each transmission session. SX See 386SX, 486SX and LaserJet. SYBASE System Family of SQL development tools from Sybase, Inc., that includes SQL Server, SQL Toolset (design, development and control) and Client/Services Interfaces (distributed database architecture). See SQL Server. SYLK file (SYmbolic LinK file) Spreadsheet file format originating with Multiplan that is used by a number of spreadsheet programs. symbol In data compression, a unit of data (byte, floating point number, spoken word, etc.) that is treated independently. symbol set In printing, a group of symbols that are extensions to standard characters for use in a particular country or specific application. Symbol sets provide codes for the non-standard upper half of the ASCII character set. symbolic language (1) Programming language that uses symbols, or mnemonics, for expressing operations and operands. All modern programming languages are symbolic languages. (2) Language that manipulates symbols rather than numbers. See list processing. symmetric multiprocessing Multiprocessing design in which any CPU can be assigned any application task. One CPU acts as a control processor, or scheduler, which boots the system, distributes work to the next available CPU and manages I/O requests. Contrast with asymmetric multiprocessing. Symphony Integrated software package for PCs from Lotus that includes word processing, database management, speadsheet, business graphics, communications and a macro language. sync character In synchronous communications systems, a special character transmitted to synchronize timing. sync generator Device that supplies synchronization signals to a series of cameras to keep them all in phase. synchronous (1) Sequence of fixed or concurrent events. See synchronous transmission. (2) Completing the current I/O operation before the next one is started. (3) In SCSI, the transfer of data without immediate acknowledgment of each byte. (4) Contrast with asynchronous. synchronous protocol Communications protocol that controls a synchronous transmission, such as bisync, SDLC and HDLC. Contrast with asynchronous protocol. synchronous transmission Transmission of data in which both stations are synchronized. Codes are sent from the transmitting station to the receiving station to establish the synchronization, and data is then transmitted in continuous streams. Modems that transmit at 1200 bps and higher often convert the asynchronous signals from a computer's serial port into synchronous transmission over the transmission line. Contrast with asynchronous transmission. syntax Rules governing the structure of a language statement. It specifies how words and symbols are put together to form a phrase. syntax error Error that occurs when a program cannot understand the command that has been entered. See parse. sysgen (SYStem GENeration) Installation of a new or revised operating system. It includes selecting the appropriate utility programs and identifying the peripheral devices and storage capacities of the system the operating system will be controlling. sysop (SYStem OPerator) Pronounced "siss-op." Person who runs an online communications system or bulletin board. The sysop may also act as mediator for system conferences. Sysplex IBM System/390 multiprocessing. The Sysplex Timer external clock is used to synchronize time-of-day clocks in multiple processors. If failure occurs in a multiprocessor complex, precise transaction time stamps are required for accurate rollback and recovery. SysReq key (SYStem REQuest key) Keyboard key on a terminal keyboard that is used to get the attention of the central computer. The key exists on PC keyboards, but is rarely used by applications. system (1) Group of related components that interact to perform a task. (2) A computer system is made up of the CPU, operating system and peripheral devices. (3) An information system is made up of the database, all the data entry, update, query and report programs and manual and machine procedures. (4) "The system" often refers to the operating system. System 2000 (1) Hierarchical, network and relational DBMS from the SAS Institute, Cary, NC, that runs on IBM, CDC and Unisys computers. It has been integrated into the SAS System. (2) See FTS 2000. System/3 Batch-oriented minicomputer from IBM. Introduced in 1969, it introduced a new punched card about half the size of previous ones. With the addition of the Communications Control Program (CCP), it could handle interactive terminals. System/32 Batch-oriented minicomputer from IBM. Introduced in 1975, it provided a single terminal for operator use. It was superseded by the System/34, which could run System/32 applications in a special mode. System/34 Multiuser, multitasking minicomputer from IBM, introduced in 1977. The typical system had from a handful to a dozen terminals and could run System/32 programs in a special mode. Most large System/34 users migrated to the System/38, while small users migrated to the System/36. System/36 Multiuser, multitasking minicomputer from IBM that was introduced in 1983. It superseded the System/34 and is mostly compatible with it. System/34 programs run in the System/36 after recompilation. The typical system supports from a handful to a couple of dozen terminals. It has been superseded by the AS/400. System/360 IBM's first family of computer systems introduced in 1964. It was the first time in history that a complete line of computers was announced at one time. Although considerable enhancements have been made, much of the 360 architecture is still carried over in current-day IBM mainframes. See IBM mainframes. System/370 Mainframe product line introduced in 1970 by IBM (superseding System/360), which added virtual memory and other enhancements. Subsequent series include the 303x, 43xx, 308x, 309x and 9370, all 370-architecture machines. The 370 architecture was brought down to the PC level in 1983 with the PC XT/370, and then again in 1989 with the VM/SP Technical Workstation. See IBM mainframes. System/38 Minicomputer from IBM that includes an operating system with an integrated relational database management system. Introduced in 1978, it was an advanced departure from previous System/3x computers. The typical system handles from a dozen to several dozen terminals. It has been superseded by the AS/400. System/390 Mainframe product line introduced in 1990 by IBM (superseding System/370) that features ESA/390 architecture and operating systems, ES/9000 hardware (18 models introduced), ESCON fiber optic channels, Sysplex multiprocessing and SystemView. System/3x IBM System/34, System/36 and System/38 midrange computers. System 7 (1) Major upgrade of the Macintosh operating system (1991). It includes virtual memory, increased memory addressing, hot links (Publish & Subscribe), multitasking (MultiFinder no longer optional), TrueType fonts and a variety of enhancements to the user interface. (2) (System/7) Sensor-based minicomputer from IBM introduced in 1970 and used for process control. It was superseded by the Series/1. System/88 Family of fault-tolerant midrange computers from IBM used for online transaction processing. Uses the System/88 virtual memory and System/88 FTX (Fault Tolerant UNIX) operating systems. Includes 4579 and 4576 multiprocessor series and 4593 entry- level models. system board Printed circuit board that contains the primary CPU. In a personal computer, it is also called the motherboard. system development cycle Sequence of events in the development of an information system (application), which requires mutual effort on the part of user and technical staff. 1. SYSTEMS ANALYSIS & DESIGN feasibility study general design prototyping detail design functional specifications 2. USER SIGN OFF 3. PROGRAMMING design coding testing 4. IMPLEMENTATION training conversion installation 5. USER ACCEPTANCE system development methodology Formal documentation for the phases of the system development cycle. It defines the precise objectives for each phase and the results required from a phase before the next one can begin. It may include specialized forms for preparing the documentation describing each phase. system disk Hard or floppy disk that contains part or all of the operating system or other control program. system failure Hardware or software malfunction. May refer to a problem with the operating system. system file Machine language file that is part of the operating system or other control program. It may also refer to a configuration file used by such programs. system folder Operating system folder in the Macintosh that contains the System, Finder and MultiFinder, printer drivers, fonts, desk accessories, INITs and cdevs. system image Memory view of current operating environment, including the operating system and running programs. system level Operation that is performed by the operating system or some other control program. system life cycle Useful life of an information system. Its length depends on the nature and volatility of the business, as well as the software development tools used to generate the databases and applications. Eventually, an information system that is patched over and over no longer is structurally sound enough to be expanded. Tools like DBMSs allow for changes more readily, but increased transaction volumes can negate the effectiveness of the original software later on. system management See systems management. system memory Memory used by the operating system. system program Component of system software. system prompt On-screen symbol that indicates the operating system is ready for a command. See DOS prompt. system software Programs used to control the computer and run application programs. It includes operating systems, TP monitors, network control programs, network operating systems and database managers. Contrast with application program. system test Running a complete system for testing purposes. system time/date Running time of day in the computer, which is maintained by a battery when the computer is turned off. It is used to time stamp all newly-created files and activate time-dependent processes. System V Release 4.0 Unified version of UNIX released in 1989. See UNIX. System V.4 See System V Release 4.0. SYSTEM.INI See WIN.INI. Systemantics Insightful book on the systems process by John Gall (1977). The following is copied with permission from Random House. A Concise Summary of the Field of General Systemantics Systems are seductive. They promise to do a hard job faster, better, and more easily than you could do it by yourself. But if you set up a system, you are likely to find your time and effort now being consumed in the care and feeding of the system itself. New problems are created by its very presence. Once set up, it won't go away, it grows and encroaches. It begins to do strange and wonderful things. Breaks down in ways you never thought possible. It kicks back, gets in the way, and opposes its own proper function. Your own perspective becomes distorted by being in the system. You become anxious and push on it to make it work. Eventually you come to believe that the misbegotten product it so grudgingly delivers is what you really wanted all the time. At that point encroachment has become complete... you have become absorbed... you are now a systems person! systems General term for the department, people or work involved in systems analysis & design activities. systems analysis & design Examination of a problem and the creation of its solution. Systems analysis is effective when all sides of the problem are reviewed. Systems design is most effective when more than one solution can be proposed. The plans for the care and feeding of a new system are as important as the problems they solve. See system development cycle and Systemantics. systems analyst Person responsible for the development of an information system. They design and modify systems by turning user requirements into a set of functional specifications, which are the blueprint of the system. They design the database or help design it if data administrators are available. They develop the manual and machine procedures and the detailed processing specs for each data entry, update, query and report program in the system. Systems analysts are the architects, as well as the project leaders, of an information system. It is their job to develop solutions to user's problems, determine the technical and operational feasibility of their solutions, as well as estimate the costs to develop and implement them. They develop prototypes of the system along with the users, so that the final specifications are examples of screens and reports that have been carefully reviewed. Experienced analysts leave no doubt in users' minds as to what is being developed, and they insist that all responsible users review and sign off on every detail. Systems analysts require a balanced mix of business and technical knowledge, interviewing and analytical skills, as well as a good understanding of human behavior. See Systemantics. systems disk Disk pack or disk drive reserved only for system software, which includes the operating system, assemblers, compilers and other utility and control programs. systems engineer Often a vendor title for persons involved in consulting and pre-sales activities related to computers. See systems analyst, systems programmer, programmer analyst and application programmer. systems house Organization that develops customized software and/or turnkey systems for customers. Contrast with software house, which develops software packages for sale to the general public. Both terms are used synonymously. systems integration Making diverse components work together. See NASI. systems integrator Individual or organization that builds systems from a variety of diverse components. With increasing complexity of technology, more customers want complete solutions to information problems, requiring hardware, software and networking expertise in a multivendor environment. See OEM, VAR and NASI. systems management (1) Management of systems development, which includes systems analysis & design, application development and implementation. See system development cycle. (2) Software that manages computer systems in an enterprise, which may include any and all of the following functions: software distribution, version control, backup & recovery, printer spooling, job scheduling and performance and capacity planning. Network management may be an integrated component of systems management. systems program See system program and system software. systems programmer (1) In the IS department of a large organization, a technical expert on some or all of the computer's system software (operating systems, networks, DBMSs, etc.). They are responsible for the efficient performance of the computer systems. They usually don't write programs, but perform a lot of technical tasks that integrate vendors' software. They also act as technical advisors to systems analysts, application programmers and operations personnel. For example, they would know whether additional tasks could be added to the computer and would recommend conversion to a new operating or database system in order to optimize performance. In mainframe environments, there is one systems programmer for about 10 or more application programmers. In smaller environments, users rely on vendors or consultants for systems programming assistance. (2) In a computer hardware or software organization, a person who designs and writes system software. SystemView IBM architecture for computer systems management introduced with System/390 that provides an enterprise-wide approach for controlling multiple systems and networks. It will be implemented in stages through the 1990s. NetView is a major component. systolic array Array of processing elements (typically multiplier- accumulator chips) in a pipeline structure that is used for applications such as image and signal processing and fluid dynamics. The "systolic," coined by H. T. Kung of Carnegie-Mellon, refers to the rhythmic transfer of data through the pipeline like blood flowing through the vascular system. SYZYGY Pronounced "SIZE-uh-gee." PC workgroup software from Information Research Corp., Charlottesville, VA. Used for coordinating schedules, resources and budgets for group projects and includes e-mail and a calendar with to-do and activity lists. T See tera. T-byte See terabyte. T-carrier Digital transmission service from a common carrier. Introduced by AT&T in 1983 as a voice service, its use for data has grown steadily. T-carrier service requires multiplexors at both ends that merge the various signals together for transmission and split them at the destination. Multiplexors analyze the traffic load and vary channel speeds for optimum transmission. T1 1.544 megabit T-carrier channel that can handle 24 voice or data channels at 64 Kbits/sec. The standard T1 frame is 193 bits long, which holds 24 8-bit voice samples and one synchronization bit. 8,000 frames are transmitted per second. See D4 and ESF. T2 6.312 megabit T-carrier channel that can handle 96 voice or data channels at 64 Kbits/sec. T3 44.736 megabit T-carrier channel that can handle 672 voice or data channels at 64 Kbits/sec. T3 requires fiber optic cable. tab character Control character in a document that represents movement to the next tab stop. See ASCII chart (9 and 11). tab delimited Text format that uses tab characters as separators between fields. Unlike comma delimited files, alphanumeric data is not surrounded by quotes. tab key Keyboard key that moves the cursor to the next tab stop. tabbing Moving the cursor on a video display screen or the print head on a printer to a specified column. table (1) In programming, a collection of adjacent fields. Also called an array, a table contains data that is either constant within the program or is called in when the program is run. See decision table. (2) In a relational database, the same as a file; a collection of records. table lookup Searching for data in a table, commonly used in data entry validation and any operation that must match an item of data with a known set of values. table view Screen display of several items or records in rows and columns. Contrast with form view. tablet See digitizer tablet. tabular form Same as table view with respect to printed output. tabulate (1) To arrange data into a columnar format. (2) To sum and print totals. tabulating equipment Punched card machines, including keypunches, sorters, collators, interpreters, reproducers, calculators and tabulators. tabulator Punched card accounting machine that prints and calculates totals. tag (1) Set of bits or characters that identifies various conditions about data in a file and is often found in the header records of such files. (2) Name (label, mnemonic) assigned to a data structure, such as a field, file, paragraph or other object. (3) Key field in a record. (4) Brass pin on a terminal block that is connected to a wire by soldering or wire wrapping. tag sort Sorting procedure in which the key fields are sorted first to create the correct order, and then the actual data records are placed into that order. Taligent (Taligent, Inc., Cupertino, CA) Joint venture of IBM and Apple that is developing the next- generation, object-oriented operating system. See Apple and Pink. talk-off Unintentional command activation when a human voice generates the same tone as a control signal. Tandem (Tandem Computers Inc., Cupertino, CA) Manufacturer of fault tolerant computers founded in 1974 by James Treybig to address the transaction processing market (reservations, financial transfers, etc.). It introduced the first commercial computer based on a fault tolerant, multiprocessor architecture. Its NonStop series is built around multiple parallel processors, thousands of which can be tied together. If a processor fails, the system distributes the workload to the remaining processors. The system can be expanded while running. tandem processors Two processors hooked together in a multiprocessor environment. Tandy (Tandy Corp., Ft. Worth, TX) Manufacturer of PCs and electronics that started as a family leather business in 1919. In 1963, it acquired the nine Radio Shack stores in Boston. Today, it has over 7,000 company-owned stores and franchises. In 1977, it introduced one of the first personal computers, the TRS-80 Model I. Tandy's Model 100 and 200 lightweight portables were also inspiration to the laptop generation. Its first computers were proprietary, and its initial PCs were non-standard. However, starting with the Model 1000 in 1984, Tandy offers a full line of IBM-compatible PCs. tap In communications, a connection onto the main transmission medium of a local area network. See transceiver. tape See magnetic disk & tape. tape backup Use of magnetic tape for storing duplicate copies of hard disk files. QIC drives are the most widely used, but DAT and 8mm (Exabyte) formats are gaining ground. See QIC, DDS (3), DATA/DAT, D/CAS and Exabyte. tape drive Physical unit that holds, reads and writes the magnetic tape. See magnetic tape & disk. tape dump Printout of tape contents without any report formatting. tape mark Control code used to indicate the end of a tape file. tape transport Mechanical part of a tape drive. tar UNIX utility for archiving files, often used in conjunction with "compress." Targa Raster graphics file format (.TGA extension) developed by Truevision, Inc., Indianapolis, IN, that handles 16-, 24- and 32-bit color. It is also the trade name of a line of video graphics boards used in high-resolution imaging. target computer Computer into which a program is loaded and run. Contrast with source computer. See cross assembler/compiler. target directory Directory into which data is being sent. target disk Disk onto which data is recorded. Contrast with source disk. target drive Drive containing the disk or tape onto which data is recorded. Contrast with source drive. target language Language resulting from a translation process (assembler, compiler, etc.). tariff Schedule of rates for common carrier services. task Independent running program. See multitasking. task management The part of the operating system that controls the running of one or more programs (tasks) within the computer at the same time. task swapping Switching between two applications by copying the current running program to disk or other high-speed storage device (auxiliary memory, EMS, etc.) and loading another program into that program space. task switching Switching between active applications. See context switching. TB, Tb See terabyte and terabit. Tbit See terabit. Tbits/sec (TeraBITS per SECond) Trillion bits per second. TBps, Tbps (TeraBytes Per Second, TeraBits Per Second) Trillion bytes per second. Trillion bits per second. TByte See terabyte. Tbytes/sec (TeraBYTES per SECond) Trillion bytes per second. TC See true color. TCAM (TeleCommunications Access Method) IBM communications program widely used to transfer data between mainframes and 3270 terminals. See access method. TCM (1) (Trellis-Coded Modulation/Viterbi Decoding) Technique that adds forward error correction to a modulation scheme by adding an additional bit to each baud. TCM is used with QAM modulation, for example. (2) (Thermal Conduction Module) IBM circuit packaging technique that seals chips, boards and components into a module that serves as a heat sink. TCMs are mostly water cooled, although some are air cooled. TCO Stringent low-radiation standards set by the Swedish Confederation of Professional Employees. See MPR II. TCP/IP (Transmission Control Protocol/Internet Protocol) Communications protocols developed under contract from the Dept. of Defense (DOD) to internetwork dissimilar systems. It is a de facto UNIX standard, but is supported on almost all systems. It is used by many corporations and most universities and federal agencies. File Transfer Protocol (FTP) and Simple Mail Transfer Protocol (SMTP) provide file transfer and e-mail. The TELNET protocol provides terminal emulation for all types of computers in the network. TCP controls data transfer. IP provides the routing. Protocol comparisons follow: TCP/IP DOD OSI 敖陳陳陳陳陳 敖陳陳陳陳陳朕 敖陳陳陳陳陳朕 Application Application 団陳陳陳陳陳調 (FTP, SMTP Process Presentation TELNET) 団陳陳陳陳陳調 Session 団陳陳陳陳陳 団陳陳陳陳陳調 団陳陳陳陳陳調 Transport Host to Host Transport (TCP) 団陳陳陳陳陳 団陳陳陳陳陳調 団陳陳陳陳陳調 Internet Internet Network (IP) 団陳陳陳陳陳 団陳陳陳陳陳調 団陳陳陳陳陳調 Network Data link Interface Network 団陳陳陳陳陳調 (IEEE 802 Access Physical X.25) 青陳陳陳陳陳 青陳陳陳陳陳潰 青陳陳陳陳陳潰 TCSEC See NCSC. TCU (Transmission Control Unit) Communications control unit controlled by the computer that does not execute internally stored programs. Contrast with front end processor, which executes its own instructions. TDM (Time Division Multiplexing) Technique that interleaves several low-speed signals into one high-speed transmission. For example, if A, B & C are three digital signals of 1,000 bps each, they can be mixed into one 3,000 bps as follows: AABBCCAABBCCAABBCC. The receiving end divides the single stream back into its original signals. Contrast with FDM. See baseband. tear-off menu On-screen menu or palette that can be moved off of its primary position and relocated to any part of the screen. tech support Technical assistance. tech writer Person who is responsible for writing documentation for a hardware or software product. telco (TELephone COmpany) Company that provides telephone services. tele Operations performed remotely or by telephone. telecom See telecommunications. telecommunications Communicating information, including data, text, pictures, voice and video. See communications. telecommunity Society in which information can be transmitted or received freely between all members without technical incompatibilities. telecommuting Working at home and communicating with the office. teleconferencing (1) Video teleconferencing. Video conference among several users provided by video cameras and monitors set up inhouse or in a public conferencing center. It requires a high-bandwidth (TV capacity) network that uses coaxial cable, optical fibers, microwave or satellite transmission. Conventional computer networks can't handle video. Video conferencing is slowly being integrated into data networks. In time, all data networks will provide this capability. (2) Audio teleconferencing. Telephone conference among several users provided internally by an organization's PBX and externally by the telephone companies. (3) Computer teleconferencing. Keyboard conference among several users at terminals or personal computers provided by specialized software in a host computer or BBS. telecopying (long distance copying) Formal term for fax. telegraph Low-speed communications device that transmits up to approximately 150 bps. Telegraph grade lines, stemming from the days of Morse code, can't transmit a voice conversation. telemanagement Management of an organization's telephone systems. telemarketing Selling over the telephone. Telematics Convergence of telecommunications and information processing. telemetry Transmitting data captured by instrumentation and measuring devices to a remote station where it is recorded and analyzed. For example, data from a weather satellite is telemetered to earth. Telenet Value-added, packet switching network that enables many varieties of terminals and computers to exchange data. It is a subsidiary of US Sprint. telephone wiring See twisted pair. telephony Science of converting sound into electrical signals, transmitting it within cables or via radio and reconverting it back into sound. teleprinter Typewriter-like terminal with a keyboard and built- in printer, often a portable unit. Contrast with video terminal. teleprocessing (long distance processing) Early IBM term for data communications. teleprocessing monitor See TP monitor. Telescript Programming language and software for communications from General Magic. It embeds intelligence in e-mail and other applications allowing them to cooperate with one another and allows messages to move intelligently through diverse public and private networks. Telescript can be added to existing and future operating systems. See Magic Cap. Teletex See Telex. teletext Broadcasting service that transmits text to a TV set that has a teletext decoder. It uses the vertical blanking interval of the TV signal (black line between frames when vertical hold is not adjusted) to transmit about a hundred frames. See videotex. Teletype Trade name of Teletype Corp. and refers to a variety of teleprinters used for communications. The Teletype was one of the first communications terminals in the U.S. teletype interface See teletype mode. teletype mode Line-at-a-time output like a typewriter. Contrast with full-screen mode. teletypewriter Low-speed teleprinter, often abbreviated "TTY." televaulting Continuous transmitting of data to vaults for backup purposes. The term was coined by TeleVault Technology Inc. Telex International dial-up communications service that uses teleprinters and transmits Baudot code at 50 bps (66 words/minute). In the U.S., it is administered by Western Union, which in 1971 purchased the Bell System's TWX service and connected it to the Telex network. In the early 1980s, a new service called Teletex was initiated that provides higher speeds and upper and lowercase text to subscribers using intelligent terminals and personal computers. Group 3 fax machines quickly supplanted Telex transmission. TeLink Xmodem protocol with batch file transfer designed for the Fido BBS. It sends file name, date and size in the first block. TELNET Terminal emulation protocol originally developed for ARPAnet. See TCP/IP. Telon Application generator from Computer Associates that generates COBOL and PL/I code for IBM mainframes and COBOL code for AS/400s. Development can be performed on mainframes or PCs. It was developed by Pansophic Systems (acquired by CA). template (1) Plastic or stiff paper form that is placed over the function keys on a keyboard to identify their use. (2) Programmatic and descriptive part of a programmable application; for example, a spreadsheet that contains only descriptions and formulas or a HyperCard stack that contains only programming and backgrounds. When the template is filled with data, it becomes a working application. temporary font Soft font that remains in the printer's memory until the printer is reset manually or by software. Contrast with permanent font. ter Third version. tera Trillion. Abbreviated "T." It often refers to the precise value 1,099,511,627,776 since computer specifications are usually binary numbers. See binary values and space/time. terabit One trillion bits. Also Tb, Tbit and T-bit. See tera and space/time. terabyte One trillion bytes. Also TB, Tbyte and T-byte. See tera and space/time. teraflops (tera FLoating point OPerations per Second) One trillion floating point operations per second. terminal (1) I/O device for a computer that usually has a keyboard for input and a video screen or printer for output. (2) Input device, such as a scanner, video camera or punched card reader. (3) Output device in a network, such as a monitor, printer or card punch. (4) Connector used to attach a wire. terminal emulation Using a computer to simulate the type of terminal required to gain access to another computer. See virtual terminal. terminal mode Operating mode that causes the computer to act like a terminal; ready to transmit typed-in keystrokes and ready to receive transmitted data. terminal server Computer or controller used to connect multiple terminals to a network or host computer. terminal session Time in which a user is working at a terminal. terminal strip Insulated bar that contains a set of screws to which wires are attached. terminate and stay resident See TSR. terminator (1) Character that ends a string of alphanumeric characters. (2) Hardware component that is connected to the last peripheral device in a series or the last node in a network. terrestrial link Communications line that travels on, near or below ground. Contrast with satellite link. test automation software Software used to test new revisions of software by automatically entering a predefined set of commands and inputs. test data Set of data created for testing new or revised programs. It should be developed by the user as well as the programmer and must contain a sample of every category of valid data as well as many invalid conditions. testing Running new or revised programs to determine if they process all data properly. See test data. TeX Typesetting language used in a variety of typesetting environments. It uses embedded codes within the text of the document to initiate changes in layout including the ability to describe elaborate scientific formulas. text Words, sentences and paragraphs. Contrast with data, which are defined units, such as name and amount due. Text may also refer to alphanumeric data, such as name and address, to distinguish it from numeric data, such as quantity and dollar amounts. A page of text takes about 2,000 to 4,000 bytes. See text field. text based Also called character based, the display of text and graphics as a fixed set of predefined characters. For example, 25 rows of 80 columns. Contrast with graphics based. text editing Ability to change text by adding, deleting and rearranging letters, words, sentences and paragraphs. text editor Software used to create and edit files that contain only text (batch files, address lists, source language programs, etc.). Unlike a word processor, it usually does not provide word wrap or formatting features such as underline, boldface or font changes. Editors designed for programming may provide automatic indention and multiple windows. See DOS Edlin and DOS Editor. text field Data structure that holds alphanumeric data, such as name and address. If a text field holds large, or unlimited, amounts of text, it may be called a memo field. Contrast with numeric field. text file File that contains only text characters. Contrast with graphics file and binary file. text management Creation, storage and retrieval of text. It implies flexible retrieval capabilities that can search for text based on a variety of criteria. Although a word processor manages text, it usually has limited retrieval capabilities. text mode (1) Screen display mode that displays only text and not graphics. (2) Program mode that allows text to be entered and edited. text to speech Converting text into voice output using speech synthesis techniques. texture mapping In computer graphics, the creation of a special surface. With algorithms, all kinds of textures can be produced: the rough skin of an orange, the metallic surface of a can and the irregularity of a brick. It can also be done by electronically wrapping a secondary image around an object. TFT (Thin Film Transistor) See thin film. TFT LCD (Thin Film Transistor LCD) See LCD. TFTP (Trivial File Transfer Protocol) Version of the TCP/IP FTP protocol that has no directory or password capability. TGA See Targa. thermal dye diffusion Printing process similar to thermal wax transfer except that a dye is used instead of ink. The printhead heats the ribbon causing the dye to turn from a solid to a gas and condense on special paper. The more heat, the denser the image. Continuous color can be produced that approaches photographic quality. thermal printer Low-cost, low- to medium-resolution non-impact printer that uses heat-sensitive paper. Where the heated pins of the print head touch the paper, the paper darkens. See printer. thermal wax transfer Printing process that transfers a waxlike ink onto paper. For example, in a color printer, a mylar ribbon is used that contains several hundred repeating sets of full pages of black, cyan, magenta and yellow ink. A sheet of paper is pressed against each color and passed by a line of heating elements that transfers the dots, or pixels, of ink onto the paper. thick film Layer of magnetic, semiconductor or metallic material that is thicker than the microscopic layers of the transistors on a chip. For example, metallic thick films are silk screened onto the ceramic base of hybrid microcircuits. Contrast with thin film. thimble printer Letter quality printer similar to a daisy wheel printer. Instead of a wheel, characters are formed facing out and around the rim of a thimble-shaped cup. For example, the NEC Spinwriters are thimble printers. thin Ethernet See Ethernet. thin film Microscopically thin layer of semiconductor or magnetic material that is deposited onto a metal, ceramic or semiconductor base. For example, the layers that make up a chip and the surface coating on high-density magnetic disks are called thin films. thin film head Read/write head for high-density disks that is made from thin layers of a conducting film deposited onto a nickel-iron core. ThinNet See Ethernet. third-generation computer Computer that uses integrated circuits, disk storage and online terminals. The third generation started roughly in 1964 with the IBM System/360. third-generation language Traditional high-level programming language such as FORTRAN, COBOL, BASIC, Pascal and C. third normal form See normalization. THOR (Tandy High-intensity Optical Recorder) Erasable CD recorder from Tandy scheduled for introduction in the early 1990s. It records audio on a special disc that can be erased and reused and also played on a standard CD player. Models for recording data are projected. thrashing Excessive paging in a virtual memory computer. If programs are not written to run in a virtual memory environment, the operating system may spend excessive amounts of time swapping program pages in and out of the disk. thread One transaction or message in a multithreaded system. threading See multithreading. three-state logic element Electronic component that provides three possible outputs: off, low voltage and high voltage. throughput Speed with which a computer processes data. It is a combination of internal processing speed, peripheral speeds (I/O) and the efficiency of the operating system and other system software all working together. thunk In PCs, to execute the instructions required to switch between segmented addressing of memory and flat addressing. THz (TeraHertZ) One trillion cycles per second. TI (Texas Instruments, Inc., Dallas, TX) Leading semiconductor manufacturer founded in 1930 as Geophysical Service, Inc., to provide services to the petroleum industry. During the war, GSI manufactured electronics for the Navy and later added them to its product line. In 1951, GSI was renamed Texas Instruments and soon after entered the semiconductor business. TI was the first to commercialize the silicon transistor, pocket radio, integrated circuit, hand- held calculator, single-chip computer and the LISP chip. In the early 1980s, TI sold a large number of its low-priced 99/4a home computers. It later introduced desktop PCs, but today offers only a line of notebook PCs. With 1991 revenues of nearly seven billion, TI's strength is integrated circuits, but, it also creates computer systems for AI applications, composite metals, electrical control products and consumer electronics, including its well-known line of calculators and educational math and reading machines. TI-RPC (Transport-Independent-Remote Procedure Call) Operating system and network-independent library of functions from Sun for executing procedures on remote computers. Allows development of distributed applications in multivendor environments. TIA See EIA. TIA/EIA-232 See RS-232. TIES (Time-Independent Escape Sequence) Modem escape sequence that uses three pluses like the Hayes sequence, but does not require a pause before and after them. If a valid AT command code and a return follows the +++, it is considered a legitimate command. See Hayes Smartmodem. TIFF (Tagged Image File Format) Widely-used raster graphics file format developed by Aldus and Microsoft that handles monochrome, gray scale, 8- and 24-bit color. Since 1986, there have been six versions of TIFF. It uses several compression methods: LZW provides ratios of about 1.5:1 to 2:1. Ratios of 10:1 to 20:1 are possible for documents with lots of white space using CCITT Group III & IV compression methods (fax). See JPEG. TIGA (Texas Instruments Graphics Architecture) Graphics standard that provides a resolution-independent interface between a program and the graphics processor. See 34010. tightly coupled Refers to two or more computers linked together and dependent on each other. One computer may control the other, or both computers may monitor each other. For example, a database machine is tightly coupled to the main processor. Two computers tied together for multiprocessing are tightly coupled. Contrast with loosely coupled, such as personal computers in a LAN. tiled Display of objects side by side; for example, tiled windows cannot be overlapped on top of each other. time base generator Electronic clock that creates its own timing signals for synchronization and measurement purposes. time-division multiplexing See TDM. time slice Fixed interval of time allotted to each user or program in a multitasking or timesharing system. time slot Continuously repeating interval of time or a time period in which two devices are able to interconnect. timer interrupt Interrupt generated by an internal clock. See interrupt. timesharing Multiuser computer environment that lets users initiate their own sessions and access selected databases as required, such as when using online services. A system that serves many users, but for only one application, is technically not timesharing. timing clock See clock. timing signals Electrical pulses generated in the processor or in external devices in order to synchronize computer operations. The main timing signal comes from the computer's clock, which provides a frequency that can be divided into many slower cycles. Other timing signals may come from a timesharing or realtime clock. In disk drives, timing signals for reading and writing are generated by holes or marks on one of the platters, or by the way the digital data is actually recorded. Tiny BASIC Subset of BASIC that has been used in first generation personal computers with limited memory. TIRIS (Texas Instruments Registration and Identification System) RF/ID system from TI that uses a 3.6x29mm cylindrical tag. Reading can be done from as far as 40 inches away. TLA (Three Letter Acronym) The epitome of acronyms! TLI (Transport Level Interface) AT&T UNIX System V transport layer protocol (OSI layer 4). It is a STREAMS module that can serve as a programming interface between an application and OSI or TCP/IP protocols. TM/1 (Tables Manager/1) Relational spreadsheet for PCs from Sinper Corp., Warren, NJ, that allows data to be viewed in up to eight dimensions. An option allows Lotus users to access a TM/1 database directly from a 1-2-3 spreadsheet. TN (Twisted Nematic) First LCD technology, which twists liquid crystal molecules 90 between polarizers. Requires bright ambient light and still used for low-cost applications. See LCD. TOF (Top Of Form) Beginning of a physical paper form. To position paper in many printers, the printer is turned offline, the forms are aligned properly and the TOF button is pressed. toggle To alternate back and forth between two states. token passing Communications network access method that uses a continuously repeating frame (the token) that is transmitted onto the network by the controlling computer. When a terminal or computer wants to send a message, it waits for an empty token. When it finds one, it fills it with the address of the destination station and some or all of its message. Every computer and terminal on the network constantly monitors the passing tokens to determine if it is a recipient of a message, in which case it "grabs" the message and resets the token status to empty. Token passing uses bus and ring topologies. token ring network (1) Communications network that uses the token passing technology in a sequential manner. Each station in the network passes the token on to the station next to it. (2) (Token Ring Network) IBM local area network (LAN) that conforms to the IEEE 802.5 standard. All stations connect to a central wiring hub (star topology) through special twisted wire cable. The central hub makes it easier to troubleshoot failed units. It uses the token passing access method transmitting at 4 or 16 Mbits/sec and passes tokens to up to 255 nodes in a ring-like sequence. TokenTalk Software for the Macintosh from Apple that accompanies its TokenTalk NB board and adapts the Mac to Token Ring Networks. toner Electrically charged ink used in copy machines and laser printers. It adheres to an invisible image that has been charged with the opposite polarity onto a plate or drum or onto the paper itself. tool (1) On-screen function in an interactive program; for example, a line draw, circle draw or paintbrush option in a graphics program. (2) Program used for software development or system maintenance. Utility programs, editors, debuggers and graphics routines are examples. A program that helps a user customize, adapt or work with a computer may be called a tool. tool palette Collection of on-screen functions, typically graphics related, that are grouped in a menu structure for interactive selection. ToolBook Application development system for Windows from Asymetrix Corp., Bellevue, WA, that uses a "page and book" metaphor analogous to HyperCard's "card and stack." Its OpenScript language is similar to HyperTalk. toolbox Same as toolkit. toolkit Set of software routines that allow a program to be written for and work in a particular environment. The routines are called by the application program to perform various functions, for example, to display a menu or draw a graphic element. TOP (Technical Office Protocol) Communications protocol for office systems from Boeing Computer Services. It uses the Ethernet access method and is often used in conjunction with MAP, the factory automation protocol developed by GM. TOP is used in the front office, and MAP is used on the factory floor. top of file Beginning of a file. In a word processing file, it is the first character in the document. In a data file, it is either the first record in the file or the first record in the index. For example, in a dBASE file that is indexed on name, goto top might go to physical record #608 if record #608 is AARDVARK. topdown design Design technique that starts with the highest level of an idea and works its way down to the lowest level of detail. topdown programming Programming design and documentation technique that imposes a hierarchical structure on the design of the program. See structured programming. topology (1) In a communications network, the pattern of interconnection between nodes; for example, a bus, ring or star configuration. (2) In a parallel processing architecture, the interconnection between processors; for example, a bus, grid, hypercube or Butterfly Switch configuration. TOPS (1) Multiuser, multitasking, timesharing, virtual memory operating system from Digital that runs on its PDP-6, DECsystem 10 and DECsystem 20 series. (2) (Transparent OPerating System) Peer-to-peer LAN from Sitka Corp., Alameda, CA, that uses the LocalTalk access method and connects Apple computers, PCs and Sun workstations. Its Flashcard plugs LocalTalk capability into PCs. TOPVIEW IBM's first PC windowing environment. It never caught on. TOTAL Early network DBMS from Cincom Systems that ran on a variety of minis and mainframes. total bypass Bypassing local and long distance telephone lines by using satellite communications. touch screen Touch-sensitive display screen that uses a clear panel over on the screen surface. The panel is a matrix of cells that transmit pressure information to the software. tower (1) Floor-standing cabinet taller than it is wide. Desktop computers can be made into towers by turning them on their side and inserting them into a floor-mounted base. (2) Tower. Series of UNIX-based single and multiprocessor computer systems from NCR that use the Motorola 68000 family of CPUs. TP monitor (TeleProcessing monitor or Transaction Processing monitor) Communications control program that manages the transfer of data between multiple local and remote terminals and the application programs that serve them. It may also include programs that format the terminal screens and validate the data entered. See CICS and Tuxedo. TP0-TP4 (Transport Protocol Class 0 to Class 4) Grades of OSI transport layers from least to most complete and specific. TP4 is a full connection-oriented transport protocol. TPA (Transient Program Area) See transient area. tpi (Tracks Per Inch) Used to measure the density of tracks recorded on a disk or drum. TPS (1) (Transactions Per Second) Number of transactions processed within one second. (2) (Transaction Processing System) Originally used as an acronym for such a system, it now refers to the measurement of the system (#1 above). track Storage channel on disk or tape. On disks, tracks are concentric circles (hard and floppy disks) or spirals (CDs and videodiscs). On tapes, they are parallel lines. Their format is determined by the specific drive they are used in. On magnetic devices, bits are recorded as reversals of polarity in the magnetic surface. On CDs, bits are recorded as physical pits under a clear, protective layer. See magnetic disk. trackball Input device used in video games and as a mouse alternative. It is a stationary unit that contains a movable ball rotated with the fingers or palm and, correspondingly, moves the cursor on screen. tractor feed Mechanism that provides fast movement of paper forms through a printer. It contains pins on tractors that engage the paper through perforated holes in its left and right borders. Contrast with sheet feeder. Tradacoms European EDI standard developed by the Article Numbering Assn. See X12 and EDIFACT. trade shows See PC EXPO and COMDEX. trailer In communications, a code or set of codes that make up the last part of a transmitted message. See trailer label. trailer label Last record in a tape file. May contain number of records, hash totals and other ID. train printer Line printer mechanism similar to a chain printer, but uses unconnected type slugs that ride in a track rather than a connected chain of type. The slugs are pushed around the track by engaging with a drive gear at one end. Slugs and track come as a replaceable cartridge. training (1) Teaching the details of a subject. With regard to software, training provides instruction for each command and function in an application. Contrast with education. (2) In communications, the process by which two modems determine the correct protocols and transmission speeds to use. (3) In voice recognition systems, the recording of the user's voice in order to provide samples and patterns for recognizing that voice. transaction Activity or request. Orders, purchases, changes, additions and deletions are typical business transactions stored in the computer. Queries and other requests are also transactions, but are usually just acted upon and not saved. Transaction volume is a major factor in figuring computer system size and speed. transaction file Collection of transaction records. The data in transaction files is used to update the master files, which contain the subjects of the organization. Transaction files also serve as audit trails and are usually transferred from online disks to the data library after some period of time. As optical disks become more economical, transaction files will remain online in the computer so that an organization's history will be immediately available for ad hoc queries. See information system. transaction processing Processing transactions as they are received by the computer. Also called online or realtime systems, master files are updated as soon as transactions are entered at terminals or arrive over communications lines. If you save receipts in a shoebox and add them up at the end of the year for taxes, that's batch processing. However, if you buy something and immediately add the amount to a running total, that's transaction processing. transceiver Transmitter and receiver of analog or digital signals. It comes in many forms; for example, a transponder or network adapter. transcribe To copy data from one medium to another; for example, from one source document to another, or from a source document to the computer. It often implies a change of format or codes. transducer Device that converts one energy into another; for example, a read/write head converts magnetic energy into electrical energy and vice versa. In process control applications, it is used to convert pressure into an electrical reading. transfer To send data over a computer channel or bus. "Transfer" generally applies to transmission within the computer system, and "transmit" refers to transmission outside the computer over a line or network. Transfers are actually copies, since the data is in both locations at the end of the transfer. Input, output and move instructions activate data transfers in the computer. transfer protocol See file transfer protocol. transfer rate Also called data rate, the transmission speed of a communications or computer channel. Transfer rates are measured in bits or bytes per second. transfer time Time it takes to transmit or move data from one place to another. It is the time interval between starting the transfer and the completion of the transfer. transformer Device that changes AC voltage. It is made of steel laminations wrapped with two coils of wire. The coil ratio derives the voltage change. For example, if the input coil has 1,000 windings, and the output has 100, 120 volts is changed to 12. In order to create direct current (DC), the output is passed through a rectifier. transient Malfunction that occurs at random intervals; for example, a rapid fluctuation of voltage in a power line or a memory cell that intermittently fails. transient area Area in memory used to hold application programs for processing. The bulk of a computer's main memory is used as a transient area. transient state Exact point at which a device changes modes, for example, from transmit to receive or from 0 to 1. transistor Semiconductor device used to amplify a signal or open and close a circuit. In a computer, it functions as an electronic switch. In its normal state, it is non-conductive. When voltage is applied at the gate, it becomes conductive and current flows from source to drain. Transistors, resistors, capacitors and diodes, make up logic gates. Logic gates make up circuits, and circuits make up electronic systems.  Source Gate Drain       青賃祖疎陳  青陳珍陳珍陳陳   Switch  Conceptual View of A Transistor  translate (1) To change one language into another; for example, assemblers, compilers and interpreters translate source language into machine language. (2) In computer graphics, to move an image on screen without rotating it. (3) In telecommunictions, to change the frequencies of a band of signals. TransLISP PLUS Version of LISP for PCs from Solution Systems, Inc., Wellesley, MA. It provides an interface to Microsoft C that allows a C routine to be added to the LISP library as a function. transmission Transfer of data over a communications channel. transmission channel Path between two nodes in a network. It may refer to the physical cable, the signal transmitted within the cable or to a subchannel within a carrier frequency. In radio and TV, it refers to the assigned carrier frequency. transmission control unit See TCU. transmit To send data over a communications line. See transfer. transmitter Device that generates signals. Contrast with receiver. transparent Refers to a change in hardware or software that, after installation, causes no noticeable change in operation. transparent bridging Communications protocol in which the stations are unaware of bridges in the network. Ethernet uses this method. Contrast with source routing. transponder Receiver/transmitter on a communications satellite. It receives a microwave signal from earth (uplink), amplifies it and retransmits it back to earth at a different frequency (downlink). A satellite has several transponders. transport protocol Communications protocol responsible for establishing a connection and ensuring that all data has arrived safely. It is defined in layer 4 of the OSI model. transport services Collective functions of layers 1 through 4 of the OSI model. transputer (TRANSistor comPUTER) Computer that contains a CPU, memory and communications capability on a single chip. Chips are strung together in hypercube or grid-like patterns to create large parallel processing machines, used in scientific, realtime control and AI applications. trap To test for a particular condition in a running program; for example, to "trap an interrupt" means to wait for a particular interrupt to occur and then execute a corresponding routine. An error trap tests for an error condition and provides a recovery routine. A debugging trap waits for the execution of a particular instruction in order to stop the program and analyze the status of the system at that moment. trapdoor Alternate way of gaining access to an interactive program. It implies a special entrance or exit that can be used if necessary. trash can Macintosh icon used for deleting files, folders and applications and ejecting a floppy disk. trashware Software that is so poorly designed that it winds up in the garbage can. tree Hierarchical structure. See directory tree. trichromatic In computer graphics, the use of red, green and blue to create all the colors in the spectrum. trillion One thousand times one billion. See tera and picosecond. Trilogy Company founded in 1979 by Gene Amdahl to commercialize wafer scale integration and build supercomputers. It raised a quarter of a billion dollars, the largest startup funding in history, but could not create its 2.5" superchip. In 1984, it abandoned supercomputer development and later the superchip project. In 1985, Trilogy acquired Elxsi Corp., a manufacturer of VAX-compatible systems, and eventually merged itself into Elxsi. triple precision Use of three computer words to hold a number used for calculation, providing an enormous amount of arithmetic precision. triple twist Supertwist variation that twists crystals to 260 for improved clarity. See LCD. troff (Typesetting RunOFF) UNIX utility that formats documents for typesetters and laser printers. Using a text editor, troff codes are embedded into the text and the troff command converts the document into the required output. See nroff. Trojan horse Program routine that invades a computer system by being secretly attached to a valid program that will be downloaded into the computer. It may be used to locate password information, or it may alter an existing program to make it easier to gain access to it. A virus is a Trojan horse that continues to infect programs over and over. TRON (The Realtime Operating System Nucleus) Advanced realtime computer architecture and operating system under development by Japanese universities and corporations. Its goal is a common architecture and user interface from the smallest consumer appliance to the largest supercomputer. TRON-based intelligent cars and houses are under research. CTRON (Central TRON) is an OSI-compliant communications system for network file servers; BTRON (Business TRON) for accounting applications; ITRON (Industrial TRON) for intelligent machinery; MTRON (Macro TRON) for intelligent objects and networks (housing and urban development); ITRON (Micro ITRON) runs on 8-bit computers for home appliances. Address: P.O.Box 23990, Tempe, AZ 85285. TRS (Tandy Radio Shack) Early Tandy trade name. In 1977, the TRS-80 was one of the three first personal computers. TRS-DOS was its operating system. See personal computer. True BASIC ANSI-standard structured-programming version of BASIC for the PC, Mac and Amiga from True BASIC, Inc., West Lebanon, NH. Developed in 1984 by BASIC's creators, John Kemeny and Thomas Kurtz, it includes many enhancements over original BASIC. It comes in both interpreter and compiler form. true color (1) Ability to generate 16,777,216 colors (24-bit color). See high color. (2) Ability to generate photo-realistic color images (requires 24-bit color minimum). TrueImage Enhanced PostScript interpreter from Microsoft that prints PostScript Type 1 and TrueType fonts. TrueType Scalable font technology from Apple (enhanced jointly by Apple and Microsoft) that renders printer and screen fonts. It is used in Windows 3.1 and Mac System 7. Unlike PostScript, in which the algorithms are maintained in the rasterizing engine, each TrueType font contains its own algorithms for converting the outline into bitmaps. The lower-level language embedded within the TrueType font allows unlimited flexibility in the design. See TrueImage. truncate To cut off leading or trailing digits or characters from an item of data without regard to the accuracy of the remaining characters. Truncation occurs when data is converted into a new record with smaller field lengths than the original. trunk Communications channel between two points. It often refers to large-bandwidth telephone channels between major switching centers, capable of transmitting many simultaneous voice and data signals. truth table Chart of a logical operation's inputs and outputs. The following example is a Boolean AND truth table:     Inputs Output  敖陳陳陳堕陳陳  0 0 0  0 1 0  1 0 0  1 1 1     青陳陳陳祖陳陳  TSAT See VSAT. TSO (Time Sharing Option) Software that provides interactive communications for IBM's MVS operating system. It allows a user or programmer to launch an application from a terminal and interactively work with it. The TSO counterpart in VM is called CMS. Contrast with JES, which provides batch communications for MVS. TSOP (Thin Small Outline Package) One-millimeter-thick package used to house dynamic RAM chips. TSR (Terminate and Stay Resident) Refers to programs that remain in memory so they can be instantly popped up over the current application by pressing a hotkey. The program is displayed either as a small window on top of the existing text or image, or it takes the full screen. When the program is exited, previous screen contents are restored. On DOS PCs, TSRs provide quick access to a calculator, calendar or dictionary; however, conflicts may arise when multiple TSRs are loaded. Older ones may not always work with newer ones. Task switching environments such as Windows and DESQview, provide the ability to switch back and forth between applications, thus making all programs function as a TSR. The term refers to loading a program, terminating its action but not removing it from memory. TTL (Transistor Transistor Logic) Digital circuit in which the output is derived from two transistors. Although TTL is a specific design method, it often refers generically to digital connections in contrast with analog connections. For example, a TTL input on a monitor requires digital output from the display board rather than analog output. TTY (TeleTYpewriter) See teletypewriter. TTY protocol Low-speed asynchronous communications protocol with limited or no error checking. tube See CRT and vacuum tube. tuner Electronic part of a radio or TV that locks on to a selected carrier frequency (station, channel) and filters out the audio and video signals for amplification and display. tuple In relational database management, a record, or row. See relational database. Turbo C C compiler from Borland used to create a wide variety of commercial products. It is known for its exceptionally well-designed debugger. The PC version of this Glossary was written in Turbo C. Turbo Mouse Macintosh trackball from Kensington Microware, Ltd., San Mateo, CA. If the ball is moved slowly, the cursor moves slowly, but if moved quickly, the same spatial movement moves the cursor a greater distance on the screen. Its PC counterpart is called the Expert Mouse. Turbo Pascal Pascal compiler for DOS from Borland used in a wide variety of applications from accounting to complex commercial products. Turbo Pascal for Windows provides an object-oriented programming environment for Windows development. Borland is responsible for moving the Pascal language from the academic halls to the commercial world. TURBOchannel 32-bit data bus from Digital introduced in 1990. It has a peak transfer rate of 100 MBytes/sec. turnaround document Paper document or punched card prepared for re- entry into the computer system. Paper documents are printed with OCR fonts for scanning Invoices and inventory stock cards are examples. turnaround time (1) In batch processing, the time it takes to receive finished reports after submission of documents or files for processing. In an online environment, turnaround time is the same as response time. (2) In half-duplex transmission, the time it takes to change from transmit to receive and vice versa. turnkey system Complete system of hardware and software delivered to the customer ready-to-run. turnpike effect In communications, a lock up due to increased traffic conditions and bottlenecks in the system. turtle graphics Method for creating graphic images in Logo. The turtle is an imaginary pen that is given drawing commands, such as go forward and turn right. On screen, the turtle is shaped like a triangle. tutorial Instructional book or program that takes the user through a prescribed sequence of steps in order to learn a product. Contrast with documentation, which, although instructional, tends to group features and functions by category. Tuxedo TP monitor from USL that runs on a variety of UNIX- based computers. TWAIN Programming interface that lets a graphics application, such as a desktop publishing program, activate a scanner, frame grabber or other image- capturing device. tweak To make minor adjustments in an electronic system or in a software program in order to improve performance. tweening Animation technique that, based on starting and ending shapes, creates the necessary "in-between" frames. See morphing. TwinAxcess IBM midrange terminal emulation system for the Macintosh from Andrew/KMW, Austin, TX. It includes a controller card and software that emulates the 5250 terminal used on System/3x and AS/400s. It allows the user to have seven concurrent sessions broadcast over LocalTalk, EtherTalk or TokenTalk networks. twinaxial Type of cable similar to coax, but with two inner conductors instead of one. It is used in IBM midrange communications environments. TWIP (TWentIeth of a Point) Equal to 1/1440th of an inch. twisted pair Abbreviated "UTP" (Unshielded Twisted Pair), a pair of thin-diameter (22 to 26 gauge) insulated wires commonly used in telephone wiring. The wires are twisted around each other to minimize interference from other twisted pairs in the cable. Twisted pairs have less bandwidth than coaxial cable or optical fiber. two-out-of-five code Numeric code that stores one decimal digit in five binary digits in which two of the bits are always 0 or 1 and the other three are always in the opposite state. two-phase commit Technique for ensuring that a transaction successfully updates all appropriate files in a distributed database environment. All DBMSs involved in the transaction first confirm that the transaction has been received and is recoverable (stored on disk). Then each DBMS is told to commit the transaction (do the actual updating). two-wire lines Transmission channel made up of only two wires, such as used in the common dial-up telephone network. TWX (TeletypeWriter eXchange Service) U.S. and Canadian dial-up communications service that uses teleprinters and transmits 5-bit Murray code or 7- bit ASCII code at up to 150 bps. Originally part of the Bell System, it was sold to Western Union in 1971 and interconnected with Telex. Tymnet (BTC Tymnet) Value-added, packet switching network that enables many varieties of terminals and computers to exchange data. It is a subsidiary of British Telecom Corp. type (1) In data or text entry, to press the keys on the keyboard. (2) In programming, a category of variable that is determined by the kind of data stored in it. For example, integer, floating point, string, logical, date and binary are common data types. (3) In DOS and OS/2, a command that displays the contents of a text file. Type 1 font See PostScript. Type 3 font See PostScript. type ball Golf ball-sized element used in typewriters and low-speed teleprinters that contains all the print characters on its outside surface. It was introduced with IBM's Selectric typewriter. type family See typeface family. type font Set of print characters of a particular design (typeface), size (point size) and weight (light, medium, heavy). See font. type scaler See font scaler. typeahead buffer See keyboard buffer. typeface Design of a set of printed characters, such as Courier, Helvetica and Times Roman. The following chart shows common typeface measurements.  様様様 樛樛樛 養 様様様様様様様様様様様様様様様  栩 Ascender area  栩 陳陳陳桀樛樛 嬬樛樛 陳陳陳陳陳陳陳  Point 栩 桎烝炳  size 栩 x-height  栩栩栩 栩栩栩  陳 烝烝烝 吊 陳 吊 壷烝烝 陳陳陳BASELINE  Descender area  様様由様様様様様様様様様様 様様様様様様様様様様   様様由様様様様様様様様様様様様様様様様様様様様様   Leading (in points, from baseline to baseline)      陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳陳BASELINE  typeface family Group of typefaces that include the normal, bold, italic and bold-italic variations of the same design. typeover mode In word processing and data entry, a state in which each character typed on the keyboard replaces the character at the current cursor location. Contrast with insert mode. typesetter See phototypesetter and imagesetter. UAE (Uninterruptible Application Error) Application program abend in Windows 3.0. See GPF. UART (Universal Asynchronous Receiver Transmitter) Electronic circuit that transmits and receives data on the serial port. It converts bytes into serial bits for transmission, and vice versa, and generates and strips the start and stop bits appended to each character. 8250A and 16450 UART chips provide a one-byte buffer for storing data. The 16550 provides two 16-byte buffers and is better for high-speed lines. See UART overrun. UART overrun Condition in which a UART cannot process the current byte fast enough before the next byte comes in. UCR (Under Color Removal) Method for reducing amount of printing ink used. It substitutes black for gray color (equal amounts of cyan, magenta and yellow). Thus black ink is used instead of the three CMY inks. See GCR and dot gain. UCSD p-System (Univ. of California at San Diego p-System) Software development system designed for portability. Source programs (BASIC, Pascal, etc.) are compiled into an interim "p-code," which is executed by an interpreter in the target machine. UDP (User Datagram Protocol) TCP/IP protocol that allows an application to send a message to one of several applications running in the destination machine. The application is responsible for reliable delivery. UHF (Ultra High Frequency) Range of electromagnetic frequencies from 300MHz to 3GHz. UI See UNIX International and user interface. UIMX (User Interface Management System for X Window) Software from Visual Edge Software, Ltd., St. Laurent, Quebec, that allows a user to design and modify Open Look and Motif interfaces. ULSI (Ultra Large Scale Integration) More than one million transistors on a chip. See SSI, MSI, LSI and VLSI. ultrafiche Pronounced "ultra feesh." Microfiche that holds up to 1,000 document pages per 4x6" sheet of film. Normal microfiche stores around 270 pages. ultraviolet Invisible band of radiation at the high-frequency end of the light spectrum. It takes about 10 minutes of ultraviolet light to erase an EPROM chip. ULTRIX Digital's version of UNIX for its PDP-11 and VAX series. UMA (Upper Memory Area) PC memory between 640K and 1024K. See PC memory map and PC conflicts. UMB (Upper Memory Block) Unused blocks in the UMA (640K-1M). A UMB provider is software that can load drivers and TSRs into this area. unary Meaning one; a single entity or operation, or an expression that requires only one operand. unbundle To sell components in a system separately. Contrast with bundle. UNC (Universal Naming Service) Standard for identifying servers, printers and other resources in a network. unconditional branch In programming, a GOTO, BRANCH or JUMP instruction that passes control to a different part of the program. Constrast with conditional branch. undelete To restore the last delete operation that has taken place. There may be more than one level of undelete, allowing several or all previous deletions to be restored. See DOS Undelete. underflow (1) Error condition that occurs when the result of a computation is smaller than the smallest quantity the computer can store. (2) Error condition that occurs when an item is called from an empty stack. underscan Area within the normal rectangular viewing are on a display screen. Contrast with overscan. undo To restore the last editing operation that has taken place. For example, if a segment of text has been deleted or changed, performing an undo will restore the original text. Programs may have several levels of undo, including being able to reconstruct the original data for all edits performed in the current session. Unibus Bus architecture from Digital that was introduced in 1970 with its PDP-11 series. Unibus peripherals can be connected to a VAX through Unibus attachments on the VAXs. unidirectional Transfer or transmission of data in a channel in one direction only. union In relational database, the joining of two files. See set theory. Unisys (Unisys Corp., Blue Bell, PA) Computer manufacturer formed in 1986 as a merger of Burroughs and Sperry corporations. This was the largest computer merger in history. Sperry started in 1933 in navigational guidance and control equipment. In 1955, it merged with Remington Rand, creator of the UNIVAC I, and became Sperry Rand. Sperry became known for its large- scale mainframes and for providing communications and realtime systems to the military and NASA. In 1971, it absorbed RCA's Spectra 70 computer line and supported it until it phased out. Burroughs started as a maker of calculating machines and cash registers in 1886. It was first involved with computers by supplying memory for the ENIAC in 1952. A decade later, it introduced the B5000 computer, which was known for its advanced operating system. Burroughs computers became well established in the banking and finance industries. Today, Unisys still provides versions of products originating from both companies. It also offers UNIX systems, a full line of PCs, and continues to provide integrated solutions to vertical markets. unit record equipment See tabulating equipment. UNIVAC I (UNIVersal Automatic Computer) First commercially- successful computer, introduced in 1951 by Remington Rand. Over 40 systems were sold. Its memory was made of mercury-filled acoustic delay lines that held 1,000 12-digit numbers. It used magnetic tapes that stored 1MB of data at a density of 128 cpi. In 1952, it predicted Eisenhower's victory over Stevenson, and UNIVAC became synonymous with computer (for a while). UNIX Multiuser, multitasking operating system from Novell, Inc., Provo, UT, that runs on computers from micro to mainframe. UNIX was developed at AT&T and is written in C (also developed at AT&T), which can be compiled into many different machine languages, causing UNIX to run in a wider variety of hardware than any other control program. UNIX has thus become synonymous with "open systems." UNIX is made up of the kernel (fundamental tasks), the file system (hierarchical directory for organizing the disk) and the shell (interface that processes user commands). The major command-line interfaces are the Bourne shell, C shell and Korn shell. The UNIX vocabulary is exhaustive with over 600 commands that manipulate data and text every way conceivable. Many commands are cryptic (see comparison below), but just as Windows hides the DOS prompt, graphical user interfaces, such as OSF/Motif and Open Look, are presenting a friendlier image to UNIX users.  Command UNIX DOS List directory ls dir Copy a file cp copy Delete a file rm del Rename a file mv rename Display contents cat type Print a file lpr print Check disk space df chkdsk  The History of UNIX UNIX was developed in 1969 by Ken Thompson at AT&T, who scaled down the sophisticated MULTICS operating system for the PDP-7. The named was coined for a single-user version (un) of MULT "ICS" (ix). More work was done by Dennis Ritchie, and, by 1974, UNIX had matured into a state-of-the-art operating system primarily on PDPs. UNIX became very popular in scientific and academic environments. Considerable enhancements were made to UNIX at the Univ. of California at Berkeley, and versions of UNIX with the Berkeley extensions became widely used. By the late 1970s, commercial versions of UNIX, such as IS/1 and XENIX, became available. In the early 1980s, AT&T began to consolidate the many UNIX versions into standards which evolved into System III and eventually System V. Before divestiture (1984), AT&T licensed UNIX to universities and other organizations, but was prohibited from outright marketing of the product. After divestiture, it began to market UNIX aggressively. In 1989, UNIX Software Operation (USO) was formed as an AT&T division. USO introduced System V Release 4.0 (SVR4), which incorporated XENIX, SunOS, Berkeley 4.3BSD and System V into one UNIX standard. System V Interface Definition (SVID) was introduced, which defines UNIX compatibility. In 1990, USO was turned into UNIX System Laboratories, Inc., (USL) an AT&T subsidiary. In 1993, USL was acquired by Novell. Although every major hardware vendor has a version of UNIX, UNIX International (UI) and the Open Software Foundation (OSF) each promote software for universal adoption. X/Open and POSIX also govern UNIX standards. UNIX has evolved into the archetype environment for distributed processing and interoperability. TCP/IP communications protocols are used in the Internet, the world's largest network. SMTP provides e-mail, NFS allows files to be distributed across the network, NIS provides a "Yellow Pages" directory, Kerberos provides network security, and X Windows allows a user to run applications on other machines in the network simultaneously. UNIX International Independent, non-profit industry association funded by its members to promote and provide future direction of the UNIX System V operating system. It has over 130 members and works closely with X/Open. Address: 20 Waterview Blvd., Parsippany, NJ 07054, 201/263-8400. UnixWare Operating system for PCs from Univel, Inc. that is based on UNIX System V Release 4.2. Univel was originally a joint venture of Novell and USL; however, in 1993, Novell acquired USL. The UnixWare Personal Edition single user version provides client access to NetWare and runs UNIX, DOS and Windows applications. DR DOS is also included. The Application Server version integrates NetWare and supports X Window, TCP/IP and NFS. unload To remove a program from memory or take a tape or disk out of its drive. UNMA (Unified Network Management Archicture) Network strategy from AT&T for managing multi-vendor networks. unmark (1) In word processing, to deselect a block of text, which usually removes its highlight. (2) To deselect an item that has been tagged for a particular purpose. unpack See pack. unzip To decompress a file with PKUNZIP. See PK software. up Refers to a device that is working. UPC (Universal Product Code) Standard bar code printed on retail merchandise. It contains the vendor's identification number and the product number, which is read by passing the bar code over a scanner. update To change data in a file or database. The terms update and edit are often used synonymously. uplink Communications channel from an earth station to a satellite. Contrast with downlink. upload See download. upper CASE See front-end CASE. UPS (Uninterruptible Power Supply) Backup power used when the electrical power fails or drops to an unacceptable voltage level. Small UPS systems provide battery power for a few minutes; enough to power down the computer in an orderly manner. Sophisticated systems are tied to electrical generators that can provide power for days. A UPS system can be connected to a file server so that, in the event of a problem, all network users can be alerted to save files and shut down immediately. An online UPS provides a constant source of electrical power from the battery, while the batteries are being recharged from AC power. An offline UPS, also known as a standby power system (SPS), switches to battery within a few milliseconds after detecting a power failure. A surge protector filters out surges and spikes, and a voltage regulator maintains uniform voltage during a brownout, but a UPS keeps a computer running when there is no electrical power. UPS systems typically provide surge suppression and may also provide voltage regulation. uptime Time during which a system is working without failure. Contrast with downtime. upward compatible Also called forward compatible. Refers to hardware or software that is compatible with succeeding versions. Contrast with downward compatible. used computers See computer exchange. USENET (USEr NETwork) Public access network on the Internet that provides user news and e-mail. It is a giant, dispersed bulletin board that is maintained by volunteers willing to provide news and mail feeds to other nodes. It began in 1979 as a bulletin board between two universities in North Carolina. user Any individual who interacts with the computer at an application level. Programmers, operators and other technical personnel are not considered users when working in a professional capacity on the computer. user area Reserved part of a disk or memory for user data. user defined Any format, layout, structure or language that is developed by the user. user friendly System that is easy to learn and easy to use. This term has been so abused that many vendors are reluctant to use it. user group Organization of users of a particular hardware or software product. Members share experiences and ideas to improve their understanding and use of a particular product. User groups are often responsible for influencing vendors to change or enhance their products. user interface Combination of menus, screen design, keyboard commands, command language and help screens, which create the way a user interacts with a computer. Mice, touch screens and other input hardware is also included. A well-designed user interface is vital to the success of a software package. In time, interactive video, voice recognition and natural language understanding will be included. USL (UNIX System Laboratories, Inc.) AT&T subsidiary formed in 1990, responsible for developing and marketing UNIX. In 1993, USL was acquired by Novell, Inc., Provo, UT. USO (UNIX Software Operation) AT&T's UNIX division before it turned into USL. USRT (Universal Synchronous Receiver Transmitter) Electronic circuit that transmits and receives data on the serial port. It converts bytes into serial bits for transmission, and vice versa, and generates the necessary signals for synchronous transmission. utility program Program that supports using the computer. Utility programs, or "utilities," provide file management capabilities, such as sorting, copying, comparing, listing and searching, as well as diagnostic and measurement routines that check the health and performance of the system. UTP See twisted pair. UTP Ethernet (1) Same as twisted pair Ethernet. See Ethernet. (2) May refer to pre-IEEE standard twisted pair Ethernet networks. UTS (Universal Timesharing System) Amdahl's version of UNIX System V. Release 4.0 is POSIX compliant. UUCP (UNIX to UNIX CoPy) UNIX utility that copies a file from one UNIX system to another. It is commonly used as a mail transfer. UUNET (UNIX to UNIX NETwork) Information and communications network from UUNET Technologies, Inc., Falls Church, VA, that provides news, mail service and an extensive library of UNIX software. Custom networking for companies is available through its AlterNet service. V Series Series of of small to medium-scale mainframes from Unisys that were the Burroughs B2500 and B3500 product lines, originally introduced in 1966. V.110 CCITT standard (1984) that specifies how data terminal equipment (DTE) with asynchronous or synchronous serial interfaces can be supported on an ISDN network. It uses rate adaption, which involves a bit-by-bit alignment between the DTE and the ISDN B channel. V.120 CCITT standard (1988) that specifies how DTEs with asynchronous or synchronous serial interfaces can be supported on an ISDN network using a protocol (similar to LAP-D) to encapsulate the data to be transmitted. It includes the capability of using statistical multiplexing to share a B channel connection between multiple DTEs. V.17 CCITT fax standard (1991) that uses TCM modulation at 12000 and 14400 bps for Group 3. It adds TCM to the V.29 standard at 7200 and 9600 bps to allow transmission over noisier lines. It also defines special functions (echo protection, turn-off sequences, etc.) for half-duplex operation. Modulation use is a half-duplex version of V.32bis. V.21 CCITT standard (1964) for asynchronous 0-300 bps full-duplex modems for use on dial-up lines. It uses FSK modulation. V.22 CCITT standard (1980) for asynchronous and synchronous 600 and 1200 bps full-duplex modems for use on dial-up lines. It uses DPSK modulation. V.22bis CCITT standard (1984) for asynchronous and synchronous 2400 bps full-duplex modems for use on dial-up lines and two-wire leased lines, with fallback to V.22 1200 bps operation. It uses QAM modulation. V.23 CCITT standard (1964) for asynchronous and synchronous 0-600 and 0-1200 bps half-duplex modems for use on dial-up lines. It has an optional split-speed transmission method with a reverse channel of 0-75 bps (1200/75, 75/1200). It uses FSK modulation. V.24 CCITT standard (1964) that defines the functions of all circuits for the RS-232 interface. It does not describe the connectors or pin assignments; those are defined in ISO 2110. In the U.S., EIA-232 incorporates the control signal definition of V.24, the electrical characteristics of V.28 and the connector and pin assignments defined in ISO 2110. V.25 CCITT standard (1968) for automatic calling and/or answering equipment on dial-up lines. It uses parallel circuits and is similar in function to RS- 366 and Bell 801 autodialers used in the U.S. The answer tone defined in V.25 is the first thing heard when calling a modem. It serves a dual function of identifying the answering equipment as being a modem and also disabling the echo suppression and echo cancellation equipment in the network so that a full-duplex modem will operate properly. V.25bis CCITT standard (1968) for automatic calling and/or answering equipment on dial-up lines. It has three modes: asynchronous (rarely used), character- oriented synchronous (bisync) and bit-oriented synchronous (HDLC/SDLC). Both synchronous versions are used in IBM AS/400 and other small-to-medium sized computers that do automatic dialing for remote job entry. Due to the popularity of the Hayes AT Command Set, V.25bis is not used as widely in North America. It does not perform modem configuration functions and is limited to dialing and answering calls. V.26 CCITT standard (1968) for synchronous 2400 bps full-duplex modems for use on four-wire leased lines. It uses DPSK modulation and includes an optional 75 bps back channel. V.26bis CCITT standard (1972) for synchronous 1200 and 2400 bps full-duplex modems for use on dial-up lines. It uses DPSK modulation and includes an optional 75 bps back channel. V.26ter CCITT standard (1984) for asynchronous and synchronous 2400 bps full-duplex modems using DPSK modulation over dial-up and two-wire leased lines. It includes a 1200 bps fallback speed and uses echo cancellation, permitting a full-duplex modem to send and receive on the same frequency. V.27 CCITT standard (1972) for synchronous 4800 bps full-duplex modems for use on four-wire leased lines. It uses DPSK modulation. V.27bis CCITT standard (1976) for synchronous 2400 and 4800 bps full-duplex modems using DPSK modulation for use on four-wire leased lines. The primary difference between V.27 and V.27bis is the addition of an automatic adaptive equalizer. V.27ter CCITT standard (1976) for synchronous 2400 and 4800 bps half-duplex modems using DPSK modulation on dial-up lines. It includes an optional 75 bps back channel. V.27ter is used in Group 3 fax transmission without the back channel. V.28 CCITT standard (1972) that defines the functions of all circuits for the RS-232 interface. In the U.S., EIA-232 incorporates the electrical signal definitions of V.28, the control signals of V.25 and the connector and pin assignments defined in ISO 2110. V.29 CCITT standard (1976) for synchronous 4800, 7200 and 9600 bps full-duplex modems using QAM modulation on four-wire leased lines. It has been adapted for Group 3 fax transmission over dial-up lines at 9600 and 7200 bps. V.32 CCITT standard (1984) for asynchronous and synchronous 4800 and 9600 bps full-duplex modems using TCM modulation over dial-up or two-wire leased lines. TCM encoding may be optionally added. V.32 uses echo cancellation to achieve full-duplex transmission. V.32bis CCITT standard (1991) for asynchronous and synchronous 4800, 7200, 9600, 12000 and 14400 bps full-duplex modems using TCM and echo cancellation. Supports rate renegotiation, which allows modems to change speeds as required. V.33 CCITT standard (1988) for synchronous 12000 and 14400 bps full-duplex modems for use on four-wire leased lines using QAM modulation. It includes an optional time-division multiplexor for sharing the transmission line among multiple terminals. V.35 CCITT standard (1968) for group band modems that combine the bandwidth of several telephone circuits to achieve high data rates. V.35 has become known as a high-speed RS-232 interface rather than a type of modem. The large, rectangular V.35 connector was never specified in V.35, but has become a de facto standard for a high-speed interface. V.42 CCITT standard (1989) for modem error checking that uses LAP-M as the primary protocol and provides MNP Classes 2 through 4 as an alternative protocol for compatibility. V.42bis CCITT standard (1989) for modem data compression. It uses the British Telecom Lempel Ziv technique to achieve up to a 4:1 ratio. V.42bis implies the V.42 error checking protocol. V.54 CCITT standard (1976) for various loopback tests that can be incorporated into modems for testing the telephone circuit and isolating transmission problems. Operating modes include local and remote digital loopback and local and remote analog loopback. V.56 CCITT standard (1972) for a method of testing modems to compare their performance. Newer procedures are currently under study. V.fast Future CCITT standard for 19200 bps modems to be approved in 1993. V20, V30 8088- and 8086-compatible processors from NEC. Versions running at 16MHz were introduced in 1991. VAC (Volts Alternating Current) See volt and AC. vacuum tube Electronic device that controls the flow of electrons in a vacuum, used as a switch, amplifier or display screen. Used as on/off switches, they allowed the first computers to perform digital computations. Today, it is primarily the CRT in monitors and TVs. VAD (Value Added Dealer) Same as VAR (value added reseller). validity checking Routines in a data entry program that tests the input for correct and reasonable conditions, such as numbers falling within a range and correct spelling, if possible. See check digit. value (1) Content of a field or variable. It can refer to alphabetic as well as numeric data. For example, in the expression, state = "PA", PA is a value. (2) In spreadsheets, the numeric data within the cell. value-added network Communications network that provides services beyond normal transmission, such as automatic error detection and correction, protocol conversion and message storing and forwarding. Telenet and Tymnet are examples of value-added networks. VAN See value-added network. VAP (Value Added Process)  Software that enhances or provides additional server functions in a NetWare 286 server. Support for different kinds of workstations, database engines, fax and print servers are examples. The NetWare 386 counterpart is the NLM. vaporware Software that has been advertised but not delivered. VAR (Value Added Reseller) Organization that adds value to a system and resells it. For example, it could purchase a CPU and peripherals from different vendors and graphics software from another and package it together as a specialized CAD system. See OEM. variable In programming, a structure that holds data and is uniquely named by the programmer. It holds the data assigned to it until a new value is assigned or the program is finished. Variables are used to hold control values. For example, the C statement for (x=0; x<5; x++) performs the instructions following it five times. X is a variable set to zero (x=0), incremented (x++) and tested to reach five (x<5). Variables also hold data temporarily that is being processed. Variables are usually assigned with an equal sign; for example, counter = 1, places a 1 in COUNTER. Numeric data is unquoted: counter = 1, character data requires quotes: product="abc4344". In some languages, the type of data must be declared before it is assigned; for example, in C, the statement, int counter; creates a variable that will only hold whole numbers. A local variable is one that is referenced only within the subprogram, function or procedure it was defined in. A global variable can be used by the entire program. variable length field Record structure that holds fields of varying lengths. For example, PAT SMITH takes nine bytes and GEORGINA WILSON BARTHOLOMEW takes 27. A couple of bytes of control information would also be added. If fixed length fields were used, 27 bytes would have to be reserved for both names. There's more programming with variable length fields, because every record has to be separated into fixed length fields after it is brought into memory. Conversely, each record has to be coded into the variable length format before it is written to disk. The same storage savings can be achieved by compressing data stored on disk and decompressing it when retrieved. All blank spaces in fixed length fields would be filtered out. For acceptable performance, this method must be well integrated into the operating system. See realtime compression. variable length record Data record that contains one or more variable length fields. varname (VARiable NAME) Abbreviation for specifying the name of a variable. VAX (Virtual Address eXtension) Family of 32-bit computers from Digital introduced in 1977 with the VAX-11/780 model. VAXes range from desktop personal computers to mainframes all running the same VMS operating system. Large models can be clustered in a multiprocessing environment to serve thousands of users. Software compatibility between models caused the VAX family to achieve outstanding success during the 1980s. VAXes also provide PDP emulation. VAXcluster Group of VAXs coupled together in a multiprocessing environment. VAXELN Realtime operating environment for VAXs from Digital. It runs under VMS and provides application development in Pascal and other languages. Resulting programs are downloaded into the target systems. VAXmate Partially IBM-compatible PC from Digital introduced in 1986, which has been superseded by the DECstation 200 and 300 series in 1989. VAXstation Single-user VAX computer that runs under VMS introduced in 1988. VBE (VGA BIOS Extension) VESA VGA standard for interrogating the capabilities of a graphics adapter. It allows the software developer to write a universal driver for all VBE-compliant VGA cards. See PC display modes for VBE specs. Vbox (video box) Hardware interface from Sony that attaches up to seven VCRs, videodiscs and camcorders to the serial port. Devices must have the Control-L (LANC) connector. VCPI (Virtual Control Program Interface) DOS extender specification for 386s and up that allows DOS extended programs to run with Real Mode programs. VCPI allows for example, Paradox 386, a DOS- extended program, to run cooperatively with DESQview, which runs multiple Real Mode programs in Virtual 8086 mode. Developed by Quarterdeck, Phar Lap Software, et al, it was the first DOS extender standard. See DPMI. VCR (Video Cassette Recorder) Videotape recording and playback machine that comes in the following formats: One inch tape is used for mastering video recordings. Sony Umatic 3/4" tape was widely used in commercial training. VHS 1/2" tape, first used only in the home, has mostly replaced the 3/4" tape. Sony's 1/2" Beta tape, the first home VCR format, is defunct. Although VCRs are analog recording machines, adapters allow them to store digital data for computer backup. VDE (1) (Video Display Editor) WordStar and WordPerfect-compatible shareware word processor written by Eric Meyer. (2) (Verband Deutscher Elektrotechniker) German counterpart of the U.S. Underwriters Lab. Vdeck (video deck) Frame-accurate, Super 8mm tape drive from Sony for serial-port connection to a personal computer. It contains an internal Vbox, is controlled by the ViSCA language and has no external play buttons. VDI (Virtual Device Interface) ANSI standard format for creating device drivers. For example, if a vendor sells a screen display and adapter board with a proprietary resolution, and also includes a driver written in the VDI format, software packages that support VDI will be able to use the new monitor. The VDI standard has been incorporated into the CGI standard. When CGI is officially endorsed by ANSI, it may supersede VDI. Vdisk See DOS RAM disks. VDM See CGM. VDS (Virtual DMA Services) Programming interface that lets bus mastering devices cooperatively manage DMA channels. VDT (Video Display Terminal) Terminal with a keyboard and display screen. VDT radiation Electromagnetic radiation emitted from a computer display screen. Exhaustive testing so far seems inconclusive, but vendors recommend keeping the face at least 18 to 20 inches from the screen. VDU (Video Display Unit) Same as VDT. vector (1) In computer graphics, a line designated by its end points (x-y or x-y-z coordinates). When a circle is drawn, it is made up of many small vectors. (2) In matrix algebra, a one-row or one-column matrix. vector display Display terminal that draws vectors on the screen. Contrast with raster display. vector font Scalable font made of vectors (point-to-point line segments). It is easily scaled as are all vector- based images, but lacks the hints and mathematically-defined curves of outline fonts, such as Adobe Type 1 and TrueType. vector graphics In computer graphics, a technique for representing a picture as points, lines and other geometric entities. See graphics. Contrast with raster graphics. vector processor Computer with built-in instructions that perform multiple calculations on vectors (one-dimensional arrays) simultaneously. It is used to solve the same or similar problems as an array processor; however, a vector processor passes a vector to a functional unit, whereas an array processor passes each element of a vector to a different arithmetic unit. See pipeline processing and array processor. Vectra PC series from HP. Vectras are noted for their ruggedness and reliability. vendors There are thousands of companies comprising the computer industry. The following hardware, software, consulting and service vendors represent all the majors and some of the more widely known. Many are individual entries in the Glossary. See software vendors and Fortune 500. ACER AMERICA CORP., San Jose, CA, 800/SEE-ACER Complete line of PCs under Acer and Acros brands. ADOBE SYSTEMS, INC., Mtn. View, CA, 800/833-6687 PostScript language and Type 1 and Type 3 font technologies. ADVANCED LOGIC RESEARCH, Irvine, CA, 800/257-1230 Complete line of PCs. "ALR" pioneered upgradable CPU architecture. ADVANCED MICRO DEVICES, Sunnyvale, CA, 800/2929-AMD Intel-compatible CPU chips. ALDUS CORP., Seattle, WA, 800/332-5387 Pioneered desktop publishing with PageMaker, originally on the Mac. AMDAHL CORP., Sunnyvale, CA, 800/538-8460 First successful IBM-compatible mainframe manufacturer. AMERICAN MEGATRENDS, INC., Norcross, GA 800/828-9264 "AMI" PC motherboards, ROM BIOS. APPLE COMPUTER, Cupertino, CA, 800/776-2333 Macintosh series and Apple IIe. Largest non-IBM compatible personal computer manufacturer. Pioneered the microcomputer revolution. ARTISTOFT, INC., Tucson, AZ, 800/TINYRAM Lantastic network operating system. Major success in peer-to-peer networking. AST RESEARCH, INC., Irvine, CA, 714/727-4141 Complete line of PCs. Known for high-end. ATARI, INC., Sunnyvale, CA, 408/745-2000 ST personal computer line. Founded in 1972 by Nolan Bushnell. Known for its video games. AUTODESK, INC., Sausalito, CA, 800/964-6432 AutoCAD software, one of the first major CAD programs for personal computers. BOLT, BARANEK & NEWMAN, Cambridge, MA, 800/422-2359 Consulting, software, research. "BBN" has been at the forefront of major projects. BORLAND INT'L. INC., Scotts Valley, CA 800/331-0877 Programming languages, dBASE, Paradox, Quattro Pro, Sidekick. First to commercialize Pascal (Turbo Pascal). BULL HN, Billerica, MA, 800/999-2181 Mini and mainframe manufacturer originally started as Honeywell's computer division, later merged with Groupe Bull of France and NEC of Japan. CLARIS CORP., Santa Clara, CA, 800/325-2747 Software subsidiary of Apple Computer MacDraw, MacWrite, FileMaker Pro, HyperCard, etc. COMMODORE BUSINESS MACHINES, Inc., West Chester, PA 800/66-AMIGA Amiga personal computer line. Founded in 1977 and introduced the PET, one of the first personal computers. COMPAQ COMPUTER CORP., Houston, TX, 800/345-1518 Complete line of PCs. First to successfuly clone IBM PC. First portable PC. First American company to reach $111 million sales in a year. COMPUSERVE, INC., Columbus, OH, 800/848-8990 Widely-used online information service. Provides many technical forums for users and developers. COMPUTER ASSOCIATES INT'L, INC., Islindia, NY 800/CALL-CAI Software from micro to mainframe. Founded in 1976 by Charles Wang. CONNER PERIPHERALS, INC., San Jose, CA 408/456-4500 Manufacturer of disk drives. CONTROL DATA SYSTEMS, INC., Minneapolis, MN 612/893-4120 Workstations to supercomputers. One of the first computer companies. Founded in 1957 under Bill Norris. CRAY RESEARCH, INC., Egan, MN, 800/284-2729 Supercomputers originally designed by Seymour Cray, leading architect at Control Data. D&B SOFTWARE, Atlanta, GA, 800/234-3867 1990 merger of MSA and McCormack & Dodge mainframe software companies. Under leadership of John Imlay, CEO of MSA. DATA GENERAL CORP., Westboro, MA, 800/328-2436 One of the pioneers in minicomputers. Founded in 1968 by Edson De Castro. DELL COMPUTER CORP., Austin, TX, 800/289-3355 Complete line of mail-order PCs. Originally "PCs Limited" brand. First to legitimize mail- order PCs with quality telephone support. DIALOG INFORMATION SERVICES, Palo Alto, CA 800/334-2564 Online service. Largest collection of databases in the world. DIGITAL EQUIPMENT CORP., Maynard, MA, 800/344-4825 "DEC" pioneered the minicomputer industry under leadership of Ken Olsen who retired in 1992. Complete line of PCs, minis and mainframes. Founded in 1957. DIGITAL RESEARCH, INC., Monterey, CA, 800/274-4DRI Creator of CP/M, first common operating system for personal computers. Later DOS-compatible DR DOS. Founded in 1976 by Gary Kildall. Acquired by Novell in 1991. ELECTRONIC DATA SYSTEMS CORP., Maryland Hgts, MO 314/344-5900 Pioneered facilities management. Founded in 1962 by Ross Perot. Acquired by GM. EVEREX SYSTEMS, INC., Fremont, CA, 800/356-8486 Complete line of PCs, high-end servers. GATEWAY 2000, N. Sioux City, SD, 800/523-2000 Complete line of mail-order PCs. Became very successful in early 1990s. GENIE, Rockville, MD, 800/638-9636 Online service. Wide variety of databases. HAYES MICROCOMPUTER PRODUCTS, INC., Atlanta, GA 404/840-9200 Pioneered the personal computer modem. Hayes AT command set is de facto standard modem language. HEWLETT-PACKARD CO., Palo Alto, CA, 800/752-0900 "HP" was one of the first minicomputer companies. Complete line of PCs, workstations and minis plus 10,000 electronic products. Founded in 1939 by Wm. Hewlett & David Packard. HITACHI AMERICA (various locations in U.S.) Monitors, CD ROM players, computers. INTERNATIONAL BUSINESS MACHINES, Armonk, NY 800/426-2468 "IBM" is the world's largest computer company. Complete line of mainframes, minis and PCs. Founded in 1911. Renamed IBM in 1924 under leadership of T. J. Watson, Sr. INTEL CORP., Santa Clara, CA, 800/538-3373 Maker of x86 CPU chips used in PCs. LOTUS DEVELOPMENT CORP., Cambridge, MA 800/343-5414 First spreadsheet (Lotus 1-2-3) for the PC, Ami Pro, Lotus Notes, etc. Founded in 1981 by Mitch Kapor. MAXTOR CORP., San Jose, CA, 800/262-9867 Disk drives manufacturer. MICRONICS COMPUTERS, INC., Fremont, CA 510/651-2300 PC motherboards, electronics, laptops. MICROSOFT CORP., Redmond, WA, 800/227-4679 DOS, Windows, programming langauges and applications. Founded in 1975 by Bill Gates and Paul Allen. MOTOROLA, INC., Schaumburg, IL, 708/576-5000 Maker of 68xxx CPU chips used in Macintoshes and various workstations. NCR CORP., Dayton, OH, 800/CALL-NCR One of the first computer companies. Leading cash register company dating back to 1884 under John Henry Patterson. Acquired by AT&T in 1991. NEC TECHNOLOGIES, INC., Boxborough, MA 800/343-4418 Pioneered multifrequency monitor with its MultiSync line. NEXT COMPUTER, INC., Redwood City, CA, 800/848-NEXT Family of UNIX-based workstations and the NeXTstep operating environment. Founded by Steve Jobs, co-founder of Apple. NORTHGATE COMPUTER SYSTEMS, INC., Minneapolis, MN 800/548-1993 Complete line of mail-order PCs. Known for its Omnikey keyboards. Founded in 1987. NOVELL, INC., Provo, UT, 800/453-1267 NetWare operating systems. Most widely-used networking software. Founded in 1983 by Ray Noorda. OPEN SOFTWARE FOUNDATION, Cambridge, MA 617/621-8700 UNIX-based open systems software for distributed computing. ORACLE CORP., Redwood Shores, CA, 800/ORACLE-1 Oracle database system runs on more platforms than any other DBMS. Founded in 1977. PACKARD BELL, INC., Chatsworth, CA, 818/886-4600 Complete line of PCs and peripherals. Founded in 1986. PHOENIX TECHNOLOGIES, INC., Norwood, MA 800/344-7200 PC ROM BIOS chips, electronics. PRODIGY, White Plains, NY, 800/776-3449 Online service for home and office computing. Shopping, news, databases. QUARK, INC., Denver, CO., 800/788-7835 QuarkXpress desktop publishing for Mac and Windows. SANTA CRUZ OPERATION (THE), Santa Cruz, CA 800/SCO-9694 UNIX and XENIX operating systems. SEAGATE TECHNOLOGY, INC., Scotts Valley, CA 800/468-3472 Largest independent manufacturer of disk drives. SOFTWARE PUBLISHING CORP., Santa Clara, CA 800/447-7991 Harvard Graphics, Superbase and other applications. SONY CORP. OF AMERICA, San Jose, CA, 800/352-7669 Monitors, CR ROM players, disk drives and diskettes. SUN MICROSYSTEMS, INC., Mtn. View, CA, 800/821-4643 Complete line of workstations using Sun's SPARC CPU. Largest supplier of UNIX-based systems. Founded in 1982 by Bill Joy. SYMANTEC CORP., Cupertino, CA, 800/441-7234 Q&A, Norton Utilities and other applications. TANDEM COMPUTERS, INC., Cupertino, CA 800/538-3107 First to make fault-tolerant computer systems. Founded in 1974 by James Treybig. TANDON CORP., Moorpark, CA, 800/800-8850 Complete line of PCs, peripherals. TANDY CORP., Ft. Worth, TX, 817/390-3011 Complete line of PCs and electronics through Radio Shack chain originally acquired in 1963. TRS-80 was one of the first personal computers. TEXAS INSTRUMENTS, INC., Dallas, TX, 800/527-3500 Chips, electronics, computer systems. Founded in 1930 as Geophysical Service. Renamed TI in 1951. TOSHIBA AMERICA INFO. SYSTEMS, INC., Irvine, CA 800/334-3445 Complete line of high-end, quality portable PCs. Pioneered laptop revolution. UNISYS CORP., Blue Bell, PA, 800-448-1424 1986 merger of Sperry and Burroughs, two of the oldest computer companies. Complete line of PCs, minis and mainframes. UNIX SYSTEMS LABORATORIES, INC., Summit, NJ 800/828-8649 AT&T subsidiary responsible for developing and marketing UNIX System V. WANG LABORATORIES, INC., Lowell, MA, 800/835-9264 Early minicomputer company and leader in WP in the 1970s. Founded by Dr. An Wang in 1951. WESTERN DIGITAL CORP., Irvine, CA, 800/832-4778 Manufacturer of disk drives, controllers and electronics. "Paradise" display boards. WORDPERFECT CORP., Orem, UT, 800/321-5906 WordPerfect is the most widely-used word processing software. Founded in 1979. WORDSTAR INT'L. INC., Novato, CA, 800/227-5609 WordStar was the first full-featured word processor for personal computers. Founded in 1978. XEROX CORP., Palo Alto, CA, 800/626-6775 Pioneered the graphical user interface at its PARC (Palo Alto Research Ctr.) on the Alto computer. Introduced concept on the Star workstation in 1981. Sells personal computer applications such as Ventura Publisher. ZENITH DATA SYSTEMS CORP., Buffalo Grove, IL 800/227-3360 Complete line of PCs, monitors. Pioneered laptop revolution. Venn diagram Graphic technique for visualizing set theory concepts using overlapping circles and shading to indicate intersection, union and complement. Ventura Publisher Desktop publishing program for PCs and the Macintosh from Ventura Software, Inc. (a Xerox company), that provides full-scale pagination for large documents. It is designed to import data created in other graphics and word processing programs, although it does have rudimentary text and graphics capabilities. Ventura is available for DOS, Windows, OS/2 and the Mac. The DOS version comes with a runtime version of the GEM interface. verify In data entry operations, to compare the keystrokes of a second operator with the files created by the first operator. VersaCAD Family of CAD systems for PCs and the Macintosh from Computervision, Bedford, MA, that features 2-D geometric and construction drafting and 3-D modeling with 16 viewports. It features complete programmability and universal CAD communications. The Mac version includes CAD-oriented HyperCard stacks. version control Management of source code in a large software project. Version-control software provides a database that keeps track of the revisions made to a program by all the programmers involved in it. version number Identification of a release of software. The difference between Version 2.2 and 2.3 can be night and day, since new releases not only add features, but often correct bugs. What's been driving you crazy may have been fixed! Numbers, such as 3.1a or 3.11, often indicate a follow-up release only to fix a bug in the previous version, whereas 3.1 and 3.2 usually mean routine enhancements. Version "1.0" drives terror into the hearts of experienced users. The program has just been released, and bugs are still to be uncovered. vertical bandwidth See vertical scan frequency. vertical recording Magnetic recording method that records the bits vertically instead of horizontally, taking up less space and providing greater storage capacity. The vertical recording method uses a specialized material for the construction of the disk. vertical redundancy checking See VRC. vertical refresh See vertical scan frequency. vertical resolution Number of lines (rows in a matrix). Contrast with horizontal resolution. vertical scan frequency Number of times an entire display screen is refreshed, or redrawn, per second. Measured in Hertz, display systems range from 45 to over 100Hz. For example, VGA in the U.S. is generally 56 to 60Hz; in Europe, 70Hz and above. TV is refreshed 60 half-frames/sec (interlaced) resulting in 30 full frames/sec. Contrast with horizontal scan frequency. VESA (Video Electronics Standards Assn.) Organization of major PC graphics vendors dedicated to improving video and multimedia standards. It has defined a local bus standard that is becoming very popular (see VL-bus). Address: 2150 N. 1st St., Suite 360, San Jose, CA 95131, 408/435-0333. vesicular film Film used to make copies of microforms. It contains its own developer and creates a pink negative or positive copy when exposed to a negative master through ultraviolet light. VGA (Video Graphics Array) IBM video display standard built into most PS/1 and PS/2 models that provides medium-resolution text and graphics. It has become the minimum standard for all PCs. VGA supports previous CGA and EGA modes and requires an analog monitor. Its highest-resolution mode is 640x480 with 16 colors, but VESA and third parties have boosted colors and resolution. See PC display modes. VGA HC (VGA HiColor) VGA board that provides 32K or 64K colors using Tseng Labs' ET4000 chip or equivalent. VGA pass through Feature of a high-resolution display adapter that couples internally with a VGA display adapter and passes its signals through to the monitor. VHD (Very High Density) Floppy disk technologies that place 20MB and more of data on a 3.5" disk. See Floptical. VHF (Very High Frequency) Range of electromagnetic frequencies from 30MHz to 300MHz. VHS VCR format introduced by JVC in 1976 (to compete with Sony's Beta format) that has become the standard for home and industry. SVHS (Super VHS) is a subsequent format that improves resolution. VHSIC (Very High Speed Integrated Circuit) Pronounced "vizik." Ultra-high-speed chips employing LSI and VLSI technologies. vi (Visual Interface) UNIX full-screen text editor that can be run from a terminal or the system console. It is a fast, programmer-oriented utility. video Audio/visual playback and recording technology used in TV. It also refers to computer screens and terminals. However, there is only one TV/video standard in the U.S., but there are dozens of computer/video display standards. video adapter Same as video display board. video bandwidth Maximum display resolution, measured in MHz, and calculated by horizontal x vertical resolution x refreshes/sec. For example, 800x600x60 = 28.8MHz. TV studio recording is limited to 5MHz; TV broadcasting is limited to 3.58Mhz. video board Same as video display board. video camera Camera that takes continuous pictures and generates a signal for display or recording. It captures images by breaking down the image into a series of lines. The U.S. and Canadian standard (NTSC) is 525 scan lines. Each line is scanned one at a time, and the continuously varying intensities of red, green and blue light across the line are filtered out and converted into a variable signal. Most video cameras are analog, but digital video cameras are also available. See digital camera. video card Same as video display board. video codec Circuit that converts NTSC video into digital code and vice versa. It incorporates a compression technique to reduce the data and may or may not provide full-motion video. video conferencing See teleconferencing. video controller (1) Device that controls some kind of video function. (2) Same as video display board. video digitizer Same as frame grabber. video display board Expansion board that plugs into a personal computer and generates the text and graphics images for the monitor's screen. Also called a display adapter, graphics adapter, graphics card, video adapter, video card or video controller, it determines the resolution and number of colors on screen. It converts the characters or graphic patterns (bitmaps) within a reserved segment of the computer's memory into signals used to refresh the display screen. In digital systems (CGA, EGA, etc.), the display board generates digital signals for the monitor. The monitor then does the conversion from digital to analog. In analog systems (VGA, Macintosh, etc.), the display board creates the analog signals sent to the monitor. The monitor must be capable of handling the frequency range of the display board (number of lines per second). Multisync monitors accept a range of frequencies and work with several display standards. video display card Same as video display board. video display terminal/unit Same as video terminal. video editor Dedicated computer that controls two or more videotape machines. It keeps track of frame numbers in its own database and switches the recording machine from playback to record. The video editor does accept video signals; only SMPTE time codes provided on professional tape formats. Video for Windows Software from Microsoft that supplements Windows 3.1 multimedia. It supports the AVI format and lets you capture, edit and play full-motion video. It includes Media Player 2.0. video graphics board Video display board that generates text and graphics and accepts video from a camera or VCR. Truevision's Targa board and Vision Technologies Vision board are examples. The terms video graphics board and video display board sound alike, but video display boards (display adapters) do not handle NTSC video. video overlay card Graphics controller that allows NTSC video and computer images to be mixed. video RAM Specially-designed memory circuits on a video display board that are used to hold the image that appears on the video screen. Often uses dual- ported RAM, which allows simultaneous reads and writes. video teleconferencing See teleconferencing. video terminal Data entry device that uses a keyboard for input and a display screen for output. Although the display screen resembles a TV, it usually does not accept TV/video signals. video window Display of NTSC video (TV) in an independent window on a computer screen. videodisc Read-only optical disc that holds up to two hours of video data. Like a phonograph record and CD player, most videodisc players provide direct access to any location on the disc. Videodiscs are recorded in an analog format like videotape. Various videodisc systems were introduced during the 1970s, but only the LaserVision optical disc technology survived. As of 1990, videodiscs have barely made a dent in the home market, where VCRs are commonplace. It appears that videotapes will continue to be the major video recording and playback medium until such time as an erasable optical system can be economically mass produced. Videodiscs are used for interactive instructional training courses, however. Videodiscs used for movies use a constant linear velocity (CLV) format that records the signal on a continuous, spiraling track, as does a phonograph record. In addition, the signal density is uniform, and the player increases or decreases the speed of rotation depending on which part of the disc is being played. Videodiscs used for interactive purposes use a constant angular velocity (CAV) format like that of a magnetic disk, in which the tracks are concentric circles, each one containing one frame of video. Each side of a CAV videodisc holds 54,000 frames, which is 30 minutes of continuous video at 30 frames per second. videotex Interactive information technology that includes shopping, banking, news, weather and e-mail services. Experiments have been tried in the U.S., but it has yet to catch on. It is delivered over a telephone line to a subscriber's TV through a decoder box and attached keyboard. Information is broadcast to and stored in the decoder as predefined screens (frames) which can be retrieved by menu. Videotex delivers simple graphics and limited animation. view (1) To display and look at data on screen. (2) In relational database management, a special display of data, created as needed. A view temporarily ties two or more files together so that the combined files can be displayed, printed or queried; for example, customers and orders or vendors and purchases. Fields to be included are specified by the user. The original files are not permanently linked or altered; however, if the system allows editing, the data in the original files will be changed. Viewdata British term for videotex. viewer See file viewer. viewport (1) In the Macintosh, the entire scrollable region of data that is viewed through a window. (2) Same as window. VIM (Vendor Independent Messaging Interface) E-mail protocol developed by Lotus, Apple, Novell and Borland that supersedes OMI. See MAPI. VINES (VIrtual NEtworking System) UNIX System V-based network operating system from Banyan Systems Inc., that runs on DOS and OS/2-based servers. It provides internetworking of PCs, minis, mainframes and other computer resources providing information sharing across organizations of unlimited size. Incorporating mainframe-like security with a global directory service, VINES allows access to all network users and resources. Options include printer sharing, e-mail, remote PC dial-in, bridges and gateways. virtual Simulated, conceptual or extended environment, which, as a result, may refer to virtually anything. Virtual 8086 Mode Operational mode in Intel 386s and up that allows it to perform as multiple 8086 CPUs. Under direction of a control program, each virtual machine runs as a stand-alone 8086 running its own operating system and applications, thus DOS, UNIX and other operating systems can be running simultaneously. All virtual machines are multitasked together. This mode divides up the computer into multiple address spaces and maintains virtual registers for each virtual machine. This is not the same as the 386's virtual memory mode, which extends main memory to disk. virtual circuit Resulting pathway created between two devices communicating with each other in a packet switching system. A message from NY to LA may actually start in New York and go through Atlanta, St. Louis, Denver and Phoenix before it winds up in Los Angeles. virtual desktop Desktop beyond the borders of the viewing screen. Rather than overlapping windows or reducing them to an icon, a virtual desktop simulates a giant desktop that lets you browse several full-size documents using a virtual screen or other navigation method, such as the "rooms" and "doors" metaphor in Xsoft's Rooms for Windows. virtual device See virtual peripheral and VxD. virtual disk Same as RAM disk. virtual image In graphics, the complete graphic image stored in memory, not just the part of it that is displayed at the current time. virtual machine (1) Computer that runs multiple operating systems with each operating system running its own programs; for example, an IBM mainframe running under VM or a 386 PC running multiple DOS applications in Virtual 8086 Mode. (2) One virtual machine (operating system and associated applications) running in a virtual machine environment. (3) Virtual memory computer. virtual memory Technique that simulates more memory than actually exists and allows the computer to run multiple programs concurrently regardless of size. Virtual memory breaks up a program into segments, called pages. Instead of bringing the entire program into memory, it brings as many pages as it can fit based on the current program mix and leaves the remaining pages on disk. When instructions are called for that are not in memory, the appropriate disk page is called in, overlaying a page in memory. If a memory page contains variables or other data that are altered by the running of the program, the page is temporarily stored on disk when room is needed for new pages. The input and output of program pages is called paging or swapping. If a program contains spaghetti code, in which its logic points back and forth to opposite ends of the program, thrashing may result (excessive disk accesses). Disk access should be reserved for retrieving data, not the same instructions over and over again. Although virtual memory can be implemented in software, efficient operation requires virtual memory hardware. Programs sometimes claim virtual memory capability, but only swap code into memory as needed. True virtual memory is a hardware implementation that works with any application. virtual monitor In the Macintosh, the ability to dynamically configure to any monitor type and to use multiple monitors of different types including displaying the same object across two or more screens. virtual networking As defined by Banyan Systems, the ability for users to transparently communicate locally and remotely across similar and dissimilar networks through a simple and consistent user interface. virtual peripheral Peripheral device simulated by the operating system. virtual printer Simulated printer. If a program is ready to print, but all printers are busy, the operating system will transfer the printer output to disk and keep it there until a printer becomes available. virtual processing Parallel processing technique that simulates a processor for applications that require a processor for each data element. It creates virtual processors for data elements above and beyond the number of processors available. virtual processor Simulated processor in a virtual processing system. virtual reality Artificial reality that projects the user into a 3-D space generated by computer. Implementations by AutoDesk and others include the use of a data glove and head-mounted stereoscopic display, which allow users to point to and manipulate illusory objects in their view. See cyberspace. virtual route Same as virtual circuit. virtual screen Screen area beyond the borders of the viewing screen. The viewing screen serves as a scrollable window that navigates around the larger screen. Video display boards may offer this capability; for example, you could browse a 1280x1024 viewing area with an 800x600 screen resolution. See virtual desktop. virtual storage Same as virtual memory. virtual terminal Terminal emulation that allows access to a foreign system. Often refers to a personal computer gaining access to a mini or mainframe. virtual toolkit Development software that creates programs for several computer environments. Its output may require additional conversions or translations to produce executable programs. virtualize (1) To activate a program in virtual memory. (2) To create a virtual screen. virus Software used to infect a computer. After the virus code is written, it is buried within an existing program. Once that program is executed, the virus code is activated and attaches copies of itself to other programs in the system. Infected programs copy the virus to other programs. The effect of the virus may be a simple prank that pops up a message on screen out of the blue or the actual destruction of programs and data. A virus cannot be attached to data. It must be attached to a runnable program that is downloaded into or installed in the computer. The virus- attached program must be executed in order to activate the virus. See worm. Be Careful Out There Before you run a shareware, public domain or freeware program, check it with a virus detection program first! virus signature Binary pattern of the actual machine code of a particular virus. Antivirus programs use virus signatures for fast detection of known viruses. VIS (Voice Information Service) Variety of voice processing service applications. Visa See VESA. ViSCA (VIdeo System Control Architecture) Platform- independent protocol from Sony for synchronized control of multiple video peripherals. ViSCA is the software interface. Control-L is the hardware interface. VisiCalc First electronic spreadsheet. It was introduced in 1978 for the Apple II. Conceived by Dan Bricklin, a Harvard student, and programmed by a friend, Bob Frankston, it became a major success. It launched an industry and was almost entirely responsible for the Apple II being used in business. Thousands of $3,000 Apples were bought to run the $150 VisiCalc. VisiCalc was a command-driven program that was followed by SuperCalc, MultiPlan, Lotus 1-2-3 and a host of others, each improving the user interface. Spreadsheets have also been implemented on minis and mainframes. It all started with VisiCalc. Visual BASIC Version of Microsoft QuickBASIC for developing Windows applications (not 100% compatible with QuickBASIC). User interfaces are developed by dragging objects from the Visual BASIC Toolbox onto the application form. visual programming Developing programs with tools that allow menus, buttons and other graphics elements to be selected from a palette and drawn and built on screen. It may include developing source code by visually interacting with flow charts that graphically display the logic paths and associated code. visualization In computer graphics, the converting of numeric data into picture form to allow humans to recognize patterns that are difficult to identify in numeric form. It is used especially in research situations, both theoretical and practical. VL-bus (VESA Local-BUS) Local bus for PCs standardized by VESA that provides a high-speed data path between the CPU and peripherals (video, disk, network, etc.). Up to three VL-bus slots can be placed onto the motherboard. See local bus. The VL-bus runs at speeds up to 40MHz or up to 66MHz for controllers built directly on the motherboard. It is currently a 32-bit bus with 64- bit capability forthcoming to handle the Pentium CPU. The VL-bus expansion slot uses one 32-bit Micro Channel slot placed adjacent to the standard ISA, EISA or Micro Channel slot, allowing vendors to design boards that use only the local bus or both buses at the same time. VL-bus also supports bus mastering. VLF (Very Low Frequency) See low radiation. VLSI (1) (Very Large Scale Integration) Between 100,000 and one million transistors on a chip. See SSI, MSI, LSI and ULSI. (2) (VLSI Technology, Inc., Tempe, AZ) Designer and manufacturer of custom chips. VM (Virtual Machine) IBM mainframe operating system, originally developed by its customers and eventually adopted as an IBM system product (VM/SP). It can run multiple operating systems within the computer at the same time, each one running its own programs. CMS (Conversational Monitor System) provides VM's interactive capability. VM/386 (Virtual Machine/386) Multiuser operating system for 386s and up from IGC Corp., San Jose, CA. Each user at a terminal runs an application within a virtual machine of the 386 (Virtual 8086 Mode). VM/SP See VM. VMEbus (VersaModule Eurocard bus) 32-bit bus developed by Motorola, Signetics, Mostek and Thompson CSF. It is widely used in industrial, commercial and military applications with over 300 manufacturers of VMEbus products worldwide. VME64 is an expanded version that provides 64-bit data transfer and addressing. VMS (1) (Virtual Memory System) Multiuser, multitasking, virtual memory operating system for the VAX series from Digital. VMS applications will run on any VAX from the MicroVAX to the largest VAX. (2) (Voice Messaging System) See voice mail. VMTP (Virtual Message Transaction Protocol) Datagram communications protocol that provides efficient and reliable transmission across networks. voice channel Transmission channel or subchannel that carries human voice. voice coil Type of motor used to move the access arm of a disk drive in very small increments. Like the voice coil of a speaker, the amount of current determines the amount of movement. Contrast with stepper motor, which works in fixed increments. voice grade Refers to the bandwidth required to transmit human voice, which is usually about 4,000Hz. voice mail Computerized telephone answering system that digitizes incoming voice messages and stores them on disk. It usually provides auto attendant capability, which uses prerecorded messages to route the caller to the appropriate person, department or mail box. voice messaging Using voice mail as an alternative to electronic mail, in which voice messages are intentionally recorded, not because the recipient was not available. voice processing Computerized handling of voice, which includes voice store and forward, voice response, voice recognition and text to speech technologies. voice recognition Conversion of spoken words into computer text. Speech is first digitized and then matched against a dictionary of coded waveforms. The matches are converted into text as if the words were typed on the keyboard. Speaker-dependent systems must be trained before using, by taking samples of actual words from the person who will use it. Speaker-independent systems can recognize limited vocabularies such as numeric digits and a handful of words. In the telephone companies, these systems will begin to replace the human operator for services, such as collect and credit card calls, for example. In the future, voice recognition systems will be able to understand large vocabularies from just about anybody; however, it could be well past the turn of the century before voice recognition is part of every computer system. voice response Generation of voice output by computer. It provides pre-recorded information either with or without selection by the caller. Interactive voice response allows interactive manipulation of a database. See audiotex. voice store and forward Technology behind voice mail and messaging systems. Human voice is digitized, stored in the computer, possibly forwarded to another mail box, and retrieved by the called party. volatile memory Memory that does not hold its contents without power. A computer's main memory, made up of dynamic RAM or static RAM chips, loses its content immediately upon loss of power. volt Unit of measurement of force, or pressure, in an electrical circuit. The common voltage of an AC power line is 120 volts of alternating current (alternating directions). Common voltages within a computer are from 5 to 12 volts of direct current (one direction only). volt-amps Measurement of electrical usage that is computed by multiplying volts times amps. See watt. voltage regulator Device used to maintain a level amount of voltage in the electrical line. Contrast with surge suppressor, which filters out excessive amounts of current, and contrast with UPS, which provides backup power in the event of a power failure. volume (1) Physical storage unit, such as a hard disk, floppy disk, disk cartridge or reel of tape. (2) Logical storage unit that spans some number of physical drives. volume label (1) Name assigned to a disk (usually optional). (2) Identifying stick-on label attached to the outside of a tape reel or disk cartridge. (3) See header label. von Neumann architecture Sequential nature of computers: an instruction is analyzed, data is processed, the next instruction is analyzed, and so on. Hungarian-born John von Neumann (1903-1957), an internationally renowned mathematician, promoted the stored program concept in the 1940s. VOS Operating system used in Stratus computers. FTX is Stratus' UNIX operating system. VP/ix See SCO VP/ix. VP Planner Lotus-compatible relational spreadsheet from Paperback Software. In 1991, it was taken off the market due to settlement of Lotus' copyright lawsuit. VP ratio (Virtual Processor ratio) Number of virtual processors that a physical processor is simulating. VPC (Virtual Processor Complex) IBM mainframe multiprocessing that uses several computers under tight central control. VPS (Vectors Per Second) Used to measure the speed of a vector or array processor. VRAM See video RAM. VRC (Vertical Redundancy Check) Error checking method that generates and tests a parity bit for each byte of data that is moved or transmitted. VS (1) (Virtual Storage) Same as virtual memory. (2) (Virtual Storage) Family of minicomputers from Wang introduced in 1977, which use virtual memory techniques. VSAM (Virtual Storage Access Method) IBM access method for storing data, widely used in IBM mainframes.  It uses the B+tree method for organizing data. VSAT (Very Small Aperture satellite Terminal) Small earth station for satellite transmission that handles up to 56 Kbits/sec of digital transmission. VSATs that handle the T1 data rate (up to 1.544 Mbits/sec) are called TSATs. VSE (Disk Operating System/Virtual Storage Extended) IBM multiuser, multitasking operating system that typically runs on IBM's 43xx series. It used to be called DOS, but due to the abundance of DOS PCs, it is now referred to as VSE. VSX (Verification Suite for X/Open) Testing procedure from X/Open that verifies compliance with their endorsed standards. VSX3 has over 5,500 tests for compliance with XPG3. VT100, 200, 300 Series of asynchronous display terminals from Digital for its PDP and VAX computers. Available in text and graphics models in both monochrome and color. VTAM (Virtual Telecommunications Access Method) Also called ACF/VTAM (Advanced Communications Function/VTAM), software that controls communications in an IBM SNA environment. It usually resides in the mainframe under MVS or VM, but may be offloaded into a front end processor that is tightly coupled to the mainframe. It supports a wide variety of network protocols, including SDLC and Token Ring. VTAM can be thought of as the network operating system of SNA. VTR (VideoTape Recorder) Video recording and playback machine that uses reels of magnetic tape. Contrast with VCR, which uses tape cassettes. VUP (VAX Unit of Performance) Unit of measurement equal to the performance of the VAX 11/780, the first VAX machine. VxD (Virtual Device Driver) Special type of Windows driver for 386 Enhanced Mode. WIN386.EXE, the 386 Enhanced Mode kernel of Windows, is itself made up of VxDs. VxDs run at the most priviledged CPU mode (ring 0) and allows low-level interaction with DOS and Windows programs running under Windows. W5086 Weitek chip set that accelerates graphics performance. WABI (Windows ABI) Software emulator from Sun that runs Windows applications under UNIX at higher performance levels than typical Windows emulation products. wafer (1) Base material in chip making. It is a slice, approx. 1/30" thick, from a salami-like silicon crystal from 3 to 6" in diameter. The wafer goes through a series of photomasking, etching and implantation steps. See chip. (2) Small, continuous-loop magnetic tape cartridge that is used for the storage of data. wafer scale integration Next evolution in semiconductor technology. It builds a gigantic circuit on an entire wafer. Just as the integrated circuit eliminated cutting apart thousands of transistors from the wafer only to wire them back again on circuit boards, wafer scale integration eliminates cutting apart the chips. This next step is difficult (see Trilogy). wait state Time spent waiting for an operation to take place. It may refer to a variable length of time a program has to wait before it can be processed, or to a fixed duration of time, such as a machine cycle. When memory is too slow to respond to the CPU's request for it, wait states are introduced until the memory can catch up. WAN (Wide Area Network) Communications network that covers wide geographic areas, such as states and countries. See MAN and LAN. wand Hand-held optical reader used to read typewritten fonts, printed fonts, OCR fonts and bar codes. The wand is waved over each line of characters or codes in a single pass. Wang (Wang Laboratories, Inc., Lowell, MA) Computer manufacturer and applications developer. Founded in 1951 by Dr. An Wang, the company specialized in electronic devices. Its desktop calculator became a standard in the late 1960s. In the 1970s, Wang introduced word processing systems and computers, which evolved into the WPS and VS series. By 1978, it was North America's largest supplier of small business computers and the world's largest supplier of CRT-based word processors. Throughout the 1980s, Wang developed integrated voice and data networks and imaging systems. It chose industry-standard platforms for the 1990s. Dr. Wang came from China in 1945 to study applied physics at Harvard. Six years later, he started Wang Labs. In 1988, two years before he died, he was inducted into the National Inventors Hall of Fame for his 1948 invention of a pulse transfer device that let magnetic cores be used for computer memory. The Hall of Fame has recognized an elite group including Edison, Pasteur and Bell. Wangnet Broadband LAN from Wang that handles data, voice and video. warm boot Restarting the computer by performing a reset operation (pressing reset, Ctrl-Alt-Del, etc.). See cold boot and boot. warm start Same as warm boot. Warnier-Orr diagram Graphic charting technique used in software engineering for system analysis and design. WARP Parallel processor developed at Carnegie-Mellon Univ. that was the predecessor of iWARP. WATCOM compilers C and FORTRAN compilers for PCs from WATCOM, Waterloo, Ontario, noted for generating fast, compact code. WATCOM C/386 is the first 32-bit compiler for extended DOS, Windows, OS/2 2.0 and AutoCAD ADS and ADI applications. Corporate mission is to provide advanced compilers for most x86 environments. watt A measurement of electrical power. One watt is one ampere of current flowing at one volt. Watts are typically rated as AMPS x VOLTS; however, AMPS x VOLTS, or VOLT-AMP (V-A) ratings and watts are only equivalent when powering devices that absorb all the energy such as electric heating coils or incandescent light bulbs. With computer power supplies, the actual watt rating is only 60 to 70% of the VOLT-AMP rating. WAV Windows sound file. .WAV files use lots of disk space; for example, one audio minute takes about 2.5MB. wave Shape of radiated energy. All radio signals, light rays, x-rays, and cosmic rays radiate an energy that looks likes rippling waves. To visualize waves, take a piece of paper and start drawing an up and down line very fast while pulling the paper perpendicular to the line. waveform Pattern of a particular sound wave or other electronic signal in analog form. waveguide Rectangular, circular or elliptical tube through which radio waves are transmitted. wavelength Distance between crests of a wave, computed by speed divided by frequency (speed / Hz). Wavelength in meters of electromagnetic waves equals 300,000,000 / Hz. Wavelength in meters for sound travelling through the air equals 335 / Hz. WDM (Wavelength-Division Multiplexing) High-speed optical fiber transmission technique that carries multiple signals, each within its own wavelength (color) of light. weak typing Programming languages that allow different types of data to be moved freely among data structures, as is found in Smalltalk and other earlier object- oriented languages. Weitek coprocessor High-performance math coprocessor from Weitek Corp. Since 1981, Weitek has been making coprocessors for CAD and graphics workstations. In order to use a coprocessor, the software must be written to activate it. well behaved Refers to programs that do not deviate from a standard. well mannered Same as well behaved. wetware Biological system. Typically refers to the human brain and nervous system. WFW See Windows for Workgroups. what if? Using a spreadsheet as a planning tool. When new data is entered, results are calculated based upon the formulas. Assumptions can be plugged in that ripple through to the bottom line. For example, "what if hourly pay is increased $2?" "What if interest rates are lowered .5%?" Whetstones Benchmark program that tests floating point operations. Results are expressed in Whetstones per second. Whetstone I tests 32-bit, and Whetstone II tests 64-bit operations. See Dhrystones. white noise Same as Gaussian noise. wide area network See WAN. widget set Group of screen structures (menu, button, scroll bar, etc.) provided in a graphical interface. widow & orphan A widow is the last line of a paragraph that appears alone at the top of the next page, and an orphan is the first line of a paragraph that appears alone at the bottom of a page. Widow and orphan settings are usually set for a minimum of two lines. width table List of horizontal measurements for each character in a font, used by word processing and desktop publishing programs. wild cards Symbols used to represent any value when naming files. See DOS wild cards. wimp interface (Windows, Icons, Menus and a Pointing device) Same as GUI. WIN.INI (WINdows INItialization) File read by Windows on startup that contains data about the current environment (desktop, fonts, sounds, etc.) and individual applications. It is often updated by an install program to provide information for the application when it runs. SYSTEM.INI, another startup file, contains data about the hardware (drivers, 386 Enhanced Mode settings, etc.). Win32 Programming specification (API) for the 386's 32- bit mode fully supported in Windows NT. Many functions are also supported in Windows 3.1, and applications can be written to this Win32 subset (Win32s) to gain improved performance on a 386 or up running Windows 3.1 or Windows NT. Winbench Series of tests that analyze computer performance from Ziff-Davis' PC Labs. See Winmark. Winchester disk Removable disk from IBM that put the access arm, read/write heads and disk platters into a sealed unit. By keeping heads and disks intact, greater speed and capacity was achieved. It was designed as a dual 30MB module, and got its name from its "Winchester rifle" 30-30 specification. Although originally a removable disk, the term later referred to any fixed hard disk. WinDisk Driver from Future Domain Corp. that converts Windows 3.1 FastDisk accesses into the SCSI CAM standard supported on its SCSI host adapters. window (1) Rectangular, scrollable viewing area. May refer to a scrollable list such as this Glossary index or to a re-sizable window that contains the entire application. See GUI and windows environment. (2) Reserved area of memory. (3) Time period. window manager Software incorporated into all popular GUIs, which displays a window with accompanying menus, buttons and scroll bars. It allows the windows to be relocated, overlapped, resized, minimized and maximized. See desktop manager. windowing software Same as windows program. Windows Graphics-based windows environment from Microsoft that integrates with and interacts with DOS. It provides a desktop environment similar to the Macintosh, in which applications are displayed in re-sizable, movable windows on screen. In order to use all the features of Windows, applications must be written for it. However, Windows also runs DOS applications and is increasingly being used as the primary operating environment from which all programs are launched. Windows 3.x Operating Modes REAL MODE (Windows 3.0 only) For computers with less than 1MB memory. Provides compatibility with earlier Windows applications (Windows 1.x, 2.x). STANDARD MODE (286 and up) Used when running on a 286. Also used in Windows 3.0 on 386s because it runs faster. Provides access to extended memory and allows users to run full-screen DOS applications. 386 ENHANCED MODE (386 and up) Uses the 386's virtual machine and virtual memory capabilities and is the common mode for 386s under Windows 3.1. Can multitask DOS applications (program continues running in the background), and DOS applications can be run within a movable window, and text can be copied between DOS applications. Windows 3.1 Evolution Windows 1.x, Windows 286 (2.x) and Windows/386 were the first attempts at Windows. But, it wasn't until 1990 and Windows 3.0 that it took off and created an industry due to its enhanced user interface and ability to break DOS' infamous 1MB memory barrier. Windows contains its own DOS extender, which allows it to manage 16MB of extended memory. Windows 3.1 (1992) is more stable and faster, supports multimedia, TrueType fonts and drag & drop commands. Compound documents (OLE) are added and Real Mode is eliminated. Windows applications are 16-bit programs that run on all x86 CPUs. Windows applications can also be written that exploit the 386's native 32-bit instructions. These "Win32s" applications require Windows 3.1 and will also run under Windows NT. WIN.INI & SYSTEM.INI WIN.INI and SYSTEM.INI are text files used to configure Windows. WIN.INI contains environment information (desktop, fonts, sounds, etc.) as well as individual applications. SYSTEM.INI contains hardware information. Install programs and Windows' own SETUP.EXE program modify these files, but they can be edited manually in Notepad or any text editor. When an application is installed, it often adds text to WIN.INI, which it may modify from time to time. If the application is deleted by the user, the lines of text remain, but have no purpose. A useful utilty, called SYSEDIT.EXE, resides in the \WINDOWS\SYSTEM directory and opens all four files: WIN.INI, SYSTEM.INI, AUTOEXEC.BAT and CONFIG.SYS, for editing. Advantages of Windows Windows' windowing capability is its major feature. The ability to keep multiple applications active is more productive than closing out one application and opening another. In addition, data can be copied from one application to another via Windows' clipboard. Applications written for Windows provide a measure of consistency, although not as unvarying as in the Macintosh. Users know how to open, close, copy, move and paste data in all Windows applications. The operation of the drop-down menus is the same and Windows' online help system functions similarly in every Windows application. The help window can be left on screen so that a user can read instructions while performing the operation. Centralized device and font management is a significant advantage. In DOS, each application is responsible for interacting with all the possible peripheral devices on the market, and the DOS installation program must set up its own application with the appropriate drivers. If a user changes to a different printer for example, each DOS application has to be notified of the change. Many DOS applications use proprietary fonts, and the same typefaces may be duplicated with different applications, wasting disk space. When a new device is installed for Windows, that information is made available to all Windows applications that use it. The same goes for fonts. Once users have installed a new font, it becomes available to all Windows applications. Windows dynamic data exchange (DDE) and object linking and embedding (OLE) allow for information in one database to automatically update information in another. Windows multimedia, built into Windows 3.1, allow graphics, video and sound to be added to traditional text-only databases. These capabilities allow for enterprise-wide integration of information and are just being exploited. Disadvantages of Windows Windows is a complicated operating environment that has its roots in DOS, which was developed for the first PCs. Fine tuning Windows on a fully-loaded PC that is running a mix of DOS and Windows applications can be a daunting task, requiring knowledge of the CONFIG.SYS, AUTOEXEC.BAT, WIN.INI and SYSTEM.INI configuration files. Windows applications can be just as intimidating as DOS. The graphics-based environment of Windows allows for enormous creativity in the design of the user interface. Too often however, the myriad of cute little icons with imaginative, but cryptic symbols, are more difficult to remember than simple menus with straightforward explanations. In addition, Windows doesn't enforce enough ridigity for common tasks. In one application, you use the Character menu to change fonts, on another, you use the Paragraph menu. Windows popularity is so high that developers can't get their new applications out fast enough. The graphical interface does not obviate the need for a well- designed and well-thought-out interaction between the user and the computer. Windows accelerator See graphics accelerator. windows environment Any operating system, operating system extension or application program that provides multiple windows on screen. DESQview, Windows, PM, MultiFinder and X Window are examples. Windows for Workgroups Version of Windows 3.1 that incorporates peer-to- peer networking and includes e-mail. Windows Metafile Windows file format that holds vector graphics, bitmaps and text. It is used as a common vector graphics format. It is also used by programs to hold data between sessions. Sometimes Windows uses it for temporary storage. The Aldus Placeable Metafile is a PageMaker variation that contains a header indicating into what size rectangle the object will be rendered. Windows NT (Windows New Technology) Advanced 32-bit operating system from Microsoft for 386s and up, MIPS and Alpha CPUs scheduled for 1993. It runs NT-specific applications as well as those written for DOS, Windows 3.x (16-bit and 32-bit), OS/2 character- mode (non-graphical) and POSIX. NT does not use DOS, it is a self-contained operating system. Features include peer-to-peer networking, preemptive multitasking, symmetric multiprocessing, multithreading, security and fault tolerance. It supports 2GB of virtual memory for applications and 2GB for Windows NT. windows program (1) Software that adds a windows capability to an existing operating system. (2) Application program written to run under Windows. Windows SNA APIs Programming interfaces that allow Windows applications to communicate with SNA protocols and functions, such as HLLAPI and APPC. Windows swap file Disk file used to store applications temporarily when there isn't enough memory to hold all active applications. On setup, Windows creates a permanent swap file for running in 386 Enhanced Mode (SPART.PAR file and 386SPART.PAR hidden file). If these files are not present, or if Windows is in Standard Mode, Windows creates temporary swap files as needed. To free up disk space, you can delete or reduce the size of the permanent swap file. In Windows 3.0, load Windows in Real Mode (win /r) and run the SWAPFILE program. In Windows 3.1, select Control Panel/386 Enhanced/Virtual Memory/Change. WINGZ Presentation-oriented Macintosh spreadsheet from Informix Software., Menlo Park, CA. Text, graphs and charts, scanned images, freehand illustration and spreadsheet data can be combined. When data is updated, related graphics and numerical references within the text are changed. WinJet High-speed PostScript emulation system for Windows and LaserJet printers from LaserMaster Corp., Eden Prarie, MN. It generates PostScript output, including Type 1 and TrueType fonts, on a PC expansion board cabled directly to the LaserJet video input. WinJet 300 and 800 provide 300 and 800 dpi for LaserJet II/III models. WinJet 1200 provides 1200 dpi for the LaserJet 4. Winmark Unit of performance based on Ziff-Davis' PC Labs Winbench tests. Graphics Winmarks rate Windows video performance as a weighted average of 12 benchmarks. Common VGA adapters are rated around two million Winmarks. Fast graphics accelerators can achieve 20 million and more. Winbench Version 3.1 provides more accurate Winmark tests and avoids slanted results from "benchmark-aware" drivers used in some graphics accelerator boards. Disk Winmarks rate the speed of disks and disk caching. See DOSmark. WinWord See Microsoft Word. wire wrap Early method of wiring circuit boards. A tool strips the end of the wire and coils it. The coil is pressed onto a metal prong on the board. wireframe modeling In CAD, a technique for representing 3-D objects, in which all surfaces are visibly outlined in lines, including the opposite sides and all internal components that are normally hidden from view. Compared to surface and solid modeling, wireframe modeling is the least complex method for representing 3-D images. wireless Same as radio. wiring closet Central distribution or servicing point for cables in a network. wizzy wig See WYSIWYG. WK1 Lotus 1-2-3 Version 2.0 file extension. WKS Lotus 1-2-3, Version 1A file extension. WMF See Windows Metafile. word (1) Computer's internal storage unit. Refers to the amount of data it can hold in its registers and process at one time. A word is often 16 bits, in which case 32 bits is called a double word. Given the same clock rate, a 32-bit computer processes four bytes in the same time it takes a 16-bit machine to process two. (2) Primary text element, identified by a word separator (blank space, comma, etc.) before and after a group of contiguous characters. (3) See Microsoft Word. word addressable Computer that can address memory only on word boundaries. Contrast with byte addressable. Word for Windows See Microsoft Word. word processing Creation of text documents. Except for labels and envelopes, it has replaced the electric typewriter in most offices, because of the ease in which documents can be edited, searched and reprinted. Advanced word processors function as elementary desktop publishing systems and support graphics and multiple fonts. Although there are still machines dedicated only to word processing, most word processing is performed on general-purpose computers using word processing software. Functions of a Full-featured Word Processor  TEXT EDITING Text can be changed by deleting it, typing over it or by inserting additional text within it. WORD WRAP AND CENTERING Words that extend beyond the right margin are wrapped around to the next line. Text can be centered between left and right margins. SEARCH & REPLACE, MOVE AND COPY Any occurrence of text can be replaced with another block of text. You can mark a block of text and move it elsewhere in the document or copy it throughout the document. LAYOUT SETTINGS Margins, tabs, line spacing, indents, font changes, underlining, boldface and italics can be set and reset anywhere within the document. HEADERS, FOOTERS AND PAGE NUMBERING Headers and footers are common text printed on the top and bottom of every page. Headers, footers and page numbering can be set and reset anywhere within the doucment. Page numbering in optional Roman numerals or alphabetic letters is common. STYLE SHEETS After designing a document, its format can be used again. Layout codes (margins, tabs, fonts, etc.) can be stored in a style sheet file and applied to a new document. MAIL MERGE Creates customized letters from a form letter and a list of names and addresses. The list can be created as a document or can be imported from popular database formats. MATH AND SORTING Columns of numbers can be summed and simple arithmetic expressions can be computed. Lines of text can be reordered into ascending (A-Z) or descending (Z-A) sequence. PREVIEW, PRINT AND GROUP PRINT A document can be previewed before it is printed to show any layout change that may not normally show on screen (page breaks, headers, footers, etc.). Documents can be printed individually or as a group with page numbers consecutively numbered from the first to the last document. FOOTNOTES Footnote entries can be made at any place in the document, and the footnotes printed at the end of a page or document. SPELLING CHECKER AND THESAURUS Spelling for an individual word, marked block of text or an entire document can be checked. When words are in doubt, possible corrections are suggested. Advanced systems can correct the misspellings automatically the next time. A thesaurus displays synonyms for the word at the current cursor location. FILE MANAGEMENT Documents can be copied, renamed and deleted, and directories, or folders, can be created and deleted from within the program. Advanced systems set up a purge list of names or glimpses of document contents in order to allow a user to easily rid the disk of unwanted files. Advanced Functions  WINDOWS Allows two or more documents to be worked on at the same time. Text can be moved or copied from one document to the other. COLUMNS Columns can be created in all word processors by tabbing to a tab stop. However, true column capability wraps words to the next line within each column. Columns are required for writing resumes with employer information on the left and work history on the right. Script writing also requires column capability. Magazine-style columns flow words from the bottom of one column to the top of the next. TABLES OF CONTENTS AND INDEXES Tables of contents and indexes can be generated from entries typed throughout the document. DESKTOP PUBLISHING Graphics can be merged into the text and either displayed on screen with the text or in a preview mode before printing. A graphic object can be resized (scaled), rotated and anchored so that it remains with a particular segment of text. Rules and borders can also be created within the text. Graphics-based Vs Text-based Graphics-based programs (Windows, Macintosh, etc.) show a close facsimile on screen of the typefaces that will be printed. Text-based programs always show the same type size on screen. Graphics-based systems are far superior for preparing newsletters and brochures that contain a variety of font sizes. Text-based screens are fine for office typing or for documents with a simple format. They are also very responsive and good for creative writing. Format Standards Every major word processing program generates its own proprietary codes for layout settings. For example, in WordStar, ^PB turns on and off boldface. In WordPerfect 5.x, [BOLD] turns boldface on, and [bold] turns it off. Conversion programs are used to translate documents from one format to another. If a conversion program doesn't exist for the two required formats, multiple search & replace commands can be performed on the original document. However, if the same code turns a mode on as well as off, as in the WordStar example above, the codes have to be changed manually one at a time. The User Interface Word processing programs run from the ridiculous to the sublime. Some of the most awkward programs have sold well. As a novice, it's difficult to tell a good one from a bad one. It takes time to explore the nuances. Also, what's acceptable for the slow typist can be horrendous for the fast typist. Repetitive functions such as centering and changing display attributes (boldface, italics, etc.) should be a snap. Changing margins, tabs, indents and fonts should also be easy. The most important components in word processing hardware are the keyboard and screen. The feel of a keyboard is personal, but proper key placement is critical. Display screens should have the highest resolution possible, and color screens are better than monochrome as long as the program allows the user to change colors. word processing machine Computer that is specialized for only word processing functions. word processor (1) Software that provides word processing functions on a computer. (2) Computer specialized for word processing. Until the late 1970s, word processors were always dedicated machines. Today, personal computers have mostly replaced the dedicated word processor. word separator Character that separates a word, such as a blank space, comma, period, -, ? and !. word wrap Word processing feature that moves words to the next line automatically as you type based on the current right margin setting. Some word processing programs allow word wrap to be turned off for writing source code. WordBASIC Subset of Microsoft QuickBASIC with added word processing functions used to customize Microsoft Word word processors. WordPerfect Full-featured word processing program from WordPerfect Corp., Orem, UT. Introduced in 1980, it runs on most all personal computers and some workstations, and is the most widely used word processor in the world. Version 5.0 introduced significant improvements that included desktop publishing features and a WYSIWYG preview mode. Version 5.1 added menus. WordStar Full-featured PC word processing program from WordStar Int'l., Novato, CA. Introduced in 1978 for CP/M machines, it was the first program to give sophisticated word processing capabilities to personal computer users at far less cost than the dedicated word processors of the time. Many WordStar keyboard commands have become de facto standards. workflow automation Automatically routing data and documents over the network to the users responsible for working with them. workgroup Two or more individuals who share files and databases. LANs designed around workgroups provide electronic sharing of required data. working directory See current directory. Workplace Shell Graphical user interface (GUI) in OS/2 Versions 2.x. See OS/2. worksheet Same as spreadsheet. worksheet compiler Same as spreadsheet compiler. workstation (1) High-performance, single-user microcomputer or minicomputer that has been specialized for graphics, CAD, CAE or scientific applications. (2) Personal computer in a network. Contrast with server and host. See client. (3) Any terminal or personal computer. worm (1) Destructive program that replicates itself throughout disk and memory, using up the computers resources and eventually putting the system down. See virus and logic bomb. (2) Program that moves through a network and deposits information at each node for diagnostic purposes or causes idle computers to share some of the processing workload. (3) (WORM) (Write Once Read Many) Optical disk that can be recorded only once. Updating requires destroying the existing data (all 0s made 1s), and writing new data to an unused part of the disk. WOSA (Windows Open System Architecture) Extensions to Windows programming that allow Windows applications to access services on the network from any software provider (e-mail, databases, network services, etc.) that supports the WOSA interface. It provides a single standard between Windows clients and servers. See SPI and ODBC. WP See word processing. WPS See Workplace Shell. Wrist Pro Wrist support from Wrist Pro, St. Louis, MO, that provides a multi-level platform that keeps the wrist in a neutral wrist position. wrist rest Platform used to raise the wrist to keyboard level for typing. wrist support Product that prevents and provides a therapy for carpal tunnel syndrome by keeping the hands in a neutral wrist position. write To store data in memory or record data onto a storage medium, such as disk and tape. Read and write is analogous to play and record on an audio tape recorder. write back cache Disk or memory cache that handles writing. Data written into the high-speed cache memory from the CPU is written onto disk or into real memory during idle machine cycles. write error Inability to store into memory or record onto disk or tape. Malfunctioning memory cells or damaged portions of the disk or tape's surface will cause those areas to be unusable. write only code Jokingly refers to source code that is difficult to understand. write protect Prohibits erasing or editing a disk file. See file protection. write protect notch Small, square cutout on the side of a floppy disk used to prevent it from being written and erased. On 5.25" floppies, the notch must be covered for protection. To protect a 3.5" diskette, press the slide lever toward the edge of the disk uncovering a hole (upper left side viewed from the back). You "cover" the notch on 5.25" disks; you "uncover" the hole on 3.5" disks. The two common formats use exact opposite methods! WSI See wafer scale integration. WUGNET (Windows Users Group NETwork) Organization of Windows users and developers founded in 1988. It provides technical information, software resources and tools, CompuServe forums and newsletters. Address: 107 S. Monroe St., Media, PA 19063, 215/565-1861. WXmodem (Window Xmodem) Faster version of the Xmodem protocol that allows the sending system to transmit data without waiting for the receiving system to acknowledge the transfer. WYSIWYG (What You See Is What You Get) Pronounced "wizzy- wig." Refers to text and graphics appearing on screen the same as they print. To have WYSIWYG text, a screen font must be installed that matches each printer font. Otherwise, a 24-point font may display in correct size relationship to a 10-point font, but it won't look like the printed typeface. It is almost impossible to get 100% identical representation, because screen and printer resolutions rarely match. Even a 300 dpi printer has a higher resolution than almost every monitor. WYSIWYG MOL (WYSIWYG More Or Less) Quite often what you get, when what you want is WYSIWYG! x (1) In programming, symbol used to identify a hexadecimal number. For example, 0x0A and \x0A specify the hex number 0A. (2) See X Window. x-axis See x-y matrix. X-based See X Window and Xbase. x-height In typography, the height of the letter x in lower case. Point size includes the x-height, the height of the ascender and the height of the descender. See typeface. X/Open Consortium of international computer vendors founded in 1984 to resolve standards issues. Incorporated in 1987 and based in London, North American offices are in San Francisco. Its purpose is to integrate evolving de facto and international standards in order to achieve an open environment, or CAE (Common Application Environent). XPG defines X/Open's specification, and VSX defines its testing and verification procedure. Telephones: U.S. 415/323-7992, U.K. 44-734-508311. X protocol Message format of the X Window System. X terminal Terminal with built-in X Window server capability. X toolkit Development software for building X Window applications. Typically includes a widget set, X Toolkit Intrinsics (Xt) libraries for managing the widget set and the X Library (Xlib). X Window Formally "X Window System," also called "X Windows" and "X," it is a windowing system developed at MIT, which runs under UNIX and all major operating systems. X lets users run applications on other computers in the network and view the output on their own screen. X generates a rudimentary window that can be enhanced with GUIs, such as Open Look and OSF/Motif, but does not require applications to conform to a GUI standard. The window manager component of the GUI allows multiple resizable, relocatable X windows to be viewed on screen at the same time. X terminology seems backward to LAN concepts. The X client resides in the computer that generates the output, and the X server resides in the computer that displays it. The server draws the image from the client. The X client and X server can also be in the same machine. x-y matrix Group of rows and columns. The x-axis is the horizontal row, and the y-axis is the vertical column. An x-y matrix is the reference framework for two-dimensional structures, such as mathematical tables, display screens, digitizer tablets, dot matrix printers and 2-D graphics images. x-y monitor In graphics, the display screen of a vector display terminal. The entire vector display comprises the monitor and vector graphics controller. x-y plotter Same as plotter. x-y-z matrix Three-dimensional structure. The x and y axes represent the first two dimensions; the z axis, the third dimension. In a graphic image, the x and y denote width and height; the z denotes depth. X.12 See X12. X.21 CCITT standard protocol for a circuit switching network. X.25 CCITT standard (1976) for the protocols and message formats that define the interface between a terminal and a packet switching network. X.28 CCITT standard (1977) for exchange of information between a DTE and a PAD; commonly known as PAD commands. X.29 CCITT standard (1977) for exchange of information between a local PAD and a remote PAD; procedures for interworking between PADs. X.3 CCITT standard (1977) for a PAD (packet assembler/disassembler), which divides a data message into packets for transmission over a packet-switched network and reassembles them at the receiving side. X.32 CCITT standard (1984) for connecting to an X.25 network by dial up. It defines how the network identifies the terminal for billing and security purposes and how default parameters are negotiated for the connection. X.400 OSI-compliant, CCITT standard mail and messaging protocol. The format of an X.400 address is: c= /admd= /prmd= /o= /s= /g= c - country admd - administrative management domain (public e-mail service) prmd - private management domain (inhouse e-mail) o - organization s - surname g - given name See XAPIA. X.500 OSI-compliant, CCITT standard protocol for maintaining online address directories. X.75 CCITT standard for connecting X.25 networks. X.PC Communications protocol developed by McDonnell Douglas for connecting a PC to its Tymnet packet- switched public data network. X11 Current version of the X Window System. X11R5 (Version 11, Release 5, Sept. 1991) provides a stable and feature-rich environment. X12 ANSI standard protocol for EDI. See Tradacoms and EDIFACT. x86 Refers to the Intel 8086 CPU family (8086, 8088, 80186, 80286, 386, 486, Pentium). Starting with the 386, Intel has dropped the "80" prefix in its reference manuals. Same as 80x86. x86 CPU SPECIFICATIONS  Bus size (bits) Typical CPU# Clock Max Floppy Hard Disk (Word Speed RAM Disk (MB)  Size) (MHz) MIPS (------Bytes------) OS 陳陳陳賃陳陳陳堕陳陳陳堕賃陳賃陳陳陳賃陳陳賃陳陳陳 8088 5 .33 8 1M5.25" 10-20 DOS (16) 360K 3.5" DR DOS 720K 8086 5-10 .33-.6616 1M 1.44M10-40 (16) 団陳陳陳 団陳陳陳 286 6-12 1.2-2.41616M5.25" 20-80 DOS (16) 360K DR DOS 1.3M OS/2 Ver 1.x 3.5" 団陳陳陳 386DX 16-40 6-15 32 4G 720K 80- (32) 1.44M 200 DOS 2.88M 386SX 16-33 2.5-5 1616M 60- DR DOS (32) 100 OS/2 386SL 20-25 3.2-4 1632M 60- Ver 1.x (32) 100Ver 2.x 486DX 25-66 20-54 32 4G 100- UNIX (32) 2000 Windows 486SX 20-25 16.5-2032 4G 80- NT (32) 500 Pentium60-100100-16864 4G 400- (32) 5000 XA See CD ROM XA and 370/XA. XAPIA (X.400 API Assn.) Consortium dedicated to standardizing X.400 specifications. Xbase dBASE-like languages such as Clipper and FoxPro. Originally almost identical to dBASE, new commands and features over the years have made them only partially dBASE compatible. XCMD (eXternal CoMmanD) User-developed HyperCard command written in a language such as C or Pascal. See XFCN. Xcopy DOS and OS/2 utility that copies files and subdirectories. See DOS Xcopy. XDOS Software from Hunter Systems, Inc., Mountain View, CA, that converts Intel 80x86 executable code into Motorola 68020 code ready to run under UNIX. A PC program can be translated into a running program on a UNIX-based 68020 computer. XDR (EXternal Data Representation) Data format developed by Sun that is part of its networking standards. It deals with integer size, byte ordering, data representation, etc. and is used as an interchange format. Different systems convert to XDR for sending and from XDR upon receipt. XENIX See SCO XENIX. xerography See electrophotographic. XFCN (eXternal FunCtioN) User-developed HyperCard function that is written in a language, such as C or Pascal. XFCNs usually return a value. See XCMD. XGA (EXtended Graphics Array) IBM video display standard (1990) optimized for graphical user interfaces. It adds 132 column text to VGA, plus additional resolutions up to 1024x768 with 256 colors interlaced. XGA-2 (1992) provides non- interlaced 1024x768x64K. XGML Family of text manipulation software for PCs, Macs, IBM mainframes, UNIX and others from Software Exoterica Corp., Ottawa, Ontario. With strong support for SGML, it includes XTRAN, a language that translates, matches and links text. XIP (Execute In Place) Ability to execute a program directly from a memory card. Xlib (X LIBrary) Functions in the X Window System. See X toolkit. XLISP Microcomputer version of the LISP programming language that has been in the public domain for a number of years. XMI High-speed bus from Digital used in large VAX machines. Xmodem First widely-used file transfer protocol for personal computers, developed by Ward Christensen for CP/M machines. Early versions used a checksum to detect errors. Later versions use the more effective CRC method (Xmodem-CRC). Programs typically include both methods and drop back to checksum if CRC is not present at the other end. Xmodem transmits 128-byte blocks. Xmodem-1K improves speed by transmitting 1,024-byte blocks. Xmodem-1K-G transmits without acknowledgment (for error-free channels or when modems are self correcting), but transmission is cancelled upon any error. XMS (eXtended Memory Specification) Interface that allows DOS programs to use extended memory in 286s and up. It provides a set of functions for reserving, releasing and transferring data to and from extended memory without conflict, including the high memory area (HMA). See HIMEM.SYS and DOS extender. XMT In communications, an abbreviation for transmit. XNS (Xerox Network Services) Early Ethernet protocol suite from Xerox.  XNS layers OSI layers  0 - Transmission media 1 & 2 1 - Internet 3 2 - Transport 4 3 - Control 5 & 6 4 - Application 7 xon-xoff In communications, a simple asynchronous protocol that keeps the receiving device in synchronization with the sender. When the buffer in the receiving device is full, it sends an x-off signal (transmit off) to the sending device, telling it to stop transmitting. When the receiving device is ready to accept more, it sends the sending device an x-on signal (transmit on) to start again. XPG (X/Open Portability Guide) Standards that specify compliance with X/Open's Common Application Environment (CAE). XPG3 (Release 3), introduced in early 1989, specifies standards for UNIX System V Release 4.0. XT (1) (EXtended Technology) First IBM PC with a hard disk, introduced in 1983. See PC. (2) (Xt) See X toolkit. XT bus See PC bus. XT class Refers to PCs that use the 8088/8086 CPU and the 8-bit bus. XT interface See XT bus. XTRAN See XGML. XTree PC disk management program and DOS shell from XTree Co., San Luis Obispo, CA. Introduced in 1985, it was the first program to help users manage hard disks by providing a hierarchical display of directories. XTreePro added a built-in text editor, and XTreePro Gold added application launching, split windows and file viewers. XTreeMac for the Mac was also introduced. XVT (EXtensible Virtual Toolkit) Developers toolkit for creating user interfaces across multiple environments from XVT Software, Inc., Boulder, CO. Programmers create the XVT functions, which are translated to DOS, Windows, OS/2, PM or the Mac. XyWrite III Plus Pronounced "zy-write." PC word processing program from The Technology Group (XYQUEST division), Baltimore, MD, used extensively by major newspapers and magazines. It is noted for its flexibility and typesetting orientation as well as its speed on slow PCs. It is both command and menu driven, has a completely-customizable interface, provides nine document windows and includes a programmer-oriented macro language. Signature, a more sophisticated version jointly developed by XYQUEST (Billerica, MA) and IBM, is the successor to XyWrite III Plus and IBM's DisplayWrite. It automatically converts XyWrite, DisplayWrite and DCA documents. XyWrite 4.0, successor to both XyWrite and Signature, includes an auto resume feature. Nota Bene, originally developed by Dragonfly Software, adds indexed text retrieval, bibliographic and citation management to XyWrite. In 1992, The Technology Group acquired all of these products and created the XYQUEST division. y-axis See x-y matrix. yacc (Yet Another Compiler Compiler) UNIX compiler that is used to create C compilers. Part of its code is included in the generated compiler. See bison. Yellow Pages See NIS and naming service. Ymodem File transfer protocol identical to Xmodem-1K plus batch file transfer (also called Ymodem Batch). It is faster than standard Xmodem and sends file name before sending the data. Ymodem-G transmits without acknowledgment (for error-free channels or when modems are self correcting), but transmission is cancelled upon any error. Z Mathematical language used for developing the functional specification of a software program. Developed in the late 1970s at Oxford University, IBM's CICS software is specified in Z. z-axis Third dimension in a graphics image. The width is the x-axis and the height is the y-axis. Z80 8-bit microprocessor from Zilog Corp. that was the successor to the Intel 8080. The Z80 was widely used in first-generation personal computers that used the CP/M operating system. Z8000 16-bit microprocessor from Zilog Corporation that is the successor to the Z80. zap Command that typically deletes the data within a file but leaves the file structure intact so that new data can be entered. ZBR (Zone Bit Recording) Technique that records more bits on a disk. The tracks on a disk become longer the farther they are from the center. However, on regular disks, the clock rate that records the bits doesn't change, which results in the outer tracks being less densely packed than the inner tracks. With ZBR, the clock rate is changed based on which track is being written, and each track is filled to capacity. zenix See SCO XENIX. zero-slot LAN Refers to transmitting between computers over a serial or parallel port, thus freeing up an expansion slot normally used by LAN cards (NICs). zero wait state Refers to a high-speed memory that transfers its data immediately upon being accessed without waiting one or more machine cycles to respond. ZiffNet Online information service from Ziff Desktop Information for PC users. Provides a wide of variety of shareware and public domain software as well as technical forums and information. ZiffNet can be accessed via PRODIGY and CompuServe. Address: 25 First St., Cambridge, MA 02141, 617/252-5000. See online services. zinc air Rechargeable battery technology that provides more charge per pound than NiCad or nickel hydride and does not suffer from the memory effect. It uses a carbon membrane that absorbs oxygen, a zinc plate and potassium hydroxide as the electrolyte. AER Energy Systems, Smyrna, GA, is the pioneer in this emerging battery technology. zip (1) To compress a file with PKZIP. See PK software. (2) (ZIP) (Zig-Zag Inline Package) Similar to a DIP, but smaller and tilted on its side for mounting on boards with limited space. Zmodem File transfer protocol that has become very popular because it handles noisy and changing line conditions very well, including satellite transmission. It sends file name, date and size first, uses variable length blocks and CRC error correction. If a download is interrupted using Zmodem or Ymodem, Zmodem will transmit only the remainder of the file on the next try. This is great insurance when sending extremely long files. Zoo Freeware compression program, including source code, used in UNIX, DOS and other environments. zoom To change from a distant view to a more close-up view (zoom in) and vice versa (zoom out). An application may provide fixed or variable levels of zoom. A video display board (graphics adapter) may also have built-in zoom, which provides zoom capability for everything that is displayed independent of and in addition to the application's zoom levels. zywrite See XyWrite. 0K (Zero Kilobytes) Typically references motherboards that do not include memory as priced. 0x In programming, the symbol for a hexadecimal number. See x. 1-2-3 See Lotus 1-2-3. 1.2M Refers to the 1.2MB high-density 5.25" floppy disk used in PCs. 1.44M Refers to the 1.44MB high-density 3.5" disk used in PCs. 10BaseT See Ethernet. 1401 Second-generation IBM computer introduced in 1959 and used until the late 1960s. It had 16K of core memory, six tape drives and used punched cards for input. It was an outstanding success due to its reliability (18,000 installed). For migration, 1401 emulators were built into IBM's 360 series. 16-bit See bit specifications. 16450, 16550 See UART. 24-bit See bit specifications. 2780, 3780 Standard communications protocols for transmitting batch data. The numbers originated with early IBM remote job entry (RJE) terminals that included a card reader and a printer. 286 Successor to the 8088 CPU used in the first PC (XT- class). Refers to the Intel 80286 CPU chip or to a PC (AT class) that uses it. It is more responsive than an XT and isn't limited to its infamous one- megabyte barrier, but is still sluggish for Windows and graphics-intensive applications. See PC and x86. 286 CPU Technical Specs 16-bit multitasking microprocessor in a 68-pin PGA, PLCC or LCC package. Has 15 16-bit registers including eight general-purpose. Operational modes: "Real Mode" performs as a fast 8086 CPU and addresses 1MB memory. "Protected Mode" addresses 16MB physical and 1GB virtual memory and provides access to memory protection capabilities. Contains 130,000 transistors. 286/12, 286/16... Specification of CPU speed for a 286. The second number is the clock rate: 286/12 means 12MHz. 3 C's See "PROCESSING" under computer. 3.5" (1) Refers to the common 3 1/2 inch microfloppy disk used in personal computers. (2) Refers to disk drives and other devices with a 3 1/2 inch horizontal form factor. 303x Series of medium to large-scale IBM mainframes introduced in 1977, which includes the 3031, 3032 and 3033. See IBM mainframes. 308x Series of large-scale IBM mainframes introduced in 1980, which includes the 3081, 3083 and 3084. See IBM mainframes. 3090 Series of large-scale IBM mainframes introduced in 1986. Before the ES/9000 models (System/390), 3090s were the largest mainframes in the System/370 line. Models 120, 150 and 180 are single CPUs. Models 200 through 600 are multiprocessor systems (first digit indicates the number of CPUs). The E, S and J models represent increased speed respectively. See IBM mainframes. 32-bit See bit specifications. 32-bit processing In a PC, refers to programs written for the 386's native mode, which run the fastest. All registers, pointers and addresses use the full 32 bits. Although the 386 is a 32-bit machine, under DOS, it runs applications in Real Mode, which functions as a 16-bit 8088, the CPU in the first PC. 3270 Family of IBM mainframe terminals and related protocols (includes 3278 mono and 3279 color terminal). See 3270 emulator. 3270 Data Stream Format for transmitting data from an application to a 3270-type terminal. 3270 emulator Plug-in board that converts a personal computer or workstation into an interactive IBM mainframe terminal. The first 3270 emulator in widespread use was the IRMAboard. 34010, 34020 General-purpose microprocessors from TI that are optimized for graphics and conform to the TIGA interface. 360 See System/360. 360K May refer to the 360K 5.25" minifloppy disk used with PCs. 370 See System/370. 370 architecture Refers to a computer that will run IBM mainframe applications. See System/370 and IBM mainframes. 370/XA (370 EXtended Architecture) Major enhancement (1981) to System/370 architecture which improved multiprocessing, introduced a new I/O system and increased addressing from 24 to 31 bits (16MB to 2GB). 3770 Standard communications protocol for batch transmission in an IBM SNA environment. 3780 See 2780, 3780. 37xx IBM communications controllers that includes the 3704, 3705, 3720, 3725 and 3745 models. The 3704 and 3705 are early units, and the 3745 models are newer and more versatile. The 3745 includes a cluster controller that can connect 512 terminals, eight token ring networks and 16 T1 lines. 386 Successor to the 286. Also known as the 386DX, it refers to the Intel 386 CPU chip or to a PC that uses it. The 386 is faster than the 286, addresses more memory, and allows both extended and expanded (EMS) memory to be allocated on demand. It is more responsive to Windows and graphics-intensive applications than the 286. See PC and x86. 386 CPU Technical Specs 32-bit multitasking microprocessor in a 132-pin PGA package. Supports 8, 16 and 32-bit data types. Has 32 32-bit registers including eight general- purpose. Operational modes: "Real Mode" performs as a fast 8086 CPU and addresses 1MB memory. "Protected Mode" addresses 4GB physical and 64TB virtual memory and provides access to memory management, paging and memory protection capabilities. "Virtual 8086 Mode" is a Protected Mode subset that runs tasks as if each were in an individual 8086 CPU. See Virtual 8086 mode.  386 CPU Family  386 Version Clock Bus Number  (Word size Speed Size Maximum of  in bits) (MHz) (bits) RAM Transistors  陳陳陳陳陳陳堕陳陳賃陳陳賃陳陳賃陳陳陳陳陳 386DX 16-40 32 4G 275,000 (32) 386SX 16-33 16 16M 275,000 (32) 386SL 20-25 16 32M 857,000 (32) 386/25, 386/33... Specification of CPU speed for a 386. The second number is the clock rate: 386/25 means 25MHz. 386 Enhanced Mode Windows operation mode. See Windows. 386DX See 386. 386MAX DOS memory manager for 386s and up from Qualitas, Inc., Bethesda, MD, noted for its advanced capabilities. BlueMAX is a version for PS/2 models. 386SL Version of the 386SX designed for laptops. It has built in power management, and its variable clock rate allows it to idle for long suspend and resume periods. Except for memory and video controller, the 386SL and the 82360SL chip make up almost the entire computer. See x86. 386SLC IBM version of the 386SX that includes an internal 8KB memory cache. It includes power management capabilities and runs as fast as a 386DX. 386SX Version of the 386 from Intel that runs at slower speeds than the 386DX, addresses only 16MB of memory (not 4GB) and supports only a 16-bit data bus (not 32). It uses less power and dispells less heat than the 386DX. See 386SL and x86. 387 Math coprocessor for the 386. 390 See System/390. 3Com 3+ Network operating systems from 3Com Corp., Santa Clara, CA. 3+Share is a DOS-based system that supports PC and Mac workstations. 3+Open is OS/2 based and supports DOS, OS/2 and Mac stations. As of May 1993, 3Com is discontinuing its operating system line and will remain in the LAN hardware business offering a wide variety of adapters, hubs and related products. 3GL See third-generation language. 4004 First microprocessor. Designed by Marcian E. "Ted" Hoff at Intel, it was a 4-bit, general-purpose CPU that was initially developed for the Japanese Busicom calculator. 43xx A series of medium-scale IBM mainframes initially introduced in 1979, which include the 4300, 4321, 4331, 4341, 4361 and 4381. 486 Successor to the 386. Also known as the 486DX, it refers to the Intel 486 CPU chip or to a PC that uses it. It runs twice as fast as the 386 and provides the speed necessary for today's graphical interfaces. Its built-in math coprocessor is often required by CAD applications. The "Speed Doubler" DX2 is a 486 CPU with double the internal speed. For example, a 486/50DX2 accesses RAM and other chips on the motherboard at 25MHz, but processes internally at 50MHz. DX chips may be replaced with Intel's OverDrive DX2 chip. See PC and x86. 486 CPU Technical Specs 32-bit multitasking microprocessor in a 168-pin PGA package. Same registers and operational modes as the 386 (see 386). Uses RISC design techniques and obtains its speed from an internal 8KB memory cache that it quickly fills in burst mode. The 486DX contains 1.2 million transistors, the 486SX contains 1.1 million. 486/25, 486/33... Specification of CPU speed for a 486. The second number is the clock rate: 486/25 means 25MHz. 486DLC 486SX-compatible CPU from Cyrix Corp. that is pin compatible with the 386DX. Designed for upgrading 386s, it comes in a variety of speeds including clock doubling versions. 486DX See 486. 486DX2 See 486. 486SL Version of the 486 from Intel designed for laptops. It runs on 3.3 volts (instead of 5) and includes power management features like the 386SL. 486SLC (1) 486SX-compatible CPU from Cyrix Corporation that is pin compatible with the 386SX, has a 1K cache and uses a 16-bit bus. It provides an upgrade path for 386SXs. (2) IBM version of the 486SX. 486SX Version of the 486 from Intel that runs at slower clock speeds than the 486DX and does not include the math coprocessor. 486SXs can be upgraded to 486DX2s with Intel's OverDrive chip, which includes the coprocessor. The DX2 chip is plugged into the empty coprocessor socket, disabling the original CPU. See 486. 487 Math coprocessor for the 486. 4GL See fourth-generation language. 4mm tape See DAT. 5.25" (1) Refers to the common 5 1/4 inch floppy disk used in personal computers. (2) Refers to disk drives and other devices with a 5 1/4 inch horizontal form factor. 5100 First IBM desktop computer (1974). It came with up to 64K of RAM, a built-in tape drive and used APL or BASIC. Eight inch floppy disks became available in 1976. 5250 Family of terminals and related protocols for IBM midrange computers (System 3x, AS/400). 586 See Pentium. 64-bit See bit specifications. 650 IBM's first major computer success. Introduced in 1954, it used magnetic drum memory, magnetic tape and punched cards. By the end of the 1950s, there were an estimated 1,800 units installed, making it the most widely used computer in the world. 6502 8-bit microprocessor from Rockwell Int'l., Corp. used in the Apple II and earlier Atari and Commodore computers. 6800 8-bit microprocessor from Motorola. The 6801 is a computer-on-a-chip version. 68000 Family of microprocessors from Motorola that are the CPUs in Macintoshes and a variety of workstations. 68000 - 32-bit CPU that can address up to 16MB of memory and uses a 16-bit data bus. 68020 - 32-bit CPU that can address up to 4GB of memory and uses a 32-bit data bus. 68030 - 32-bit CPU that can address up to 4GB of memory and uses a 32-bit data bus. The 68030 runs at higher clock speeds than the 68020 and has built-in cache memory. 68040 - Redesigned version of the 68030 that can run up to three times as fast. 7-bit ASCII Refers to transferring ASCII text in which an 8-bit byte holds the ASCII character plus a parity bit. Some PBXs allow only 7-bit transmission. 7-track Refers to older magnetic tape formats that record 6-bit characters plus a parity bit. 720K May refer to the 720K microfloppy disk used in PCs. 750 See i750. 8-bit See bit specifications. 8-N-1 (8 bits, No parity, 1 stop bit) Common parameters for modem transmission. 80186/80188 Integrated version of the 8086/8088 CPU that includes additional system components, such as the clock, DMA and interrupt controller, on the same chip. 802.1, 802.2, etc. See IEEE 802. 80286 See 286. 80287 See 286. 80386 See 386. 80386DX See 386. 80386SL See 386SL. 80386SX See 386SX. 80387 See 386. 80486 See 486. 80486DX See 486. 80486SX See 486SX. 80487 See 486SX. 8080 Intel 8-bit CPU chip introduced in 1974. It was the successor to the first commercial 8-bit microprocessor (8008) and precursor to the x86 family. 8086 Introduced in 1978, the CPU chip that defines the base architecture of Intel's x86 family (XT, AT, 386, 486, Pentium). 8086s are used in some XT- class machines. See PC and x86. 8086 CPU Technical Specs 16-bit microprocessor in a 40-pin CERDIP package. Has 14 16-bit registers including eight general- purpose. Addresses 1MB memory using base addresses contained in segment registers. Contains 29,000 transistors. 80860 See 860. 8087 Math coprocessor for the 8086/8088. 8088 Intel CPU chip used in first-generation PCs (XT class). It is a slower version of the 8086, chosen for migration from CP/M programs, the predominate business applications of the early 1980s. See PC and x86. 8088 CPU Technical Specs Same as the 8086 CPU except that is uses an 8-bit data bus instead of a 16-bit data bus. Designed to ease conversion from 8-bit, Z80-based CP/M programs. Contains 25,000 transistors. 80x86 See x86. 8100 IBM minicomputer introduced in 1978 that was designed for departmental computing and used the DPPX/SP operating system. 82385 Intel controller chip that manages the memory cache in 386 and 486 CPUs. 8250A See UART. 8514 IBM monitor used with its 8514/A display adapter. 8514/A IBM high-resolution display adapter that provides an interlaced display of 1024x768 with 256 colors or 64 shades of gray. It contains an on-board coprocessor for performing 2-D graphics and it is designed to coexist with VGA for dual monitor capability. Introduced on Micro Channel machines, third-party vendors provide non-interlaced versions for the ISA bus. 860 See i860. 88000 Family of 32-bit RISC microprocessors from Motorola. The 88100 is the first processor in the 88000 family. Introduced in 1988, it incorporates four built-in execution units that allow up to five operations to be performed in parallel. 8mm tape Tape format used in high-capacity tape drives for backup. See Exabyte. 9-track Refers to magnetic tape that records 8-bit bytes plus parity, or nine parallel tracks. This is the common format for 1/2" tape reels. 9370 Series of IBM entry-level mainframes introduced in 1986 that use the 370 architecture. In 1990, the Enterprise System models (ES/9370) were introduced, which use the Micro Channel bus and a 386 for I/O processing. The ES/9370 Model 14 biprocessor system adds a second 386 that can run DOS and OS/2 applications. A high-speed link is available between the 386 and 370 processors.