What is OS/2? OS/2, Operating System 2, is the successor to MS DOS, the operating system that drives IBM PC's and their clones. Good News! OS/2 has three main advantages over DOS. l. It breaks the 640 kb memory barrier which allows it to run larger and more useful applications. 2. It takes better advantage of the microprocessor's communication ability by providing a better networking platform than was available up to now. Previously, you had to choose between a proprietary operating system or a 640K RAM limitation. 3. It allows several different applications to run simultaneously on one machine. In multi-tasking, a user could begin a complex calculation on Lotus 123 and hide it in the background, call up Le Systeme OnLine and read E-mail or upload/download a file and wile away the time palying Flight Simulator or Chessmaster with all three programs running at the same time. How does OS/2 manage all these chores? One of the major developments made by IBM and which makes the OS/2 so surprisingly agile is the "Microchannel Bus" which comes either in the 16 bit or 32 bit data path versions. Here, it should be emphasized that OS/2 is not specific to the micro bus, but OS/2 will never have to be changed or upgraded as more advantage is taken of the bus's seemingly unlimited capabilities. The micro bus overlaps I/O and multiple out- standing I/O requests; then, by overlapping these requests, it schedules multiple seeks. In fact, multiple disk controllers and multiple micro- processors possibly required by network servers to serve requests in parellel (parellel processing) might be used with the bus. The microchannel bus also permits the switchless installation of add-on boards which are activated by OS/2 at the keyboard level. The role of the bus The bus in a computer is the primary roadway along which data and instructions move from component to component. A distinguishing feature of the 16/32 bit bus is the capacity to control many system components, for example, high resolution color display or monochrome displays with grey shares, etc. A single bus with several processing nodes becomes congested under heavy data traffic. One solution is to build faster buses. Equally necessary then is operating system software that can break down computing tasks into parts and allocate these parts to individual processors. The IBM Microchannel Bus, with its 32 bit transfers and "multiple masters" with a built-in arbritration scheme which allows up to 16 divices to share the microprocessor`s processing power at the same time, makes a formidable statement for multi-tasking. And, OS/2, as we will see below (see also PC Magazine, Vol.6 No.13 July 21, 1987), is an equally sophisticated system, truly designed for multi-tasking. The OS/2 method OS/2 is designed to run the 80286 or 80386 microprocessor under a true multi-tasking environment. In this protected mode, OS/2, by implementing virtual memory, allocates more memory than is physically present in the machine by swapping memory to the hard disk. At any given time, the system can use up to 15 megabytes of memory, which allow OS/2 to move code and data segments in memory and to use the same code segments for multiple instances of a program. One development which contributes to OS/2 versatility is the inclusion of the presentation manager. The presentation manager is a modified version of MS Windows which allows OS/2 to maintain up to 16 screen groups, all with different programs running under them. Using the presentation manager menu, which lists all current screen groups identified by names of the programs running under them as reference. OS/2 permits switching from one program to another without exiting and reloading the application (context switching) by switching from screen group to menu to screen group using the Alt Esc, Alt and the Start a program options. All this is carried out in the protected mode, safely and efficiently, with OS/2 taking care of memory management, file locking and task isolation. Is it useful to run DOS applications under OS/2? One of the 16 screen groups is called the "DOS COMPATIBILITY BUS". This is a screen group in which existing DOS programs run in a real mode, i.e. on the low 640K of memory. Here, it should be remembered that OS/2 by itself runs only one existing application at a time. It cannot run existing applications in the background. So, OS/2 does not provide any advantage if you are working with current applications. The application first has to be ported across or created anew for the OS/2 environment. The bad news ... costly adjustments. Millions of PC's will not be able to run OS/2 without costly hardware ad- justments. Owners of classic PC's or XT's must add a 286 or 386 microchip to their machines along with lots of memory. In fact, to run the basic version of OS/2 with the commonly used applications, your computer will need a minimum of 1.5 to 2.0 megabytes of RAM. To run more advanced versions like OS/2E, that is, OS/2 Extended, which will come with better built-in communications/data base features, a minimum of 3 to 4 megabytes of RAM will be required. So, about 10 million MS DOS computers will be effectively blocked from the OS/2 market ... or will they? Challengers to OS/2. 1. A new version of expanded memory (EMS) that permits MS DOS to operate beyond 640K. Ems version 4.0, endorsed by Lotus, Intel, Microsoft and others, and which will come with an Intel aboveboard, will extend the useful life of MS DOS computers and give them many OS/2-like functions, including multi-tasking. The price of conversion will be much less than required to convert to OS/2. 2. The Berkeley version of Unix developed by the University of California at Berkeley, and Uni System 5, will both support virtual memory, graphics and high speed data communications. These will be available early next year. The immediate future - the impact on computing. MultiŠtasking will allow us to run several computational and communications programs simultaneously. Large screen displays and advanced windows software will allow us to view, simultaneously, a full page document - including text and graphics - side by side. With virtual memory, we will gain access to sophisticated programs and data bases limited only by our computer's disk capacity or network services. For example, data base program software that assumes that all the data are resident in the same machine is funda- mentally different from software that assumes that the software and processors are distributed in a network system. Screens with resolutions of 1024 X 1024 pixels or more will let us do sophisticated animation to visualize a variety of concepts. Scanners that digitize drawings and photographs will allow us to enter and manipulate images as easily as texts on screens the details of which is as good as today's printed page. Overall, computer simulation of all types will make modern methods of investigation and discovery accessible to many more people. ~~~~~~~~~~~~~~~