From ts@uwasa.fi Wed Mar 21 00:00:00 1993 Subject: FAQPAS.TXT contents (All rights reserved) FAQPAS.TXT Frequently (and not so frequently) asked Turbo Pascal questions with answers Comments, corrections, and additions are solicited. .................................................................. Prof. Timo Salmi Co-moderator of comp.archives.msdos.announce Moderating at garbo.uwasa.fi anonymous FTP archives 128.214.87.1 Faculty of Accounting & Industrial Management; University of Vaasa Internet: ts@uwasa.fi Bitnet: salmi@finfun ; SF-65101, Finland ------------------------------------------------------------------- 1) How do I disable or capture the break key in Turbo Pascal? 2) How do I get a printed documentation of my students' TP runs? 3) What is the code for the weekday of a given date? 4) Need a program to format Turbo Pascal source code consistently 5) Can someone give me advice for writing a tsr program? 6) Why can't I read / write the com ports? 7) What are interrupts and how to use them in Turbo Pascal? 8) Should I upgrade my Turbo Pascal version? 9) How do I execute an MsDos command from within a TP program? 10) How is millisecond timing done? 11) How can I customize the text characters to my own liking? 12) How to find the files in a directory and subdirectories? 13) I need a power function but there is none in Turbo Pascal. 14) How can I create arrays that are larger than 64 kilobytes? 15) How can I test that the printer is ready? 16) How can I clear the keyboard type-ahead buffer. 17) How can I utilize expanded memory (EMS) in my programs? 18) How can I obtain the entire command line? 19) How do I redirect text from printer to file in my TP program? 20) Turbo Pascal is for wimps. Use standard Pascal or C instead? 21) How do I turn the cursor off? 22) How to find all roots of a polynomial? 23) What is all this talk about "Pascal homework on the net"? 24) How can I link graphics drivers directly into my executable? 25) How can I trap a runtime error? 26) How to get ansi control codes working in Turbo Pascal writes? 27) How to evaluate a function given as a string to the program? 28) How does one detect whether input (or output) is redirected? 29) How does one set the 43/50 line text mode? 30) How can I assign a value to an environment variable in TP? 31) How does one store, and then restore the original screen? 32) How can I convert a TPU unit of one TP version to another? 33) Which error is e.g. Runtime error 205, etc 34) Why can't I open read-only files? I get "File access denied". ------------------------------------------------------------------- Unless otherwise stated the answers cover versions 4.0, 5.0, 5.5, 6.0 and 7.0 (real mode). The Q&As are not for Turbo Pascal version 3 or earlier. Objects, TVision, or Windows are not covered. (I do not use them myself.) From ts@uwasa.fi Wed Mar 21 00:00:01 1993 Subject: Disabling or capturing the break key 1. ***** Q: I don't want the Break key to be able to interrupt my TP programs. How is this done? Q2: I want to be able to capture the Break key in my TP program. How is this done? Q3: How do I detect if a certain key has been pressed? A: This very frequently asked question is basically a case of RTFM (read the f*ing manual). But this feature is, admittedly, not very prominently displayed in the Turbo Pascal reference. (As a general rule we should not use the newsgroups as a replacement for our possibly missing manuals, but enough of this line.) There is a CheckBreak variable in the Crt unit, which is true by default. To turn if off use uses Crt; : CheckBreak := false; : Besides turning off break checking this enables you to capture the pressing of the break key as you would capture pressing ctrl-c. In other words you can use e.g. : procedure TEST; var key : char; begin repeat if KeyPressed then begin key := ReadKey; case key of #3 : begin writeln ('Break'); exit; end; {ctrl-c or break} else write (ord(key), ' '); end; {case} end; {if} until false; end; (* test *) : This is, however, not all there can be to it, since the capturing is possible only at input time. It is also possible to write a break handler to interrupt a TP program at any time. For more details see Ohlsen & Stoker, Turbo Pascal Advanced Techniques, Chapter 7. -------------------------------------------------------------------- From ts@uwasa.fi Wed Mar 21 00:00:02 1993 Subject: Directing output also to printer 2. ***** Q: I want to have a printed documentation of my students' Turbo Pascal program exercises. How is all input and output directed also to the printer? A1: Use a screen capturing program to put everything that comes onto the screen into a file, and print the file. See FAQPROGS.TXT in /pc/ts/tsfaq33.zip (or whatever version number is the current) for more about these programs. Available by anonymous ftp or mail server from garbo.uwasa.fi. A2: See the code in TSPAS.NWS (item: Redirecting writes to the printer) in the /pc/ts/tspa32??.zip (or whatever is the current version number) Turbo Pascal units package (?? = 40, 50, 55, 60, or 70 depending on your TP version). Alternatively use USECON and USEPRN routines in the TSUNTG unit of the same package. +------------------------------------------+ ! To get these and other packages given as ! ! /dir/subdir/name ! ! see the instructions in PD2ANS.TXT ! +------------------------------------------+ A3: But the really elegant solution to the problem of getting a logfile (or a printed list) of a Turbo Pascal run is to rewrite the write(ln) and read(ln) device driver functions. In itself writing such driver redirections is very advanced Turbo Pascal programming, but when the programming has once been done, the system is extremely easy to use as many times as you like. It goes like this. The driver redirections are programmed into a unit (say, tpulog or tpuprn). All that is needed after that is to include the following uses statement into the program (the target program) which has to be logged: uses TPULOG; ( or ) uses TPUPRN; This is all there is to it. Just adding one simple line to the target program. (If you call any other units, "uses tpulog" must come AFTER the system units (eg Dos), but BEFORE any which you may define yourself.) The reason that I have named two units here instead of just one in the above example is that the preferred log for the target program may be a logfile or the printer. The better solution of these two is to use the logfile option, and then print it. The reason is simple. If the target program itself prints something, your printout will look confused. The logging also has obvious limitations. It works for standard input and output (read(ln) and write(ln)) only. 1) It does not support graphics, in other words it is for the textmode. 2) It does not support direct (Crt) screen writes. 3) And, naturally it only shows the input and output that comes to the screen. Not any other input or output, such as from or to a file. 4) Furthermore, you are not allowed to reassign input or output. Statements like assign (output, '') will result in a crash, because the rewritten output device redirections are invalidated by such statements. 5) The device on the default drive must not be write protected, since else the logfile cannot be written to it. 6) It does not work for Turbo Pascal 4.0. Despite these restrictions, the method is perfectly suited for logging students' Turbo Pascal escapades. It is advisable first to test and run your target program without "tpulog", so that if you get any strange errors you'll know whether they are caused by the logging. Where to get such a unit. The code can be found in Michael Tischer (1990), Turbo Pascal Internals, Abacus, Section 4.2. Next a few of my own tips on this unit Tischer calls Prot. 1) The code is in incorrect order. The code that is listed on pages 142 - 145 goes between pages 139 and 140. 2) You can change the logfile name (const prot_name) to lpt1 for a printed list of the target program run. In that case it is advisable to include a test for the online status of the printer within Tischer's unit. 3) I see no reason why the two lines in Tischer's interface section couldn't be transferred to the implementation section. Why have any global definitions? But all in all, it works like magic! A4: From: abcscnuk@csunb.csun.edu (Naoto Kimura (ACM)) Subject: Re: Printing a log of students' exercises revisited To: ts@uwasa.fi Date: Fri, 2 Nov 90 20:52:03 pdt [Reproduced with Naoto's kind permission] By the way, several months ago, I had submitted a file (nktools.zip) file on Simtel20 that contains sources to a unit (LOGGER), which allows logging of I/O going through the standard input and output files, while still being able to use the program interactively. I believe that I also submitted a copy to your site. It was something I put together for use by students here at California State University at Northridge. The source works equally well in all presently available versions of Turbo Pascal. The only requirements are that * you place it as one of the last entries in the USES clause. If there is anything that redirects the standard input and output file variables, you should put that unit before my unit in the USES clause, so that it can see the I/O stream. * Don't use the GotoXY and similar screen display control procedures in the Crt unit and expect it to come out the same way you had it on the display. Since all my unit does is just capture the I/O stream to send it through the normal channels and also to the log file, all screen control information is not sent to the log file. * All I/O you want logged should go through the standard input and output file variables. * Don't close the standard input and output file variables, because it will cause problems. Basically, as far as I have checked, it just causes the logging to stop at that point. -------------------------------------------------------------------- From ts@uwasa.fi Wed Mar 21 00:00:03 1993 Subject: Code to give the weekday of a date 3. ***** Q: I want code that gives the weekday of the given date. A1: There is a wkdayfn function is /pc/ts/tspa32??.zip (or whatever version number is the latest, and where ?? is either 40 50 55 60 or 70) Turbo Pascal units collection to give the modern weekday based on Zeller's congruence. Available by anonymous ftp or mail server from garbo.uwasa.fi. Also you can find a more extensive Julian and Gregorian weekday algorithm with source code in Dr.Dobb's Journal, June 1989, p. 148. Furthermore Press & Flannery & al (1986), Numerical Recipes, Cambridge University Press, present a weekday code. The Numerical Recipes codes are available as /pc/turbopas/nrpas13.zip (big, 404k!). A2: Some will recommend the following kludge. Store the current date, change it, and let MsDos get you the weekday. This is a bad suggestion. On top of being sloppy programming, there are several snags. The trick works only for years 1980-2079. A crash the program may leave the clock at a wrong date. And even if multitasking is rare, in a multitasking environment havoc may result for the other tasks. And you may have a TSR that requires the correct date, etc. -------------------------------------------------------------------- From ts@uwasa.fi Wed Mar 21 00:00:04 1993 Subject: Pretty printers (or uniform code) 4. ***** Q: Where can I find a program that formats my (or my students') Turbo Pascal code in a consistent matter. A: What you are asking for is often called "a pretty printer". TurboPower Software's (the usual disclaimer applies) commercial Turbo Analyst has a facility for this with many options. There are also PD pretty printers, such as /pc/turbopas/pritprn.zip and others at garbo.uwasa.fi available by anonymous ftp or mail server. See /pc/INDEX.ZIP for a list of the files. -------------------------------------------------------------------- From ts@uwasa.fi Wed Mar 21 00:00:05 1993 Subject: How to write TSR programs 5. ***** Q: Can someone give me advice for writing a tsr program. A: Writing a terminate and stay resident program can be considered advanced programming and is beyond the scope of an electronic message with limited space. Instead, here are some references to Turbo Pascal books and papers which have a coverage of the subject. Stephen O'Brien, Turbo Pascal, The Complete Reference, Chapter 16; Stephen O'Brien, Turbo Pascal, Advanced Programmer's Guide, Chapter 6; Michael Tischer, Turbo Pascal Internals, Chapter 11 (a definite bible of TP programming!); Michael Yester, Using Turbo Pascal, Chapter 19; Kent Pottebaum, "Creating TSR Programs with Turbo Pascal", Dr. Dobb's Journal, May 1989 and June 1989; Kris Jamsa, Dos Power User's Guide, pp. 649-. -------------------------------------------------------------------- From ts@uwasa.fi Wed Mar 21 00:00:06 1993 Subject: Programming com ports 6. ***** Q: Why can't I read / write the com ports. A: Com port programming (most often writing telecommunication programs) is much much more complicated than simply trying to use write (com, whatever); read (com, whatever); This is a very advanced subject (frankly, beyond me), and the best way to learn is to try to obtain some code to show you how. One place to look at is Turbo Pascal text-books (I have a long list of them at garbo.uwasa.fi archives in /pc/ts/tsfaq32.zip, or whatever is the latest version number). It also has an example by David Rind in garbo.uwasa.fi/pc/pd2/faquote.zip. Another source is International FidoNet pascal conference at some bulletin board near you. The conference has had some very good discussions in it. (No, I don't have them stored for distribution, nor any further information.) -------------------------------------------------------------------- From ts@uwasa.fi Wed Mar 21 00:00:07 1993 Subject: Primers to interrupt programming 7. ***** Q: What are interrupts and how to use them in Turbo Pascal? A: An interrupt is a signal to the processor from a program, a hardware device, or the processor itself, to suspend temporarily what the program is doing, and to perform a routine that is stored in the operating system. There are 256 such interrupt routines, with many subservices stored in memory at locations, which are given in the so called interrupt table. Turbo Pascal (somewhat like C) has a special keyword Intr, and a predefined variable registers (in the Dos unit) to access these interrupt routines. One way of looking at them is as Turbo Pascal (complicated lowlevel) subroutines that are already there ready for you to call. A detailed description of interrupt routines is way beyond a single message with limited space. Instead I shall give a simple example, and good references to the subject. : uses Dos; (* This procedure turns on the border color for CGA and VGA *) procedure BORDER (color : byte); var regs : registers; begin FillChar (regs, SizeOf(regs), 0); {not really necessary} regs.ax := $0B00; {service number} regs.bh := $00; {subservice number} regs.bl := color; Intr ($10, regs); end; (* border *) If you are new the subject and / or want ideas on the most useful interrupts in Turbo Pascal programming, Ben Ezzel (1989), Programming the IBM User Interface Using Turbo Pascal, is definitely the best reference to look at. There are also many other good references for a novice interrupt user, such as Jamsa & Nameroff, Turbo Pascal Programmer's Library. If you are a more advanced interrupt user you'll find the following references very useful. Michael Tischer (1990), Turbo Pascal Internals; Norton & Wilton (1988), The New Peter Norton Programmer's guide to the IBM PC & PS/2; Ray Duncan (1988), Advanced MS-DOS Programming; Terry Dettmann (1989), Dos Programmer's Reference, Second edition, Que. Furthermore, there is an impressive list of interrupts collected and maintained by Ralf Brown. His extensive /pc/programming/inter33a.zip, inter33b.zip and inter33c.zip (or whatever are the current versions when you read this) is available by anonymous ftp or mail server from garbo.uwasa.fi. A definite must for an advanced user. Also see the reference to Brown's and Kyle's book in the bibliography at the end of this FAQ. Another useful (but in many respects a replicate) list is contained in the file /pc/programming/dosref22.zip (or, sigh, whatever is the current version). There is also a good hypertext advanced programmer's quick reference /pc/programming/helppc21.zip which you might find useful. One more point for Turbo Pascal users. When Borland upgraded from version 3 to 4.0 quite a number of tasks that needed to be done using interrupts (such as getting the current time) were included as normal TP routines. This means that while definitely useful, interrupt programming is now relevant only in advanced Turbo Pascal programming. Turbo Pascal 5.0 introduced a few more, but you can find some of the missing TP 4.0 routines in the compatibility unit in my garbo.uwasa.fi:/pc/ts/tspa32??.zip TP units collection. -------------------------------------------------------------------- From ts@uwasa.fi Wed Mar 21 00:00:08 1993 Subject: Borland's Turbo Pascal upgrades 8. ***** Q: Should I upgrade my Turbo Pascal version? A1: Depends on what version you are using, and for what purposes. If you are using version 3, the answer is a definite yes. There are so many useful additions in the later version, including the concept of units, and a great number of new useful keywords. The only reason that I can think of for using TP 3 is that it makes .com files (which reside in one memory segment only) instead of .exe files. As an accounting and business finance teacher and researcher I've been somewhat surprised to see postings stating that some users still have to program in TP 3.0 because their employer doesn't want to take the cost of upgrading. I find this cost argument ridiculous. How about some consideration for cost effectiveness and productivity? If you are currently using version 4.0, the most important point in considering upgrading is the integrated debugger in the later versions. It is really good, and useful if you write much code. There are some minor considerations, as well. Later versions contain some useful routines which 4.0 does not. (I have programmed some of them to be available for 4.0 in my /pc/ts/tspa3240.zip collection, or whatever is the latest when you read this). Furthermore, I find somewhat annoying that the executables will always end up in the default directory. If you are currently using version 5.0 the rational reasons for upgrading are needing objects, and a better overlay manager. I have also version 5.5 myself, but switched back to version 5.0 after I had some problems with its linking of object files. (This is a false statement from me, since it turned out that I had made a mistake myself. My thanks are due to bj_stedm@gould2.bristol-poly.ac.uk (Bruce Stedman) for questioning this item). Anyway, I don't use nor need OOP objects (don't confuse linking object files and object oriented programming here). One further point for 5.5. It has a better help function than 5.0, and a few more procedures and predefined constants. The TP 5.5 help includes examples, which can be even pasted into your program. This is handy. The real snag in upgrading (waiving the reasonable cost) is the fact that the units of the different versions are incompatible. If you have a large library of units (as I do) you will have to recompile the lot. This is something that has caused a fair amount of justifiable flak against an otherwise excellent product. A tip. Don't throw away your Turbo Pascal version 3.0 manual, if you have one. It is of use if you resort to the Turbo3 and Graph3 compatibility units. They give you access e.g. to turtle graphics. At the time of first writing this Turbo Pascal 6.0 version had just been announced. I didn't have it yet myself, but I had been (correctly) informed that its units are not compatible with the earlier versions. I now have Turbo Pascal 6.0, and I must say that my reactions have been disappointment and frustration. This is probably partly (but not entirely) my own fault, since Turbo Pascal seems to be headed from a common programming language into a full professional's specialized tool, with many features I don't know how to utilize. The only advancement from my point of view really is the multiple file editing, but I have long had alternative programs for that. If I used assembler (I don't) I am sure that I would find useful TP 6.0's potential to include assembler code as such instead of having to use the cumbersome Inline procedure of entering the assembler code. There is also a Windows Turbo Pascal, as the latest addition to the plethora. Since I don't use Windows at all, I have no futher information on it. I think a pattern is emerging here. Rather than being different versions of the same product, the consecutive Turbo Pascals are really different products for different purposes. Version 3.0 was a simple programming language. Version 4.0 extended it into a full scale programming modular platform. Version 5.0 introduced the debugger. And there an advanced hobbyist's path ended. Version 5.5 introduced object oriented programming, which I'm sure is important for the initiated, but personally I just don't need it even if I write a lot of programs. And with the 6.0 we go completely out of the realm of conventional programming into Turbo Pascal visions. And Windows Turbo Pascal is for a different platform, altogether. I find the new integrated user interface of TP 6.0 awkward in comparison to what was used in the 4.0, 5.0, and 5.5 versions. The IDE of TP leaves less free memory than the previous versions. Furthermore TP 6.0 IDE performs frequent disk accesses which cause slowdowns making it virtually unusable from a floppy. And I wonder why Borland didn't at once go all the way to Windows, because that is what 6.0 really is. An intermediate, incomplete step in that direction. This means that we have a 5th upgrade in line with incompatible units. This is aggravating even for a TP fan, isn't it? For information on Turbo Pascal version 7.0 and Borland email contact numbers see garbo.uwasa.fi:/pc/turbopas/bp7-info.zip. A2: From: dmurdoch@watstat.waterloo.edu (Duncan Murdoch), Newsgroups: comp.lang.pascal. Included with Duncan's kind permission. (Duncan is one of the most knowledgeable and useful contributors to the comp.lang.pascal UseNet newsgroup). One other reason: there's a bug in the code generator for 4.0 and 5.0 that makes it handle the Extended (10 byte) real type poorly. The code generated makes very poor use of the 8 element internal stack on the coprocessor, so that expressions with lots of operands like e1+e2+e3+e4+e5+e6+e7+e8+e9 always fail, if all the e's are of type extended. (The generated code pushes each operand onto the stack, then does all the adds. It's smarter to push and add them one at a time.) This makes it a real pain translating numerical routines from Fortran, especially since constants are taken to be of type extended. The bug was fixed in 5.5. A3: From: Bengt Oehman (d92bo@efd.lth.se): A difference between v4.0 and v5.5 is that you can calculate constants in tp55, but not in 4.0. I see this as a big advantage. For example: CONST MaxW = 10; MaxH = 20; MaxSize = MaxW*MaxH; { or } MaxX = 100; HalfMaxX = MaxX DIV 2; cannot be compiled with 4.0. -------------------------------------------------------------------- From ts@uwasa.fi Wed Mar 21 00:00:09 1993 Subject: Shelling from a TP program 9. ***** Q: How do I execute an MsDos command from within a TP program? A: The best way to answer this question is to give an example. {$M 2048, 0, 0} (* <-- Important *) program outside; uses dos; begin write ('Directory call from within TP by Timo Salmi'); SwapVectors; Exec (GetEnv('comspec'), '/c dir *.*'); (* Execution *) SwapVectors; (* Testing for errors is recommended *) if DosError <> 0 then writeln ('Dos error number ', DosError) else writeln ('Mission accomplished, exit code ', DosExitCode); (* For DosError and DosExitCode details see the TP manual *) end. Alternatively, take a look at execdemo.pas from demos.arc which is on the accompanying Turbo Pascal disk. I have also seen it asked how one can swap the Turbo Pascal program to the disk when shelling. It is unnecessary to program that separately because there is an excellent program to do that for you. It is garbo.uwasa.fi:/pc/sysutil/shroom20.zip. -------------------------------------------------------------------- From ts@uwasa.fi Wed Mar 21 00:00:10 1993 Subject: Millisocond timing 10. ***** Q: How is millisecond timing done? A: A difficult question. TurboPower Software's commercial Turbo Professional (don't confuse with Borland's Turbo Professional) has a facility for this. (The usual disclaimer applies). This one has been released to the PD. It is called tptimer and is part of the /pc/turbopas/bonus507.zip package. I have also seen a SIMTEL20 upload announcement of a ztimer11.zip for C and ASM, but I have no further information on that. It is quite another question whether you really need the millisecond timing. The most common purpose for millisecond timing is testing the efficiency of alternative procedures and functions, right? The way I compare mine is simple. I call the procedures or functions I want to compare for speed, say, a thousand times in a loop. And test this for elapsed time. This way the normal resolution (18.2 cycles per second) of the system clock becomes sufficient. This is accurate enough for the comparisons. var elapsed : real; i : word; elapsed := TIMERFN; (* e.g. from /pc/ts/tspa3255.zip *) for i := 1 to 1000 do YOURTEST; (* Try out the alternatives *) elapsed := TIMERFN - elapsed; writeln ('Elapsed : ', elapsed : 0 : 2); If you want to make more elaborate evaluations of the efficiency of your code, Borland's Turbo Profiler is a useful tool. (The usual disclaimer naturally applies.) -------------------------------------------------------------------- From ts@uwasa.fi Wed Mar 21 00:00:11 1993 Subject: Text font customizing 11. ***** Q: How can I customize the text characters to my own liking? A: As far as I know, text-mode characters are hard-coded, and cannot be customized at all unless you have an EGA or VGA adapter. But you can always retrieve the bitmap information for the ascii characters from your PC. The bitmap table for the lower part of the character set (0-127) starts at memory position $F000 and ends at $FA6E. The upper part is not at a fixed memory location. The pointer to the memory address of upper part of the ascii table (provided that graftabl has been loaded) is at an address $007C. One way of saying this is that the segment address of the upper part's memory location is at $007E, and its offset at $007C. Going into more details is beyond the scope of this posting. If you want more information see Kent Porter (1987), Stretching Turbo Pascal, Chapter 12, and Kent Porter & Mike Floyd (1990), Stretching Turbo Pascal. Version 5.5. Revised Edition. Brady, Chapter 11. If you are interested in a demonstration of utilizing the bitmapped character information (no source code available), take a look at the demo in the garbo.uwasa.fi anonymous ftp archives file /pc/ts/tsdemo15.zip (or whatever version number is current). Turbo Pascal also supports what is called stroked fonts (the .chr) files which draw characters instead of bitmapping them. The user should be able to write one's own .chr definitions, but I have no experience nor information on how this can be done. There is something called bgikit10.zip which has facilities for making fonts and adding graphics drivers. The problem is that I cannot make it publicly available, since I think that it is not PD. I am still missing the information. -------------------------------------------------------------------- From ts@uwasa.fi Wed Mar 21 00:00:12 1993 Subject: Finding files in TP 12. ***** Q: How to find the files in a directory AND subdirectories? A: Writing a program that goes through the files of the directory, and all the subdirectories below it, is based on Turbo Pascal's file finding commands and recursion. This is universal whether you are writing, for example, a directory listing program, or a program that deletes, say, all the .bak files, or some other similar task. To find (for listing or other purposes) the files in a directory you need above all the FindFirst and FindNext keywords, and testing the predefined file attributes. You make these a procedure, and call it recursively. If you want good examples with source code, please see PC World, April 1989, p. 154; Kent Porter & Mike Floyd (1990), Stretching Turbo Pascal. Version 5.5. Revised Edition. Brady, Chapter 23; and Michael Yester (1989), Using Turbo Pascal, p. 437; dirtree.pas in /pc/pcmag/vol8n01.zip. The simple (non-recursive) example listing all the read-only files in the current directory shows the rudiments of the principle of Using FindFirst, FindNext, and the file attributes, because some users find it hard to use these keywords. uses Dos; var FileInfo : SearchRec; begin FindFirst ('*.*', AnyFile, FileInfo); while DosError = 0 do begin if (FileInfo.Attr and ReadOnly) > 0 then writeln (FileInfo.Name); FindNext (FileInfo); end; end. (* test *) A2: While we are on the subject related to FindFirst and FindNext, here are two useful examples: (* Number of files in a directory (not counting directories) *) function DFILESFN (dirName : string) : word; var nberOfFiles : word; FileInfo : searchRec; begin if dirName[Length(dirName)] <> '\' then dirName := dirName + '\'; dirName := dirName + '*.*'; {} nberOfFiles := 0; FindFirst (dirName, AnyFile, FileInfo); while DosError = 0 do begin if ((FileInfo.Attr and VolumeId) = 0) then if (FileInfo.Attr and Directory) = 0 then Inc (nberOfFiles); FindNext (FileInfo); end; {while} dfilesfn := nberOfFiles; end; (* dfilesfn *) (* Number of immediate subdirectories in a directory *) function DDIRSFN (dirName : string) : word; var nberOfDirs : word; FileInfo : searchRec; begin if dirName[Length(dirName)] <> '\' then dirName := dirName + '\'; dirName := dirName + '*.*'; {} nberOfDirs:= 0; FindFirst (dirName, AnyFile, FileInfo); while DosError = 0 do begin if ((FileInfo.Attr and VolumeId) = 0) then if (FileInfo.Attr and Directory) > 0 then if (FileInfo.Name <> '.') and (FileInfo.Name <> '..') then Inc (nberOfDirs); FindNext (FileInfo); end; {while} ddirsfn := nberOfDirs; end; (* ddirsfn *) -------------------------------------------------------------------- From ts@uwasa.fi Wed Mar 21 00:00:13 1993 Subject: A generic power function code for TP 13. ***** Q: I need a power function but there is none in Turbo Pascal. A: Pascals do not have an inbuilt power function. You have to write one yourself. The common, but non-general method is defining function POWERFN (number, exponent : real) : real; begin powerfn := Exp(exponent*Ln(number)); end; To make it general use: (* Generalized power function by Prof. Timo Salmi *) function GENPOWFN (number, exponent : real) : real; begin if (exponent = 0.0) then genpowfn := 1.0 else if number = 0.0 then genpowfn := 0.0 else if abs(exponent*Ln(abs(number))) > 87.498 then begin writeln ('Overflow in GENPOWFN expression'); halt; end else if number > 0.0 then genpowfn := Exp(exponent*Ln(number)) else if (number < 0.0) and (Frac(exponent) = 0.0) then if Odd(Round(exponent)) then genpowfn := -GENPOWFN (-number, exponent) else genpowfn := GENPOWFN (-number, exponent) else begin writeln ('Invalid GENPOWFN expression'); halt; end; end; (* genpowfn *) -------------------------------------------------------------------- From ts@uwasa.fi Wed Mar 21 00:00:14 1993 Subject: Arrays > 64K 14. ***** Q: How can I create arrays that are larger than 64 kilobytes? A: Turbo Pascal does not directly support the so-called huge arrays but you can get by this problem with a clever use of pointers as presented in Kent Porter, "Handling Huge Arrays", Dr.Dobb's Journal, March 1988. In this method you point to an element of a two dimensional array using a^[row].col^[column]. The idea involves too much code and explanation to be repeated here, so you'll have to see the original reference. But I know from my own experience, that the code works like magic. (The code is available from garbo.uwasa.fi archives as /pc/turbopas/ddj8803.zip). Kent Porter, "Huge Arrays Revisited", Dr.Dobb's Journal, October 1988, presents the extension of the idea to huge virtual arrays. (Virtual arrays mean arrays that utilize disk space). Another possibility is using TurboPower Software's (the usual disclaimer applies) commercial Turbo Professional (don't confuse with Borland's Turbo Professional) package. It has facilities for huge arrays, but they involve much more overhead than Kent Porter's excellent method. (* ================================================================= My code below is based on a UseNet posting in comp.lang.pascal by Naji Mouawad nmouawad@watmath.waterloo.edu. Naji's idea was for a vector, my adaptation is for a two-dimensional matrix. The realization of the idea is simpler than the one presented by Kent Porter in Dr.Dobb's Journal, March 1988. (Is something wrong, this is experimental.) ================================================================= *) {} const maxm = 150; maxn = 250; {} type BigVectorType = array [1..maxn] of real; BigMatrixType = array [1..maxm] of ^BigVectorType; {} var BigAPtr : BigMatrixType; {} (* Create the dynamic variables *) procedure MAKEBIG; var i : word; heapNeeded : longint; begin heapNeeded := maxm * maxn * SizeOf(real) + maxm * 4 + 8196; if (MaxAvail <= heapNeeded) then begin writeln ('Out of memory'); halt; end; for i := 1 to maxm do New (BigAPtr[i]); end; (* makebig *) {} (* Test that it works *) procedure TEST; var i, j : word; begin for i := 1 to maxm do for j := 1 to maxn do BigAPtr[i]^[j] := i * j; {} writeln (BigAPtr[5]^[7] : 0:0); writeln (BigAPtr[maxm]^[maxn] : 0:0); end; (* test *) {} (* The main program *) begin writeln ('Big arrays test by Prof. Timo Salmi, Vaasa, Finland'); writeln; MAKEBIG; TEST; end. (For a better test of the heap than in MAKEBIG see Swan (1989), pp. 462-463.) -------------------------------------------------------------------- From ts@uwasa.fi Wed Mar 21 00:00:15 1993 Subject: Testing printer status 15. ***** Q: How can I test that the printer is ready? A: The usually advocated method in Turbo Pascal is to test the status of regs.ah after a call to interrupt 17 Hex, service 02: regs.dx := PrinterNumber; {LPT1 = 0} regs.ah := $02; {var regs : registers, uses DOS} Intr ($17,regs); {Interrupt 17 Hex} status := regs.ah {var status : byte} But this is not a good method since the combinations of the status bits which indicate a ready state can vary from printer to printer and PC to PC. If you want a list of the status bits, see eg Ray Duncan (1988), Advanced MS-DOS Programming, p. 587. For an example of a code using interrupt 17 Hex see Douglas Stivison (1986), Turbo Pascal Library, pp. 118-120. Also see Michael Yester (1989), Using Turbo Pascal, pp. 494-495. The more generic alternative is to try to write a #13 to the printer having the i/o checking off, that is, while {$I-} is in effect. But then you must first alter the printer retry times default (and restore it afterwards). Else the method can take up to a minute instead of an immediate response. Also, you must have set the FileMode for LPT1 appropriately (and restore it afterwards). Sounds a bit complicated, but you don't have to do all this yourself. There is a boolean function LPTONLFN for this purpose in my /pc/ts/tspa32??.zip (or whatever version number is the latest) Turbo Pascal units collection available by anonymous ftp or mail server from garbo.uwasa.fi. -------------------------------------------------------------------- From ts@uwasa.fi Wed Mar 21 00:00:16 1993 Subject: Clearing the keyboard buffer 16. ***** Q: How can I clear the keyboard type-ahead buffer. A: Three methods are usually suggested for solving this problem. a) The first is to use something like uses Crt; var dummy : char; while KeyPressed do dummy := ReadKey; This kludge-type method has the disadvantage of requiring the Crt unit. Also, in connection with procedures relying on ReadKey for input, it may cause havoc on the programs logic. b) The second method accesses directly the circular keyboard buffer var head : word absolute $0040:$001A; tail : word absolute $0040:$001C; procedure FLUSHKB; begin head := tail; end; c) The third method is to call interrupt 21Hex (the MsDos interrupt) with the ax register set as $0C00. This method has the advantage of not being "hard-coded" like the second method, and thus should be less prone to incompatibility. -------------------------------------------------------------------- From ts@uwasa.fi Wed Mar 21 00:00:17 1993 Subject: Utilizing expanded memory 17. ***** Q: How can I utilize expanded memory (EMS) in my programs? A: I have no experience (yet?) on this subject myself, but I can give you a list of references: Michael Tischer (1990), Turbo Pascal Internals, Abacus, Chapter 9; Stephen O'Brien (1988), Turbo Pascal, Advanced Programmer's Guide, Borland-Osborne, Chapter 4; Chris Ohlsen & Gary Stoker (1989), Turbo Pascal Advanced Techniques, Que, Chapter 11. Furthermore, Turbo Pascal delivery disks (at least 5.0) contain a demos.arc archive which includes a ems.pas file. -------------------------------------------------------------------- From ts@uwasa.fi Wed Mar 21 00:00:18 1993 Subject: Capturing the entire command line 18. ***** Q: How can I obtain the entire command line (spaces and all)? A: ParamCount and ParamStr are for parsed parts of the command line and cannot be used to get the command line exactly as it was. See what happens if you try to capture "Hello. I'm here" you'll end up with a false number of blanks. For obtaining the command line unaltered use type CommandLineType = string[127]; var CommandLinePtr : ^CommandLineType; begin CommandLinePtr := Ptr(PrefixSeg, $80); writeln (CommandLinePtr^); end; A warning. If you want to get this correct (the same goes for TP's own ParamStr and ParamCount) apply them early in your program. At least they must be used before any disk I/O takes place! -------------------------------------------------------------------- From ts@uwasa.fi Wed Mar 21 00:00:19 1993 Subject: Redicting from printer to file 19. ***** Q: How do I redirect text from printer to file in my TP program? A: Simple. This is done in Turbo Pascal by using the assign command (think what the word 'assign' implies). Here is a simple example of the idea. uses Printer; begin assign (lst, 'printer.log'); rewrite (lst); writeln (lst, 'Hello world'); close (lst); end. -------------------------------------------------------------------- From ts@uwasa.fi Wed Mar 21 00:00:20 1993 Subject: Turbo Pascal users are just wimps 20. ***** Q: Turbo Pascal is for wimps. Why don't you use standard Pascal or better still why don't you use C? A: These kinds of "real-programmers" statements often reflect what is called self-over-others attitude, and they are a part of a kind of a programming lore or cult. Basically, these attitudes waive the simple fact that one should select one's tools according to the task at hand, not vice versa. On the other hand one's productivity is usually best when being able to use tools which one is familiar and comfortable with. (Note however that the real-programmer's lore is not really interested in producing results.) In very rough terms there are two attitudes to programming languages. They can be seen as tools for writing applications, or (by surprisingly many) as ends themselves. If we first look at standard Pascal (versus Turbo Pascal), considering the language primary and its usage secondary is common. This results from the history of Pascal, since as we all know it was originally meant as a means for teaching programming concepts, not at all for writing applications. But because Pascal turned out to be useful also for writing applications, it has been extended for some operating systems, most notably MsDos (Turbo Pascal) and VAX/VMS (VAX Pascal). Both remedy a lot of flaws from the application programmer's point of view. Most notably they have a true file I/O interface, and enhanced string handling. Turbo Pascal (the more generic of these two) clearly draws from the structure and ideas of advanced BASICs (and vice versa). While in standard Pascal the language is an end by itself, for Turbo Pascal the only relevant issue is its usefulness for writing applications. One problem that one encounters when moving away from standard Pascal is the problem of portability. This is a truly serious problem, since most often extensive rewriting is necessary from converting say a Turbo Pascal to, say, Unix Pascal. I have taken Unix Pascal as the extreme example, since Unix Pascal in almost nothing but the standard Pascal having no useful file I/O. If one considers C, its best aspect from applications point of view is portability, and its strength for system programming. But it is not an easy language to learn. Proponents of C also often have the tendency discussed above, that is seeing the language as primary, and its utilization as secondary. Now why this tendency, not only for C, but in general? I've had the opportunity of writing programs starting from the late 1960's, and one observation I have made, and often propounded the view is that it is not writing code that is the really difficult part. What is really difficult it is coming up with good and original ideas for programs to write. I see applications as primary, and the tools as secondary. As to Turbo Pascal, I've written in many languages (including Cobol, Fortran, several Basics and Pascals, and command languages) and I like Turbo Pascal because it is one of the most convenient and flexible tools for writing the kind of applications that I usually write and distribute for the Public Domain. That is I use Turbo Pascal because I'm comfortable with it in writing applications, and have thus gathered a very useful modular libary for it over the years, not because of any inherent value attached to Turbo Pascal per se. -------------------------------------------------------------------- From ts@uwasa.fi Wed Mar 21 00:00:21 1993 Subject: Turning off the cursor 21. ***** Q: How do I turn the cursor off? A: The usually advocated trick for turning the cursor off is to equate the lower and the upper scan line of the cursor as explained eg in Stephen O'Brien (1988), Turbo Pascal, Advanced Programmer's Guide. uses Dos; var regs : registers; begin regs.ax := $0100; regs.cl := $20; {Top scan line} regs.ch := $20; {Botton scan line} Intr ($10, regs); end; To turn the cursor back on this (and many other) sources suggest setting regs.ch and regs.cl as 12 and 13 for mono screen, and 6 and 7 for others. This is not a good solution since it is equipment dependent, and may thus produce unexcepted results. Better to store the current scan line settings, and turn off the cursor bit. I won't present the details of the code, but I have it preprogrammed in my Turbo Pascal units collection /pc/ts/tspa32??.zip (or whatever version number is the latest) available by anonymous ftp from garbo.uwasa.fi archives. -------------------------------------------------------------------- From ts@uwasa.fi Wed Mar 21 00:00:22 1993 Subject: Finding the roots of a polynomial 22. ***** Q: How to find all roots of a polynomial? A: If you need the code, see Turbo Pascal Numerical Toolbox and/or Press & Flannery & Teukolsky & Vetterling (1986), Numerical Recipes, The Art of Scientific Computing, Cambridge University Press. The Numerical Recipes codes are available as /pc/turbopas/nrpas13.zip (big, 404k!). If you just need to solve such a task (without code available), get /pc/ts/tsnum12.zip (or whatever version number is the latest) from garbo.uwasa.fi archives by anonymous ftp or mail server. -------------------------------------------------------------------- From ts@uwasa.fi Wed Mar 21 00:00:23 1993 Subject: Pascal homework on the net 23. ***** Q: What is all this talk about "Pascal homework on the net"? A: This is one of the subjects that seems to pop up at regular intervals, cause some heated exchange for awhile, and then die down again leaving some users harboring warranted or unwarranted grudges. Some posters to comp.lang.pascal have been very concerned of the possibility that the questions posed on the net are related to students' homework assignments. I don't have any unequivocal answers or a clearcut stand on this question, just some comments. The most important task of a newsgroup like comp.lang.pascal is the exchange of information between the users. If you think that what you are going to post is interesting and useful to the group, that should be your topmost criterion. If it is really a student that wants his/her work done on the net (how do we know anyway?) also consider the following fact. Being able to use a newsgroup amounts to having learned at least something about using computers, and that is something per se. Even if the student may short-sightedly not see it, providing ALL the code for a student's homework is detrimental to the student, since it is he/she that foregoes understanding what he/she is doing. The group should not condone outright cheating. Being (partly) a teacher myself, I understand also this view. If a student is stuck with a problem in his/her code, I don't see any real harm in helping out, especially if the problem has general interest. Instructing is what teaching is about, anyway, isn't it? But, on the other hand, I must admit that I find a it rather flagrant if a posting asks for something of the kind "I have to complete my term assignment to write a function plotter by the end of this month. Send me the code, since I'm too busy with my other exams to write it myself" (a true quote). Finally, let's not jump to premature conclusions about anyone's questions. That's what most often triggers off a vicious circle of flaming. -------------------------------------------------------------------- From ts@uwasa.fi Wed Mar 21 00:00:24 1993 Subject: Linking bgi drivers into executables 24. ***** Q: How can I link graphics drivers directly into my executable? A: This is a complicated, yet a very useful task, because then you won't need any separate graphics drivers (or fonts) to go separately along with your program. Unfortunately, Turbo Pascal documentation on this task is a bit confusing. 1) The very first step is to get the necessary files from the Turbo Pascal disks to your working directory. To start with, you'll need binobj.exe and all the .bgi files. 2) Run the following commands (best to place them in a batch, call it eg makeobj.bat): binobj cga.bgi cga CGADriverProc binobj egavga.bgi egavga EGAVGADriverProc binobj herc.bgi herc HercDriverProc binobj pc3270.bgi pc3270 PC3270DriverProc binobj att.bgi att ATTDriverProc rem binobj ibm8514.bgi 8514 IBM8514DriverProc 3) Get drivers.pas from the Turbo Pascal disk and compile it with Turbo Pascal. Now you have a drivers.tpu unit which contains all the graphics drivers. 4) Now you won't need the .bgi and the .obj files any more. You may delete them from your working directory. 5) Write your graphics program in the usual manner. But before putting your program in the graphics mode use the following procedure if you want to link e.g. the EGAVGA graphics driver directly into your executable. (Link just the driver(s) you'll need, since the drivers take up a lot of space.) uses Graph, Drivers; : procedure EGAVGA2EXE; begin if RegisterBGIdriver(@EGAVGADriverProc) < 0 then begin writeln ('EGA/VGA: ', GraphErrorMsg(GraphResult)); halt(1); end; end; (* egavga2exe *) : Incidentally, although this is a slightly different matter, you can link any data material into your executable. See Stephen O'Brien, (1988), Turbo Pascal, Advanced Programmer's Guide, pp. 31 - 35 for more details. -------------------------------------------------------------------- From ts@uwasa.fi Wed Mar 21 00:00:25 1993 Subject: Trapping runtime errors 25. ***** Q: How can I trap a runtime error? A: What you are probably asking for is a method writing a program termination routine of your own. To do this, you have to replace Turbo Pascal's ExitProc with your own customized exec procedure. Several Turbo Pascal text books show ho to do this. See eg Tom Swan (1989), Mastering Turbo Pascal 5.5, Third edition, Hayden Books, pp. 440-454; Michael Yester (1989), Using Turbo Pascal, Que, pp. 376-382; Stephen O'Brien (1988), Turbo Pascal, Advanced Programmer's Guide, pp. 28-30; Tom Rugg & Phil Feldman (1989), Turbo Pascal Programmer's Toolkit, Que, pp. 510-515. Here is an example var OldExitProcAddress : Pointer; x : real; {$F+} procedure MyExitProcedure; {$F-} begin if ErrorAddr <> nil then begin writeln ('Runtime error number ', ExitCode, ' has occurred'); writeln ('The error address in decimal is ', Seg(ErrorAddr^):5,':',Ofs(ErrorAddr^):5); writeln ('That''s all folks, bye bye'); ErrorAddr := nil; ExitCode := 0; end; {... Restore the pointer to the original exit procedure ...} ExitProc := OldExitProcAddress; end; (* MyExitProcedure *) (* Main *) begin OldExitProcAddress := ExitProc; ExitProc := @MyExitProcedure; x := 7.0; writeln (1.0/x); x := 0.0; writeln (1.0/x); {The trap} x := 7.0; writeln (4.0/x); {We won't get this far} end. : Actually, I utilize this idea in my /pc/ts/tspa32??.zip Turbo Pascal units collection, which includes TSERR.TPU. If you put TSERR in your program's uses statement, all the run time errors will be given verbally besides the usual, cryptic error number. -------------------------------------------------------------------- From ts@uwasa.fi Wed Mar 21 00:00:26 1993 Subject: Using ansi codes in a TP program 26. ***** Q: How to get ansi control codes working in Turbo Pascal writes? A: It is very simple, but one has to be aware of the pitfalls. Let's start from the assumption that ansi.sys or a corresponding driver has been loaded, and that you know ansi codes. If you don't, you'll find that information in the standard MsDos manual. To apply ansi codes you just include the ansi codes in your write statements. For example the following first clears the screen and then puts the text at location 10,10: write (#27, '[2J'); { the ascii code for ESC is 27 } write (#27, '[10;10HUsing ansi codes can be fun'); If you want to test (as you should) whether ansi.sys or some some replacement driver has been loaded, you can use the ISANSIFN function from my garbo.uwasa.fi:/pc/ts/tspa32??.zip. Now the catches. If you have a uses Crt; statement in your program, direct screen writes will be used, and the ansi codes won't work. You have either to leave out the Crt unit, or include assign (output, ''); rewrite (output); : close (output); Occasionally I have seen it suggested that one should just set DirectVideo := false; This is a popular misconception. It won't produce the desired result. I'm not claiming to know the reason for this quirk of Turbo Pascal. Rather it is an observation I've made. -From: Bengt Oehman (d92bo@efd.lth.se) The `DirectVideo:=False' statement only tells the Crt unit to use BIOS calls instead of using direct video-memory writes. A demo program to illustrate the screen writing modes follows: Program ScreenWriteDemo; USES Crt; BEGIN Writeln('This is written directly to the video memory'); DirectVideo:=False; Writeln('This is written via BIOS interrupt calls (int 10h)'); Assign(Output,''); Append(Output); Writeln('This is written via DOS calls (int 21h)'); END. -------------------------------------------------------------------- From ts@uwasa.fi Wed Mar 21 00:00:27 1993 Subject: Writing an expression parser 27. ***** Q: How to evaluate a function given as a string to the program? A: To do this you have to have a routine for parsing and evaluating your expression. This is a complicated task requiring a clever use of recursion. You can find such code in Stephen O'Brien (1988), Turbo Pascal, The Complete Reference. Borland-Osborne/McGraw-Hill, Chapter 10. Another, simpler piece of code can be found in Michael Yester (1989), Using Turbo Pascal, Que, Chapter 5. I've also written such a function evaluation program myself, and much of it is based on the ideas in O'Brien with my own corrections and enhancements. The resulting program is available as fn.exe function evaluator in the /pc/ts/tsfunc13.zip package (or whatever version number is the latest). Note however, that the source code is not included, nor available. -------------------------------------------------------------------- From ts@uwasa.fi Wed Mar 21 00:00:28 1993 Subject: Detecting redirection 28. ***** Q: How does one detect whether input (or output) is redirected? A: As we know input to a program can come from a file, from the console, or from a pipe or redirection. Examples of the latter are type text.dat | program program < text.dat A Turbo Pascal program can be made to detect the redirections using Interrupt 21Hex, function 44Hex, subfunction 00Hex. See PC Magazine April 16, 1991, p. 374 for the code, and Duncan (1988), Advanced MS-DOS Programming, pp. 412-413 for more information. Alternatively, you can utilize the routines in my garbo.uwasa.fi:/pc/ts/ tspa32??.zip units. -------------------------------------------------------------------- From ts@uwasa.fi Wed Mar 21 00:00:29 1993 Subject: Setting the 43/50 line text mode 29. ***** Q: How does one set the 43/50 line text mode? A: Quite simple. Just apply TextMode (C80 + font8x8). Requires a "uses Crt;". First, however, you should test that you have a at least an EGA video adapter. (See DetectGraph in your TP manual). Also see TSUTLE.NWS in garbo.uwasa.fi:/pc/ts/tsutle21.zip (or whichever version number is the current) for the non-standard wide text modes like 132x43. -------------------------------------------------------------------- From ts@uwasa.fi Wed Mar 21 00:00:30 1993 Subject: Assigning environment variable values 30. ***** Q: How can I assign a value to an environment variable in TP? A: For assigning a value to (a parent process's) environment value you have to access and manipulate the Program Segment Prefix and Memory Control Blocks. This is a rather complicated undertaking. A source code with an accompanying article by Trudy Neuhaus can be found in PC Magazine Volume 11 Number 1 pages 425-427. The budding TP programmers should note that the elementary trick of Exec (GetEnv('comspec'), '/c set key=whatever') will achieve only a transient result for the diration of the exec shell. When you exit the shell after this endeavor the environment will be as it was. Alternatively, if you don't want to try to go through this rather complicated task yourself, the routines can be found in my TP TPU collection garbo.uwasa.fi:/pc/ts/tspa32*.zip (* = 40,50,55,60,70). No source code is included, though. -------------------------------------------------------------------- From ts@uwasa.fi Wed Mar 21 00:00:31 1993 Subject: Saving the screen 31. ***** Q: How does one store, and then restore the original screen? A: Here is a simple outline for storing and restoring a text mode screen. Note that it is incomplete in a sense that it works for a color monitor only, because the monochrome screen address is $B000:$0000. For storing and restoring the graphics screen see Ohlsen & Stoker (1989), Turbo Pascal Advanced Techniques, Que, pp 333-337. uses Crt; type ScreenType = array [1..4000] of byte; var ColorScreen : ScreenType Absolute $B800:$0000; SavedScreen : ScreenType; posx, posy : byte; begin SavedScreen := ColorScreen; posx := WhereX; posy := WhereY; writeln ('A simple demo storing and restoring the color text screen'); writeln ('By Prof. Timo Salmi, ts@uwasa.fi'); writeln; write ('Press <-'''); readln; ColorScreen := SavedScreen; GotoXY(posx,posy); end. If you would prefer not using the Crt unit, you can apply WHEREXFN, WHEREYFN, and GOATXY from TSUNTG.TPU from /pc/ts/tspa32*.zip. -------------------------------------------------------------------- From ts@uwasa.fi Wed Mar 21 00:00:32 1993 Subject: Converting TPUs 32. ***** Q: How can I convert a TPU unit of one TP version to another? A: Forget it. In practical terms such a conversion is not on. The Turbo Pascal TPU units are strictly version dependent. If there were a working solution I assume I would have heard of it by now. The hacks that have been tried won't solve this dilemma. You need the source code and the relevant compiler version. You may nevertheless wish to ascertain for which version a TPU unit has been compiled. This is very simple. Just look at the first four character of a TPU file. The codes are TPU0 for 4.0 TPU5 for 5.0 TPU6 for 5.5 TPU9 for 6.0 TPUQ for 7.0 real mode But don't go editing these. It will not get you anywhere. -------------------------------------------------------------------- From ts@uwasa.fi Wed Mar 21 00:00:33 1993 Subject: Finding about runtime errors 33. ***** Q: Which error is e.g. Runtime error 205 A: Basically this is a case of RTFM (read the f*ing manual). But it is very easy to find out even without resorting to the manual. Put temporarily the statement RunError (205); as the first statement of your program. Then run your program from the Turbo Pascal IDE, that is from within the TP editor. The description of the error will appear. If you run a program from within a Turbo Pascal IDE, it is advisable to turn on the debug options on. You'll get both the error number and the description. Futhermore by pressing F1 after the error you get its description in a more verbal format. One further trick is to put "uses TSERR"; (Include verbal run-time error messages) into your program. If you do that, the run-time errors will be given with a verbal description not just as a number. TSERR.TPU is part of my TPU collection /pc/ts/tspa*.zip. -------------------------------------------------------------------- From ts@uwasa.fi Wed Mar 21 00:00:34 1993 Subject: Opening read-only files 34. ***** Q: Why can't I open read-only files? I get "File access denied". A: The answer is rather simple, but it is not well displayed in the manuals. In order to read a read-only file you have to set the FileMode as 0 like below. Else you'll get runtime error 005 "File access denied". var f : text; savefm : byte; begin savefn := FileMode; FileMode := 0; assign (f, 'readonly.txt'); reset (f); { have your wicked ways } close (f); FileMode := savefn; end. -------------------------------------------------------------------- From ts@uwasa.fi Wed Mar 21 00:00:59 1993 Subject: Turbo Pascal Bibliography A. ***** Q: BIBLIOGRAPHY, text-books: Bielig-Schulz, G. & Schulz, Ch. (1990). 3D Graphics in Pascal. John Wiley & Sons Ltd. Brown, Ralf & Kyle, Jim (1991). PC Interrrupts, A Programmer's Reference to Bios, Dos, and Third-Party Calls. Addison-Wesley Publishing Company. Inc. (This is not a Turbo Pascal text-book, but a very useful reference book for advanced Turbo Pascal and other programmers. Ralf Brown is the author of the well-known garbo.uwasa.fi:/pc/programming/inter*.zip interrupt list. The book is based on the list, but the material is arranged by subjects instead of chronological interrupt numbers). Cooke, D & Craven, A H & Clarke, G M (1985). Statistical Computing in Pascal. Mathematics Division, Edward Arnold Publishers Ltd. Cooper, Doug (1992). Oh! Pascal! for Turbo Pascal 6.0 (3rd. Ed.), W.W. Norton & Co, N.Y. (A description from the author: 894 pages, 16 full color, with 1.2 or 1.44 meg diskette. This edition was written directly for TP6.0, and fully covers objects. The emphasis is on modification of existing code; many long (100-500) line projects, all using graphics, are supplied). Duncan, Ray (1988). Advanced MS-DOS Programming. The Microsoft guide for Assembly Language and C programmers. Microsoft Press. (Much useful information on interrupts also for Turbo Pascal programmers). Dettmann, Terry (1989). Dos Programmer's Reference. Second edition, revised by Jim Kyle. Que. Duntemann, Jeff (1989). Complete Turbo Pascal. Third edition. Scott, Foresman and Company. Dutton, Frank (1989). Turbo Pascal Toolbox. Second edition. Sybex. Ezzel, Ben (1989). Programming the IBM User Interface Using Turbo Pascal. Addison-Wesley. (Especially well suited for beginning interrupt users.) Jamsa, Kris (1988). Dos Power User's Guide. Osborne McGraw-Hill. (In a way oldish, but has a very good number of examples of interrupt programming mainly in Turbo Pascal.) Jamsa, Kris & Nameroff, Steven (1987). Turbo Pascal Programmer's Library. Borland-Osborne / McGraw-Hill. Jamsa, Kris & Nameroff, Steven (1988). Turbo Pascal Programmer's Library. Second edition. Borland-Osborne / McGraw-Hill. Norton, Peter & Wilton, Richard (1988). The New Peter Norton Programmer's guide to the IBM PC & PS/2. Microsoft Press. (Much useful information on interrupts and their background also for Turbo Pascal programmers). O'Brien, Stephen (1988). Turbo Pascal, Advanced Programmer's Guide. Borland-Osborne / McGraw-Hill. O'Brien, Stephen (1988). Turbo Pascal, The Complete Reference. Borland-Osborne / McGraw-Hill. (Much useful tricks including fast input handling with BlockRead. But some of the codes have not been properly updated since TP 3.) O'Brien, Stephen (1989). Turbo Pascal 5.5, The Complete Reference. Borland-Osborne / McGraw-Hill. Ohlsen, Chris & Stoker, Gary (1989). Turbo Pascal Advanced Techniques. Que. (Also includes some useful inside tips.) Porter, Kent (1987). Stretching Turbo Pascal. Advanced Programming in the MS-DOS Environment. Brady, Prentice Hall. Porter, Kent & Floyd, Mike (1990). Stretching Turbo Pascal. Version 5.5. Revised Edition. Brady, Prentice Hall. (In my opinion late Porter's books are not up to his impressive standards shown in Dr. Dobb's Journal.) Press, William & Flannery, Brian & Teukolsky, Saul & Vetterling, William (1986). Numerical Recipes. The Art of Scientific Computing. Cambridge University Press. (The shareware version of the extensive pascal codes of this book are available as garbo.uwasa.fi:/pc/turbopas/nrpas13.zip). Rugg, Tom & Feldman, Phil (1989). Turbo Pascal Programmer's Toolkit. Que. (I just hate it when TP text-books use include files which I have to hunt high and low throughout the earlier text.) Schildt, Herbert (1988). Advanced Turbo Pascal Version 4. Borland-Osborne / McGraw-Hill. Stivison, Douglas (1986). Turbo Pascal Library. Sybex. Swan, Tom (1989). Mastering Turbo Pascal 5.5. Third edition. Hayden Books. (Best as a nice alternative reference of Turbo Pascal keywords.) Tischer, Michael (1990). PC System Programming. An in-depth reference for the DOS programmer. Third printing. Abacus. Tischer, Michael (1990). Turbo Pascal Internals. Abacus. (Can be recommended for a deeper understanding of Turbo Pascal. Not for beginners.) Wood, Steve (1989). Using Turbo Pascal 5. Borland-Osborne / McGraw-Hill. Yester, Michael (1989). Using Turbo Pascal. Que. (Useful also as an introduction to more advanced usages.) BIBLIOGRAPHY, program etc handbooks: 5.0 Turbo Analyst. TurboPower Software (1988). 5.0 Turbo Professional. TurboPower Software (1988). Later 5.5 Turbo Objective? Not to be confused with Borland's Turbo-Assembler- Debugger Turbo Professional package. Microsoft MS-DOS User's Guide and User's Reference. Operating System Version 3.3. Microsoft Corporation (1987). Turbo Pascal. Numerical Methods Toolbox. Version 4.0. Borland International, Inc. Turbo Profiler. Version 1.0. User's Guide. Borland International, Inc. (1990).