Fix for "`Runtime Error 200`" bug
of Borland Pascal 7 on fast PCs

Explains the cause of this bug and sumarizes solutions both for users and developers (people who do have / don't have pascal source of their programs).

Contents:

Preface
Cause explained
Solutions Index
Comments

Preface

Borland Turbo Pascal 7 is a great Pascal compiler for PC's. Unfortunately it has not been updated by Borland for many years.

All programs compiled with Borland Pascal 7 that use the system unit Crt (almost all programs do that) abort with the error message "Runtime Error 200" on all fast PCs, for example Pentium II with 233 MHz.

Programs compiled with Borland Pascal 6 are said to not abort with a runtime error, but their delay is completely wrong on fast PCs (and the problem starts there at much lower speeds than the problem of version 7).

This Web page tries to explain the problem and summarize some existing solutions.

Borland (aka Inprise) does not offer a solution for this bug (shame on them!).

Cause

The bug is in the initialization for the delay procedure that is part of the initialization of the Crt unit. The delay initialization is called in every program that uses the Crt unit, not just on those that use the delay procedure. The Crt unit is included in most programs that are written in Borland Pascal.

The delay initialization counts how often a tiny do-nothing loop must be called in order to delay by 55 milliseconds (time measured by reading the Bios Time Counter at memory address 40:6C that ticks 18.2 times a second, i.e. each 55 milliseconds).

This number is then divided by 55 to get the number of calls for one millisecond. The result is written to a word (16 bit) variable. The overflow of this variable triggers the run time error (the meaning of Runtime Error 200 is division by zero, but it is caused by an overflow in this case).

Solutions

The following list shows all solutions that I currently know.

Index of recommended solutions

You have only an EXE file, no Pascal source
- ask the person who does have the pascal source for a new or recompiled version
- TpPatch Patch program for existing executable files
  (caution: only for programs that no not require correct timing)
You have Turbo Pascal 7.01
- T7TplFix patch program for Run Time Library file (TURBO.TPL)
You have Borland Pascal 7.01
- if you need only real mode, use T7TplFix from the section above
- extract the file CRT.DIF from T7TplFix, apply the listed changes to CRT.ASM and then recompile the run time library
You have Turbo Pascal or Borland Pascal version 7.0
- Contact Borland / Inprise to obtain version 7.01 because version 7.0 contains several bugs. Lately there have been reports in usenet that Borland doesn't know about a 7.01 bug fix version, it's still called 7.0, so it may be better to ask for replacement disks for version 7.0 (will come as one cdrom containing version 7.01).
- Risk using one of the other solutions below

Index of other solutions

bppatch Solution by German computer magazine c't

contains description, program patch, source patch and copy of patched run time library
problem: rtl is based on version 7.0, thus reintroducing several old errors while fixing one new one, description and patch are very good though.

bp7patch patch program for all Run Time Library files ( TP 7.x )

problem: does much more changes than can be easily explained Recommended by Borland
Recommended for TP 7

Comments
Looking through the list of files above, most of you will probably come to the conclusion that no real solution seems to be available.
Programmers using Turbo Pascal 7.01 can now solve their problem since t7tplfix.zip is available. Programmers using Borland Pascal 7.01 and still must search and apply the patch themselves to get a working version of TPP.TPL (for protected mode). Users without source of their programs can still not get a real solution if the programs rely on a precise delay function. Such a solution will probably never exist.
Of the two files recommended by Borland, one will cause the delay procedure to not run correct on fast computers, the other can be used only by owners of the full Borland Pascal package because the file TPP.TPL is required and it does a lot of suspicions changes to other units as well.
By using any of the other files, you must send your customers a program that is patched to patch itself at runtime with even its authors saying that this is not very nice. Or you can prevent the run time error but must live with a delay procedure that is known to run at unpredictable speeds. Or you must persuade your customers to install a TSR program that you don't know precisely what it does. Or you reintroduce all the bugs of Borland Pascal 7.0 when replacing a otherwise correct version 7.01 with a patched version 7.0. Or you can used a patched run time library that contains a lot of additional changes that nobody has yet explained.
It is a shame for Borland that they seem to be unable or unwilling to solve this bug themselves and offer download of fixed TURBO.TPL and TPP.TPL files from their web page!
If you feel like you should say Borland what you think about their support, please remember they have changed their name to Inprise, so you may try mailing to customer-service@inprise.com.