TPU2TPS - Extracts SYSTEM.TPS from TP6.0/TPW1.0 run-time library

Written by D.J. Murdoch for the public domain, July 1991, after
having my curiosity piqued by Mitch Davis.

Syntax:

  TPU2TPS

will read SYSTEM.TPU, and create SYSTEM.TPS, suitable for recompiling
into a new version of SYSTEM.TPU.


What does it do?

Turbo Pascal keeps most of the run-time library in the SYSTEM unit,
which is usually stored in SYSTEM.TPU within TURBO.TPL or TPW.TPL.
To recompile it, you need a special "bootstrap file" called SYSTEM.TPS.
This program, TPU2TPS, extracts the bootstrap file from a compiled
version of SYSTEM.TPU.


What use is it?

If you have SYSTEM.TPS in the current directory, you can compile a new
SYSTEM unit and change the run-time library.  Why bother?  Perhaps you
don't need any of the standard library; if you're writing a tiny
utility that doesn't use any of its services, there's no point linking
in several K of it that won't be used.  The included SYSTEM.PAS is an
absolutely minimal replacement; using it, you can shrink the sample
TEST.PAS from an .EXE size of 1400 bytes down to 128 bytes.  Everyone
will think you wrote it in assembler.


How do I use it?

First, get a copy of SYSTEM.TPU from TP 6.0 or TPW 1.0 (or compatible
later versions) in the current directory. You may have to use TPUMOVER
to get it out of TURBO.TPL or TPW.TPL; the syntax to use is

  TPUMOVER TURBO *SYSTEM
     or
  TPUMOVER TPW   *SYSTEM

Then, run TPU2TPS. It'll create SYSTEM.TPS (or tell you that something
has gone wrong).

Next, get rid of the original SYSTEM.TPU (keeping a copy of course!),
and compile SYSTEM.PAS.  (You may want to make some changes to it
first.) This should give you a new version of SYSTEM.TPU. Don't put it
into *.TPL unless you're very sure of yourself; it is almost certainly
not the one you want to use as a default.

Finally, hide the old SYSTEM.TPU and *.TPL; be sure they aren't on the
path, in the .TPU directory, or in the same directory as your compiler.
Make sure that the new SYSTEM.TPU is available in one of those places,
and compile TEST.PAS or another program of your choice. Don't use any
system procedures or functions; don't use strings, sets, longints,
floating point, or files; don't use dynamic memory or overlays;
disable stack and range checking, IEEE reals, and floating point
emulation.  All of those need a real SYSTEM.TPU.

If you use one of those by mistake, you'll be in real trouble:  the
compiler doesn't expect you to fool around with SYSTEM.TPU this way,
and it can get very, very confused if it goes looking for services
that aren't there.  A more robust SYSTEM replacement would halt with
an error if you tried any of those things, but the included one won't.
(There are over 130 functions/procedures in the real thing; I was too
lazy to code that many stubs!)


What does it cost?

Absolutely nothing!  Play around with it.  Buy the real run-time
library if you want something a little less minimalist. If you really
like it, and want to send money somewhere, send it to a local charity.


Where do I complain if it doesn't work?

You expect support for freebies?  Give me a break.  TPU2TPS comes with
no warranties of any kind; I haven't tested it very well; if you like
playing with things like this, you'd better be prepared to reboot
frequently.


 D.J. Murdoch
 DJ Murdoch at Fidonet node 1:221/177.40
 dmurdoch@watstat.waterloo.edu
 71631,122 on Compuserve