CP/M/CPM_CDROM.iso/jsage/znode3/uploads/tpatch.lbr/TPATCH.DZC/TPATCH.DOC

Text File | 1993-06-07 | 12.3 KB | 282 lines

        Patches for Turbo Pascal V3.00A and V3.01A
        ------------------------------------------

Release:    January 9, 1993 (finally!)
Author:        Herbert Oppmann
Address:    Drausnickstrasse 29, W8520 Erlangen, Germany
Phone:        [phone]
eMail:        [e-mail]


        1. Introduction and overall design

While Turbo Pascal is a very fine product I really like to work with,
it hasn't been upgraded for a while now (and will probably never be).
Over time I noticed several bugs and limitations that annoyed me more
and more. And, with ZCPR3, I really missed the support for user areas.

So I decided to do something against it, and talked with other Turbo
Pascal users here in Germany and compiled a "wish list". Astonishingly
for me, this list grew quite large, and I soon realized that it was
unfeasable to achive the goal just by layering some new code over the
old one with e.g. some include file. I needed to change some intrinsic
things.

As I don't have the copyright on Turbo Pascal, it was impossible to
distribute a modified version of it, so the only way left was writing
a patch. This was not easy, because I needed a lot of information
about the internal workings, and squeezing something into the very
limited space sometimes was more work than to implement the feature.
From the first ideas to this release version, it took me more than a
year ...

While addressing my needs (and the needs of my friends), I took care
to retain everything machine-independant and backward-compatible, and
to make things installable even when I didn't needed the flexibility.

Now I have to explain something about COM and CHN files:
The only difference between compiling to a COM file or to a CHN file
is that the runtime library is omitted in the latter case. While you
can run COM files directly from the CP/M command line, you need to
run a (COM) program first that "chains" to your desired CHN file.
Such a program (usually CHAIN.COM) is a Turbo Pascal program, that in
fact does little more than getting the filename of the desired CHN file
from the command line and then calling the library procedure "chain" that
loads the CHN file directly after the memory image of the runtime libary,
thus overloading the current Pascal program. That way, the runtime library
is inherited from the CHAIN program.

So, if I patch the runtime library of CHAIN.COM, _all_ CHN files profit
without the need to recompile them (if that is possible, i.e. if you
have the source for them). To allow for even more old programs to profit
of the new runtime library, I wrote a small program (COMTOCHN) that cuts
away the runtime library of your old Turbo Pascal COM files, thus making
them CHN files. This does not only save a lot of space, it has the big
advantage that any changes in installation (terminal or my patch) will
immediately apply to all your CHN files, or, you could have more than
one CHAIN program with different installation.

The patches to the runtime library need to be self-sufficient. But the
other patches I did to the editor and compiler rely on the patched run-
time library. So I put all the patches together in one file that is to be
applied to TURBO.COM. Now, when you compile a program to a COM file, the
patched runtime library that is within TURBO.COM is inherited by your
program.


        2. Patches for the runtime library

ZCPR3 support:

The beginning of the runtime library, i.e. the beginning of all Turbo
Pascal COM files (including the compiler itself) now has a ZCPR3 type
1 header. When running under ZCPR3 the address of the environment de-
scriptor is stored in the header (zero means "not available"):
    VAR z3ptr : ^z3env absolute $109;
The include file Z3ENV.INC contains this line and the definition of the
environment descriptor structure (incomplete). Include file NAMEDDIR.INC
serves as a good example on how to use the environment descriptor from
withing a Turbo Pascal program.


line editor:

The built-in line editor of Turbo is somewhat better than the one CP/M
2.2 had, but at least users of a Memotech computer have a far better
line editor in their system. I added an installable option to use the
BDOS line editor function 10 instead of the built-in one.
Warning: if you use the BDOS function and press a ^C at the beginning
of the line, the program is aborted. This cannot be caught in your Turbo
Pascal program via a user supplied error handler.


command line:

To access the command line from within your Turbo Pascal program, there
are two library functions "ParamCount" and "ParamStr". Because of Turbo's
variables residing between $B0 and $FF, the length of the command line
was limited to 30 characters. The rest was overwritten while initializing.
Now the command line is copied into the heap space before the initializa-
tion, thus allowing for the maximum of 126 characters.
Warning: this will reduce the available data space by a maximum of 128
byte. This reduction occurs at runtime, so when compiling, it doesn't
show. Don't lower the end address too much.

terminal reset string: (upon special request)

If you have a program that modifies your terminal setting, it has been
quite difficult to ensure its restauration under all circumstances.
You had to supply your own error handler, or re-rout the warmboot entry.
To facilitate this there is now an installable terminal reset string
that is issued everytime the program ends, no matter why.
Warning: if you selected the BDOS line editor and press ^C at the be-
ginning of the line, the program is aborted without sending this reset
string.

error in Int2Real:

The routine in the runtime library that converts integer numbers to
real numbers has a bug: integer $8000 causes an endless loop!
Astonishingly, Turbo Pascal version 2 was ok. Some ignorant at Borland
deleted two opcodes that treated this special case ...
Is now fixed.

DU form support:

Now Turbo Pascal supports DU form! Everywhere you were able to enter
a filename with a drive designator you can now enter a user too!
Ironically, I had problems with old programs that handle the user
itself. After some thought, I was able to come up with a solution.
There is an include file NAMEDDIR.INC that adds DIR form support
for your own programs. Sorry, but the limited space didn't allow to
include the DIR form into the patch.
Warning: some old programs store filenames in strings that are only
e.g. 14 chars long. Drive and user and long filename doesn't fit in
there! If you have problems, use a shorter filename (rename the file)
or recompile the program with bigger strings.

Overlays:

Overlay≤ are searched on the current user on the drive supplied
via the procedure OvrDrive. Now you can install a DU where Turbo looks
for the overlay after this search has failed.ì

Chain/Execute:

Space for patches was very scarce in the runtime library. Either I had
to give up most of my wishes, or I had to remove something to gain some
space. After some investigation I decided to remove the Chain and Execute
procedures, because a) I hope they are used infrequently and b) I wanted
to rewrite them anyway. Using the old entry points now results in a run-
time error CE. If you need Chain or Execute, use the new, much more
sophisticated version in the include file NEWCHAIN.INC.


        3. Patches for the editor/compiler

ZCPR3 support:

When compiling to a COM file, the runtime library is first copied from
the memory image of TURBO.COM. The address of the environment descriptor
that is possibly stored in the header musn't be copied to the COM file!
It must be filled with zero instead.

TURBO startup:

To get some badly needed space for the patches in the compiler
the opening menu had to be removed. Whether the error message file
should be read in is now installable.
The command line is evaluated, you may now optionally provide a workfile
name and a main file name (of course in DU form, an extension of PAS is
assumed if none is given). e.g.
    TURBO a4:workfile.inc b2:mainfileì
ì
path for TURBO.MSG, TURBO.OVR, *.COM (eXecute):

Without the patch, Turbo searched on the (supplied or) current drive,
then on the drive that was current when Turbo was started, and then
on drive A (all on the current user).
Now Turbo searches on the (supplied or) current DU, then on the DU
that was current when Turbo was started, and then on an installable DU.

DU form support:

Here too, you can support a user anywhere you like.
The editor had an input line for the filenames that was only 15 char-
acters long. I increased that string by one while decreasing the
string for the options (e.g. when searching/replacing). The latter is
now only 9 characters long instead of 10.

saving workfile:

When typing blindly, it sometimes happened to a friend of mine that
he pressed "W" (new workfile) and Turbo asked him "modified. Save?".
Not seeing this, he entered his new filename. Unluckily for him, his
name contained an "N" and so his modifications were lost ...
I have put an ASCII BELL character in that message now, so he knows
when it's time to look what's going on.


        4. New overlay

The old one was so hopelessly buggy ... When I tried the old one, nearly
2/3 of the programs didn't execute properly, a lot of times my machine
crashed. So I wrote a new one. It needs a bit more space on disk and in
memory, but it runs ok as far as I could test it.
It mimics a BDOS and BIOS interface to protect its code, and it supports
user areas. When failing to find TURBO.COM, it does not only ask the user
about retrying, but it also offers the possiblity to abort.
The old overlay was really bad in this respect, because it constantly
asked me to "insert disk with TURBO.COM in drive A:", which is my Ramdisk,
sigh! I always had to reboot when I accidently hit the "X" key.
Warning: this new overlay is designed to work with the patched TURBO.COM
only! While probably nothing fatal will happen, I don't recommend using it
with the unpatched TURBO.COM. Using the old overlay with the patched TURBO
works, but why would you want to do this?


        5. Installation

First, compile the public domain general installation program TheInst.

Determine what version of Turbo Pascal you have. Versions 3.00A and
3.01A are supported. After extracting the library, you have to rename some
files according to your version: the files ending with "0" are for version
3.00A, the ones ending with "1" are for version 3.01A, e.g. for v3.00A:

    ren newchain.inc=newchai0.inc
    era newchai1.inc
    ...

Now we need TURBO.COM: we need a "fresh" one, i.e. it has to be installed
properly (with e.g. TINST), but no patches are allowed at this point!
(see discussion about compatibility with other patches below).
Apply patches by using mload:

    mload turbo.com,tpatch.hex

I'm not sure if using TINST after applying my patch is safe; better don't
do it. If you must, don't change the terminal name! This string isn't used
anymore and there is some code at this place instead.
Install the patched TURBO.COM:

    theinst turbo

Use the supplied TURBO.OVR and TURBO.MSG instead of yours.
Install the new TURBO.OVR:

    theinst turbovr

Now compile COMTOCHN and CHAIN with the new TURBO.COM.
Install CHAIN.COM:

    theinst chain


        6. Compatiblity with other patches

I badly needed every bit of space for my patches, thatswhy I asked every-
body about his wishes and included them. I hope your favourite patches are
included too. Most of the patches I know of use the space at the beginning
of the runtime library. Unfortunately, nothing is free there anymore, so
they are not compatible. I included the source for my patches (sorry, the
comments are in german) so you can easily check if there is a conflict in
affected locations.

Definitely incompatible:        affected address(es) (V3.00A)
- break entry at 30h instead of 38h
  for Schneider/Amstrad computers    0372h,0378h
- no opening menue            2177h-2179h
- don't ask for error message        222Ch-222Eh

Definitely compatible:
- assign with wildcards            03F3h
- UpCase for german umlaut characters    04AAh
- sign of the MOD function        0745h-074Bh
- no backup file            268Bh
- other extension            2D2Bh-2D2Eh


If you have problems, suggestions, comments, ... feel free to contact me.