DOS ain't dead - Decompiling an old custom dos executable file

PGN_DOS88

31.07.2023, 23:28
(edited by PGN_DOS88, 01.08.2023, 01:54)

Decompiling an old custom dos executable file (Users)

I have an old custom dos program going back to about 1989. From what I recollect it was created in the dBase language and compiled with an old version of Clipper.

The problem is I can't decompile it with any version of Valkyrie, because it can't find the clipper signature in the file. I am assuming it must of been protected in some way.

Does anyone know of any way to decompile with this being the case, or perhaps to use another way of disassembly even if it only results in partial success of source code recovery, which I might be able to patch or fix up.

Laaca

Czech republic,
01.08.2023, 06:25

@ PGN_DOS88

Decompiling an old custom dos executable file

Post reply

> The problem is I can't decompile it with any version of Valkyrie, because
> it can't find the clipper signature in the file. I am assuming it must of
> been protected in some way.
>
Maybe it is not protection but EXE pack. Maybe some tool like UnPkLite or similar could help.

---
DOS-u-akbar!

dggionco

Buenos Aires - Argentina,
01.08.2023, 13:32

@ Laaca

Decompiling an old custom dos executable file

Post reply

> > The problem is I can't decompile it with any version of Valkyrie,
> because
> > it can't find the clipper signature in the file. I am assuming it must
> of
> > been protected in some way.
> >
> Maybe it is not protection but EXE pack. Maybe some tool like UnPkLite or
> similar could help.

Also try the old:

UNLZEXE.EXE Ver.0.5 written by Mitugu(Kou) Kurizono , 05/17/90

UNLZEXE converts the executable file which is compressed by Fabrice Bellard's LZEXE (ver.0.90,0.91) to decompressed executable one.

Guti

01.08.2023, 14:55

@ dggionco

Decompiling an old custom dos executable file

Post reply

I would suggest you going for UNP, a generic EXE packer decompressor.

UNP - Unpacks files compressed with PKLite, Diet, LZExe, EXECOMP, etc.
ftp://garbo.uwasa.fi/pc/execomp/unp411.zip

> > > The problem is I can't decompile it with any version of Valkyrie,
> > because
> > > it can't find the clipper signature in the file. I am assuming it must
> > of
> > > been protected in some way.
> > >
> > Maybe it is not protection but EXE pack. Maybe some tool like UnPkLite
> or
> > similar could help.
>
> Also try the old:
>
> UNLZEXE.EXE Ver.0.5 written by Mitugu(Kou) Kurizono , 05/17/90
>
> UNLZEXE converts the executable file which is compressed by Fabrice
> Bellard's LZEXE (ver.0.90,0.91) to decompressed executable one.

---
Visit my personal blog at https://www.javiergutierrezchamorro.com

bocke

19.08.2023, 12:22

@ Guti

Decompiling an old custom dos executable file

Post reply

> I would suggest you going for UNP, a generic EXE packer decompressor.
>
> UNP - Unpacks files compressed with PKLite, Diet, LZExe, EXECOMP, etc.
> ftp://garbo.uwasa.fi/pc/execomp/unp411.zip

Garbo FTP server is not available anymore. It got closed a while ago (back in 2012?) because of the server failure. And modern web browsers anyway seem to have dropped FTP with the excuse of security concerns (sic).

Slovak Antivirus Center (SAC) makes its stuff also available over http:
https://www.sac.sk/download/pack/unp411.zip

There is also a beta 4.12b version (without docs):
https://www.sac.sk/download/pack/unp412b.zip

PGN_DOS88

01.08.2023, 17:33

@ PGN_DOS88

Decompiling an old custom dos executable file

Post reply

> I have an old custom dos program going back to about 1989. From what I
> recollect it was created in the dBase language and compiled with an old
> version of Clipper.
>
> The problem is I can't decompile it with any version of Valkyrie, because
> it can't find the clipper signature in the file. I am assuming it must of
> been protected in some way.
>
> Does anyone know of any way to decompile with this being the case, or
> perhaps to use another way of disassembly even if it only results in
> partial success of source code recovery, which I might be able to patch or
> fix up.

Don't know if this is any help but according to some info I was able to get out of Valkyrie using the analysis tool was that the linker used was: Phoenix plink86.

PGN_DOS88

15.08.2023, 01:55

@ PGN_DOS88

Decompiling an old custom dos executable file

Post reply

> > I have an old custom dos program going back to about 1989. From what I
> > recollect it was created in the dBase language and compiled with an old
> > version of Clipper.
> >
> > The problem is I can't decompile it with any version of Valkyrie,
> because
> > it can't find the clipper signature in the file. I am assuming it must
> of
> > been protected in some way.
> >
> > Does anyone know of any way to decompile with this being the case, or
> > perhaps to use another way of disassembly even if it only results in
> > partial success of source code recovery, which I might be able to patch
> or
> > fix up.

An update to this not sure if this helps but... the exe in question was compiled with Quicksilver 1.2.

Is there a decompiler for this?

bocke

19.08.2023, 12:43

@ PGN_DOS88

Decompiling an old custom dos executable file

Post reply

> An update to this not sure if this helps but... the exe in question was
> compiled with Quicksilver 1.2.
>
> Is there a decompiler for this?

I actually never heard of Quicksilver. It seems to be a 3rd party Clipper compiler. I found very few valid items in Google query results.

These are a couple of Google Books links with some more info:

This is an article from PC Mag 1987-07 that reviews several compilers for DBase.

This is a review of a Quicksilver release from 1988-05 release of PC Mag:

Not very useful for you, but does give a bit more background info for others.

Anyways there is no any mention of Quicksilver beyond 87-88, so I guess it's lost in the history. But plink 86 might not be Quicksilver specific. It seems to have been also used by Clipper in early versions.

The Computer Languages magazine from 1985-04 ran an add for programmer's tools by authors of Latttice C. Included is plink 86:

Plink 86 — a two-pass overlay linkage editor
that helps solve memory problems.

https://archive.org/details/Computer_Language_Issue_08_1985-04_CL_Publications_US

This might well be the early version of this utility. As it likely does some overlay mangling, it's likely to be hard to decompile with standard tools.

Well, at least if I'm right that it's the same tool.

PGN_DOS88

20.08.2023, 19:16

@ bocke

Decompiling an old custom dos executable file

Post reply

> > An update to this not sure if this helps but... the exe in question was
> > compiled with Quicksilver 1.2.
> >
> > Is there a decompiler for this?
>
> I actually never heard of Quicksilver. It seems to be a 3rd party Clipper
> compiler. I found very few valid items in Google query results.
>
> These are a couple of Google Books links with some more info:
>
> This is
> an
> article from PC Mag 1987-07 that reviews several compilers for
> DBase.
>
> This is
> a
> review of a Quicksilver release from 1988-05 release of PC Mag:
>
>

Thanks for that info, that is more than I was able to find! Looks like this may be too difficult a task to decompile though, but hopefully I will find a way.