COMPACK

File Format
Name	COMPACK
Ontology	Electronic File Formats Compression Executable compression COMPACK
Released	1990?

For a similarly-named format, see COM-Pack library‎.

COMPACK is an executable compression utility for DOS. It was developed by W. J. Collis and Prominence Computer Services, and distributed as shareware. It compresses EXE files (to EXE), and COM files (to COM).

Self-extracting archives

COMPACK also includes a utility named BUILDSFX (integrated into COMPACK.EXE in v5.x), which creates self-extracting archives in EXE format.

More research may be needed, but self-extracting archives seem to be built by first making a kind of intermediate non-compressed self-extracting archive, then compressing the whole thing with COMPACK's usual executable compression. It is not so easy to identify a COMPACK self-extracting archive as distinct from any other COMPACK-compressed EXE file, as all the distinctive parts are compressed.

Identification

More research is needed, but EXE files made by the known versions of COMPACK are observed to have the following byte pattern at offset 32 through 62:

bd ?? ?? 50 06 8c cb 03 dd 8c d2 4b 8e db be ??
00 bf 00 07 8e c2 b9 08 00 f3 a5 4a 4d 75 ec

V4.4 EXE files have, at offset 80: "Copyright (c) 1990 W. Collis".

V4.5 EXE files have, at offset 81: "Copyright (c) 1991 W Collis".

V5.1 EXE files have, at offset 79: "Copyright (c) 1991 W Collis".

The string "Copyright (C) 1995 W Collis" at offset 79 may or may not be legitimate; see PEPI207.ZIP in the "Sample files" section.

V4.4 COM files have, at offset 38: "Copyright (C) 1991  W. Collis".

V4.5 COM files have, at offset 41: "Copyright (C) 1991 W Collis".

V5.1 COM files have, at offset 40: "Copyright (C) 1993 W Collis".

Software

COMPACK:

If the documentation is to be believed, there were at least six versions of COMPACK: 4.2, 4.3, 4.4, 4.5, 5.0, and 5.1. Only the ones listed below have been located.

• COMPACK v4.4
• COMPACK v4.5 (1991-11-14?)
  • cpk45.zip → CPK45.EXE
  • CPK45.ZIP (pre-installed)
• COMPACK v5.1 (1993)

Decompression:

• COMPACK v4.5+ has a -v option that can decompress COM files. It will also decompress the compressed part of EXE files, but doesn't reconstruct the original file.
• See Executable compression#Decompression software for some DOS programs that might be able to decompress COMPACK-compressed files. Suggest UNP for v4.4-4.5, or CUP386 for other versions.

Sample files

• V4.5(?) EXE samples: CRUSH18.ZIP, JUP162US.ZIP
• PEPI207.ZIP - Unknown COMPACK version, or faked "1995" copyright message
• CSPC120.ZIP → CSPACE.EXE - Example of a file with an altered copyright message
• TCHA103.ZIP → DEMO.EXE, INTRO.EXE - More files with an altered copyright message