aPACK

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File Format
Name aPACK
Ontology
Released ~1997

aPACK is an executable compression utility for DOS, developed by Jørgen Ibsen, a.k.a. Jibz. It compresses EXE files (to EXE), and COM files (to COM).

It has some relationship to X-pack for Executable.

Contents

Disambiguation

This aPACK is not related to apack, a component of the atool archive management utility.

Identification

Identification of EXE

Based on information from the file command, compressed EXE files have bytes 8e c0 b9 08 00 f3 a5 4a 75 eb 8e c3 8e d8 33 ff be 30 00 05 at offset 53.

Identification of COM

Compressed COM files are observed to match one of the following three byte patterns at the beginning of the file. (Versions tested: 0.61, 0.74, 0.90, 0.91, 0.94, 0.96, 0.98, 0.99, 1.00.)

[0.61-0.74, and 0.90+ with -m option:]

8c c8 05 ?? ?? 8e c0 59 8e d0 51 be ?? ?? bf 00
01 50 57 fc

[Most 0.90-0.94 files, and 0.96-1.00 large files (source file > ~32KB):]

8c c8 80 c4 10 8e c0 fc b9 ?? ?? be 00 01 8b fe
57 f3 a5 5f be ?? ?? 06

[0.96-1.00 small files (source file < ~32KB):]

be 0d 01 bf 00 ?? 8b cf fc 57 f3 a4 c3 bf 00 01
57

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