XPACK

XPACK (often written XPAck in later versions) is a multi-function compression utility for DOS, probably best known for its executable compression. It was developed by JauMing Tseng. Some versions were distributed as freeware, others as shareware.

This article covers the executable compression and single-file compression formats, and the software in general. Some native XPACK formats have their own articles:
 * XPACK archive
 * XPACK disk image

Disambiguation
This XPACK is not the same thing as...
 * X-pack for Executable (XE.EXE)
 * xpa32 - File archive demo / xpack-archiver for win32
 * "Xpa v0.93b - Archiver for Win32" ([ xpagui.zip]) - 32-bit Windows GUI utility (Untested; don't know what this is.)
 * "XPA v1.4.3 demo - Packer" ([ xpa.zip]) - 32-bit Windows GUI utility (Seems to be a single-file compressor/destroyer. Replaces the original file, and has no decompress function.)
 * XPACK - A collection of DOS utilities from around 1990.

See also the XPA disambiguation page.

Format details
XPACK does executable compression of .EXE and .COM files.

It supports single-file compression of arbitrary data files, and has a TSR utility to do transparent decompression. Such files are presumably expected to retain their original filename.

It has an .XPA compressed archive format.

It has an .XDI compressed floppy disk image format.

Identification
At least some compressed EXE files have "" at offset 28.

Compressed data files are identified by signature bytes at offset 2. They are also observed to start with, and end with.

Software

 * Various versions of XPACK at old-dos.ru
 * (last version with full documentation?)
 * [ XPAck v1.67.r]
 * (last version with full documentation?)
 * [ XPAck v1.67.r]
 * (last version with full documentation?)
 * [ XPAck v1.67.r]
 * [ XPAck v1.67.r]

''Ed. note: Unable to get v1.64 or earlier to run in DOSBox -- it just says "XPACK is corrupt".''

Links

 * XPACK website (2001 archive)