EXEPACK
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== Identification == | == Identification == | ||
| − | Apparently, bytes <code>80 00</code> always appear at offset 16. In other words, the ''SP'' field is 128. | + | Apparently, bytes <code>80 00</code> always appear at offset 16. In other words, the ''SP'' field is 128 (refer to [[MS-DOS EXE#Header structure]]). |
Bytes <code>10 00</code> or <code>12 00</code> appear at offset 20. In other words, the ''IP'' field is 16 or 18. | Bytes <code>10 00</code> or <code>12 00</code> appear at offset 20. In other words, the ''IP'' field is 16 or 18. | ||
| − | The ASCII signature "{{magic|RB}}" appears immediately preceding the start-of-execution point in the file | + | The ASCII signature "{{magic|RB}}" appears immediately preceding the start-of-execution point in the file (refer to [[MS-DOS EXE#Special file positions]]). |
The characteristic error message "{{magic|Packed file is corrupt}}" appears about 200 to 300 bytes after the signature. In rare cases, this message may be translated or erased. D. Fifield suggests searching for the byte sequence {{magic|cd 21 b8 ff 4c cd 21}} that immediately precedes the error message. | The characteristic error message "{{magic|Packed file is corrupt}}" appears about 200 to 300 bytes after the signature. In rare cases, this message may be translated or erased. D. Fifield suggests searching for the byte sequence {{magic|cd 21 b8 ff 4c cd 21}} that immediately precedes the error message. | ||
Revision as of 21:29, 3 July 2022
EXEPACK is an executable compression utility by Microsoft. It compresses DOS EXE files using run-length encoding. It was originally written by Reuben Borman.
It was a part of some development SDKs, and was not a separate product. The compression can be done by the EXEPACK.EXE program, or by a feature integrated into the LINK.EXE program.
There are about a half dozen different versions of the compressed format.
Some of the EXE files included with some versions of MS-DOS were compressed with EXEPACK.
Contents |
Identification
Apparently, bytes 80 00 always appear at offset 16. In other words, the SP field is 128 (refer to MS-DOS EXE#Header structure).
Bytes 10 00 or 12 00 appear at offset 20. In other words, the IP field is 16 or 18.
The ASCII signature "RB" appears immediately preceding the start-of-execution point in the file (refer to MS-DOS EXE#Special file positions).
The characteristic error message "Packed file is corrupt" appears about 200 to 300 bytes after the signature. In rare cases, this message may be translated or erased. D. Fifield suggests searching for the byte sequence cd 21 b8 ff 4c cd 21 that immediately precedes the error message.
See also
Software
Compression:
- Microsoft's EXEPACK.EXE (or LINK.EXE with /E or /EXEPACK option) - Included with some development SDKs.
- ANORMAL's DOSEXE collections → Executable Tools Pack → packers/exepack.*
- Microsoft Macro Assembler v5.1 - Includes EXEPACK 4.06 (on Disk 2)
- David Fifield's exepack
Decompression, general:
- unEXEPACK by Samuel Chevet
- David Fifield's exepack
- UNEXEPACK from openKB
Decompression, for DOS:
- See Executable compression#Decompression software for some multi-format utilities that support EXEPACK.
- UNEXEPAC by Dan Norstedt. Includes source code.
- UPACKEXE by Fabrice Bellard - Included with LZEXE.
- UnPack (archived) by Tenth Planet Software / Clive Turvey
Patchers:
Links
- ModdingWiki: Microsoft EXEPACK
- Website for David Fifield's exepack
- EXEPACK and the A20-Gate, from the OS/2 Museum
