ArcMac format is a variant of the ARC compressed archive format, with extended features relevant to classic Macintosh computers. It is associated with the ArcMac software by Don Gilbert and dogStar Software.
There are three applications:
- ArcMac - The full software for Mac (shareware)
- ArcPop - Decompression-only software for Mac
- xArcMac - Decompression-only software for DOS
Some "ArcMac" or "ArcPop" distributions contain all three; others omit ArcMac.
The version numbers and release dates of these things, and of the included documentation, do not seem to have been updated consistently, and are difficult to make sense of.
The documentation claims that the distribution includes source code for ArcPop and xArcMac, in a file named "MARCS.ARC". Unfortunately, we have not located such a file.
ArcMac files start with
0x1b, and have
0x1a at offset 59, as the start of an ARC-compatible header.
- Refer to the "ArcMac File Structure" section in the ArcMac2.Doc or ARCMAC.DOC file included with most ArcMac distributions.
- macutil → macunpack/arc.h has some info (though macunpack does not support the format)
- xArcMac v1.1a
- ARCMACRC.BIN (ArcMac v1.2a?) - MacBinary-encoded (self-extracting?) ArcMac file
- Macintosh Repository: "ArcMac"
- Macintosh Garden: "ArcMac v1.3"
- Mac GUI: "ArcPop 1.2a"
- Mac GUI: "ArcMac v1.2a"
- Mac GUI: "ArcMac"
- Mac GUI: "Arcmac1.3e"
- Mac GUI: "Arcpop"
The extent to which ArcMac format is backward-compatible with ARC decompressors that are not ArcMac-aware is unclear. It can work in some limited cases, but is not reliable.