PackIt

PackIt was for a time in the mid-1980s the leading archiver for the Macintosh platform, until it was eclipsed by StuffIt.

Originally an archiver which merely appended multiple files into one file with no compression, it later added compression, but when StuffIt came out, that program compressed files better, so it became more popular. Encryption was also supported, but not much used.

As with most Mac-specific archiving systems, PackIt stored the Resource Fork of the files along with the regular file data (data fork).

Links

 * PackIt page with source code
 * Archive format info, including PackIt
 * Mac file converter utility for Linux