From Just Solve the File Format Problem
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Revision as of 01:14, 6 December 2012Crunch was a method of compressing single files popular on CP/M, devised by Steve Greenberg circa 1986. It superseded Squeeze and was succeeded by CrLZH, and crunched files were common in LBR archives. The underlying compression uses the LZW algorithm.
Similar to Squeeze, crunched files were signified in CP/M's 8.3 filename format by replacing the middle letter of the extension with Z (.?Z?), with the extension .ZZZ used for corner cases such as a blank extension.
- CFX (DOS/Unix)
- On CP/M (or emulators):
- The file header is described in the text file LZDEF20.DOC shipped with CRUNCH20.LBR.
- FIXME: is the exact compression algorithm documented anywhere?
- CRUNCH20.DOC shipped in CRUNCH20.LBR says: It embodies all of the concepts employed in the UNIX COMPRESS / ARC512 algorithm, but is additionally enhanced by a "metastatic code reassignment" facility. This is one of several concepts I am developing as part of an effort to advance data compression techniques beyond current performance limits. I believe this is the first time this principle has been proposed or implemented.
- See also "Technical Abstract" by Steven Greenberg, 16 November 1986: CRUNCH.ABS