Squeeze

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File Format
Name Squeeze
Ontology
Extension(s) .?q?, .qqq
Squeeze was a method of compressing single files popular on CP/M, devised by Richard (Dick) Greenlaw(?) circa 1981. It was superseded by Crunch and later CrLZH. Squeezed files were common in LBR archives. It uses Huffman compression.

Squeezed files were signified in CP/M's 8.3 filename format by replacing the middle letter of the extension with Q (.?Q? -- so FOO.TXT became FOO.TQT), with the extension .QQQ used for corner cases such as a blank extension.

The /usr/share/misc/magic file on Linux systems suggests that it was perhaps also in use on the Apple ][ platform, and in fact Binary II files are often found squeezed (as .bqy instead of .bny). Versions for PC/MS-DOS were also in use in the early 1980s before ARC caught on as the dominant archiver.

Tools

  • CFX (DOS/Unix)
  • lbrate by Russell Marks, c. 2001 (Unix, GPL2)
  • On CP/M (or emulators):
    • The original tools were SQ/USQ. See for instance the SQUSQ directory of the Oakland CP/M archive.
    • The later LT31 deals with extracting from all of Squeeze, Crunch, CrLZH and LBR formats. Widely available in CP/M archives, e.g. LT31.LBR

References

  • See the SQUSQ directory on CP/M archives for various source code and documentation (much of it, unfortunately, itself squeezed/crunched).
  • The file header follows a similar/compatible structure to Crunch and CrLZH.
  • FIXME: is the exact compression algorithm documented anywhere?
  • Wikipedia:SQ (program)
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