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SQ (squeeze) is a computer program, devised by Richard (Dick) Greenlaw circa 1981, which was used in the early 1980s on bothDOS andCP/M computer systems to compress files so they use less space.
Files compressed by SQ are identified by changing the middle initial of the extension to "Q", so that text files ended with the extension .TQT, executable files ended with the extension .CQM or .EQE, documents with .DQC, batch files with .BQT, etc. SQ used staticHuffman coding as the compression algorithm.
Groups of files were often combined into an archive using theLU program, which created.LBR files containing all the files needed for a particular group, such as all the files needed to install an application. Typically such files were either individually compressed (because LU did not compress files) or the LBR archive was itself compressed with SQ (similarly to the use oftar andgzip together).
With the development of the ARC program (which combined both compression and archiving into one program) and itsARC archive file format, SQ essentially became obsolete on most systems, except CP/M, which lacked an ARCport for several years. On CP/M systems, the CRUNCH compression program was written to implement theLZW algorithm (as ARC did) and plug the gap.
| Archiving only | |
|---|---|
| Compressing only | |
| Archiving and compressing | |
| Software packaging and distributing | |
| Document packaging and distributing | |
