compress

Compress
Filename extension .Z
Internet media type application/x-compress
Developed by Spencer Thomas
Type of format data compression

Compress is a UNIX compression program based on the LZC compression method, which is an LZW implementation using variable size pointers as in LZ78.

Contents

Description of program

Files compressed by compress are typically given the extension .Z. Most tar programs will pipe their data through compress when given the command line option -Z (tar in itself does not compress, it just stores multiple files within one tape archive file).

Files can be returned to their original state using uncompress. The usual action of the program is not merely to create an uncompressed copy of the file, but to uncompress the compressed file (so that the uncompressed version retains the timestamp and other attributes of the compressed file).

History

The LZW algorithm used in compress was patented by Sperry Research Center in 1983. Terry Welch published an IEEE article on the algorithm in 1984,[1] but failed to note that he had applied for a patent on the algorithm. Spencer Thomas took this article and implemented compress in 1984, without realizing that a patent was pending on the LZW algorithm. The GIF image format also incorporated LZW compression in this way, and Unisys later claimed royalties on implementations of GIF. Joseph M. Orost led the team and worked with Thomas et al. to create the 'final' (4.0) version of compress and published it as free software to the 'comp.sources.unix' USENET group in 1985. U.S. Patent 4,558,302 was granted in 1985, and this is why compress could not be used without paying royalties to Sperry Research, which was eventually merged into Unisys. compress has fallen out of favor in particular user-groups because it makes use of the LZW algorithm, which was covered by a Unisys patent — because of this, gzip and bzip2 increased in popularity on Linux-based operating systems due to their alternative algorithms. compress has, however, maintained a presence on Unix and BSD systems. The US LZW patent expired in 2003, so it is now in the public domain in the United States. All patents on the LZW worldwide have also expired (see Graphics Interchange Format#Unisys and LZW patent enforcement).

See also

External links

References

  1. ^ Welch, Terry A., "A technique for high performance data compression", IEEE Computer, 17(6), pp.8-19, June 1984.

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  • Compress — is a UNIX compression program based on the LZC compression method, which is an LZW implementation using variable size pointers as in LZ78. Description of program Files compressed by compress are typically given the extension .Z. Most tar programs …   Wikipedia

  • Compress — Extension de fichier .Z, .TAZ, .tar.Z Type MIME application/x compress Développé par Spencer W. Thomas James A. Woods Type de format Compression de données …   Wikipédia en Français

  • compress — Extension .Z, .TAZ, .tar.Z Type MIME application/x compress Développé par Spencer W. Thomas James A. Woods Type de format Compression de données Spécification Format ouvert …   Wikipédia en Français

  • Compress — ist ein historisches Packprogramm unter UNIX ähnlichen Betriebssystemen. Die erzeugten Dateien nutzen die Dateinamenserweiterung .Z und werden von dem zugehörigen Programmgegenstück uncompress wieder entpackt. Wie auch gzip und bzip komprimiert… …   Deutsch Wikipedia

  • compress — ist ein historisches Packprogramm unter UNIX ähnlichen Betriebssystemen. Die erzeugten Dateien nutzen die Dateinamenserweiterung .Z und werden von dem zugehörigen Programmgegenstück uncompress wieder entpackt. Wie auch gzip und bzip2 komprimiert… …   Deutsch Wikipedia

  • Compress — Com*press , v. t. [imp. & p. p. {Compressed}; p. pr & vb. n. {Compressing}.] [L. compressus, p. p. of comprimere to compress: com + premere to press. See Press.] 1. To press or squeeze together; to force into a narrower compass; to reduce the… …   The Collaborative International Dictionary of English

  • compress — com‧press [kəmˈpres] verb [transitive] COMPUTING to make a computer file smaller, so that it takes up less space and is easier to store or send: • Compressing data reduces storage and communication costs. compare decompress * * * compress UK US… …   Financial and business terms

  • compress — (v.) late 14c., to press (something) together, from O.Fr. compresser compress, put under pressure, from L. compressare to press together, frequentative of comprimere to squeeze, from com together (see COM (Cf. com )) + premere to press (see PRESS …   Etymology dictionary

  • Compress — Com press, n. [F. compresse.] (Surg.) A folded piece of cloth, pledget of lint, etc., used to cover the dressing of wounds, and so placed as, by the aid of a bandage, to make due pressure on any part. [1913 Webster] …   The Collaborative International Dictionary of English

  • compress — index abridge (shorten), abstract (summarize), cohere (adhere), concentrate (consolidate) …   Law dictionary

  • Compress —   [engl.], komprimieren …   Universal-Lexikon


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