Editing Compress (software) (section)

== History ==
The LZW algorithm used in {{Mono|compress}} was patented by [[Sperry Corporation|Sperry Research Center]] in 1983. [[Terry Welch]] published an IEEE article on the algorithm in 1984,<ref>{{cite journal|author=Welch, Terry A.|author-link=Terry Welch|url=https://www.cs.duke.edu/courses/spring03/cps296.5/papers/welch_1984_technique_for.pdf|title=A technique for high performance data compression|journal=IEEE Computer|volume=17|issue=6|pages=8–19|year=1984|doi=10.1109/MC.1984.1659158|s2cid=2055321 }}</ref> but failed to note that he had applied for a patent on the algorithm. Spencer Thomas of the [[University of Utah]] took this article and implemented {{Mono|compress}} in 1984, without realizing that a patent was pending on the LZW algorithm. The [[Graphics Interchange Format|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 {{Mono|compress}} and published it as free software to the 'net.sources' [[USENET]] group in 1985. {{US patent|4558302}} was granted in 1985, and this is why {{Mono|compress}} could not be used without paying royalties to Sperry Research, which was eventually merged into Unisys. 

{{Mono|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{{snd}}because of this, [[gzip]] and [[bzip2]] increased in popularity on [[Linux]]-based operating systems due to their alternative algorithms, along with better file compression. ''compress'' has, however, maintained a presence on [[Unix]] and [[BSD]] systems and the {{Mono|compress}} and {{Mono|uncompress}} commands have also been ported to the [[IBM i]] operating system.<ref>{{cite web |title=IBM System i Version 7.2 Programming Qshell |language=en |author=IBM |website=[[IBM]] |author-link=IBM |url=https://www.ibm.com/support/knowledgecenter/ssw_ibm_i_74/rzahz/rzahzpdf.pdf?view=kc |access-date=2020-09-05 }}</ref>

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]]).

As of [[POSIX#POSIX.1-2024|POSIX.1-2024]] ''compress'' supports the [[DEFLATE]] algorithm used in [[gzip]].<ref>{{cite web |title=compress |url=https://pubs.opengroup.org/onlinepubs/9799919799/utilities/compress.html |publisher=opengroup |access-date=2 November 2024}}</ref>