View source for History of Unix

{{Short description|none}}
{{Use dmy dates|date=September 2024}}
{{Infobox OS
| name               = [[Unix]]
| logo               = 
| screenshot         = Unix_history-simple.svg
| caption            = Evolution of Unix and Unix-like systems
| website            = {{URL|http://opengroup.org/unix}}
| developer          = [[Ken Thompson]], [[Dennis Ritchie]], [[Brian Kernighan]], [[Douglas McIlroy]], and [[Joe Ossanna]] at [[Bell Labs]]
| source_model       = Historically [[Closed source software|closed source]], now some Unix projects ([[Berkeley Software Distribution|BSD]] family and [[Illumos]]) are [[Open-source software|open source]]d.
| programmed_in      = [[C (programming language)|C]] and [[Assembly language]]
| kernel_type        = [[Monolithic kernel|Monolithic]]
| ui                 = [[Command-line interface]] & [[Graphical user interface|Graphical]] ([[X Window System]])
| language           = English
| family             = Unix
| released           = {{start date and age|df=yes|1969}}
| license            = [[Proprietary software|Proprietary]]
| working_state      = Current
}}

The '''history of Unix''' dates back to the mid-1960s, when the [[Massachusetts Institute of Technology]], [[Bell Labs]], and [[General Electric]] were jointly developing an experimental [[time-sharing]] operating system called [[Multics]] for the [[GE-600 series|GE-645]] mainframe.<ref>
{{cite book
|title=Principles of operating systems: design & applications
|last=Stuart |first=Brian L.
|year=2009
|publisher=Thompson Learning
|location=Boston, Massachusetts
|isbn=978-1-4188-3769-3
|page=23}}</ref>
Multics introduced many [[Multics#Novel ideas|innovations]], but also had many problems. Bell Labs, frustrated by the size and complexity of Multics but not its aims, slowly pulled out of the project. Their last researchers to leave Multics – among them [[Ken Thompson]], [[Dennis Ritchie]], [[Douglas McIlroy|Doug McIlroy]], and [[Joe Ossanna]]<ref>{{cite web |url=https://www.princeton.edu/~hos/Mahoney/unixpeople.htm |title=In the Beginning: Unix at Bell Labs |last=Mahoney |author-link=Michael Sean Mahoney |publisher=self}}</ref> – decided to redo the work, but on a much smaller scale.<ref name="Evolution">{{cite journal |first=Dennis M. |last=Ritchie |title=The Evolution of the Unix Time-sharing System |url=http://cm.bell-labs.com/cm/cs/who/dmr/hist.html |archive-url=http://webarchive.loc.gov/all/20100506231949/http://cm.bell-labs.com/cm/cs/who/dmr/hist.html |archive-date=6 May 2010 |journal=AT&T Bell Laboratories Technical Journal |volume=63 |number=6 Part 2 |year=1984 |pages=1577–93 |doi=10.1002/j.1538-7305.1984.tb00054.x |s2cid=571269 |access-date=22 September 2013 |url-status=live |url-access=subscription }} As [https://www.read.seas.harvard.edu/~kohler/class/aosref/ritchie84evolution.pdf PDF]</ref>

In 1979, Ritchie described the group's vision for [[Unix]]:<ref name=Evolution />

{{blockquote|What we wanted to preserve was not just a good environment in which to do [[computer programming|programming]], but a system around which a fellowship could form. We knew from experience that the essence of communal computing, as supplied by remote-access, [[time-sharing|time-shared]] machines, is not just to type programs into a [[computer terminal|terminal]] instead of a [[keypunch]], but to encourage close communication.}}

== 1960s ==
===Multics===
In the late 1960s, Bell Labs was involved in a project with [[Massachusetts Institute of Technology|MIT]] and [[General Electric]] to develop a [[time-sharing]] system, called [[Multics]], allowing multiple users to access a [[mainframe computer|mainframe]] simultaneously. A key concept of the Multics system was the use of a [[single-level store]]. In this concept, there is no directly accessible [[file system]]. Instead, programs simply refer to data as if it is already in memory; if it is not, the [[virtual memory]] (VM) system loads it automatically. This means programs do not have to write code to explicitly read and write data from files into memory to manipulate it, the operating system does this all invisibly.{{sfn|Cooke|1999|p=60}}

The Multics project began to bog down, and it became clear to the Bell team that the system was unlikely to deliver a working operating system in the near term, let alone a reasonably performant one.{{sfn|Cooke|1999|p=60}} Bell Labs management ultimately withdrew from the project, and it seemed likely the company was going to end their lease on the very expensive [[GE 645]] mainframe.{{sfn|Ritchie|1984|p=1}} [[Ken Thompson]], a programmer in the Labs' computing research department, enjoyed the flexibility of Multics and began considering a new operating system that could run on less sophisticated machines.{{sfn|Cooke|1999|p=60}}

===New system===
The basic concept was to use Multics' [[hierarchical file system]], but remove the single-level store.{{sfn|Cooke|1999|p=60}} Thompson felt that the idea of a single-level store was ultimately a bad one, as it treats all memory the same, whether program code or data, when in actual use they were treated very differently. Program code is rarely modified at runtime, may be placed in a read-only area of memory, and is randomly accessed due to [[Branch (computer science)|branching]]. In contrast, data are almost always writable, as runtime modification of file data is often the entire point of the program, and sequential access, as opposed to random, is a normal means of access. While his new system would require programmers to write their own routines to load and save data, that did not appear to be unreasonable.{{sfn|Cooke|1999|p=60}}

Thompson began writing simulations of the new system under Multics, to understand the paging performance of the system. As this appeared promising, Thompson began writing the system for the GE 645, starting with a new custom [[assembly language]]. It soon became clear that the 645 would be gone in some months, and the work was abandoned.{{sfn|Ritchie|1984|p=2}} Throughout this period, Thompson also repeatedly petitioned management to purchase a smaller system than the GE 645 in order to build a similarly programmer-friendly operating system. Management refused all of these requests.{{sfn|Ritchie|1984|p=1}}

===Space Travel, move to PDP-7===
In 1969, Thompson had also written a [[video game]], [[Space Travel (video game)|''Space Travel'']], under the [[General Comprehensive Operating System|GECOS]] operating system on the smaller GE 635 machine. This had the problem that a typical game cost $75 {{USDCY|75.00|1969}} worth of billable CPU runtime.{{sfn|Ritchie|1984|p=2}} When he learned that Visual and Acoustics Research<ref>{{cite web | url=https://doc.cat-v.org/unix/oral-history/precis/mcilroy.htm | title=Doug McIlroy }}</ref> department had a small [[PDP-7]] that was largely unused, he began to rewrite the game for this machine.{{sfn|Ritchie|1984|p=2}} This was initially performed by building a binary for the PDP-7 using a [[cross compiler]] on the 635, and then moving the resulting code to the PDP-7 using [[paper tape]].{{sfn|Ritchie|1984|p=2}}

This became tedious, and Thompson began considering writing his new operating system on the new machine. This was aided by a timely vacation by his wife, leaving him with a month to work on it full time.<ref name="penguin">{{cite book |first=Peter H. |last=Salus |author-link=Peter H. Salus |title=The Daemon, the Gnu and the Penguin |url=http://www.groklaw.net/article.php?story=20050414215646742 |publisher=[[Groklaw]] |year=2005}} "In August 1969, Ken Thompson's wife Bonnie took their year-old son on a trip to California to show off to their families. As a temporary bachelor, Ken had time to work. 'I allocated a week each to the operating system, the shell, the editor and the assembler [he told me]... and during the month she was gone, it was totally rewritten in a form that looked like an operating system'"</ref> Aided by Ritchie and [[Rudd Canaday]], they implemented a version of the [[File system#Aspects of file systems|hierarchical file system]] Thompson had studied on the 645. The ability to [[Process (computing)|start programs]] stored in that file system soon followed,{{sfn|Ritchie|1984|p=2}} and then small programs to copy, delete, print and edit those files, along with a [[command-line interpreter]] to allow the user to perform all of these operations interactively. With these in place, a new assembler was written for the machine, and ''Space Travel'' moved entirely to the new platform.{{sfn|Ritchie|1984|p=3}}

A key concept that was added during this period was made by Ritchie,{{sfn|Ritchie|1984|p=2}} the concept of a [[device file]]. This was a file in the file system with the special ability to perform [[input/output]] operations. This allowed different devices to be supported simply by placing a file in an appropriate location in the file system. Read and write operations accessing these pseudo-files would perform operations on the device itself. This meant that devices were abstracted away through the file system, and programs could manipulate files no matter what sort of device they were on.{{sfn|Ritchie|Thompson|1978|p=1909}}

[[Douglas McIlroy]] then ported [[TMG (language)|TMG]] compiler-compiler to PDP-7 assembly, creating the first high-level language running on Unix. Thompson used this tool to develop the first version of his [[B (programming language)|B programming language]].<ref name=Evolution />

== 1970s ==
[[File:Ken Thompson and Dennis Ritchie.jpg|thumb|[[Ken Thompson]] and [[Dennis Ritchie]] ]]
[[File:Version 7 Unix SIMH PDP11 Emulation DMR.png|thumb|[[Version 7 Unix]] for the [[PDP-11]], running in [[SIMH]] ]]
[[File:Unix Timesharing UW-Madison 1978.jpeg|thumb|Unix [[time-sharing]] at the [[University of Wisconsin–Madison|University of Wisconsin]], 1978]]

The new operating system was initially without organizational backing, and also without a name. At this stage, the new operating system was a singletasking operating system,<ref name=Evolution /> not a multitasking one such as Multics. The name ''Unics'' (Uniplexed Information and Computing Service, pronounced as "[[eunuch]]s"), a [[word play|pun]] on ''[[Multics]]'' (Multiplexed Information and Computer Services), was initially suggested for the project in 1970. [[Brian Kernighan]] claims the coining for himself, and adds that "no one can remember" who came up with the final spelling ''Unix''.<ref>{{cite web |website=[[Linux Journal]] |first=Aleksey |last=Dolya |date=29 July 2003 |url=http://www.linuxjournal.com/article/7035|title=Interview with Brian Kernighan}}</ref> Dennis Ritchie and Doug McIlroy also credit Kernighan.<ref name="Evolution" />{{r|reader}}

When the Computing Sciences Research Center wanted to use Unix on a machine larger than the PDP-7, while 
Bell Labs Patent Department<ref>{{cite web | url=https://www.bell-labs.com/unix-history/firstport.html | title=The Creation of the UNIX* Operating System: Porting UNIX for its first commercial application }}</ref> needed a [[word processor]], Thompson and Ritchie added text processing capabilities to Unix and received funding for a [[PDP-11]]/45.{{sfn|byte198308}} For the first time in 1970, the Unix operating system was officially named and ran on the PDP-11. A text-formatting program called [[roff (software)|roff]] and a [[text editor]] were added. All three were written in PDP-11 [[assembly language]]. Bell Labs used this initial text-processing system, consisting of Unix, roff, and the editor, for text processing of [[patent]] applications. Roff soon evolved into [[troff]], the first electronic publishing program with full [[typesetting]] capability.

As the system grew in complexity and the research team wanted more users, the need for a manual grew apparent. The ''[[man page|UNIX Programmer's Manual]]'' was published on 3 November 1971; commands were documented in the "[[man page]]" format that is still used, offering terse reference information about usage as well as bugs in the software, and listing the authors of programs to channel questions to them.<ref name="reader">{{cite tech report |first1=M. D. |last1=McIlroy |author-link1=Doug McIlroy |year=1987 |url=http://www.cs.dartmouth.edu/~doug/reader.pdf |title=A Research Unix reader: annotated excerpts from the Programmer's Manual, 1971–1986 |series=CSTR |number=139 |institution=Bell Labs}}</ref>

As other Bell Labs departments purchased [[Digital Equipment Corporation|DEC]] PDP-11s, they also chose<ref>{{cite web | url=https://research.swtch.com/bell-labs | title=Research!RSC: Computing History at Bell Labs }}</ref> to run Unix instead of DEC's own operating system. By Version 4 it was widely used within the laboratory and a Unix Support Group was formed, helping the operating system survive by formalizing its distribution.{{sfn|byte198308}}{{r|reader}}

In 1973, Version 4 Unix was rewritten in the [[High-level programming language|higher-level language]] [[C (programming language)|C]], contrary to the general notion at the time that an operating system's complexity and sophistication required it to be written in assembly language.<ref name="Stallings">{{cite book |first=William |last=Stallings |title=Operating Systems: Internals and Design Principles |publisher=Pearson Education |year=2005 |isbn=978-8131703045 |page=91 |edition=5th }}</ref>{{sfn|byte198308}} The C language appeared as part of [[Version 2 Unix|Version 2]]. Thompson and Ritchie were so influential on early Unix that McIlroy estimated that they wrote and debugged about 100,000 lines of code that year, stating that "[their names] may safely be assumed to be attached to almost everything not otherwise attributed".{{r|reader}} Although assembly did not disappear from the man pages until [[Version 8 Unix|Version 8]],{{r|reader}} the migration to C suggested [[Software quality#Portability|portability]] of the software, requiring only a relatively small amount of machine-dependent code to be replaced when porting Unix to other [[computing platform]]s. Version 4 Unix, however, still had considerable PDP-11-dependent code and was not suitable for porting. The first port to another platform was made five years later (1978) for [[Interdata 7/32 and 8/32|Interdata 8/32]].<ref>{{cite web|url=http://www.bell-labs.com/usr/dmr/www/portpap.html |title=Portability of C Programs and the UNIX System |publisher=Bell-labs.com | access-date=2017-11-04}}</ref>

The Unix operating system was first presented formally to the outside world at the 1973 [[Symposium on Operating Systems Principles]], where Ritchie and Thompson delivered a paper.{{sfn|Ritchie|Thompson|1978}} This led to requests for the system, but under a 1956 consent decree in settlement of an antitrust case, the [[Bell System]] (the parent organization of Bell Labs) was forbidden from entering any business other than "common carrier communications services", and was required to license any patents it had upon request. Unix could not, therefore, be turned into a product. Bell Labs instead shipped the system for the cost of media and shipping.{{r|penguin}} Ken Thompson quietly began answering requests by shipping out tapes and disks, each accompanied by{{snd}} according to legend{{snd}} a note signed, "Love, Ken".<ref name="faqs.org">{{cite web |url=http://www.faqs.org/docs/artu/ch02s01.html |title=Origins and History of Unix, 1969–1995 |publisher=Faqs.org |access-date=2010-11-09 |archive-url=https://web.archive.org/web/20101109165942/http://www.faqs.org/docs/artu/ch02s01.html |url-status=dead |archive-date=2010-11-09 }}</ref>

In 1973, AT&T released [[Version 5 Unix]] and licensed it to educational institutions, and licensed 1975's [[Version 6 Unix|Version 6]] to companies for the first time.<ref name="fiedler198310">{{cite news | url=https://archive.org/stream/byte-magazine-1983-10/1983_10_BYTE_08-10_UNIX#page/n133/mode/2up | title=The Unix Tutorial / Part 3: Unix in the Microcomputer Marketplace | work=BYTE | date=October 1983 | access-date=30 January 2015 | author=Fiedler, Ryan | pages=132}}</ref> While commercial users were rare because of the {{US$|20,000|1975}} cost, the latter was the most widely used version into the early 1980s. Anyone could purchase a license, but the terms were very restrictive; licensees only received the source code, on an [[as is|as-is]] basis.{{r|fiedler198310}} The licenses also included the machine-dependent parts of the kernel, written in PDP-11 assembly language. Copies of the ''[[Lions' Commentary on UNIX 6th Edition, with Source Code]]'' circulated widely, which led to considerable use of Unix as an educational example. The first meeting of Unix users took place in New York in 1974, attracting a few dozen people; this would later grow into the [[USENIX]] organization. The importance of the user group stemmed from the fact that Unix was entirely unsupported by AT&T,{{r|penguin}} although from about 1975 it was the standard for building operational systems within the company.{{r|rdbmsinformix20070612}}

Versions of the Unix system were determined by editions of its user manuals;{{r|fiedler198310}} for example, "Fifth Edition UNIX" and "UNIX Version 5" have both been used to designate the same version. The Bell Labs developers did not think in terms of "releases" of the operating system, instead using a model of continuous development, and sometimes distributing tapes with patches (without AT&T lawyers' approval).{{r|penguin}} Development expanded, adding the concept of pipes, which led to the development of a more modular code base, and quicker development cycles. Version 5, and especially Version 6, led to a plethora of different Unix versions both inside and outside Bell Labs, including [[PWB/UNIX]] and the first commercial Unix, [[Interactive Systems Corporation|IS/1]].

Unix still only ran on DEC systems.{{r|fiedler198310}} As more of the operating system was rewritten in C (and the C language extended to accommodate this), portability also increased; in 1977, Bell Labs procured an [[Interdata 8/32]] with the aim of porting Unix to a computer that was as different from the PDP-11 as possible, making the operating system more machine-independent in the process. Unix next ran as a [[hardware virtualization|guest operating system]] inside a [[VM/370]] hypervisor at [[Princeton University|Princeton]]. Simultaneously, a group at the [[University of Wollongong]] [[Wollongong Unix|ported Unix]] to the similar [[Interdata 7/32]].<ref name="johnsonport"/> Target machines of further Bell Labs ports for research and AT&T-internal use included an [[Intel 8086]]-based computer (with custom-built [[Memory management unit|MMU]]) and the [[UNIVAC 1100]].<ref>{{Cite journal| doi = 10.1002/j.1538-7305.1984.tb00064.x| title = UNIX Operating System Porting Experiences| journal = AT&T Bell Laboratories Technical Journal| volume = 63| issue = 8| pages = 1769–90| year = 1984| last1 = Bodenstab | first1 = D. E.| last2 = Houghton | first2 = T. F.| last3 = Kelleman | first3 = K. A.| last4 = Ronkin | first4 = G.| last5 = Schan | first5 = E. P.| s2cid = 35326182}}</ref>{{sfn|byte198308}}

In May 1975, [[DARPA|ARPA]] documented the benefits of the Unix time-sharing system which "presents several interesting capabilities" as an [[ARPANET|ARPA network]] mini-host in [[#ARPANET|RFC 681]].

In 1978, [[UNIX/32V]] was released for [[Digital Equipment Corporation|DEC]]'s then new [[VAX]] system. By this time, over 600 machines were running Unix in some form. [[Version 7 Unix]], the last version of [[Research Unix]] to be released widely, was released in 1979. In Version 7, the number of [[system call]]s was only around 50, although later Unix and Unix-like systems would add many more:<ref>{{cite book |first1=W. Richard |last1=Stevens |author-link=W. Richard Stevens |last2=Rago |first2=Stephen A. |title=Advanced Programming in the UNIX Environment |publisher=Addison-Wesley |year=2013 |isbn=978-0321638007 |page=21 |chapter=1.11 System Calls and Library Functions |chapter-url=https://books.google.com/books?id=kCTMFpEcIOwC&pg=PA21 |edition=3rd}}</ref>

{{blockquote|Version 7 of the Research UNIX System provided about 50 system calls, [[4.4BSD]] provided about 110, and [[SVR4]] had around 120. The exact number of system calls varies depending on the operating system version. More recent systems have seen incredible growth in the number of supported system calls. [[Linux]] 3.2.0 has 380 system calls and [[FreeBSD]] 8.0 has over 450.}}

A microprocessor port of Unix, to the [[LSI-11]], was completed in 1978,<ref>{{Cite journal | doi = 10.1002/j.1538-7305.1978.tb02143.x| title = UNIX Time-Sharing System: UNIX on a Microprocessor| journal = Bell System Technical Journal| volume = 57| issue = 6| pages = 2087–2101| year = 1978| last1 = Lycklama | first1 = Heinz| s2cid = 39236801}}</ref> and an [[Intel 8086]] version was reported to be "in progress" the same year.<ref name="johnsonport">{{cite journal |title=Portability of C Programs and the UNIX System |first1=Stephen C. |last1=Johnson |author-link1=Stephen C. Johnson |first2=Dennis M. |last2=Ritchie |author-link2=Dennis Ritchie |journal=Bell System Technical Journal |volume=57 |issue=6 |year=1978 |pages=2021–48 |doi=10.1002/j.1538-7305.1978.tb02141.x|s2cid=17510065 }}</ref> The first microcomputer versions of Unix, and [[Unix-like]] operating systems like [[Whitesmiths]]' [[Idris (operating system)|Idris]], appeared in the late 1970s.{{r|fiedler198310}}

== 1980s ==
[[File:adm3aimage.jpg|thumb|LSI [[ADM-3A]] terminal, physical interface for BSD [[Unix]] ]]

[[File:DEC VT100 terminal.jpg|thumb|The [[Digital Equipment Corporation|DEC]] [[VT100]] terminal, widely used for [[Unix]] [[timesharing]] ]]

[[File:Usenix84 1.jpg|thumb|[[USENIX]] 1984 Summer speakers. USENIX was founded in 1975, focusing primarily on the study and development of Unix and similar systems.]]
[[File:X-Window-System.png|thumb|The [[X Window System]] with [[twm]] and a number of core X applications]]

Bell developed multiple versions of Unix for internal use, such as [[CB UNIX]] (with improved support for databases) and [[PWB/UNIX]], the "Programmer's Workbench", aimed at large groups of programmers. It advertised the latter version, as well as 32V and V7, stating that "more than 800 systems are already in use outside the Bell System" in 1980,<ref>{{cite news |title=(Advertisement) |author=Bell System Software |newspaper=Australian Unix Users Group Newsletter |page=8 |volume=2 |issue=4 |date=April 1980 |url=http://www.tuhs.org/Archive/Documentation/AUUGN/AUUGN-V02.4.pdf}}</ref> and "more than 2000" the following year.<ref>{{cite web|title=Unix Advertising |first=Dennis M. |last=Ritchie |url=http://cm.bell-labs.com/cm/cs/who/dmr/unixad.html |archive-url=https://archive.today/20130102004255/http://cm.bell-labs.com/cm/cs/who/dmr/unixad.html |url-status=dead |archive-date=2 January 2013 |access-date=17 February 2014 |website=former Bell Labs Computing and Mathematical Sciences Research }}</ref> [[Research Unix]] versions [[Version 8 Unix|8]] (1985<ref>{{cite web | title=V8 | website=The Unix Heritage Society | date=1 August 1985 | url=https://www.tuhs.org/cgi-bin/utree.pl?file=V8 | access-date=27 April 2024}}</ref><ref name="what_is_unix"/>), [[Version 9 Unix|9]] (1986<ref>{{cite web | title=V9 | website=The Unix Heritage Society | date=12 May 1989 | url=https://www.tuhs.org/cgi-bin/utree.pl?file=V9 | access-date=27 April 2024}}</ref><ref name="what_is_unix"/>), and [[Version 10 Unix|10]] (1989<ref name=tenthed>{{cite web | url=https://9p.io/10thEdMan/ | archive-url=https://web.archive.org/web/20210513190803/https://9p.io/10thEdMan/ | archive-date=13 May 2021 | title=Unix Tenth Edition Manual }}</ref><ref>{{cite web | title=V10 | website=The Unix Heritage Society | date=18 September 1984 | url=https://www.tuhs.org/cgi-bin/utree.pl?file=V10 | access-date=27 April 2024}}</ref><ref name="what_is_unix">
*[https://www.theregister.com/2024/02/16/what_is_unix/ What is Unix?] theregister.com 16 February 2024</ref><ref>{{cite web |last=Chirgwin |first=Richard |date=30 March 2017 |title=Samizdat no more: Old Unix source code opened for study |url=https://www.theregister.com/2017/03/30/old_unix_source_code_opened_for_study/ |access-date=27 April 2024 |website=The Register}}</ref>) were developed through the 1980s but were only released to a few universities, though they did generate papers<ref>* M. [[Douglas McIlroy]] ''A Research UNIX Reader: Annotated Excerpts from the Programmer’s Manual, 1971-1986''
* [https://www.cs.dartmouth.edu/~doug/reader.pdf A Research UNIX Reader: Annotated Excerpts from the Programmer’s Manual] cs.dartmouth.edu
* [[iarchive:a research unix reader|A research Unix reader]] archive.org
</ref> describing the new work.{{citation needed|date=February 2024}}

* "Many of the (Version 10 Unix) medium-size tool programs (and their documentation) survived into the Plan 9 system, and are described in its programmer's manual and its own collection of papers."
* "Even so, the lesser-known editions within AT&T's Unix System Laboratories were the Eighth Edition in 1985, the Ninth Edition in 1986, and in 1989 the Tenth Edition".<ref name="tenthed" /><ref>* [https://web.archive.org/web/*/http://9p.io/7thEdMan/ 7th Edition]
* [https://web.archive.org/web/*/https://9p.io/cm/* Bell Labs]
</ref>

This research focus then shifted to the development of [[Plan 9 from Bell Labs|Plan 9]], a new portable distributed operating system, and later of [[Inferno (operating system)|Inferno]].

Microcomputer Unix became commercially available in 1980, when [[Onyx Systems]] released its [[Zilog Z8000]]-based C8002{{r|fiedler198310}} and [[Microsoft]] announced its first Unix for [[16-bit]] microcomputers called [[Xenix]], which the [[Santa Cruz Operation]] (SCO) ported to the 8086 processor in 1983. Other companies began to offer commercial versions of Unix for their own minicomputers and [[workstations]]. Many of these new Unix flavors were developed from the System V base under a license from AT&T; others were based on BSD. One of the leading developers of BSD, [[Bill Joy]], went on to co-found [[Sun Microsystems]] in 1982 and created [[SunOS]] for its workstations.

Because AT&T widely and inexpensively licensed Unix,<ref name="morgan198201">{{cite news | url=https://archive.org/stream/byte-magazine-1982-01/1982_01_BYTE_07-01_The_IBM_Personal_Computer#page/n7/mode/2up | title=Of IBM, Operating Systems, and Rosetta Stones | work=BYTE | date=January 1982 | access-date=19 October 2013 | author=Morgan, Chris | page=6}}</ref><ref name="rdbmsearlyyearsoh20070612">{{Cite interview |interviewer=Burton Grad |title=RDBMS Plenary 1: Early Years |url=https://archive.computerhistory.org/resources/access/text/2013/05/102702562-05-01-acc.pdf |pages=30-31 |access-date=2025-05-30 |publisher=Computer History Museum |date=2007-06-12}}</ref> by the early 1980s thousands of people used Unix at the company and elsewhere, and as computer science students moved from universities into companies they wanted to continue to use it. Observers began to see Unix as a potential universal operating system, suitable for all computers. Less than 20,000 lines of code{{snd}} almost all in C{{snd}} composed the Unix kernel as of 1983, and more than 75% was not machine-dependent. By that year Unix or a Unix-like system was available for at least 16 different processors and architectures from about 60 vendors; ''[[Byte (magazine)|BYTE]]'' noted that computer companies "may support other [operating] systems, but a Unix implementation always happens to be available".{{sfn|byte198308}}{{r|fiedler198310}}<ref name="tilson198310">{{cite news | url=https://archive.org/stream/byte-magazine-1983-10/1983_10_BYTE_08-10_UNIX#page/n267/mode/2up | title=Moving Unix to New Machines | work=BYTE | date=October 1983 | access-date=31 January 2015 | author=Tilson, Michael | pages=266}}</ref> The [[Ingres database]] was an example of software that benefited from running on Unix compared to [[IBM System R]], which did not.{{r|rdbmsearlyyearsoh20070612}}

DEC and IBM were examples of companies that supported Unix.{{r|hinnant198408}} Although DEC<ref name="rdbmsfinancing20070612">{{Cite interview |interviewer=Luanne Johnson |title=RDBMS Workshop: Financing |url=https://archive.computerhistory.org/resources/access/text/2013/05/102702564-05-01-acc.pdf |access-date=2025-05-30 |publisher=Computer History Museum |date=2007-06-12}}</ref> and IBM{{r|sullivan19850520}} were both reluctant to offer alternative to their proprietary operating systems, by the mid-1980s they and most other computer companies did so. An industry analyst said that [[Prime Computer]] released [[Primix]], for example, to prevent customers from leaving for lack of Unix support.<ref name="desmond19850520">{{Cite magazine |last=Desmond |first=John |date=1985-05-20 |title=Prime adds Unix environment for 50 series users |url=https://books.google.com/books?id=ygHfUXZWXlcC&pg=PA7#v=onepage&q&f=true |access-date=2025-06-07 |magazine=Computerworld |page=7 |volume=XIX |issue=20}}</ref>

AT&T announced [[UNIX System III]]{{snd}} based on Version 7, and PWB{{snd}} in 1981. Licensees could sell binary sublicenses for as little as {{US$|100|1981}}, which observers believed indicated that AT&T now viewed Unix as a commercial product.{{r|fiedler198310}} This also included support for the VAX. AT&T continued to issue licenses for older Unix versions. To end the confusion between all its differing internal versions, AT&T combined them into [[UNIX System V]] Release 1. This introduced a few features such as the [[Vi (text editor)|vi]] editor and [[curses (programming library)|curses]] from the [[Berkeley Software Distribution]] of Unix developed at the [[University of California, Berkeley]] [[Computer Systems Research Group]]. This also included support for the [[Western Electric]] [[3B series computers]]. AT&T provided support for System III and System V through the Unix Support Group (USG), and these systems were sometimes referred to as USG Unix.{{citation needed|date=October 2011}}

In 1983, the U.S. Department of Justice settled its second antitrust case against AT&T, causing the [[breakup of the Bell System]]. This relieved AT&T of the 1956 consent decree that had prevented the company from commercializing Unix. AT&T promptly introduced Unix System V into the market. The newly created competition nearly destroyed the long-term viability of Unix, because it stifled the free exchanging of source code and led to fragmentation and incompatibility.<ref name="faqs.org"/> The [[GNU Project]] was founded in the same year by [[Richard Stallman]].

Since the newer commercial UNIX licensing terms were not as favorable for academic use as the older versions of Unix, the Berkeley researchers continued to develop BSD as an alternative to UNIX System III and V. Many contributions to Unix first appeared in BSD releases, notably the [[C shell]] with [[job control (Unix)|job control]] (modelled on [[Incompatible Timesharing System|ITS]]). Perhaps the most important aspect of the BSD development effort was the addition of [[Internet protocol suite|TCP/IP]] [[Computer network|network]] code to the mainstream Unix [[Kernel (operating system)|kernel]]. The BSD effort produced several significant releases that contained network code: 4.1cBSD, 4.2BSD, 4.3BSD, 4.3BSD-Tahoe ("Tahoe" being the nickname of the [[Computer Consoles Inc.]] Power 6/32 architecture that was the first non-DEC release of the BSD kernel), Net/1, 4.3BSD-Reno (to match the "Tahoe" naming, and that the release was something of a gamble), Net/2, 4.4BSD, and 4.4BSD-lite. The network code found in these releases is the ancestor of much TCP/IP network code in use today, including code that was later released in AT&T System V UNIX and early versions of [[Microsoft Windows]]. The accompanying [[Berkeley sockets]] [[API]] is a de facto standard for networking APIs and has been copied on many platforms.

During this period, many observers expected that UNIX, with its portability, rich capabilities, and support from companies like DEC and IBM, was likely to become an industry-standard operating system for microcomputers.{{r|hinnant198408}}<ref>{{cite episode | title = UNIX | url = https://archive.org/details/UNIX1985 | series = The Computer Chronicles | series-link = Computer Chronicles | airdate = 1985 }}</ref> Industry analyst Jean Yates said that IBM lacked enthusiasm for Unix, however, and AT&T was the only company that could afford the "multimillion-dollar investment" necessary to help create software. Unix's lack of a [[killer app]] like [[VisiCalc]] or [[Lotus 1-2-3]] prevented widespread adoption of the operating system on corporate desktops, she said.<ref name="sullivan19850520">{{Cite magazine |last=Sullivan |first=Kathleen |date=1985-05-20 |title=Unix needs push to win in corporate micro market |url=https://books.google.com/books?id=ygHfUXZWXlcC&pg=PA42#v=onepage&q&f=true |access-date=2025-06-07 |magazine=Computerworld |page=42 |volume=XIX |issue=20}}</ref> Citing its much smaller software library and installed base than that of [[MS-DOS]] and the [[IBM Personal Computer|IBM PC]], others expected that customers would prefer personal computers on [[local area network]]s to Unix multiuser systems.<ref name="howitt19841210">{{cite news | url=https://books.google.com/books?id=si4EAAAAMBAJ&pg=PA29 | title=Unix and the Single User | work=InfoWorld | date=1984-12-10 | access-date=7 February 2015 | author=Howitt, Doran | pages=28}}</ref> Microsoft planned to make Xenix MS-DOS's multiuser successor;{{r|fiedler198310}} by 1983 a Xenix-based [[Altos 586]] with 512 KB RAM and 10 MB hard drive cost {{US$|8,000|1983}}.<ref name="yates198310">{{cite news | url=https://archive.org/stream/byte-magazine-1983-10/1983_10_BYTE_08-10_UNIX#page/n161/mode/2up | title=Unix and the Standardization of Small Computer Systems | work=BYTE | date=October 1983 | access-date=30 January 2015 | author=Yates, Jean L. | pages=160–166}}</ref> ''BYTE'' reported that the Altos "under moderate load approaches DEC VAX performance for most tasks that a user would normally invoke", while other computers from Sun and [[MASSCOMP]] were much more expensive but equaled the VAX. The magazine added that both [[PC/IX]] and [[Venix]] on the IBM PC outperformed Venix on the PDP-11/23.<ref name="hinnant198408">{{cite news | url=https://archive.org/stream/byte-magazine-1984-08/1984_08_BYTE_09-08_Modula-2#page/n137/mode/2up | title=Benchmarking UNIX Systems | work=BYTE | date=Aug 1984 | access-date=23 February 2016 | author=Hinnant, David F. | pages=132–135, 400–409}}</ref> [[uNETix]], a commercial microcomputer Unix, implemented the first Unix color windowing system.{{citation needed|date=April 2015}}

Thompson and Ritchie were given the [[Turing Award]] in 1983 for their work on Unix.

''[[UnixWorld]]'' in November 1985 reported that "the supermicro has yet to live up to its expectations; in fact, the market now seems hopelessly stalled". Unix vendors like [[Fortune Systems]], [[Convergent Technologies]], and [[Tandy Corporation]] had not been as successful as expected because of high prices, lack of distribution channels, difficulty in ongoing support, and competition from PC LANs and traditional minicomputers like [[IBM System/36]] or DEC [[MicroVAX II]].<ref name="serlin198511">{{Cite magazine |last=Serlin |first=Omri |date=November 1985 |title=Whatever Happened to the Supermicro Market? |url=https://archive.org/details/Unix_World_Vol02_10.pdf/page/n17/mode/1up?view=theater |access-date=2025-05-17 |magazine=Unix World |pages=16-19}}</ref> Ingres ported the database from Unix to DEC's [[VMS (operating system)|VMS]] for commercial viability. Demand for the VMS version was at first so much greater that the company neglected the original.<ref name="rdbmsingressybase20070613">{{Cite interview |interviewer=Doug Jerger |title=RDBMS Workshop: Ingres and Sybase |url=https://archive.computerhistory.org/resources/access/text/2013/05/102702565-05-01-acc.pdf |access-date=2025-05-30 |publisher=Computer History Museum |date=2007-06-13}}</ref> The beginning in 1984 of the annual [[Unix Expo]] trade show in New York reflected the growing commercial presence of Unix,<ref>{{cite news | url=https://books.google.com/books?id=dTAEAAAAMBAJ&pg=PA41 | title=Hopes of Reunification Highlight Eventful Year for Unix Community | first=Martin | last=Marshall | newspaper=InfoWorld | date=18 December 1989 | page=41}}</ref> although [[Roger Sippl]] said that the first UniForum was "80 percent [[Birkenstock]] attendees".{{r|rdbmsfinancing20070612}} [[Microsoft]]'s [[Bill Gates]] wrote in the same ''UnixWorld'' issue that that Unix installed base was still too small, citing the lack of [[binary compatibility]] unlike MS-DOS as a reason, although he thought that Xenix could achieve 400,000 installations in the next 18 months.<ref name="gates198511">{{Cite magazine |last=Gates |first=Bill |date=November 1985 |title=The Future of Xenix |url=https://archive.org/details/Unix_World_Vol02_10.pdf/page/n21/mode/1up?view=theater |access-date=2025-05-17 |magazine=[[UnixWorld]] |pages=20-37}}</ref> (When Ingres ported its software back to Unix it had to support more than 40 variants of the operating system.{{r|rdbmsingressybase20070613}})

In 1986, ''[[Computerworld]]'' wrote that "Until very recently, almost no one associated Unix with corporate data processing. [...] the operating system traveled almost exclusively in academic and technical circles ... But now&nbsp;— almost entirely because of strenuous efforts by AT&T&nbsp;— some people are beginning to perceive Unix as a viable option for large commercial installations". Unix became commercially available for the [[Mainframe computer|mainframe]] via [[Amdahl UTS]] in 1981, and now IBM started offering Unix as IX/370 and [[VM/IX]]. The total installed base of Unix, however, remained small at some 230,000 machines.{{sfn|Kelleher|1986|pp=37,44}}

Despite its academic reputation{{snd}} ''[[InfoWorld]]'' stated in 1989, "Until recently, Unix conjured up visions of long-haired bearded technoids stuck in the bowels of an R&D lab, coding software until the wee hours of the morning"{{snd}} the increasing power of microcomputers in the late 1980s, and in particular the introduction of the [[32-bit]] [[i386|Intel 80386]], caused Unix to "explode" in popularity for business applications; Xenix, [[386/ix]], and other Unix systems for the [[IBM PC compatible|PC-compatible]] market competed with [[OS/2]] in terms of networking, multiuser support, multitasking, and MS-DOS compatibility.<ref>{{cite journal |title=Unix on the desktop: 80386-based Unix multiuser operating systems present an alternative to LANs |journal=[[InfoWorld]] |date=10 July 1989 |url=https://books.google.com/books?id=ijAEAAAAMBAJ&pg=PT68 |author1=Jeff Tye |author2=Lauren Black |author3=Gregory Smith}}</ref> A few years after the first UniForum "ties were outnumbering the sandals", Sippl said.{{r|rdbmsfinancing20070612}}<ref name="rdbmsinformix20070612">{{Cite interview |interviewer=Luanne Johnson |title=RDBMS Workshop: Informix |url=https://archive.computerhistory.org/resources/access/text/2013/05/102702566-05-01-acc.pdf |access-date=2025-05-30 |publisher=Computer History Museum |date=2007-06-12}}</ref>

By the late 1980s the industry recognized that [[RISC]] technology had much better performance per cost than traditional computer architectures. Minicomputer vendors developed their own RISC-based workstations to divert customers migrating from VAX VMS and other legacy systems. Whether from large older companies like DEC, [[Hewlett-Packard]] (HP), [[Data General]], or newer ones like Sun or [[Solbourne]], these systems ran Unix.{{r|marshall19890206}} Small [[value-added reseller]]s customizing Unix systems for customers were vital to the industry's growth.{{r|rdbmsinformix20070612}}{{r|rdbmsfinancing20070612}} During this time a number of vendors including DEC, Sun, and [[Addamax]] began building [[Trusted operating system|trusted versions]] of UNIX for high security applications, mostly designed for military and law enforcement applications.

=== Standardization and the Unix wars ===
{{Main article|Unix wars}}
A problem that plagued Unix in this period was the multitude of implementations, based on either System V, BSD, or what [[Poul-Henning Kamp]] later described as a "more or less competently executed" combination of the two,<ref>{{cite journal |first=Poul-Henning |last=Kamp |author-link=Poul-Henning Kamp |title=A Generation Lost in the Bazaar |year=2012 |journal=ACM Queue |volume=10 |issue=8|pages=20–23 |doi=10.1145/2346916.2349257 |s2cid=11656592 |doi-access=free }}</ref> usually with home-grown extensions to the base systems from AT&T or Berkeley.{{sfn|Kelleher|1986|p=38}} Xenix was effectively a third lineage, being based on the earlier System III.{{r|security}} The rivalry between vendors was called the [[Unix wars]]; customers soon demanded standardization<ref name="security">{{cite book |title=Practical UNIX and Internet Security |first1=Simson |last1=Garfinkel |first2=Gene |last2=Spafford |author2-link=Gene Spafford |first3=Alan |last3=Schwartz |publisher=O'Reilly |year=2003 |pages=15–17 |chapter-url=https://books.google.com/books?id=50maN7VmpusC&pg=PT47 |chapter=2 Unix History and Lineage |isbn=978-1449310127}}</ref> as did vendors such as [[Informix Corporation]], which by the late 1980s had more than 1000 SKUs of its products to serve variants.{{r|rdbmsinformix20070612}}

AT&T responded by issuing a standard, the [[System V Interface Definition]] (SVID, 1985), and required conformance for operating systems to be branded "System V".
In 1984, several European computer vendors established the [[X/Open]] consortium with the goal of creating an open system specification based on Unix (and eventually the SVID).<ref>{{cite book |title=Life With UNIX: A Guide For Everyone |first1=Don |last1=Libes |first2=Sandy |last2=Ressler |first3=Sanford |last3=Ressler |publisher=Prentice Hall |year=1989 |page=74 |isbn=978-0-13-536657-8}}</ref>
Yet another standardization effort was the [[IEEE]]'s [[POSIX]] specification (1988), designed as a compromise [[API]] readily implemented on both BSD and System V platforms. In 1993, POSIX was mandated by the [[United States government]] for many of its own systems.<ref>{{Cite web |date=2014-02-20 |title=FIPS 151-2 – (POSIX), Portable Operating System Interface – [C Language] |url=http://www.itl.nist.gov/fipspubs/fip151-2.htm |access-date=2023-02-18 |archive-url=https://web.archive.org/web/20140220130516/http://www.itl.nist.gov/fipspubs/fip151-2.htm |archive-date=20 February 2014 }}</ref>

In the spring of 1988, AT&T took the standardization a step further. First, it collaborated with SCO to merge System V and Xenix into System V/386.{{r|security}} Next, it sought collaboration with Sun Microsystems (vendor of the 4.2BSD derivative SunOS and its [[Network File System]]) to merge System V, BSD/SunOS and Xenix into a single unified Unix, which would become [[System V Release 4]]. AT&T and Sun, as [[Unix International|UNIX International]] (UI), acted independently of X/Open and drew ire from other vendors, which started the [[Open Software Foundation]] to work on their own unified Unix, [[OSF/1]], ushering in a new phase of the Unix wars.{{r|security}}

== 1990s ==
[[File:Unix Workstation Collection.jpeg|thumb|Unix [[workstation]]s of the 1990s, including those made by [[Digital Equipment Corporation|DEC]], [[Hewlett-Packard|HP]], [[Silicon Graphics|SGI]], and [[Sun Microsystems|Sun]] ]]
[[File:CDE 2012 on Linux.png|thumb|The [[Common Desktop Environment]] (CDE) was widely used on [[Unix]] [[workstation]]s.]]

An industry analyst said in 1989 that despite OSF and UI's fierce rivalry, "Two Unixes are a lot better than 225 — which is what we have had until now".<ref name="marshall19890206">{{Cite magazine |last=Marshall |first=Martin |date=1989-02-06 |title=The Year of the Workstation |url=https://books.google.com/books?id=OzoEAAAAMBAJ&pg=PT42#v=onepage |access-date=2025-06-27 |magazine=InfoWorld |pages=43-44 |volume=11 |issue=6}}</ref> The Unix wars continued into the 1990s, but turned out to be less of a threat than originally thought: AT&T and Sun went their own ways after System V.4, while OSF/1's schedule slipped behind.{{r|security}} 
By 1993, most commercial vendors changed their variants of Unix to be based on [[UNIX System V|System V]] with many BSD features added. The creation of the [[Common Open Software Environment]] (COSE) initiative that year, by the major players in Unix, marked the end of the most notorious phase of the Unix wars, and was followed by the merger of UI and OSF in 1994. The new combined entity retained the OSF name and stopped work on OSF/1. By that time the only vendor using it was [[Digital Equipment Corporation]], which continued its own development, rebranding their product [[Tru64 UNIX|Digital UNIX]] in early 1995.
POSIX became the unifying standard for Unix systems (and some other operating systems).{{r|security}}

Meanwhile, the BSD world saw its own developments. The group at Berkeley moved its operating system toward POSIX compliance and released a stripped-down version of its networking code, supposedly without any code that was the property of AT&T. In 1991, a group of BSD developers (Donn Seeley, Mike Karels, [[William Jolitz|Bill Jolitz]], and Trent Hein) left the University of California to found [[Berkeley Software Design|Berkeley Software Design, Inc.]] (BSDi), which sold a fully functional commercial version of BSD Unix for the Intel platform, which they advertised as free of AT&T code. They ran into legal trouble when AT&T's Unix subsidiary [[UNIX System Laboratories, Inc. v. Berkeley Software Design, Inc.|sued BSDi]] for copyright infringement and various other charges in relation to BSD; subsequently, the University of California countersued.<ref name="kirk">{{cite encyclopedia |editor1-first=Chris |editor1-last=DiBona |editor2-first=Sam |editor2-last=Ockman |editor3-first=Mark |editor3-last=Stone |encyclopedia=Open Sources: Voices from the Revolution |publisher=O'Reilly |year=1999 |isbn=978-1-56592-582-3 |first=Marshall Kirk |last=McKusick |author-link=Marshall Kirk McKusick |url=https://archive.org/details/isbn_9781565925823 |title=Twenty Years of Berkeley Unix – From AT&T-Owned to Freely Redistributable |url-access=registration }}</ref>
Shortly after it was founded, Bill Jolitz left BSDi to pursue distribution of [[386BSD]], the free software ancestor of [[FreeBSD]], [[OpenBSD]], and [[NetBSD]].

In 1991, USL and [[Novell]] teamed up to develop a version of System 4 for i386 and i486 computers that would combine TCP/IP and Novell's IPX/SPX networking protocols, called the Destiny Project. They formed the Univel subsidiary as a jointly owned company to develop, market, and support the product, which was given the official name [[UnixWare]] (aka SVR4.2) and was sold as Univel UnixWare 1.0 that same year. Shortly after Univel released UnixWare 1.0 produced, AT&T sold USL and its share of Univel to [[Novell]] meaning Novell now owned all of AT&T's rights to Unix. Dennis Ritchie likened this sale to the Biblical story of [[Esau]] selling his birthright for the [[mess of pottage]].<ref>{{cite web|url=https://groups.google.com/group/comp.unix.questions/browse_frm/thread/2f0b5e719fa3a3ec/3fa5e5fe4d58f96b |title=comp.unix.questions &#124; Google Groups |access-date=2010-11-09}}</ref> Novell tried to use the fact that UnixWare combined both TCP/IP and NetWare networking technologies as a marketing tool against [[Windows NT]], but their core markets suffered considerably. It also quickly settled the court battles with BSDi and Berkeley.{{r|kirk}}

In 1993, Novell decided to transfer the UNIX [[trademark]] and certification rights to the [[X/Open]] Consortium.<ref name="autogenerated2">{{cite web|author=Chuck Karish |url=https://groups.google.com/group/comp.std.unix/msg/c9974cf0022884f8 |title=The name UNIX is now the property of X/Open – comp.std.unix &#124; Google Groups |access-date=2010-11-09}}</ref> In 1996, X/Open merged with [[Open Software Foundation|OSF]], creating the [[The Open Group|Open Group]]. Various standards by the Open Group now define what is and what is not a UNIX operating system, notably the post-1998 [[Single UNIX Specification]].

In 1993, Unix was used as a minor plot element in the blockbuster film ''[[Jurassic Park (film)|Jurassic Park]]''.<ref>[https://lwn.net/Articles/881431/ Brian Kernighan on the origins of Unix] LWN.net. 2022.</ref>

In 1995, the business of administering and supporting the existing UNIX licenses, plus rights to further develop the System V code base, were sold by Novell to the Santa Cruz Operation.<ref name="autogenerated1">{{cite web|url=http://www.novell.com/news/press/archive/1995/09/pr95220.html |title=HP, Novell and SCO To Deliver High-Volume UNIX OS With Advanced Network And Enterprise Services |publisher=Novell.com |date=20 September 1995 |access-date=2010-11-09}}</ref> Whether Novell also sold the copyrights would later become the subject of litigation (see below).

With the legal troubles between AT&T/Novell and the University of California over, the latter did two more releases of BSD before disbanding its Computer Systems Research Group in 1995. The BSD code lived on, however, in its free derivatives and in what Garfinkel ''et al.'' call a second generation of commercial Unix systems, based on BSD. The first exponent of these was BSDi's offering, popular at [[internet service provider]]s but eventually not successful enough to sustain the company.{{sfn|Garfinkel|Spafford|Schwartz|2003|p=22}} The other main exponent would be [[Apple Inc.|Apple Computer]].

In 1997, Apple sought a new foundation for its Macintosh operating system and chose [[NeXTSTEP]], an operating system developed by [[NeXT]]. The core operating system, which was based on [[Berkeley Software Distribution|BSD]] and the [[Mach (kernel)|Mach kernel]], was renamed [[Darwin (operating system)|Darwin]] after Apple acquired it. The deployment of Darwin in [[macOS|Mac OS X]] makes it, according to a statement made by an Apple employee at a [[USENIX]] conference, the most widely used Unix-based system in the [[desktop computer]] market.{{Citation needed|date=March 2014}}

[[File:Operating systems used on top 500 supercomputers.svg|thumb|In supercomputer list [[Top500]] Linux eclipsed Unix 1998–2017]]
Meanwhile, Unix got competition from the copyleft [[Linux]] kernel, a reimplementation of Unix from scratch, using parts of the [[GNU]] project that had been underway since the mid-1980s. Work on Linux began in 1991 by [[Linus Torvalds]]; in 1998, a [[Halloween documents|confidential memo]] at Microsoft stated, "Linux is on track to eventually own the x86 UNIX market," and further predicted, "I believe that Linux&nbsp;– moreso than NT&nbsp;– will be the biggest threat to SCO in the near future."<ref>{{cite web|url=http://www.catb.org/~esr/halloween/halloween1.html|title=Open Source Software: A (New?) Development Methodology|author=Vinod Valloppillil|date=11 August 1998|access-date=3 February 2014}}</ref>

== 2000s ==
{{History of computing}}
In 2000, [[Santa Cruz Operation|SCO]] sold its entire UNIX business and assets to [[Caldera Systems]], which later changed its name to [[SCO Group|The SCO Group]].

The bursting of the [[dot-com bubble]] (2001–03) led to significant consolidation of versions of Unix. Of the many commercial variants of Unix that were born in the 1980s, only [[Solaris (operating system)|Solaris]], [[HP-UX]], and [[IBM AIX|AIX]] were still doing relatively well in the market, though SGI's [[IRIX]] persisted for quite some time. Of these, Solaris had the largest market share in 2005.<ref>{{cite web | url = http://news.zdnet.com/2100-9584_22-5984747.html | title = Itanium: A cautionary tale | access-date = 2006-10-04|author = Stephen |date = 7 December 2005 | work = Tech News | publisher = ZDNet | quote = In the third quarter of this year, 7,845 Itanium servers were sold, according to research by Gartner. That compares with 62,776 machines with Sun Microsystems' UltraSparc, 31,648 with IBM's Power, and 9,147 with HP's PA-RISC. |archive-url = https://web.archive.org/web/20060923185730/http://news.zdnet.com/2100-9584_22-5984747.html <!-- Bot retrieved archive --> |archive-date = 23 September 2006}}</ref>

In 2003, the SCO Group started legal action against various users and vendors of Linux. SCO had alleged that Linux contained copyrighted Unix code now owned by the SCO Group. Other allegations included trade-secret violations by [[IBM]], or contract violations by former Santa Cruz customers who had since converted to Linux. However, Novell disputed the SCO Group's claim to hold copyright on the UNIX source base. According to Novell, SCO (and hence the SCO Group) are effectively franchise operators for Novell, which also retained the core copyrights, veto rights over future licensing activities of SCO, and 95% of the licensing revenue. The SCO Group disagreed with this, and the dispute resulted in the ''[[SCO Group, Inc. v. Novell, Inc.|SCO v. Novell]]'' lawsuit.  On 10 August 2007, a major portion of the case was decided in Novell's favor (that Novell had the copyright to UNIX, and that the SCO Group had improperly kept money that was due to Novell). The court also ruled that "SCO is obligated to recognize Novell's waiver of SCO's claims against IBM and Sequent". After the ruling, Novell announced they have no interest in suing people over Unix and stated, "We don't believe there is Unix in Linux".<ref>{{cite web|url=http://www.groklaw.net/staticpages/index.php?page=20070810205256644 |title=Memorandum and Decision Order in SCO v. Novell |publisher=Groklaw.net |access-date=2010-11-09}}</ref><ref name="doc377">{{cite web |url=http://sco.tuxrocks.com/Docs/Novell/Novell-377.pdf |title=Tuxrocks.com |access-date=2012-01-06 |archive-date=24 June 2009 |archive-url=https://web.archive.org/web/20090624114128/http://sco.tuxrocks.com/Docs/Novell/Novell-377.pdf |url-status=dead }}</ref><ref>[http://www.pcworld.com/article/id,135959-c,unix/article.html Novell Won't Pursue Unix Copyrights] {{Webarchive|url=https://web.archive.org/web/20080409092650/http://www.pcworld.com/article/id,135959-c,unix/article.html |date=9 April 2008 }} 15 August 2007</ref> SCO successfully got the 10th Circuit Court of Appeals to partially overturn this decision on 24 August 2009 which sent the lawsuit back to the courts for a jury trial.<ref>{{cite web |title=Appeal Ruling: 08-4217: The SCO Group v. Novell |date=24 August 2009 |publisher=United States Court of Appeals, Tenth Circuit |id=01018260169 |url=http://www.groklaw.net/pdf/AppealRuling.pdf}}</ref><ref>[http://www.novell.com/prblogs/?p=1134 Novell.com] 24 August 2009</ref><ref>{{cite magazine |first=David |last=Kravets |title=It's Baaaack … Appeals Court Resurrects SCO Lawsuit |magazine=Wired |date=24 August 2009 |url=https://www.wired.com/threatlevel/2009/08/sco/ }}</ref>

On 30 March 2010, following a jury trial, Novell, and not The SCO Group, was "unanimously [found]" to be the owner of the UNIX and UnixWare copyrights.<ref name=glNovell-846>{{cite web|url=http://www.groklaw.net/pdf2/Novell-846.pdf |url-status=dead |archive-url=https://web.archive.org/web/20100808165723/http://www.groklaw.net/pdf2/Novell-846.pdf |archive-date=2010-08-08 |title=03/30/2010&nbsp;– 846&nbsp;– JURY VERDICT for Defendant Novell. (slm) (Entered: 03/30/2010) |access-date=2024-11-12}}{{cbignore}}</ref> The SCO Group, through bankruptcy trustee Edward Cahn, decided to continue the lawsuit against IBM for causing a decline in SCO revenues.<ref name=sltrib14786202>{{cite news |first=Tom |last=Harvey |title=Decision in SCO-Novell case ripples beyond Utah |url=http://archive.sltrib.com/story.php?ref=/news/ci_14786202 |newspaper=The Salt Lake Tribune |date=30 March 2010 }}</ref> On 1 March 2016, SCO's lawsuit against IBM was dismissed with prejudice.

{{See also|SCO-Linux controversies}}

In 2005, [[Sun Microsystems]] released the bulk of its Solaris system code (based on [[UNIX System V]] Release 4) into an [[Open-source software|open source]] project called [[OpenSolaris]]. New [[SunOS]] technologies, notably the [[ZFS]] file system, were first released as open source code via the OpenSolaris project. Soon afterwards, OpenSolaris spawned several non-Sun distributions. In 2010, after Oracle acquired Sun, OpenSolaris was officially discontinued, but the development of derivatives continued.

Since the early 2000s, [[Linux]] is the leading Unix-like operating system and [[macOS]] leads for all Unix variants, with all other Unix variants having only a negligible market share (see [[Usage share of operating systems]]).

== See also ==
* [[Comparison of operating systems]]
* [[The Unix Heritage Society]]
* [[History of the Berkeley Software Distribution]]
* [[List of Unix systems]]
* [[Timeline of operating systems]]
* [[Plan 9 from Bell Labs]]

== References ==
===Citations===
{{reflist}}

===Bibliography===
* {{cite magazine
 |first=Daniel |last=Cooke
 |title=Unix and Beyond: an Interview with Ken Thompson
 |magazine=IEEE Computer
 |volume=32 |issue=5
 |date=May 1999
 |pages=58–64
 |doi=10.1109/MC.1999.762801
 |url=http://cse.unl.edu/~witty/class/csce351/howto/ken_thompson.pdf
}}
* {{cite news |newspaper=Computerworld |title=Corporate Unix: A system struggles to earn its stripes |date=3 February 1986 |first=Joanne |last=Kelleher |url=https://books.google.com/books?id=UE1HODexHKoC&pg=PA37}}
* {{cite tech report
 |first=Dennis |last=Ritchie
 |title=The Evolution of the Unix Time-sharing System
 |url=https://www.bell-labs.com/usr/dmr/www/hist.pdf
 |date=September 1979
}}
* {{cite journal
 |first1=Dennis |last1=Ritchie
 |first2= Ken |last2= Thompson
 |title=The UNIX Time-Sharing System
 |journal=Bell System Technical Journal
 |volume=57 |number=6
 |date= July–August 1978
 |pages=1905–1929
 |doi=10.1002/j.1538-7305.1978.tb02136.x
 |url=https://archive.org/details/bstj57-6-1905/mode/2up
}}
* {{cite web
 |url=http://www.bell-labs.com/history/unix/pdp7.html 
 |title=The Creation of the UNIX* Operating System: The famous PDP-7 comes to the rescue 
 |publisher=Bell-labs.com 
 |archive-url=https://web.archive.org/web/20140402194704/http://www.bell-labs.com/history/unix/pdp7.html 
 |archive-date=2014-04-02 
 |access-date=2015-04-20 
 |url-status=dead
}}
* {{cite magazine
 | title=The History of Unix
 | magazine =BYTE 
 | date=August 1983 
 | access-date=31 January 2015 
 | pages=188
 | url=https://archive.org/stream/byte-magazine-1983-08/1983_08_BYTE_08-08_The_C_Language#page/n189/mode/2up
 |ref=CITEREFbyte198308
}}

== Further reading ==
;Books
*{{cite book |first=Brian W. |last=Kernighan |author-link=Brian W. Kernighan |title=UNIX: A History and a Memoir |publisher=Independently published |year=2019 |isbn=978-1695978553 }}
*{{cite book |first=Peter H. |last=Salus |author-link=Peter H. Salus |title=A Quarter Century of UNIX |publisher=Addison Wesley |year=1994 |isbn=978-0-201-54777-1 }}
;Television
* {{cite episode | title = UNIX | url = https://archive.org/details/UNIX1985 | series = The Computer Chronicles | series-link = Computer Chronicles | airdate = 1985 }}
* {{cite episode | title = Unix | url = https://archive.org/details/unix_2 | series = The Computer Chronicles | airdate = 1989 }}
;Talks
* {{cite interview | author = Ken Thompson | title = VCF East 2019 -- Brian Kernighan interviews Ken Thompson | date = 2019 | url = https://www.youtube.com/watch?v=EY6q5dv_B-o}}
* {{cite AV media | author = Dr Marshall Kirk McKusick | title = History of the Berkeley Software Distributions (three one-hour lectures) | date = 2006 | url = http://www.mckusick.com/history/index.html}}

== External links ==
{{Wiktionary|Unix}}
* [http://www.unix.org The UNIX System], at [[The Open Group]].
* [https://web.archive.org/web/20140402194704/http://www.bell-labs.com/history/unix/pdp7.html The Creation of the UNIX Operating System]
* [https://www.tuhs.org/ The Unix Heritage Society]
** [https://minnie.tuhs.org/cgi-bin/utree.pl The Unix Tree: files from historic releases]
* [http://man.cat-v.org/unix-1st/ The Unix 1st Edition Manuals].
* [http://techchannel.att.com/play-video.cfm/2012/2/22/AT&T-Archives-The-UNIX-System 1982 film about Unix featuring Dennis Ritchie, Ken Thompson, Brian Kernighan, Alfred Aho, and more]
* [https://www.youtube.com/watch?v=EY6q5dv_B-o Video: VCF East 2019 -- Brian Kernighan interviews Ken Thompson]
* [http://www.darwinsys.com/history/hist.html A History of UNIX before Berkeley: UNIX Evolution: 1975-1984]
* [https://archive.org/details/bsdtalk170 audio bsdtalk170 – Marshall Kirk McKusick at DCBSDCon -- on history of tcp/ip (in BSD) -- abridgement of the three lectures on the history of BSD.]
* [https://www.levenez.com/unix/ UNIX History timeline diagram with 150 versions over 50 years] [https://www.tech-insider.org/unix/research/2002/0601.html diagram]
* {{GitHub|dspinellis/unix-history-repo|Unix History Repository}}

{{unix-like}}
{{Operating System}}

[[Category:Unix history]]