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# Unix

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Unix is a portable operating system originally developed by a group of AT&T Bell Labs including Ken Thompson and Dennis Ritchie, who were pulled out of the original MULTICS collaboration after the failure of 1966/7 era hardware to support its implementation. Inspired by his work on the MULTICS (Multiplexed Information and Computing Service) project in 1969 Ken Thompson wrote the first version of Unix in PDP-8? assembly language. After this initial version drew the attention of other Bell Labs scientists they teamed up in 1970/1 to reimplement the operating system using Dennis Ritchie's new C language. Interestingly the initial C language version development was funded by AT&T as an electronic documentation system since an OS has no intrinsic appeal to a phone company. In 1973/4 the Unix team managed to offer tapes of the new OS to universities for research purposes up through Seventh Edition. Of the schools to take avantage of this opportunity UCB was notable for making it the center of its Computer Science OS research and porting it to all of their mini-computers including the DEC PDP-11?. Though AT&T stopped distributing the source for Unix after Seventh Edition, UCB continued to develop what became known as Berkeley Unix often matching and sometimes exceeding the capabilities being developed by the team at Bell Labs. Once Berkeley Unix became sufficiently mature it was packaged as the Berkeley Standard Distribution (BSD), and close to the same time Bell Labs began packaging AT&T Unix as System V (five).

Starting in about 1980 various companies started marketing commercial distributions of Unix for their mini-computers and workstations. While some companies chose to use the AT&T System V version many of these companies started out using the Berkeley BSD version because of its interesting enhancements. In about 1987 the AT&T team decided to standardize Unix by developing System V Release 4 which incorporated and normalized the technologies used by all of the different distributions and vendors. Despite a fracture in the standardization effort resulting in the creation of OSF/1 which was used by only one vendor, the AT&T team released SVR4 in 1989 with Data General being the first vendor to use the new operating system on their AViiON? server machines in 1990. By 1993 most of the original commercial BSD based Unix distribution vendors including Sun and SGI moved to SVR4 as the foundation of their operating systems with vendor and BSD enhancements layer on top of the new standard foundation. The first published description of the system's inner workings was a book by an Australian university teacher, the so-called [Lions book]?.

Not long after SVR4 had been formalized with Sun, AT&T sold it remaining interest in UNIX together with the Unix Labs to Novell who at that time were becoming increasingly frightened by Microsoft's entry into the networked computers business, and saw UNIX as a chance to offset their progress. Unix at Novell languished in the financial difficulties of the company as their sales growth was bounded. Eventually Novell was forced to sell off many of its assets including UNIX to concentrate on its core software.

UNIX was split into three parts upon leaving Novell. The UNIX trademark was transferred to an industry consortium, the X/Open? group, (now just The Open Group) for certifying UNIX implementations as standard. The source base was sold to [Santa Cruz Operation (SCO)]? who sold SVR4 on Intel hardware alongside their traditional Xenix-like SCO-UNIX offering. The operating system laboratory were transferred to Hewlett-Packard where they became mired in internal politics when asked to design the eventual replacement for HP's UNIX, HP-UX?. Eventually the remaining employees were absorbed into the broader HP Corporation.

Later an open operating system standardization effort known as POSIX provided a common baseline for all operating systems including Unix. In 1991 this standard provided an opportunistic target via the GNU project for Linus Torvalds who wanted to have an operating system which would run on standard Intel 386 PC hardware. Torvalds produced a kernel called Linux to which he and others ported the Free Software Foundation's GNU tools. The GNU tools when combined with the Linux kernel provided the foundation for a POSIX compliant "Unix like" operations system commonly known as GNU/Linux or simply Linux. Notably the GNU is Not Unix or simply GNU project is based on the GPL, or GNU Public License conceived by Richard Stallman to propagate the philosophy that source code should be provided with software products. It is important to note that the original intent was NOT that software should be free, but rather that the person getting the software would have free access to the source code without paying extra for it.

Unix is more a class of operating system than a specific operating system. There are two basic variants: BSD and System V. Most versions of Unix fall more or less into one of these two categories. Strictly speaking, some Unix variants which are generally regarded as being Unix are in actuality only unix-like, since Unix is a trademark and only those operating systems which meet the [Open Group]?'s Unix98? criteria are technically Unix. Another common Unix standard is [System V Interface Definition]? (SVID). The word Unix is often used in a more generic way, however. See http://www.unix-systems.org

Some Unix (and Unix-like) Operating Ssytems which are currently in widespread use: AIX?, FreeBSD, HP-UX?, Irix, Linux, Macintosh [OS X]?, [SCO UNIX]?, Solaris, Tru64?

See also:

- BSD License
- The GNU Project

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Last edited August 10, 2001 12:19 am (diff)
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