What is UNIX?
Unix (officially trademarked as UNIX, sometimes also written as Unix) is a multitasking, multi-user
computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs,
including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna. The Unix
operating system was first developed in assembly language, but by 1973 had been almost entirely
recoded in C, greatly facilitating its further development and porting to other hardware. Today's Unix
system evolution is split into various branches, developed over time by AT&T as well as various
commercial vendors, universities (such as University of California, Berkeley's BSD), and non-profit
organizations.
The Open Group, an industry standards consortium, owns the UNIX trademark. Only systems
fully compliant with and certified according to the Single UNIX Specification are qualified to use the
trademark; others might be called Unix system-like or Unix-like, although the Open Group
disapproves[1] of this term. However, the term Unix is often used informally to denote any operating
system that closely resembles the trademarked system.
During the late 1970s and early 1980s, the influence of Unix in academic circles led to large-scale
adoption of Unix (particularly of the BSD variant, originating from the University of California, Berkeley)
by commercial startups, the most notable of which are Solaris, HP-UX and AIX. Among all variants of
Unix, the most widely used are Linux[citation needed], which is used to power data centers, desktops,
mobile phones, and embedded devices such as routers, set-top boxes or e-book readers, and Mac OS
X[citation needed], as the underpinnings of Apple's desktop and mobile phone operating systems.
Today, in addition to certified Unix systems such as those already mentioned, Unix-like
operating systems such as MINIX, Linux, Android, and BSD descendants (FreeBSD, NetBSD, OpenBSD,
and DragonFly BSD) are commonly encountered. The term traditional Unix may be used to describe a
Unix or an operating system that has the characteristics of either Version 7 Unix or UNIX System V.
In 1994 Novell (who had acquired the UNIX systems business of AT&T/USL) decided to get out of
that business. Rather than sell the business as a single entity, Novell transferred the rights to the UNIX
trademark and the specification (that subsequently became the Single UNIX Specification) to The Open
Group (at the time X/Open Company). Subsequently, it sold the source code and the product
implementation (UNIXWARE) to SCO. The Open Group also owns the trademark UNIXWARE.
Today, the definition of UNIX takes the form of the worldwide Single UNIX Specification
integrating X/Open Company's XPG4, IEEE's POSIX Standards and ISO C. Through continual evolution, the
Single UNIX Specification is the defacto and dejure standard definition for the UNIX system application
programming interfaces. As the owner of the UNIX trademark, The Open Group has separated the UNIX
trademark from any actual code stream itself, thus allowing multiple implementations. Since the
introduction of the Single UNIX Specification, there has been a single, open, consensus specification that
defines the requirements for a conformant UNIX system.
There is also a mark, or brand, that is used to identify those products that have been certified as
conforming to the Single UNIX Specification, initially UNIX 93, followed subsequently by UNIX 95, UNIX
98 and now UNIX 03.
The Open Group is committed to working with the community to further the development of
standards conformant systems by evolving and maintaining the Single UNIX Specification and
participation in other related standards efforts. Recent examples of this are making the standard freely
available on the web, permitting reuse of the standard in open source documentation projects ,
providing test tools ,developing the POSIX and LSB certification programs.
From this page you can read about the history of the UNIX system over the past 40 years or
more. You can learn about the Single UNIX Specification, and read or download online versions of the
specification. You can also get involved in the ongoing development and maintenance of the Single UNIX
Specification, by joining the Austin Group whose approach to specification development is "write once,
adopt everywhere", The Open Group's Base Working Group or get involved in the UNIX Certification
program.