[Unix history as recorded at http://en.wikipedia.org/wiki/Unix on March 29,
2009.  This wikipedia snapshot was borrowed as a convenient and topical
text file to use for our Unix tutorial.]

In the 1960s, the Massachusetts Institute of Technology, AT&T Bell Labs, and
General Electric worked on an experimental operating system called Multics
(Multiplexed Information and Computing Service), which was designed to run on
the GE-645 mainframe computer. (Eventually Multics became a commercial
product, although sales did not meet expectations). Multics was an interactive
operating system with many novel capabilities, including enhanced security.

AT&T Bell Labs pulled out of the Multics project and deployed its resources
elsewhere. One of the developers on the Bell Labs team, Ken Thompson,
continued to develop for the GE-645 mainframe, and wrote a game for that
computer called Space Travel.[1] However, he found that the game was too slow
on the GE machine and was expensive, costing $75 per execution in scarce
computing time.[2]

Thompson thus re-wrote the game in assembly language for Digital Equipment
Corporation's PDP-7 with help from Dennis Ritchie. This experience, combined
with his work on the Multics project, led Thompson to start a new operating
system for the PDP-7. Thompson and Ritchie led a team of developers, including
Rudd Canaday, at Bell Labs developing a file system as well as the new
multi-tasking operating system itself. They included a command line
interpreter and some small utility programs.[3]

1970s

In the 1970s the project was named Unics, and eventually could support two
simultaneous users. Brian Kernighan invented this name as a contrast to
Multics; the spelling was later changed to Unix.

Up until this point there had been no financial support from Bell Labs. When
the Computer Science Research Group wanted to use Unix on a much larger
machine than the PDP-7, Thompson and Ritchie managed to trade the promise of
adding text processing capabilities to Unix for a PDP-11/20 machine. This led
to some financial support from Bell. For the first time in 1970, the Unix
operating system was officially named and ran on the PDP-11/20. It added a
text formatting program called roff and a text editor. All three were written
in PDP-11/20 assembly language. Bell Labs used this initial "text processing
system", made up of Unix, roff, and the editor, for text processing of patent
applications. Roff soon evolved into troff, the first electronic publishing
program with a full typesetting capability. The UNIX Programmer's Manual was
published on November 3, 1971.

In 1973, Unix was rewritten in the C programming language, contrary to the
general notion at the time "that something as complex as an operating system,
which must deal with time-critical events, had to be written exclusively in
assembly language".[4] The migration from assembly language to the
higher-level language C resulted in much more portable software, requiring
only a relatively small amount of machine-dependent code to be replaced when
porting Unix to other computing platforms.

AT&T made Unix available to universities and commercial firms, as well as the
United States government under licenses. The licenses included all source code
including the machine-dependent parts of the kernel, which were written in
PDP-11 assembly code. Copies of the annotated Unix kernel sources circulated
widely in the late 1970s in the form of a much-copied book by John Lions of
the University of New South Wales, the Lions' Commentary on UNIX 6th Edition,
with Source Code, which led to considerable use of Unix as an educational
example.

Versions of the Unix system were determined by editions of its user manuals,
so that (for example) "Fifth Edition UNIX" and "UNIX Version 5" have both been
used to designate the same thing. Development expanded, with Versions 4, 5,
and 6 being released by 1975. These versions added the concept of pipes,
leading to the development of a more modular code-base, increasing development
speed still further. Version 5 and especially Version 6 led to a plethora of
different Unix versions both inside and outside Bell Labs, including PWB/UNIX,
IS/1 (the first commercial Unix), and the University of Wollongong's port to
the Interdata 7/32 (the first non-PDP Unix).

In 1978, UNIX/32V, for DEC's then new VAX system, was released. 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. Versions
8, 9 and 10 were developed through the 1980s but were only released to a few
universities, though they did generate papers describing the new work. This
research led to the development of Plan 9 from Bell Labs, a new portable
distributed system.

1980s
An early-1990s style Unix desktop running the X Window System graphical user
interface. Shown are a number of client applications common to the MIT X
Consortium's distribution, including Tom's Window Manager, an X Terminal,
Xbiff, xload, and a graphical manual page browser.

AT&T licensed UNIX System III, based largely on Version 7, for commercial use,
the first version launching in 1982. 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 editor and
curses from the Berkeley Software Distribution of Unix developed at the
University of California, Berkeley. This also included support for the Western
Electric 3B series of machines.

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 Unix as an alternative to UNIX System III and V, originally on
the PDP-11 architecture (the 2.xBSD releases, ending with 2.11BSD) and later
for the VAX-11 (the 4.x BSD releases). Many contributions to Unix first
appeared on BSD releases, notably the C shell with job control (modelled on
ITS). Perhaps the most important aspect of the BSD development effort was the
addition of TCP/IP network code to the mainstream Unix 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.

Other companies began to offer commercial versions of the UNIX System for
their own mini-computers and workstations. Most of these new Unix flavors were
developed from the System V base under a license from AT&T; however, others
were based on BSD instead. One of the leading developers of BSD, Bill Joy,
went on to co-found Sun Microsystems in 1982 and created SunOS for their
workstation computers. In 1980, Microsoft announced its first Unix for 16-bit
microcomputers called Xenix, which the Santa Cruz Operation (SCO) ported to
the Intel 8086 processor in 1983, and eventually branched Xenix into SCO UNIX
in 1989.

For a few years during this period (before PC compatible computers with MS-DOS
became dominant), industry observers expected that UNIX, with its portability
and rich capabilities, was likely to become the industry standard operating
system for microcomputers.[5] In 1984 several companies established the X/Open
consortium with the goal of creating an open system specification based on
UNIX. Despite early progress, the standardization effort collapsed into the
"Unix wars," with various companies forming rival standardization groups. The
most successful Unix-related standard turned out to be the IEEE's POSIX
specification, designed as a compromise API readily implemented on both BSD
and System V platforms, published in 1988 and soon mandated by the United
States government for many of its own systems.

AT&T added various features into UNIX System V, such as file locking, system
administration, STREAMS, new forms of IPC, the Remote File System and TLI.
AT&T cooperated with Sun Microsystems and between 1987 and 1989 merged
features from Xenix, BSD, SunOS, and System V into System V Release 4 (SVR4),
independently of X/Open. This new release consolidated all the previous
features into one package, and heralded the end of competing versions. It also
increased licensing fees.

During this time a number of vendors including Digital Equipment, Sun, Addamax
and others began building trusted versions of UNIX for high security
applications, mostly designed for military and law enforcement applications.


1990s

In 1990, the Open Software Foundation released OSF/1, their standard Unix
implementation, based on Mach and BSD. The Foundation was started in 1988 and
was funded by several Unix-related companies that wished to counteract the
collaboration of AT&T and Sun on SVR4. Subsequently, AT&T and another group of
licensees formed the group "UNIX International" in order to counteract OSF.
This escalation of conflict between competing vendors gave rise again to the
phrase "Unix wars".

In 1991, a group of BSD developers (Donn Seeley, Mike Karels, Bill Jolitz, and
Trent Hein) left the University of California to found Berkeley Software
Design, Inc (BSDI). BSDI produced a fully functional commercial version of BSD
Unix for the inexpensive and ubiquitous Intel platform, which started a wave
of interest in the use of inexpensive hardware for production computing.
Shortly after it was founded, Bill Jolitz left BSDI to pursue distribution of
386BSD, the free software ancestor of FreeBSD, OpenBSD, and NetBSD.

By 1993 most commercial vendors had changed their variants of Unix to be based
on System V with many BSD features added on top. The creation of the 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, which retained the OSF name, stopped
work on OSF/1 that year. By that time the only vendor using it was Digital,
which continued its own development, rebranding their product Digital UNIX in
early 1995.

Shortly after UNIX System V Release 4 was produced, AT&T sold all its rights
to UNIX to Novell. (Dennis Ritchie likened this to the Biblical story of Esau
selling his birthright for the proverbial "mess of pottage".[6]) Novell
developed its own version, UnixWare, merging its NetWare with UNIX System V
Release 4. Novell tried to use this to battle against Windows NT, but their
core markets suffered considerably.

In 1993, Novell decided to transfer the UNIX trademark and certification
rights to the X/Open Consortium.[7] In 1996, X/Open merged with OSF, creating
the 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 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.[8] Whether Novell also sold the copyrights
is currently the subject of litigation (see below).

In 1997, Apple Computer sought out 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 BSD and the Mach kernel, was
renamed Darwin after Apple acquired it. The deployment of Darwin in 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.

2000 to present

In 2000, SCO sold its entire UNIX business and assets to Caldera Systems,
which later on changed its name to The SCO Group.

The Dot-com crash (2001–2003) has led to significant consolidation of versions
of Unix. Of the many commercial flavors of Unix that were born in the 1980s,
only Solaris, HP-UX, and AIX are still doing relatively well in the market,
though SGI's IRIX persisted for quite some time. Of these, Solaris has the
largest market share.[9]

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 v. Novell lawsuit. On August 10, 2007, a major portion of
the case (the fact that Novell had the copyright to UNIX, and that the SCO
Group had improperly kept money that was due to Novell) was decided in
Novell's favor. 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".[10][11][12]
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 project called OpenSolaris.
New Sun OS technologies such as the ZFS file system are now first released as
open source code via the OpenSolaris project; as of 2006[update] OpenSolaris
has spawned several non-Sun distributions such as SchilliX, Belenix, Nexenta,
and MarTux.