In the late 1960s a combined project between researchers at MIT, Bell Labs and
General Electric led to the design of a third generation of computer operating
system known as MULTICS (MULTiplexed Information and Computing Service). It was
envisaged as a computer utility, a machine that would support hundreds of
simultaneous timesharing users. They envisaged one huge machine providing
computing power for everyone in Boston. The idea that machines as powerful as
their GE-645 would be sold as personal computers costing only a few thousand
dollars only 20 years later would have seemed like science fiction to them.
However MULTICS proved more difficult than imagined to implement and Bell Labs
withdrew from the project in 1969 as did General Electric, dropping out of the
computer business altogether.
One of the Bell Labs researchers (Ken Thompson) then decided to rewrite a
stripped down version of MULTICS, initially as a hobby. He used a PDP-7
minicomputer that no was using and wrote the code in assembly. It was initially
a stripped down, single user version of MULTICS but Thompson actually got the
system to work and one of his colleagues jokingly called it UNICS (UNiplexed
Information and Computing Service). The name stuck but the spelling was later
changed to UNIX. Soon Thompson was joined on the project by Dennis Richie and
later by his entire department.
UNIX was moved from the now obsolete PDP-7 to the much more modern PDP-11/20 and
then later to the PDP-11/45 and PDP-11/70. These two latter computers had large
memories as well as memory protection hardware, making it possible to support
multiple users at the same time. Thompson then decided to rewrite UNIX in a
high-level language called B. Unfortunately this attempt was not successful and
Richie designed a successor to B called C. Together, Thompson and Richie rewrote
UNIX in C and subsequently C has dominated system programming ever since. In
1974, Thompson and Richie published a paper about UNIX and this publication
stimulated many universities to ask Bell Labs for a copy of UNIX. As it happened
the PDP-11 was the computer of choice at nearly all university computer science
departments and the operating systems that came with this computer was widely
regarded as being dreadful and hence UNIX quickly came to replace them. The
version that first became the standard in universities was Version 6 and within
a few years this was replaced by Version 7. By the mid 1980s, UNIX was in
widespread use on minicomputers and engineering workstations from a variety of
In 1984, AT&T released the first commercial version of UNIX, System III, based
on Version 7. Over a number of years this was improved and upgraded to System V.
Meanwhile the University of California at Berkeley modified the original Version
6 substantially. They called their version 1BSD (First Berkeley Software
Distribution). This was modified over time to 4BSD and improvements were made
such as the use of paging, file names longer than 14 characters and a new
networking protocol, TCP/IP. Some computer vendors like DEC and Sun Microsystems
based their version of UNIX on Berkeley\'s rather than AT&T\'s. There was a few
attempts to standardise UNIX in the late 1980s, but only the POSIX committee had
any real success, and this was limited.
During the 1980s, most computing environments became much more heterogeneous,
and customers began to ask for greater application portability and
interoperability from systems and software vendors. Many customers turned to
UNIX to help address those concerns and systems vendors gradually began to offer
commercial UNIX-based systems. UNIX was a portable operating system whose source
could easily be licensed, and it had already established a reputation and a
small but loyal customer base among R&D organisations and universities. Most
vendors licensed source bases from either the University of California at
Berkeley or AT&T(r) (two completely different source bases). Licensees
extensively modified the source and tightly coupled them to their own systems
architectures to produce as many as 100 proprietary UNIX variants. Most of these
systems were (and still are) neither source nor binary compatible with one
another, and most are hardware specific.
With the emergence of RISC technology and the breakup of AT&T, the UNIX systems
category began to grow significantly during the 1980s. The term "open systems"
was coined. Customers began demanding better portability and interoperability
between the many incompatible UNIX variants. Over the years, a variety of
coalitions (e.g. UNIX International) were formed to try to gain control over and
consolidate the UNIX systems category, but their success was always limited.
Gradually, the industry turned to standards as a way of achieving the
portability and interoperability