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 vendors.
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)...