In the late 1960's Ken Thompsom joined the computing-science research group at BellLaboratories, which is the research arm of the giant American corporation ATT. He and manycolleagues had been collaborating with MIT and GE on the development of an operatingsystem called Multics which aimed to improve the performance of multi-user time-sharingcomputer systems. But the resultant system was too big and too slow, so Bell lab'swithdrew leaving the computing science group without a computer.
A cast-off PDP-7 computer became available, so that Thompsom set about rewriting aplanetary motion simulation program previously implemented on the GE system. At the sametime he experimented with many of the concepts used for Multics, working in PDP-7assembler he developed a hierarchical filestore, a number of utility programs and centralsupervisory program (known as the kernel) which together made up a rudimentary single-useroperating system. He called it UNIX, a poor pun on uni-MULTICS i.e. single-user MULTICS orwas it a pun on eunuch version of MULTICS ?
Thompson's system found favour with his colleagues in the Bell labs computer sciencedepartment because it made software development work easier. Some text and processingutilities were added to the system, which were used by the legal department and earned thedevelopers enough funds to obtain a PDP-11 a more reliable and modern system. The 16-bitPDP-11 became the second UNIX port, and enabled multi-user facilities because of thememory management hardware.
One of Thompson's colleagues was Dennis Ritchie who had been impressed with the BCPLlanguage developed at the University of Cambridge, which he used as a template for alanguage he designed called B. This language developed into C which begged the questionwhat would the next language be called would it be D ?, or would it be P?. The answer we now know is C++.
The language C was then used to completely rewrite UNIX apart from a few hundred linesof assembler code. This enabled the first port of UNIX onto a non-DEC computer, a 32-bitINTERDATA 8/32 minicomputer system (with a similar architecture to the IBM 370) andhighlighted some of the more non-portable aspects of the system.
The combination of a environment designed for program development and the use of high-level language to code systems software greatly enhanced the possibility of a single programmer understanding the workings of a multi-user multiprogramming system. Thus UNIX flourished within BELL labs and they made public Version 6 which ran on the PDP-11 rangeand was licensed to universities without any support, but with all the source code for themedia cost. Commercial organisations could obtain UNIX for about 20,000 pounds.Surprisingly some did!. Version 6 was still small enough to appear on micro-processor systems (e.g. Z80, Motorola 6809, Intel 8085 etc...) as well as a variety of mini andmain-frame systems. Other companies like Whitesmiths consolidated around V6 (IDRIS)because of its small size made it suitable for smaller real-time control applications,whilst others like Motorola opted for choosing the best ideas (OS9) but not attemptingUNIX compatibility.
By Version 7 UNIX had developed and matured into a relatively bug-free product whichran on many different types of processor. Bell labs were using UNIX extensively withoutany central support, nor could the parent company ATT provide support, because of Americanlaw. This opened the door for the University of Berkeley (BSD) to become prominent in thefield as an advocate of UNIX and also offer software support and useful extensions to thesystem especially after Ken Thompsom spent a couple of years there as a visitingprofessor. The more useful advances (e.g. TCP/IP) have been duplicated on the ATTversions. As a result of commercial pressure ATT changed their licensing agreement whichenabled many OEM's (e.g. MICROSOFT and XENIX) to bring out re-writes as well as offeringthe infra-structure expected of a mature software product, i.e. good documentation,training, consultancy services, software support etc...
At this point in time there was an explosion of apparently different proprietaryversions of UNIX but they were united by the use of IX in the name, they paidroyalties to AT&T and that their extensions to v7 were (they said) the best thingsince sliced bread!
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