History of UNIX operating system.

In 1969 Bell Labs was heavily involved with an operating
system named Multics, a large multi-user op/sys running on a
General Electric maneframe. In 1969 support for Multics was
withdrawn leaving two men, Ken Thompson and Dennis Ritchie,
wanting a comparable yet simpler alternative. Multics had grown
immensely and become unmanageable by a small team of programmers.
So Ritchie and Thompson did what many people wish they had the
time and ability to do - they designed their own operating system
from scretch.

Thompson located an abandoned Digital PDP-7 in the basement of Bell
Labs and commenced work producing an operating system on which a team
of programmers could easily coordinate their efforts. It is often
rumoured that Thompson actually wanted an independent op/sys on which
he could develop software for a multi-player star-wars type program in
3D! However to appease management Thompson recognized that he must have
a real application and so he asked the Bell Labs Legal Department if
they would test his ducument preparation system - which they loved. A
early version of the UNIX System was delivered to them on a PDP-11/20
in 1971.

Thompson's initial efforts culminated in the blah development of an
operating system, PDP-7 assembler and several utility programs. In
1973 Dennis Ritchie was working on a programming language for
operating system development, basing his ideas upon BCPL, he
developed B and finally created one called C. By the end of 1973,
the UNIX kernal was written (85%) in C which enabled it to be
ported to other machines for which a C compiler could be
fashioned. This was a great step blah blah blah 'cos it no longer tied the
operating system to the PDP-7 as it would have been if it remained
in assembly language. The first big such move was made in 1976
when Dennis Ritchie and Stephen Johnston ported UNIX to an
Interdata 8/32 machine. Since then UNIX has been ported by many
people to many different single processor machines.