Grex Systems Conference

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Grex Systems Item 2: The Unix item
Entered by cross on Sat Sep 16 18:54:18 UTC 2006:
This is the Unix item, for discussion of Unix and its many variants.

The Unix system was originally written by Ken Thompson at Bell Labs in 1969
for an abandoned PDP-7 minicomputer.  Thompson's motivation was to provide a
time sharing environment similar to that provided by the MULTICS system that
he had recently worked on, and also to provide a dedicated system for
playing the game "Space Travel."  Unix was initially implemented in assembly
language on the PDP-7, but the system quickly attracted attention from other
members of Thompson's group and was moved to the far more capable PDP-11
minicomputer.  In the early to mid 1970's, it was re-implemented in the C
programming language by Dennis Ritchie, who had in some sense created that
language for the task.  While Unix was certainly not the first system to be
written in a high level language (and many would scoff at calling C high
level), it was one of the first to run on such a small computer (other
systems written in high level languages ran on mainframes many times larger
and more powerful than the Unix PDP machines).  Unix supported a rich
document preparation environment (indeed - one of the justifications the
Bell Labs team used for getting management to buy a PDP-11 was a promise to
build a document preparation system for use by the Bell Labs patent
department), comfortable tools for program development, a hierarchical
filesystem, a shell separate from the operating system kernel, pipelines,
and an exciting atmosphere of learning and creativity based around a
timesharing system.  It had a philosophy that "small is beautiful," that
devices should, if at all possible, look like files, that programs should do
one thing and do it well and be connected via pipelines in the shell, that
text would be a universal data format for connecting programs, and that
programs act as "filters": reading data from a "standard input" and writing
to a "standard output" that could be redirected to pipes and files.  A far
more complete account of the early history of the Unix system may be found
here:

http://plan9.bell-labs.com/who/dmr/hist.html

Due to its early licensing terms and source code availability, Unix became
tremendously popular in academic and research circles, and entire
generations of computer science students "grew up" using Unix systems.  Its
consequent influence is indisputable, and it has been imitated many times.
Of the many variants of Unix have been created, the Berkeley Software
Distribution (BSD) of Unix from the University of California, Berkeley, has
had the biggest impact.  BSD Unix systems formed the early backbone of the
Internet as the successor to the Arpanet, and were heavily represented at
government and academic research labs and in academic departments.
Eventually, AT&T and the Bell Operating Companies were created out of the
old Bell system and AT&T marketed commercial versions of Unix during the
1980's and 1990's.  These competed against the Berkeley version, and vendors
attempting to grab market share borrowed freely from both strains and
created incompatible versions of the system specific to their offerings in
attempts to lure customers and lock them in.  This led to the "OS wars."
Eventually, however, standardization efforts began and now the disparate
systems have more or less converged to a single whole again.

In the time since its creation, Unix has grown steadily in terms of power,
popularity, and size.  It is one of - if not the - most ported systems in
computing history, having run on everything from small 8 and 16 bit
microprocessors to massively parallel, multiprocessor mainframes and super
computers.  Versions and variants of the system, such as those of the
GNU/Linux project and various distributions of the BSD system are available
free of charge and run on most computer systems.  Unix continues to play a
major role on the Internet as a server operating system capable of hosting
many services under intense load, and it still continues to provide a
comfortable environment for program development, document preparation, and
time sharing.

Unix was - and remains - unique not so much for its technical innovation
(there was actually very little of note in the system itself) but because it
filled a niche: it combined concepts in a package that was implemented very
well in a time and a place where they hadn't been before, and was available.
The original Bell Labs research group that spawned Unix left it as a
research focus long ago, moving on to other systems and activities.  Some
members have even said that Unix is dead.  That may be true, but we're still
learning from it and doing good work on it, and for that it has utility.
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