Information Technology Reference
In-Depth Information
4
Time-Sharing, Third Party Vendors, Antitrust, PLATO, and the Rise of the
Integrated Circuit
"People think that computer science is the art of geniuses but the actual reality is the
opposite, just many people doing things that build on each other, like a wall of mini
stones."
- Donald Knuth, computer programmer
UNIX was largely a product of researchers and engineers at Bell Labs who needed, for
their own purposes, a system for computer capacity time-sharing. The concept of time-shar-
ing is simply this: many users in an organization concurrently and interactively (or "conver-
sationally") share the capacity of a single computer resource by means of multiprogramming
and multitasking - thus dramatically lowering the cost of computing capability.
By the mid 1960s, MIT had developed an experimental, elementary time-sharing system
- the Compatible Time-Sharing System (CTSS) - capable of servicing only three or four
users simultaneously. CTTS employed the IBM 7094. At about this same time, the Defense
Advances Research Project Agency (DARPA) chose GE computers (specifically the GE-635
and 645 lines of machines) for its own time-sharing experiments.
The popular IBM System/360 lacked dynamic address translation - the capability of
stopping program execution, moving it out of core memory and back to disk, and then load-
ing it back to core memory on demand. The GE machines, on the other hand, contained this
feature, which was viewed by most engineers as essential for efficient and economical time-
sharing. IBM's hasty 1965 introduction of a jury-rigged "Model 67" machine incorporating
time-sharing system software (TSS) proved a fiasco, as the randomly engineered machine in
no way matched the capabilities of the GE computers. The product failed, and would even-
tually become infamous in antitrust proceedings as evidence of IBM sometimes launching
products not with the idea of enhancing real value for clients, but rather to use its marketing
clout to undermine competition. (Eventually, IBM's System/370, popular through the 1970s
and 1980s, would incorporate IBM's robust and elegant Conversational Monitoring System
[CMS] software for data-intensive time-sharing work.)
But even the GE machines, though far better suited than the 360 or Model 67, were
not absolutely optimal. GE wound up killing its time-sharing project, which it had dubbed
MULTICS, in 1969. It was in the midst of this that Bell Labs began development of UNIX
- a superb simplification of both the CTSS and MULTICS paradigms which, as has already
been mentioned, they ran on a DEC PDP-7 and later a PDP-11. Thus, for the near future at
least, DEC machines would be closely associated with the UNIX operating system, to the
benefit of both.
