dollars. As a point of comparison, a $7 million system today (at the time of this writ‐
ing, in late 2017) would have cost about $44 million then. Having a system that could
support only a single user at a time was just not cost-effective—thus the development
of Multics by MIT, Bell Labs, and GE was a way of making computers more cost-
effective.
Inevitably, the project slowly fell apart, though the operating system was eventually
released. One of the programmers assigned to the project from Bell Labs returned to
his regular job and eventually decided to write his own version of an operating sys‐
tem in order to play a game he had originally written for Multics but wanted to play
on a PDP-7 that was available at Bell Labs. Ken Thompson needed a decent environ‐
ment to redevelop the game for the PDP-7. In those days, systems were largely
incompatible. They had entirely different hardware instructions (operation codes),
and they sometimes had different memory word sizes. As a result, programs written
for one environment, particularly if very low-level languages were used, would not
work in another environment. The resulting environment, developed by a program‐
mer to make his life easier as he was getting Space Travel working on the PDP-7, was
named Unics. Eventually, other Bell Labs programmers joined the project, and it was
eventually renamed Unix.
Unix had a simple design. Because it was developed as a programming environment
for a single user at a time, it ended up getting used, first within Bell Labs and then
outside, by other programmers. One of the biggest advantages to Unix over other
operating systems was that the kernel was rewritten in the C programming language
in 1972. Using a higher-level language than assembly, which was more common then,
made it portable across multiple hardware systems. Rather than being limited to the
PDP-7, Unix could run on any system that had a C compiler in order to compile the
source code needed to build Unix. This allowed for a standard operating system
across numerous hardware platforms.
In addition to having a simple design, Unix had the advantage of being distributed
with the source code. This allowed researchers not only to read the source code in
order to understand it better, but also to extend and improve the source. Unix has
spawned many child operating systems that all behaved just as Unix did, with the
same design. In some cases, these other operating system distributions started with
the Unix source that was provided by AT&T. In other cases, Unix was essentially
reverse engineered based on documented functionality and was the starting point for
two popular Unix-like operating systems: BSD and Linux.
