Unix was born in 1969 and has been in continuous production use
ever since. That's several geologic eras by computer-industry
standards — older than the PC or workstations or microprocessors
or even video display terminals, and contemporaneous with the first
semiconductor memories. Of all production timesharing systems today,
only IBM's VM/CMS can claim to have existed longer, and Unix machines
have provided hundreds of thousands of times more service hours;
indeed, Unix has probably supported more computing than all other
timesharing systems put together.
Unix has found use on a wider variety of machines than any other
operating system can claim. From supercomputers to handhelds and
embedded networking hardware, through workstations and servers and PCs
and minicomputers, Unix has probably seen more architectures and more
odd hardware than any three other operating systems combined.
Unix has supported a mind-bogglingly wide spectrum of uses. No
other operating system has shone simultaneously as a research vehicle,
a friendly host for technical custom applications, a platform for
commercial-off-the-shelf business software, and a vital component
technology of the Internet.
Unix's durability and adaptability have been nothing short of
astonishing. Other technologies have come and gone like mayflies.
Machines have increased a thousandfold in power, languages have
mutated, industry practice has gone through multiple revolutions —
and Unix hangs in there, still producing, still paying the bills,
and still commanding loyalty from many of the best and brightest
software technologists on the planet.
One of the many consequences of the exponential
power-versus-time curve in computing, and the corresponding pace of
software development, is that 50% of what one knows becomes obsolete
over every 18 months. Unix does not abolish this phenomenon, but does
do a good job of containing it. There's a bedrock of unchanging
basics — languages, system calls, and tool invocations —
that one can actually keep using for years, even decades. Elsewhere
it is impossible to predict what will be stable; even entire operating
systems cycle out of use. Under Unix, there is a fairly sharp
distinction between transient knowledge and lasting knowledge, and one
can know ahead of time (with about 90% certainty) which category
something is likely to fall in when one learns it. Thus the loyalty