Information Technology Reference
In-Depth Information
controlled automatically. A Jacquard loom, for instance, used a series of
steel cards, as many as twenty thousand at a time, to control the weaving
of patterns on fabric.
15
Tabulating machines could also be programmed
to a certain degree by rewiring their components. But the combination
of speed and fl exibility provided by the combination of an electronic
digital computer and well-designed software was unprecedented. The
electronic digital computer would eventually become a universal machine
whose potential applications were limited only by the imagination of its
programmers.
Therein lies the rub: the very aspect of electronic computing that made
it so powerful and appealing was the aspect of least interest to its original
designers. Computer programming began as little more than an after-
thought in most of the pioneering wartime electronic computing projects,
an offhand postscript to what was universally regarded as the much more
pressing challenge of hardware development.
There were certainly legitimate reasons for privileging hardware
over software; simply managing to keep the early electronic computers
running without failure for more than a few minutes was an engi-
neering challenge of heroic proportions. As was mentioned earlier,
the core computational units of the ENIAC machine relied on more
than eighteen thousand vacuum tubes, each of which had an average
lifespan of just three thousand hours. This meant that statistically speak-
ing, six of these tubes would fail every hour; or in other words, at least
one tube failed every ten minutes. Figuring out how to control the rate
of failure of vacuum tubes was one of the great contributions of the
ENIAC's brilliant chief engineer, J. Presper Eckert. Similarly, the con-
struction of mercury delay lines, which were an early form of short-term
memory used in the Cambridge University EDSAC, the world's fi rst
working stored-program computer, required the precise coordination of
acoustical waves moving at 1,450 meters per second. There is no ques-
tion that overcoming the engineering challenges posed by the electronics
of electronic computing was essential to the further development of
computer technology.
But solving the programming hurdles was equally vital. Although in
the decades after the ENIAC we have come to regard the electronic
computer as an almost infi nitely protean and useful machine, this is
largely a refl ection of the successes of software. In the immediate postwar
period even programmable computers like the ENIAC were considered
impressive but limited. It was not hard to imagine that the military and
the government might have a need for a small number of such devices,
