Motorola M500 Manuel d'utilisateur Page 18

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Page 16 M500 180
The irascible genius
Eddie Kent
We use the word ‘bit’ quite a bit these days, and we are not talking of horses.
Everyone except my mum knows bit is short for binary digit, but someone
must have thought of it first. That person was Claude Shannon, who died
on February 24. He was born in Michigan in 1916, thus he made it to 84,
though his last few years were spent in a nursing home with Alzheimer’s
disease.
He graduated from Michigan University in electrical engineering and
mathematics, doing less than brilliantly in the latter. This was unfortunate
as much of his work in later life needed mathematics so he had to invent it
as he went along. He was fascinated by George Boole’s Laws of Thought,
where logical expressions were formalized in the way that we now know as
Boolean algebra.
At MIT he was something of a loner, partly because his imagination
was always leaping far beyond the intellects of his colleagues, and not least
because of his practice of travelling though the corridors of the university
on a unicycle. People grew used to warning one another of his unsteady
advance.
For his masters degree he worked under Vannevar Bush, the inventor
of the differential analyser. This was the heart of the analog computer.
Contemporary thinking saw the message as inextricably bound up with the
waveform that carried it: the medium was the message. Shannon realised
that Boole’s precision could be used to convert messages into strings of
binary digits (which he called bits) and thus free them from the medium
that carried them.
His thesis, published in 1940, was called ‘A symbolic analysis of relay
and switching circuits.’ It showed how to treat Boole’s symbols as switches:
Yes, No; True, False; On, Off. This would work on an electric circuit and
could use a very simple notation, strings of 0s and 1s. It was immediately
apparent that this was the springboard from analogue to digital computers,
and Bell snapped him up.
His next paper, 1948, ‘A mathematical theory of communication,’ con-
tained his ideas on separating message and medium. It provided a basis
for information theory, showing how to measure the efficiency of a trans-
mission. He called this a measure of entropy, taking the word from another
discipline.
In the fifties he was programming a computer to play chess, and man-
aged to arrange a meeting with Mikhail Botvinnick (the world champion).
Unfortunately neither spoke the other’s language, and their interpreters
knew nothing about either chess or computers. The discussion, though in-
teresting, was degraded by being carried through a ‘noisy channel’ as he
called it. However, he was around in 1980 when Bell’s computer Belle won
the International Computer Chess Championship.
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