| By 1942 Alan Turing was the genius loci at
Bletchley Park, famous as 'Prof', shabby, nail-bitten, tie-less,
sometimes halting in speech and awkward of manner, the source of
many hilarious anecdotes about bicycles, gas masks, and the Home
Guard; the foe of charlatans and status-seekers, relentless in long
shift work with his colleagues, mostly of student age. To one of
these, Joan Clarke, he proposed marriage, and was gladly accepted.
But then he retracted, telling her of his homosexuality.
Turing crossed the Atlantic in November 1942, for highest-level
liaison not only on the desperate U-boat Enigma crisis, but on the
electronic encipherment of speech signals between Roosevelt and
Churchill. Before his return in March 1943, logical weaknesses in
the changed U-boat system had been brilliantly detected, and U-boat
Enigma decryption was effectively restored for the rest of the war.
With the battle of the Atlantic regained for the Allies, crisis
resolved, chess champion C. H. O'D. Alexander, hitherto Turing's
deputy, took charge of Hut 8.
Turing became an all-purpose consultant to the by now vast
Bletchley Park operation. As such he saw the 'Fish' material cracked
by the Colossus machines, brought into operation just before D-Day,
demonstrating the feasibility of large-scale digital electronic
technology. Turing himself devoted much time to learning
electronics: ostensibly for creating his own, elegant speech secrecy
system, which he effected with the aid of one assistant, Donald
Bayley, at nearby Hanslope Park. But he had another and more
ambitious end in view: in the last stage of the war (for his part in
which he was awarded an OBE) he planned the embodiment of the
Universal Turing Machine in electronic form, or in effect, invented
the digital computer.
In 1944, at the invasion of Normandy that Allied control of the
Atlantic allowed, Alan Turing was almost uniquely in possession of
three key ideas:
- his own 1936 concept of the universal machine
- the potential speed and reliability of electronic technology
- the inefficiency in designing different machines for different
logical processes.
Combined, these ideas provided the
principle, the practical means, and the motivation for the modern
computer, a single machine capable of handling any programmed task.
He himself was as eager as anyone in the world to bring them
together, and was spurred even more by a fourth idea: that the
universal machine should be able to acquire and exhibit the
faculties of the human mind. Even in 1944 he spoke to Donald Bayley
of 'building a brain'.
Turing was captivated by the potential of the computer he had
conceived. Although his 1936 work had shown the absolute limitations
of the computable, he had become fascinated by what Turing machines
could do, rather than by what they could not. He had long abandoned
his youthful expectations of finding free will or free spirits
through quantum mechanics. His later thought was strongly
determinist and atheistic in character. And by the end of the Second
World War he had turned against the tentative idea that there were
steps of 'intuition' in human thought corresponding to uncomputable
operations. Instead, he held that the computer would offer unlimited
scope for practical progress towards embodying intelligence in an
artificial form.
For the second time, he experienced being pre-empted by a
parallel American publication, in this case the EDVAC plan for an
electronic computer, with Von Neumann's name attached. Nonetheless,
this publication when it appeared in June 1945 worked in practice to
Turing's advantage, American competition stimulating the National
Physical Laboratory to plan a rival project, to which he was
appointed a Senior Principal Scientific Officer. Turing despised his
nominal superior J. Womersley, but at least initially this applied
mathematician showed a rapid appreciation of the scope of Turing's
ideas, and with a eye for acronyms steered Turing's design towards
formal approval in early 1946 as the Automatic Computing Engine, or
ACE. |
