The centenary of a genius: Alan Turing 1912 - 1954
Alan Turing, without whom the 21st
century as we know it would not have come about, was born 100 years ago this Saturday 23rd
June. He laid the foundations of
computing, and without him, our information dependent civilisation would not
have been possible: and the little devices with illuminated window and attached
keyboard, which all of us carry around everywhere and on which our lives
seemingly depend, would not exist. Although
less known, he stands without doubt beside Newton, Maxwell, Darwin and Einstein as the one of the giants who laid the
scientific foundations of our world.
He was born on 23rd June 1912,
grew up in England, showed early signs of mathematical genius, and went to
Cambridge University, embarking on an illustrious academic career.
In 1935, long before the construction of
any practical computer, Turing published a seminal paper called “On computable
numbers”. This paper was far more than
to do with numbers. It explained what it
really meant for a problem to be ‘computable’, i.e. solvable, what an algorithm
was, and how information was not just a vague concept but really a definable quantity
which could be processed, from an input or question, to an output or final
answer. He proposed a machine,
ridiculously simple in principle, which could be built to solve any computable
problem. It consisted just of a long
tape containing symbols which embodied the problem. A reading head travelled along the head, one
symbol at a time, reversing direction if necessary, reading each symbol and
rewriting it according to the ‘program’ built into the head (like the machines
which used to be used for printing plastic labels or name tags). One of the instructions in the head might be
to stop – in which case the program was terminated and the symbols now on the
tape constituted the answer to the problem!
This was the famous Turing machine.
A machine could be designed for every problem, as we said. But wait – a Turing machine could be designed
to simulate another Turing machine – in fact, a machine could be designed in
theory to emulate all other Turing
machines. This was the universal Turing
machine, which could be programmed to solve any computable problem! In other words, it was the computer! However, tantalisingly at the same time,
Turing showed that there are problems, depressingly an infinite number of them,
which are insoluble, not just because they are hard, but because it can be
proved that they are ‘undoable’ or undecidable.
Computing cannot solve everything!
Turing’s greatest practical achievement
during World War II, well known and documented by movies such as Breaking the
Code, was to tackle the German encryption system for their military communications. This was their Enigma machine, a fiercely
complex device which consisted of spinning wheels which transformed one letter
into another but on a highly variable basis.
The code proved uncrackable by normal means, and the Allies were unable
to decipher encrypted messages sent between German submarines (‘U-boats’),
which devastated shipping and supplies sent between Britain and America. The British government empowered Turing to
set up a team of mathematicians and logical specialists who worked at a country
house outside London and built the world’s first applied working computer
called Colossus. The enigma code was
eventually broken, without which it is very likely that the western allies
would have lost the war. Turing’s
contribution, in the world of information, was just as valuable as that of the
battlefield generals.
After the war, Turing fell foul of the
authorities, not because of any technical failing, but due to the bizarre
reason of his homosexuality, which was illegal in Britain at the time. He was prosecuted and was offered the
alternatives of being sent to prison or submitting to a humiliating hormone
treatment. Shortly afterwards he was
found dead of cyanide poisoning – it might have been an accident but was
generally assumed to be suicide, at the tragic early age of 41,
After Turing’s death, Britain lost its lead
in the development of computing machines and the initiative passed to the
United States, to such an extent that Turing’s contribution and those of other
British pioneers were nearly
forgotten. The reason for this was
simple: whereas the Americans saw computers as systems of huge technical
importance and commercial potential, to be promoted by all means, the British
saw them as strategic military devices to be kept secret at all costs. Turing’s discoveries were kept out of the
public eye for years under Britain’s Official Secrets Act, and his code
breaking computer with all its records was destroyed by official order. Not until 2009 did the Prime Minister Gordon
Brown officially apologise for the treatment meted out to the genius who
invented computing and won the world war for his country.
