The centenary of a genius:  Alan Turing 1912 - 1954

Alan Turing, without whom the 21^st century as we know it would not have come about, was born  100 years ago this Saturday 23^rd 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 23^rd 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.