Because of war and his lifestyle, Turing’s genius was not fully recognised during his lifetime. Decades later, the importance of his work is more fully understood.
By the time he was 22, Turing was studying at Kings College Cambridge. In 1935 he attended a course of lectures on the foundations of mathematics. They focused on the work of the Austrian Kurt Gödel, in particular his incompleteness theorems, which can be very roughly summarised as:
There are some true statements that cannot be proved.
Turing’s 1936 paper “On Computable Numbers” extended Gödel’s work, taking it into the realms of Turing machines, a simple, hypothetical device that would be capable of solving any problem if it were described in terms of an algorithm. The concept meant such a computer could do any computation using processor and memory, where the data was stored. Anything that any calculating machine can perform can be done with a Turing machine.
Such concepts of a universal computing machine were truly radical, but in a sense, we all take these ideas of Turing’s for granted today. Word processing, for example, is a task that is carried out on a computer, because it can be broken down into steps and the computer can make consistent decisions based on user input. Removing red eye from a photograph is another example.
This, and Turing’s further work, laid down the fundamentals of what we now call Artificial Intelligence. Turing envisaged feeding a tape marked with 0s and 1s, a series of digits representing a computer program. The device began to become a reality when he started working at Princeton in New Jersey. He called his machine a "binary adder", which he began to construct from bits and pieces of electronic equipment he could find in different university departments. Before it was built, however, war broke out and Turing was called back to England. He would begin work at Bletchley Park, helping, among other things, in the attempt to decipher the Germans’ Enigma Code.
In June 1941, Prime Minister Winston Churchill was advised that Britain was just months away from starvation. U-Boats were sinking supply ships from North America so effectively that our only option would be surrender.
That same month, after painstaking work, Hut 8 at Bletchley Park began reading U-Boat messages in real time. Turing and his colleagues had cracked the U-Boat Enigma code in the nick of time. During the following month, U-Boats did not manage to sight a single convoy. They had turned the course of the war.
After the war, work began on developing powerful computers in various centres across the UK. Turing was known only as theorist because of the papers he had published. His practical work, largely carried out during wartime, was unknown because of the Official Secrets Act.
But he had seen great calculating machines in action, such as the Colossus at Bletchley Park. Nobody knew of Turing's expertise in these areas; neither was it certain that any computing machine would be electrical. So, as a surprise to many, Turing was appointed at the National Physics Laboratory to work on their ACE (Automatic Computing Engine) computer.
He recognised that the wartime calculating machines lacked the flexibility that data storage – memory – could bring. They were not true Turing Machines.
Turing worked on developing electrical memory. First he built giant pipes of liquid mercury, 5 feet long, in which pulses of supersonic sound were stored. These vessels could hold only a tiny amount of data, but it was a start in the process of giving the computer a data storage device.
However, because of conflicts between team members, progress was disappointing for 2 years. Rival teams in Cambridge and Manchester were making far better progress.
In Manchester, three principle engineers had been hired who were experts on circuits for radar, again expertise that had been built up during the war. They had free access to stores at Malvern for electronic parts. Between the months of January and October 1947, the Manchester team went from storing 1 bit to 2000 bits stored in computer memory.
At the time, the Manchester team had computer memory, but no computer to use it, so, with help from a grant from the Royal Society, they built the computer called Baby to use this new memory. The first stored program computer Baby ran was to find the highest factor of a number – it demonstrated that both the memory and the computer were working and that they could work together.
Alan Turing wrote a second program for Baby – an algorithm to perform long division - and sent it to the Manchester team. Before long, Turing had moved to Manchester and worked there developing the first computer programs.
In his own words, Turing was interested in producing models of the action of the brain. Meanwhile, the ACE was now working at NPL. It has since been reconstructed at the Science Museum in London.
Turing's homosexuality resulted in a criminal prosecution in 1952, when homosexual acts were still illegal in the UK. On 7 June 1954 Turing committed suicide at his home in Manchester because of persistent persecution by the British Government for his homosexuality.
Turing’s tragic death robbed us of an amazing talent. At the time, very little attention was paid to the death of this great logician. His work was largely unknown among the British public, although his breakthroughs had, without a doubt, changed the course of the Second World War. And his inventions had turned the history of computing. Today, Turing is widely considered to be the father of computer science and artificial intelligence.
When he was found after his suicide, a half-eaten apple lay by his bed. It may have been the delivery mechanism for the poison.
There is a story that the developers of Apple Computers used the symbol of an apple with a bite taken out for their logo to honour Turing. Sadly, this fitting tribute is probably nothing more than a legend.
On 10 September 2009, following an Internet campaign, British Prime Minister Gordon Brown made an official public apology on behalf of the British government for the way in which Turing was treated after the war.