Bletchley park

By the time he received his Ph.D. in June 1938, a number of things had happened which set his course for the next few years. Yon Neumann had become aware of, and admired, "Computable Numbers" and had offered him a research assistantship at the institute of Advanced Study. Turing had built an electronic multiplier and developed is earlier interest in codes and ciphers. And Hitler's war was threatening.

Bravely he turned down von Neumann's offer and returned to Cambridge in the hope that Hitler will not have invaded England-before I come back". He arrived at Southampton on July 18 with his electronic multiplier wrapped in brown paper. Within weeks he was on a course at the Government Code and Cipher School, one of sixty or so people earmarked for recruitment if war should break out. The day after war was declared he reported to Bletchley Park in Buckinghamshire, the home of the Code and Cipher School, and set to work on the German ciphers. He was ideal for the job.

The British effort at breaking the German codes initially depended on work done in Poland. It is a complex story and one that has already been described, for example by Hodges in his biography of Turing. The Germans used a machine called Enigma to encipher their messages but the Poles had, in effect, obtained a logical copy of the basic machine. To break the cipher they had built other machines which, because of the ticking noises they made, came to be known as bombes. The Germans increased the complexity of Enigma and rendered the Polish bombes ineffective.

He arrived at Southampton with his electronic multiplier wrapped in brown paper...

The Bletchley team, especially Alan Turing and Gordon Welchman, brought new ideas to the problem and new bombes were designed and built. According to Hodges they were "impressive and rather beautiful machines, making noises like that of a thousand knitting needles". There began what Hodges has termed the "relay race" as each side sought to stay one step ahead of the other but with the Germans never believing that Enigma had been broken, only that spies were at work.

When America came into the war Turing was despatched on the Queen Elizabeth to brief them on the cipher breaking work. During his visit he spent a couple of months at Bell Laboratories, meeting Nyquist and Claude Shannon amongst others. Meanwhile Max Newman had arrived at Bletchley and had started work on electronic counting machines which became known as the Robinsons. These were followed by a series of electronic computers, each known as Col­ossus. Turing played little, if any. part. He moved on to a new pet project on speech encipherment which reduced speech to meaningless white' noise and then recovered it. He designed the machine, built it. called it Delilah - and it worked. By the end of the war Turing had returned to his pre-war ideas, developed now into a Universal Turing Machine. Strengthened by his experiences with electronics he faced the question of whether this could now become something more than an intellectual concept. Could it become a real machine? He wanted to build an electronic "brain", essentially what we would now recognize as' ah automatic digital computer, with internal program storage.

Of course, he was now not alone in thinking such thoughts, for in America the ENIAC was now built and plans had been published for another machine to be called -EDVAC. Such news probably influenced the National Physical Laboratory in its plan to build a national computer with Turing's help: a Universal Turing Machine. It was to be known as the Automatic Computing Engine or ACE. Turing's design used binary arithmetic and was to have the simplest possible hardware based on the logical functions And, Or and Not, and a large and fast memory. The rest would be performed by the sets of instructions, the programs. As a design it was unique and owed little to the other pioneer computers.

Funds were allocated in 1946 to begin work on a small machine, later known a Pilot ACE. Internal politics and delays did not augur well, however, for the urgency of wartime had not carried forward into peace. Turing left before even the Pilot ACE was completed. He was on sabbatical at Cambridge when the new computer team at Manchester University offered him a position. He accepted in May 1948 and joined them in the autumn. The Manchester prototype ran its first program on June 21, 1948, and in February 1951 the first of the Ferranti Mkl computers was delivered, based on the university machine. Pilot ACE (which is now in the Science Museum, London) ran its first program on May 10, 1950, and the full ACE was not completed until late in 1957. At Manchester, Turing came to spend much of his time in develop­ing programming techniques, even doing manual arithmetic in base 32.

Turing was always a loner. Many found him difficult to get on with. He received the OBE* in June 1946 as official thanks for his wartime work. It came through the post. And in March 1951 he was elected a Fellow of the Royal Society, probably a more fitting tribute. Glasgow's Turing Institute opened in 1984. Perhaps one more tribute is yet to come, when someone finds those silver bars near the M25 motorway.

• OBE - Officer of the British Empire –– кавалер ордена Британской империи 4-й степени.