Computing with Quantum Cats by John Gribbin Read Free Book Online Page A

couldn't believe it!…I don't think they understood very clearly what I was proposing until they actually had the machine.” 12
    The re-assembled Colossus broke its first message on 5 February 1944. It was ten times faster than Heath Robinson, and, equally important, more reliable. Orders for more Robinsons were canceled, and Flowers was asked how quickly Dollis Hill could produce more “Colossi.”
    One of the Wrens 13 who worked on Colossus, Betty Houghton (née Bowden), now lives in a neighboring village to us. She was fourteen when the war broke out, and three years later joined the WRNS. She was told that there were two kinds of jobs available—cook/steward or “P5.” Having no wish to be a cook/steward, she asked what P5 was. “That's secret,” she was told, and promptly volunteered. She ended upas a Watch Leader in Hut 8 at Bletchley Park, working on Tunny, and recalls Turing as “a very nice man, very quiet; a bit daft, like most of them.”
    Colossus was the first electronic computer. It was also programmable, in a limited sense, because Flowers had deliberately designed it so that it could be adapted to new requirements by switches, and by plugging cables linking the logic units in different arrangements. The crucial difference from a modern computer, though, is that it did not store programs in its memory, the way Turing had envisaged; the programming had to be done literally “by hand” at the switches and plugboards. Even so, this adaptability proved an enormous asset, and Colossi could be adapted to use new codebreaking methods as they were invented, carrying out tasks that its designer could not have imagined.
    Flowers was asked to have an improved Colossus up and running at Bletchley by June 1, 1944. He was not told why, but the urgency was stressed. The tight deadline was met by having the machine, containing 2,400 valves and running 125 times faster than electromechanical machines, assembled and tested on site. It began operating on June 1, as requested; although Flowers did not know it at the time, this was intended to be D-Day, the date of the invasion of German-occupied France. Bad weather delayed the invasion, and as it continued there were serious doubts about whether the Allies would be able to ship enough men and matériel across the rough English Channel to support the invasion against a counter-attack. But on June 5 Colossus II was instrumental in breaking a message which revealed that Hitler had completely fallen for the Allied deception plan (Operation Fortitude), which led him to believe that the invasion would strike at thePas de Calais, with a diversionary raid in Normandy. In the intercepted Tunny signal, he ordered Rommel to hold his forces in the Pas de Calais area to repel the “real” invasion, due five days after the expected Normandy landing. It was this piece of information, combined with a forecast of slightly improving weather, that clinched Eisenhower's decision to go ahead on June 6, knowing that even in bad weather five days would give his forces time to build up the beachhead.
    By the end of the war in 1945 eight more Colossi had been installed at Bletchley Park, and Eisenhower himself later said that without the work of the codebreakers the war would have lasted at least two years longer than it did. The two men who did more than anyone else to make all this possible were Turing and Flowers. They should each have been knighted at the end of hostilities, and given every support to develop their ideas further. But that isn't the way it happened.
    ANTICLIMAX: AFTER BLETCHLEY
    Harry Fenson, a member of Flowers’ team, has said that he was well aware at the time that Colossus was “a data processor rather than a mere calculator, and rich in logical facilities.” It had the potential to manipulate many kinds of data, “such as text, pictures, movement, or anything which could be given a value.” It