How Alan Turing ushered in modern computing (photos)

On Feb. 19, 1946, Alan Turing submitted his now famous "Proposal for the Development in the Mathematics Division of an Automatic Computing Engine" - later known as "ACE" - at a meeting of the National Physical Laboratory in England. It was a breakthrough idea for the time: a design for a stored-program computer. (Here's a video with a couple of Turing's colleagues reminiscing about their work together.) Four years later, the Pilot ACE, built at England's National Physical Laboratory in 1950, came into being. This was an early version of a computer system Turing had designed. The system, which was state-of-the-art for its time, was an early stored program computer. It used about 800 vacuum tubes and had a clock speed of 1 MHz.