At the end of the war, Wilkes returned to Cambridge University, with the mission to rebuild the Mathematical Laboratory. Electronic computing was in the air. At the Moore School of Electrical Engineering, University of Pennsylvania, the ENIAC, the world’s first electronic computer for defense calculations, designed by J. Presper Eckert and John Mauchly, had just been completed. Eckert and Mauchly, together with John von Neumann, subsequently produced a proposal for the EDVAC, the blueprint of the modern stored-program digital computer. In the summer of 1946, Wilkes was one of a handful of Britishers invited to attend a course on electronic computers at the Moore School. Sailing home on the Queen Mary he began the design of a machine he called the Electronic Delay Storage Automatic Calculator, EDSAC for short, an acronym consciously chosen as a tribute to the EDVAC.
Work started on building the EDSAC in early 1947. The following spring Wilkes married Nina Twyman, a classicist he had met in Cambridge; they had three children.
Almost everything in the EDSAC had to be done from first principles—memory technology, electronic arithmetic and logic, and control circuits. The machine sprang to life on May 6, 1949, the world’s first practical electronic computer. (Manchester University had got there first in June 1948 with an experimental machine, but the EDSAC was the first capable of running realistic programs.) By the beginning of 1950 the Mathematical Laboratory was offering a regular computing service. Wilkes decided that the laboratory would specialize in writing programs rather than building computers. He was perhaps the first person to recognize that what we now call software (a term not used until about 1960) would prove to be a worthwhile academic pursuit. Heavy use of the laboratory’s facilities was made by Cambridge University’s researchers, including some of its luminaries—such as John Kendrew, Fred Hoyle, and Martin Ryle. Kendrew’s calculations for determination of the molecular structure of myoglobin, for which he received a Nobel Prize in 1962, were largely done on the EDSAC.