In 1945 Douglas Hartree had been Professor of Theoretical Physics at Manchester for some 14 years. He was one of the world's experts in numerical computation, having played a major part in developing the Hartree-Fock method of investigating complex atomic systems.


In 1946, Hartree was asked by Colonel Paul Gillon to visit the Moore School in the USA to help with the application of ENIAC to scientific calculations in which he was a world leader. In the course of this work he became the first European to program ENIAC. When he returned to the UK he encouraged Maurice Wilkes to attend a course at the School in the autumn of that year. Wilkes returned to Cambridge intent on constructing a computer to the von Neumann ‘specification’.


Wilkes, working with his chief engineer, Renwick, achieved his aim in about 30 months and in May 1949 the EDSAC (Electronic Digital Store And Computer) became the first fully practical, operational, working, digital, electronic, automatic computer with conditional branching, a stored program in a read-write store and (unlike the Manchester 'Baby') good input/output facilities. Essentially EDSAC was the first fully-fledged computer, as we understand them today.


EDSAC used a store based on pulses circulating through mercury tanks known as delay lines. The design for these delay lines was another product of the Second World War which had seen the advent of Radar. Wilkes was lucky enough to find that another Cambridge man, Tom Gold, had worked on Radar's development at the Admiralty Signal Establishment, and subsequently Gold gave Wilkes the blueprint design for the store.

THE FIRST FULLY OPERATIONAL COMPUTER

The contribution of Radar to the Allied Forces' victory on D-day and to saving lives throughout the war was at least as great as that of COLOSSUS, and its contribution to the history of computing is yet a further testament to the ingenuity of the men and women who worked at the Telecommunications Research Establishment. As a result of this collaboration Wilkes and Gold worked together on the delay lines, with Wilkes improving the performance of the mercury storage device Gold had helped design.


Wilkes and his team achieved 2 other firsts. From day one, unlike a number of other early computers, EDSAC was used to pre-process its own programs and thus the difficulty of programming it was reduced significantly. Also, from its very early days, EDSAC was used to provide a computing service for others in the University who normally wrote their own programs. Later, with D. J. Wheeler (who did much of the initial programming for EDSAC) and S. Gill, Wilkes wrote the first textbook on computer programming to be published though this was preceded in 1947/48 by Goldstine and von Neumann in a circulated account.

Douglas Hartree and

Albert Einstein

together at Leiden

Maurice Wilkes