Professor Sir Maurice Wilkes

The computer, known as EDSAC (Electronic Delay Storage Automatic Calculator) was a huge contraption that took up a room in what was the University’s old Mathematical Library. It contained 3,000 vacuum valves arranged on 12 racks and used tubes filled with mercury for memory. Despite its impressive size, it could only carry out 650 operations per second.

Before the development of EDSAC, digital computers, such as the American Moore School’s ENIAC (Electronic Numeral Integrator and Computer), were only capable of dealing with one particular type of problem. To solve a different kind of problem, thousands of switches had to be reset and miles of cable re-routed. Reprogramming took days.

In 1946, a paper by the Hungarian-born scientist John von Neumann and others suggested that the future lay in developing computers with memory which could not only store data, but also sets of instructions, or programs. Users would then be able to change programs, written in binary number format, without rewiring the whole machine. The challenge was taken up by three groups of scientists — one at the University of Manchester, an American team led by JW Mauchly and JP Eckert, and the Cambridge team led by Wilkes.

Eckert and Mauchly had been working on developing a stored-program computer for two years before Wilkes became involved at Cambridge. While the University of Manchester machine, known as “Baby”, was the first to store data and program, it was Wilkes who became the first to build an operational machine based on von Neumann’s ideas (which form the basis for modern computers) to deliver a service.

Wilkes chose to adopt mercury delay lines suggested by Eckert to serve as an internal memory store. In such a delay line, an electrical signal is converted into a sound wave travelling through a long tube of mercury at a speed of 1,450 metres per second. The signal can be transmitted back and forth along the tube, several of which were combined to form the machine’s memory.

This memory meant the computer could store both data and program. The main program was loaded by paper tape, but once loaded this was executed from memory, making the machine the first of its kind.

After two years of development, on May 6 1949 Wilkes’s EDSAC “rather suddenly” burst into life, computing a table of square numbers. From early 1950 it offered a regular computing service to the members of Cambridge University, the first of its kind in the world, with Wilkes and his group developing programs and compiling a program library. The world’s first scientific paper to be published using computer calculations — a paper on genetics by RA Fisher – was completed with the help of EDSAC.

Wilkes was probably the first computer programmer to spot the coming significance of program testing: “In 1949 as soon as we started programming”, he recalled in his memoirs, “we found to our surprise that it wasn’t as easy to get programs right as we had thought. Debugging had to be discovered. I can remember the exact instant when I realised that a large part of my life from then on was going to be spent in finding mistakes in my own programs.”

In 1951 Wilkes (with David J Wheeler and Stanley Gill) published the world’s first textbook on computer programming, Preparation of Programs for an Electronic Digital Computer. Two years later he established the world’s first course in Computer Science at Cambridge.

EDSAC remained in operation until 1958, but the future lay not in delay lines but in magnetic storage and, when it came to the end of its life, the machine was cannibalised and scrapped, its old program tapes used as streamers at Cambridge children’s parties.

Wilkes, though, remained at the forefront of computing technology and made several other breakthroughs. In 1958 he built EDSAC’s replacement, EDSAC II, which not only incorporated magnetic storage but was the first computer in the world to have a micro-programmed control unit. In 1965 he published the first paper on cache memories, followed later by a book on time-sharing.

In 1974 he developed the “Cambridge Ring”, a digital communication system linking computers together. The network was originally designed to avoid the expense of having a printer at every computer, but the technology was soon developed commercially by others.

When EDSAC was built, Wilkes sought to allay public fears by describing the stored-program computer as “a calculating machine operated by a moron who cannot think, but can be trusted to do what he is told”. In 1964, however, predicting the world in “1984”, he drew a more Orwellian picture: “How would you feel,” he wrote, “if you had exceeded the speed limit on a deserted road in the dead of night, and a few days later received a demand for a fine that had been automatically printed by a computer coupled to a radar system and vehicle identification device? It might not be a demand at all, but simply a statement that your bank account had been debited automatically.”

Maurice Vincent Wilkes was born at Dudley, Worcestershire, on June 26 1913. His father was a switchboard operator for the Earl of Dudley whose extensive estate in south Staffordshire had its own private telephone network; he encouraged his son’s interest in electronics and at King Edward VI’s Grammar School, Stourbridge, Maurice built his own radio transmitter and was allowed to operate it from home.

Encouraged by his headmaster, a Cambridge-educated mathematician, Wilkes went up to St John’s College, Cambridge to read Mathematics, but he studied electronics in his spare time in the University Library and attended lectures at the Engineering Department. After obtaining an amateur radio licence he constructed radio equipment in his vacations with which to make contact, via the ionosphere, with radio “hams” around the world.

Wilkes took a First in Mathematics and stayed on at Cambridge to do a PhD on the propagation of radio waves in the ionosphere. This led to an interest in tidal motion in the atmosphere and to the publication of his first book Oscillations of the Earth’s Atmosphere (1949). In 1937 he was appointed university demonstrator at the new Mathematical Laboratory (later renamed the Computer Laboratory) housed in part of the old Anatomy School.

When war broke out, Wilkes left Cambridge to work with R Watson-Watt and JD Cockroft on the development of radar. Later he became involved in designing aircraft, missile and U-boat radio tracking systems.

In 1945 Wilkes was released from war work to take up the directorship of the Cambridge Mathematical Laboratory and given the task of constructing a computer service for the University.

The following year he attended a course on “Theory and Techniques for Design of Electronic Digital Computers” at the Moore School of Electrical Engineering at the University of Pennsylvania, the home of the ENIAC. The visit inspired Wilkes to try to build a stored-program computer and on his return to Cambridge, he immediately began work on EDSAC.

Wilkes was appointed Professor of Computing Technology in 1965, a post he held until his retirement in 1980. Under his guidance the Cambridge University Computer Laboratory became one of the country’s leading research centres. He also played an important role as an adviser to British computer companies and was instrumental in founding the British Computer Society, serving as its first president from 1957 to 1960.

After his retirement, Wilkes spent six years as a consultant to Digital Equipment in Massachusetts, and was Adjunct Professor of Electrical Engineering and Computer Science at the Massachusetts Institute of Technology from 1981 to 1985. Later he returned to Cambridge as a consultant researcher with a research laboratory funded variously by Olivetti, Oracle and AT&T, continuing to work until well into his 90s.

Maurice Wilkes was elected a fellow of the Royal Society in 1956, a Foreign Honorary Member of the American Academy of Arts and Sciences in 1974, a Fellow of the Royal Academy of Engineering in 1976 and a Foreign Associate of the American National Academy of Engineering in 1977. He was knighted in 2000.

Among other prizes he received the ACM Turing Award in 1967; the Faraday Medal of the Institute of Electrical Engineers in 1981; and the Harry Goode Memorial Award of the American Federation for Information Processing Societies in 1968.

In 1985 he provided a lively account of his work in Memoirs of a Computer Pioneer.

Maurice Wilkes married, in 1947, Nina Twyman. They had a son and two daughters.