Kilburn, Tom

Tom Kilburn, (born August 11, 1921, Dewsbury, Yorkshire, England—died January 17, 2001, Manchester), British engineer and coinventor of the first working computer memory. Kilburn also designed and built the first stored-program computer and led a team that produced a succession of pioneering computers over the next 25 years.

Ferranti Mark I

In 1942 Kilburn graduated from the University of Cambridge with a degree in mathematics. He immediately converted, however, to electronics research when he was recruited to join Frederic Williams’s wartime radar group at the Telecommunications Research Establishment (TRE). In December 1946 Williams left TRE to become a professor at the University of Manchester, and Kilburn accompanied him in order to help develop an electronic storage system for electronic computers. They devised a storage device—later known as the Williams tube—based on cathode-ray tubes. A working model was completed late in 1947, and by June 1948 they had incorporated it in a small electronic computer that they built to prove the device’s effectiveness. The computer was called the Small Scale Experimental Machine (SSEM) or just “Baby.” It was the world’s first working stored-program computer, and the Williams tube became one of the two standard methods of storage used by computers worldwide until the advent of magnetic-core storage in the mid-1950s. By April 1949 the SSEM had developed into a full-sized machine, and by October 1949 secondary storage had been added (using a magnetic drum). This machine, the Manchester Mark I, was the prototype for the Ferranti Mark I, manufactured by Ferranti Ltd. (See photograph.)

From 1951 Kilburn formally led the computer group within Williams’s electrical engineering department. In 1953 the group completed an experimental computer using transistors instead of vacuum tubes. In 1954 the group completed MEG, which provided floating-point arithmetic (calculations using exponential notation—e.g., 3.27 × 10¹⁷) and was manufactured by Ferranti as the Mercury beginning in 1957.

In 1956 Kilburn started his most ambitious project, MUSE, renamed Atlas when Ferranti joined the project in 1959. In parallel with two similar projects in the United States (LARC and Stretch; see supercomputer) but largely independent of them, Atlas made the massive jump from running one program at a time to multiprogramming. With multiprogramming a computer can “interleave” several programs, allocating various computer resources (memory, storage, input, and output) to each program through an operating system. Atlas was also the first computer to employ a technique, now known as virtual memory or virtual storage, of using some slower external memory (such as magnetic drums) as though it were an extension of the computer’s faster internal memory. Operational by 1962, Atlas was probably the most sophisticated computer of its time.

In 1964 Kilburn created the first department of computer science in the United Kingdom. In 1966 he started his last computer project, MU5. Operational by 1972, MU5 pioneered an architecture geared to the requirements of high-level languages (languages with more humanlike syntax).

Kilburn was made a professor in 1960 and was elected a fellow of the Royal Society in 1965. He retired in 1981.