Tom Kilburn

Tom Kilburn (11 August 1921 – 17 January 2001) was an English mathematician and computer scientist.

Over his 30-year career, he was involved in the development of five computers of great historical significance.

With Freddie Williams he worked on the Williams–Kilburn tube and the world's first electronic stored-program computer, the Manchester Baby, while working at the University of Manchester.

His work propelled Manchester and Britain into the forefront of the emerging field of computer science.

A graduate of Sidney Sussex College, Cambridge, Kilburn worked on radar at the Telecommunications Research Establishment (TRE) in Malvern under Frederic Calland Williams during the Second World War.

After the war ended, he was recruited by Williams to work on the development of computers at the University of Manchester.

He led the development of a succession of innovative Manchester computers that incorporated a host of ground-breaking innovations and developments, including the Ferranti Mark 1, the world's first commercial computer, and the Atlas, one of the first time-sharing multiprocessing computers that incorporated job scheduling, spooling, interrupts, instruction pipelining and paging.

Tom Kilburn was born in Earlseaton near Dewsbury, Yorkshire, on 11 August 1921, the only son of John William Kilburn, a wool mill clerk who later became a company secretary, and his wife, Ivy Mortimer.

From 1932 to 1940, he attended the Wheelwright Grammar School for Boys, where the headmaster encouraged his aptitude for mathematics.

He also played sports, notably running.

In 1940, Kilburn entered Sidney Sussex College, Cambridge, with a state scholarship, a county major scholarship, and a minor open scholarship, where he studied mathematics.

Although many university dons were absent performing war work at places like Bletchley Park, the University of Cambridge maintained a vigorous mathematical community, and Kilburn became the Sidney Sussex College representative in the New Pythagoreans, a clique with the Cambridge University Mathematical Society that also numbered Gordon Welchman and Geoff Tootill among its members.

Due to the outbreak of the Second World War, courses were compressed to two years, and he graduated in 1942 with First Class Honours in Part I of the Mathematical Tripos and preliminary examinations for Part II.

On graduation, Kilburn was recruited by C.P. Snow.

He was given a quick course in electronics, and was posted to the Telecommunications Research Establishment (TRE) in Malvern, where he worked on radar in Group 19 under Frederic Calland Williams.

The group was responsible for designing and debugging electronic circuitry.

Although Williams was initially disappointed at being given someone with so little practical experience, Kilburn became a valued member of the team.

On 14 August 1943, he married Irene Marsden, a shop assistant.

They went on to raise a son, John, and a daughter, Anne.

Kilburn's wartime work inspired his enthusiasm for some form of electronic computer.

The principal technical barrier to such a development at that time was the lack of any practical means of storage for data and instructions.

In July 1946, Kilburn and Williams collaboratively developed a storage device based on a cathode ray tube (CRT) called the Williams–Kilburn tube.

A patent was filed in 1946.

Initially they used it to store a single bit.

The CRT image soon faded, so they devised a scheme by which it was read and refreshed continually, effectively making the data storage permanent.

In December 1946, Williams took up the Edward Stocks Massey Chair of Electrotechnics at the University of Manchester, and recruited Kilburn on secondment from Malvern.

By December 1947, they were able to store 2,048 bits on one 6 in diameter CRT.

The two developed their storage technology and, in 1948, Kilburn put it to a practical test in constructing the Manchester Baby, which became the first stored-program computer to run a program, on 21 June 1948.

He received the degree of PhD in 1948 for his work at Manchester, writing his thesis on A storage system for use with binary digital computing machines under Williams's supervision.

Kilburn anticipated a return to Malvern but Williams persuaded him to stay to work on the university's collaborative project developing the Ferranti Mark 1, the world's first commercial computer.

Max Newman withdrew from the project, believing that the development of computers required engineers and not mathematicians at this point, but Williams preferred to return to electrotechnics, leaving Kilburn in charge.

He was assisted by Alan Turing, who arrived at Manchester in 1948.

The Mark I incorporated innovations such as index registers, and combined CRTs with magnetic drum storage.

Nine Mark I computers were sold by between 1951 and 1957.

Over the next three decades, Kilburn led the development of a succession of innovative Manchester computers.

The first, commenced in 1951, was a development of the Mark I known as the megacycle machine or Meg, that replaced the vacuum tube diodes with solid state ones.

This permitted an order of magnitude increase in the clock rate.

To add further speed, Kilburn provided for 10-bit parallel CRT memory.

It was also one of the first computers, if not the first, to have floating point arithmetic.

Meg operated for the first time in 1954, and nineteen were sold by Ferranti under the name 'Mercury', six of them to customers overseas.