Tom Kilburn (1921 – 2001)


Kilburn together with Fredric Williams and Geoff Tutill built the first transistor-only computer in the world at Manchester university the SSEM – dubbed the “baby”. The baby was the first ever computer which could run a program stored electronically in memory. The birth of the baby marked a new era in computing and introduced the concept of “software”.

The main challange for such a development was the lack of any practical means of storage for data and instructions. Kilburn and Williams collaboratively developed a storage device based on a cathode ray tube called Williams-Kilburn tube patented in 1946. The baby was not built as a functional computer, but only to test the viability of the tube design.

The Mark I of the baby became the blueprint for the worlds first commercially available general purpose computer produced in partnership between Manchester university and Ferranti Ltd., known as the Ferranti Mark I. It was released in Feb. 1951 before the UNIVAC I which was delivered 31st March 1951.

Before the baby, computers were re-programmed by being re-wired. By contrast the baby used the store to hold both the data being worked on and the instructions about what to do with it.

It had the first Random Access Memory (RAM) in the form of the CRT tubes. Modern computers typically sport a RAM several gigabytes in size compared to the baby’s 1024 bits (128 bytes).

Fun facts:

  • Celebration of that first successful run was muted, said Tootill. “We went to lunch in the canteen as usual and probably discussed what we were going to do next,” he said.
  • When they decided to extend and expand the baby into the Manchester Mark I and cannibalized it for the parts to build the new machine. Even the rack on which it was mounted was reused for the next model.

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