The world’s first stored-program electronic digital computer, the English Small Scale Experimental Machine (SSEM, also known as “the Manchester Baby”), executed its first program on June 21, 1948. It had been written by Tom Kilburn, who helped build the machine along with his colleague and mentor, Frederic “Freddie” Williams.
Kilburn, born in Dewsbury, Yorkshire, UK, on August 11, 1921, was one of the “preeminent figures in the early history of computer design”, says the Association for Computing Machinery. “Over the course of some 30 years, he made significant contributions to the development of five historically significant computers.”
In its obituary for Kilburn, who died on January 17, 2001, The Telegraph newspaper describes his “Baby” as the first computer that could store data and a program in an electronic memory, and then process it at high speed. “It was thus the direct ancestor of the modern digital stored-program computer, and the program, written by Kilburn, was the first example of computer software.”{%recommended 6023%}
The Baby stood more than two metres tall and four metres long, and took up most of a large room. The first program to run successfully was one that could determine the highest factor of a given number, according to the newspaper report.
“The first number chosen was a low one, but within a few days Kilburn and Williams had built up the program to cope with two to the power of 18,” the obituarist writes. “The correct answer to this was found by the computer in 52 minutes, involving approximately 2.1 million instructions with some 3.5 million accessions of the stored program.”
Kilburn began working with Williams during World War II at the British government’s Telecommunications Research Establishment in Dorset, England. In 1946 they developed a form of digital storage using a cathode ray tube (CRT). They managed to store a “bit”, short for binary digit, in the form of a charge on the CRT screen’s phosphor, which could be controlled by an electron beam to write a 0 or a 1.
As described in an article on the History of Computers website, the charge would leak away in a second, so Williams and Kilburn arranged that it would be read and then rewritten continuously at electronic speed so that the information was, in effect, stored permanently.
“This process of regeneration is the principle still used today to replenish the charge in modern random access memory,” the site notes.
By December 1947, they had managed to store 2048 bits on a single 15-centimetre diameter CRT, which they patented as the Williams Tube. To test their new invention, they built the SSEM computer.
The website of the Computer History Museum says that in the early 1950s, Kilburn led the development of two new pioneering computers that were turned into commercial machines by British manufacturers.
“He then led the development of the Atlas computer system, which pioneered such modern concepts as paging, virtual memory, and multiprogramming, influencing the development of computer systems for generations,” the museum records.
“In 1962, it was considered the most powerful computer in the world.”
Kilburn retired in 1981, and lived in the English coastal town of Blackpool. Ironically enough, he did not own a personal computer. He died in 2001, from complications following stomach surgery.
