Kathleen Hylda Valerie Booth ( Britten, 9 July 1922 – 29 September 2022) was a British computer scientist and mathematician who wrote the first assembly language and designed the assembler and autocode for the first computer systems at Birkbeck College, University of London. She helped design three different machines including the ARC (Automatic Relay Calculator), SEC (Simple Electronic Computer), and APE(X)C. Early life and education Kathleen Britten was born in Stourbridge, Worcestershire, England, on 9 July 1922. She obtained a BSc in mathematics from the University of London in 1944 and went on to get a PhD in Applied Mathematics in 1950. She married her colleague Andrew Donald Booth in 1950 and had two children. Career Kathleen Booth worked at Birkbeck College, 1946–62. She travelled to the United States as Andrew Booth's research assistant in 1947, visiting with John von Neumann at Princeton. Upon returning to the UK, she co-authored "General Considerations in the Design of an All Purpose Electronic Digital Computer," describing modifications to the original ARC redesign to the ARC2 using a von Neumann architecture. Part of her contribution was the ARC assembly language. She also built and maintained ARC components. Kathleen and Andrew Booth's team at Birkbeck were considered the smallest of the early British computer groups. From 1947 to 1953, they produced three machines: ARC (Automatic Relay Computer), SEC (Simple Electronic Computer), and APE(X)C (All-purpose Electronic (Rayon) Computer). She and Mr. Booth worked on the same team. He built the computers and she programmed them. This was considered a remarkable achievement due to the size of the group and the limited funds at its disposal. Although APE(X)C eventually led to the HEC series manufactured by the British Tabulating Machine Company, the small scale of the Birkbeck group did not place it in the front rank of British computer activity. Booth regularly published papers concerning her work on the ARC and APE(X)C systems and co-wrote "Automatic Digital Calculators" (1953) which illustrated the 'Planning and Coding' programming style. In 1957, She, her husband, and J.C. Jennings co-founded Birkbeck College's Department of Numerical Automation, now the School of Computer Science and Information Systems, in 1957. In 1958, she taught a programming course. In 1958, Booth wrote one of the first books describing how to program APE(X)C computers. From 1944 she was a Junior Scientific Officer at the Royal Aircraft Establishment in Farnborough. From 1946 to 1962, Booth was a