
Kathleen Booth worked intimately with some of the oldest electronic digital computers. The Automatic Relay Calculator (ARC), Simple Electronic Computer (SEC), and All Purpose Electronic (X) Computer (APE(X)C) were all projects she was involved heavily in.
Booth developed the first assembly language, and often developed the machines her husband (who was a member of her research team) constructed. The book she wrote on writing software for the APE(X)C was one of the first books concerning software development in general.