Howard Hathaway Aiken (1900-1973) was a major figure of the early digital era. He is best known for his first machine, the IBM Automatic Sequence Controlled Calculator or Harvard Mark I, conceived in 1937 and put into operation in 1944. But he also made significant contributions to the development of applications for the new machines and to the creation of a university curriculum for computer science. This biography of Aiken, by a major historian of science who was also a colleague of Aiken's at Harvard, offers a clear and often entertaining introduction to Aiken and his times.