John Mauchly

Mauchly stayed involved in computers for the rest of his life. He was a founding member and president of the Association for Computing Machinery (ACM) and also helped found the Society for Industrial and Applied Mathematics (SIAM), serving as its fourth president. The Eckert–Mauchly Corporation was bought by Remington Rand in 1950 and for ten years Mauchly remained as Director of Univac Applications Research. Leaving in 1959 he formed Mauchly Associates, a consulting company that later introduced the critical path method (CPM) for construction scheduling by computer. In 1967 he founded Dynatrend, a computer consulting organization. In 1973 he became a consultant to Sperry Univac.

Mauchly and Eckert's patent on the ENIAC was invalidated by U.S. Federal Court decision in October, 1973 for several reasons. Some had to do with the time between publication (the First Draft) and the patent filing date (1947). The federal judge who presided over the case ruled that "the subject matter was derived" from the earlier Atanasoff–Berry computer (ABC). This statement has become the center of a controversy.

Critics note that while the court said that the ABC was the first electronic digital computer, it did not define the term computer. It had originally referred to a person who computes, but was adapted to apply to a machine.

Critics of the court decision also note that there is, at a component level, nothing in common between the two machines. The ABC was binary; the ENIAC was decimal. The ABC used regenerative drum memory; The ENIAC used electronic decade counters. The ABC used its vacuum tubes to implement a binary serial adder, while the ENIAC used tubes to implement a complete set of decimal operations. The ENIAC's general-purpose instruction set, together with the ability to automatically sequence through them, made it a general-purpose computer. However, the later EDVAC computer, developed without the immediate pressures of wartime projects, harked back more to the ABC in that it was a binary computer employing regenerative memory.

Proponents for the court decision emphasize that the testimony established that Mauchly definitely visited Atanasoff's lab at Iowa State College, had complete access to Atanasoff's machine and the documents describing it. Letters he wrote to Atanasoff show that he was at one time at least considering building on Atanasoff's approach.

Mauchly consistently maintained that it was the use of high-speed electronic flip-flops in cosmic-ray counting devices at Swarthmore College that gave him the idea for computing at electronic speeds.