John Mauchly met on a number of occasions between 1940 and 1941 with Dr. John Atanasoff (the creator of the Atanasoff Berry Computer, or ABC) to discuss his ideas. Atanasoff gave Mauchly details of his own computer design, but how far Dr. Atanasoff’s ideas influenced John Mauchly remains a matter of dispute.

Working with John Presper Eckert, a first class engineer, John Mauchly started work to build an Electronic Digital Automatic Computer in June 1943.

ENIAC (the Electronic Numeric Integrator And Computer) was ready for work at the very end of 1945. A huge machine; it contained 18,000 vacuum tubes and weighed 30 tons; a testament to Eckert's technical skill that it worked at all. Unusually it operated in decimal rather than the ‘usual’ binary.

Presper Eckert

In the USA, World War II brought the need for the calculation of Firing Tables for different types of gun. The complex calculation (a partial differential equation) for just one type of gun required 3 months' work by a team of 176 human calculators.

Lieutenant Herman Goldstine, a mathematician, was in charge of calculating work carried out on this at the Moore School of Engineering at the University of Pennsylvania.

In a chance conversation he had heard of the interest of John Mauchly, a Professor at the Moore School, of using vacuum tubes (an American word for valves) for computation. Goldstine persuaded his superiors to commission a machine.

John Mauchly