Penn Library

John W. Mauchly and the Development of the ENIAC Computer

Project PX: The ENIAC Project, 1942-1946

Mauchly drafted a memo during the summer of 1942, outlining the first large-scale digital electronic computer designed for general numerical computations. Having spent a year at the Moore School, he had come to have a better understanding of electronic engineering and the mathematics of ballistics computations. A budding association with J. Presper Eckert, who had been the laboratory assistant for the course that Mauchly had taken during the previous summer, provided valuable technical support. Indeed, Mauchly and Eckert together discussed what it might entail to build a large electronic computer.

The memo was carefully drafted to bring together the various interests that would justify an electronic computing project. This included the ability of such a computer to produce ballistics tables--a task on which the Moore School was falling increasingly behind. It also drew attention to the engineering expertise of the Moore School. Most important, Mauchly laid out the design as a general purpose digital computer. His own research interests in meteorology and cryptography precluded a device limited only to ballistics computations. Too esoteric for the Moore School's senior faculty, and perhaps in conflict with a separate effort to produce an electronic version of the differential analyzer, Mauchly's memo remained idle for the time being.


Cover for "ENIAC Progress Report," 30 June 1944 (ENIAC Museum, SEAS, UP). (click to expand to 83k)

President Truman in front of ENIAC (U.S. Army photo, from archives of ARL/SLAD/BVLD, courtesy of Mike Muuss). (click to expand to 165k)
It did become the basis for a formal proposal submitted the following year. At this point, the impetus came from Lt. Herman Goldstine of the Ballistics Research Laboratory. Having received a Ph.D. in applied mathematics from the University of Chicago, Goldstine quickly assessed the computational advantages of Mauchly's machine. Excited at the prospects of having a machine that could eliminate the backlog of ballistics computations, Goldstine encouraged both the Moore School and the Ordnance Department to support the project. An official proposal was submitted in April of 1943, and the resulting contract, Project PX, gave birth to the ENIAC computer. All together, the U.S. Army provided approximately $500,000 for the ENIAC's development.

Mauchly was never officially a researcher on Project PX. Given his designated duties as an instructor, he was permitted only to act as a consultant to the project. In his spare time, however, Mauchly worked closely with Eckert and others to realize the ENIAC computer. An extensive collection of laboratory notebooks, blueprints, and correspondence that document the ENIAC work can be found in the University Archives and Records Center of the University of Pennsylvania.


Accumulator Decade Plug-in Unit, from "ENIAC Progress Report," 30 June 1944 (ENIAC Museum, SEAS, UP). (click to expand to 83k)

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