1946 ENIAC

The book of science

Tom Sharp

John Grist Brainerd, John Mauchly, J. Presper Eckert computer science ENIAC


The Electronic Numerical Integrator and Computer, assembled at the Moore School of Electrical Engineering at 200 South 33rd Street in Philadelphia, was the first digital programmable Turing-complete general-purpose electronic computer. John Grist Brainerd was the manager of the project. John Mauchly and J. Presper Eckert designed it. John von Neumann acted as a consultant. ENIAC had 17,468 vacuum tubes, 70,000 resistors, 10,000 capacitors, and 1,500 relays. ENIAC was programmed by turning up to 6,000 manual switches and moving jumper cables. Kay McNulty (Mauchly, Antonelli), Betty “Jean” Jennings (Bartik), Francis “Betty” Snyder (Holberton), Marlyn Meltzer (Spence), Fran Bilas (Spence), and Ruth Lichterman (Teitelbaum) were ENIAC’s first programmers.

Spawn of ENIAC

“Baby,” Manchester Small-Scale Experimental Machine, 1948 Manchester Mark 1, 1949 EDSAC, Electronic Delay Storage Automatic Calculator, 1949 BINAC, Binary Automatic Computer, 1949 CSIRAC, Council for Scientific and Industrial Research Automatic Computer, 1949 SEAC, Standards Eastern Automatic Computer, 1950 SWAC, Standards Western Automatic Computer, 1950 ERA 1101, Engineering Research Associates 1101, 1950 EDVAC, Electronic Discrete Variable Automatic Calculator, 1951 UNIVAC I, Universal Automatic Computer I, 1951 ORDVAC, Ordnance Variable Automatic Computer, 1952


Even when operating vacuum tubes at half their normal voltage, tube failures were regular occurrences but worth the time to find and replace them for the tubes provided much faster operation than mechanical switches would have.


The six women who programmed ENIAC without an operating system or programming language, given only the logical diagrams of the machine, were not given credit at the time, nor were some recognized in their lifetimes, nor were they all invited or honored at the fiftieth anniversary event. Let’s think of this before we complain of men who don’t get their due rewards.

While ENIAC was being built, J. Presper Eckert, John Mauchly, John von Neumann, A. W. Burks, and Captain H. Goldstine were selected to work on a new computer that would take advantage of the lessons that they were learning from ENIAC. They called this new computer EDVAC. The EDVAC was smaller than the ENIAC, eliminated parallel operations, and stored its own program code. It was completed in August 1949 and it started limited operations in late 1951. Meanwhile, von Neumann’s report on the EDVAC inspired similar projects in England, Australia, and elsewhere in the United States.

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