ENIAC Unveiled

In February 1946, the University of Pennsylvania publicly unveiled ENIAC, the Electronic Numerical Integrator and Computer. Built for the United States Army, it is widely regarded as the first general-purpose electronic digital computer, a machine that could be reprogrammed to tackle many kinds of problems at speeds no mechanical or electromechanical device could approach. Its debut is often treated as the opening of the modern computing age, though, as with many technological milestones, the story is more tangled than a single "first."

The project grew out of wartime need. The Army's Ballistic Research Laboratory required firing tables, which predicted where artillery shells would land under varying conditions, and producing them by hand or with mechanical calculators was slow and laborious. At Penn's Moore School of Electrical Engineering, John Mauchly and J. Presper Eckert proposed an electronic calculator built from vacuum tubes, which could switch far faster than relays or gears. Work began in 1943 under Army funding, with a large team contributing to the design and construction.

ENIAC was enormous. It filled a large room, used thousands of vacuum tubes along with miles of wiring, and consumed substantial electrical power. Reliability was a real concern, since tubes burned out, though the engineers managed to keep failures manageable. The machine was programmed not by loading stored instructions but by setting switches and plugging cables to route data between its units, a process that could take days. Much of this work was done by a group of women mathematicians, including Kay McNulty, Betty Jennings, and Frances Bilas, who became some of the first programmers, though their contributions went underrecognized for decades.

Although the machine was completed too late to affect the war, its early calculations reportedly included problems related to nuclear weapons research, in addition to ballistics and other scientific tasks. The cumbersome rewiring process pushed designers toward a new idea: storing programs in memory alongside data. Discussions among the ENIAC team and mathematician John von Neumann helped shape the stored-program concept, described in a 1945 report on its successor, EDVAC. Who deserves credit for the idea remains debated.

ENIAC's status as "first" has also been contested. Britain's Colossus machines, used for codebreaking, were electronic and earlier but were secret and special-purpose. Konrad Zuse's electromechanical machines and the Atanasoff-Berry Computer also figure in the debate, and a 1973 U.S. court ruling invalidated the ENIAC patent partly because of Atanasoff's earlier work. Even so, ENIAC's public unveiling captured the world's imagination, helped launch a commercial computer industry through Eckert and Mauchly's later ventures, and showed that electronic computation was practical at scale.