ENIAC

The Electronic Numerical Integrator and Calculator, developed at the University of Pennsylvania, was the world's first general-purpose electronic digital computer, built around 18,000 vacuum tubes and programmable only by manual rewiring.

ENIAC was not a machine one simply turned on and used. Programming meant reconfiguring a forest of patch cords and switches, 6,000 of them, by hand, a labor-intensive process that could take days to shift from one problem to another². Designed by J. Presper Eckert and John W. Mauchly, it was physically immense: 40 panels, each man-high, spread across 1,800 square feet and weighing over 30 tons²⁶⁸. Its 17,000 to 18,000 vacuum tubes, sources vary, demanded constant attention, with reports that valves required replacement every six hours to prevent burnout due to heat¹⁵⁷. Cooling systems were essential, not optional⁵⁷.

Despite its bulk and fragility, ENIAC’s performance was unprecedented. It executed about 100,000 operations per second and completed a multiplication in 200 milliseconds¹¹¹. This made it roughly 1,000 times faster than the electromechanical relay computers it displaced³⁶⁸. Input and output were handled via punched cards, and internal storage relied on registers that doubled as adders and fast-access memory locations²⁶⁸. The architecture had no stored program; instructions were physically embodied in wiring and switch settings⁶⁸.

The machine’s first test problem, a shakedown run in 1946, was formulated by Dr. Nicholas Metropolis and Dr. Stanley Frankel for the Manhattan Project¹⁰. By the time it was operational, however, it was already considered nearly obsolete, overtaken conceptually by the stored-program model later formalized by John von Neumann, who had consulted on the Manhattan Project and in 1945 outlined a simpler, fixed-structure computer design¹⁰⁸. A 1973 court decision invalidated the ENIAC patent, ruling that its design derived from John Atanasoff’s earlier work, a judgment that retroactively credited Atanasoff as the inventor of the first electronic digital computer after 34 years of obscurity¹³.

Its legacy is both monumental and ironic. While ENIAC is widely credited with launching the electronic computing age¹, later comparisons highlight its limitations: a $5 pocket calculator from the 1980s could match its speed, and a $100 programmable model could surpass it². The CS-9000, a desktop computer of that era, performed a multiplication in under 2 microseconds, 100,000 times faster than ENIAC¹¹. Eckert and Mauchly went on to design the UNIVAC I, the first computer widely used in business and government, capable of handling both numeric and alphabetic data with equal facility³. ENIAC, EDVAC, BINAC, and UNIVAC are often cited together as the foundational lineage of early electronic computing¹².

References

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