ENIAC (Electronic Numerical Integrator and Computer)

What ENIAC was

ENIAC — the Electronic Numerical Integrator and Computer — was announced on 14 February 1946, and the University of Pennsylvania describes it as the first general-purpose electronic computer^[1]. It was a room-sized machine: when fully operational it occupied a room 30 by 50 feet and weighed 30 tons^[1]. Its 40 panels were arranged in a U-shape measuring 80 feet across the front, and the machine used 18,000 vacuum tubes^[1]. Behind those figures sits a great deal of wiring and hardware: 500,000 soldered joints, 70,000 resistors and 10,000 capacitors, with 150 kilowatts of electricity drawn over dedicated power lines^[1].

How it computed

The arithmetic units were twenty accumulators for addition and subtraction, a multiplier, and a combined divider and square rooter^[1]. Internal memory was formed by those twenty ten-digit accumulators together with 6,000 switches and cables on the function tables^[1].

Where it came from

Development began after a contract from the military's Ballistics Research Laboratory, motivated by the wartime need to calculate the speed and trajectory of bombs and missiles^[1]. The machine was constructed and operated at The Moore School of Electrical Engineering, now part of Penn's School of Engineering and Applied Science^[1]. Two people shaped it: John W. Mauchly, its visionary, and J. Presper Eckert, the engineer who solved its technical problems — among them tube reliability, which he addressed by running the tubes at one-quarter power^[1].

The team that ran it

ENIAC was run by a team of six women: the ENIAC programmers Kathleen Antonelli, Jean Bartik, Betty Holberton, Marlyn Meltzer, Frances Spence and Ruth Teitelbaum^[1].

Results

After construction the machine was shipped to the military's Aberdeen Proving Ground in Maryland, where it produced firing tables^[1]. The gain in speed was large: a ballistics calculation that took 12 hours on a hand calculator could be done in 30 seconds on ENIAC, a factor of 1,440^[1].

Why it matters

For the next nine years ENIAC served as the primary computing engine for the Army^[1]. Its place in the record rests on the properties Penn names together: electronic, general-purpose, and built as a working computer rather than a device for a single task. The scale of the hardware also shows what electronic computing cost at the time — 18,000 tubes, 30 tons and 150 kilowatts for a machine whose accumulators worked on ten-digit numbers^[1].