The History of the ENIAC Computer

The Groundbreaking Device from John Mauchly and John Presper Eckert

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As technology progressed in the early and mid-1900s, the need for enhanced computational speed grew. In response to this deficit, the American military invested half a million dollars to create the ideal computing machine.

Who Invented the ENIAC?

On May 31, 1943, the military commission for the new computer began with the partnership of John Mauchly and John Presper Eckert, with the former serving as the chief consultant and Eckert as the chief engineer. Eckert had been a graduate student at the University of Pennsylvania's Moore School of Electrical Engineering when he and Mauchly met in 1943. It took the team about one year to design the ENIAC and then 18 months plus half a million dollars in tax money to build it. The machine wasn't officially turned on until November 1945, by which time the war was over. However, not all was lost, and the military still put ENIAC to work, performing calculations for the design of a hydrogen bomb, weather predictions, cosmic-ray studies, thermal ignition, random-number studies, and wind-tunnel design.


In 1946, Mauchly and Eckert developed the Electrical Numerical Integrator And Calculator (ENIAC). The American military sponsored this research because it needed a computer for calculating artillery-firing tables, the settings used for different weapons under varied conditions for target accuracy.

As the branch of the military responsible for calculating the tables, the Ballistics Research Laboratory (BRL) became interested after hearing about Mauchly's research at the Moore School. Mauchly had previously created several calculating machines and in 1942 began designing a better calculating machine based on the work of John Atanasoff, an inventor who used vacuum tubes to speed up calculations.

The patent for ENIAC was filed in 1947. An excerpt from that patent, (U.S.#3,120,606) filed on June 26, read, "With the advent of everyday use of elaborate calculations, speed has become paramount to such a high degree that there is no machine on the market today capable of satisfying the full demand of modern computational methods."

What Eas Inside the ENIAC?

The ENIAC was an intricate and elaborate piece of technology for the time. Housed within 40 9-foot-tall cabinets, the machine contained 17,468 vacuum tubes along with 70,000 resistors, 10,000 capacitors, 1,500 relays, 6,000 manual switches, and 5 million soldered joints. Its dimensions covered 1,800 square feet (167 square meters) of floor space and weighed 30 tons, and running it consumed 160 kilowatts of electrical power. Two 20-horsepower blowers delivered cool air to keep the machine from overheating. The vast extent of energy being used led to a rumor that turning on the machine would cause the city of Philadelphia to experience brownouts. However, the story, which was first reported incorrectly by the Philadelphia Bulletin in 1946, has since been discounted as an urban myth.

In just one second, the ENIAC (1,000 times faster than any other calculating machine to date) could perform 5,000 additions, 357 multiplications, or 38 divisions. The use of vacuum tubes instead of switches and relays resulted in the increase in speed, but it was not a quick machine to reprogram. Programming changes would take the technicians weeks, and the machine always required long hours of maintenance. As a side note, research on the ENIAC led to many improvements in the vacuum tube.

Contributions of Dr. John Von Neumann

In 1948, Dr. John Von Neumann made several modifications to the ENIAC. The ENIAC had performed arithmetic and transfer operations concurrently, which caused programming difficulties. Von Neumann suggested that using switches to control code selection would make it so that pluggable cable connections could remain fixed. He added a converter code to enable serial operation.

Eckert-Mauchly Computer Corporation

Eckert and Mauchly's work extended beyond just ENIAC. In 1946, Eckert and Mauchly started the Eckert-Mauchly Computer Corporation. In 1949, their company launched the BINAC (BINary Automatic Computer) that used magnetic tape to store data.

In 1950, the Remington Rand Corporation bought the Eckert-Mauchly Computer Corporation and changed the name to the Univac Division of Remington Rand. Their research resulted in the UNIVAC (UNIVersal Automatic Computer), an essential forerunner to today's computers.

In 1955, Remington Rand merged with the Sperry Corporation and formed Sperry-Rand. Eckert remained with the company as an executive and continued with the company when it later merged with the Burroughs Corporation to become Unisys. Eckert and Mauchly both received the IEEE Computer Society Pioneer Award in 1980.

The End of the ENIAC

Despite its significant advances in computation in the 1940s, ENIAC's tenure was short. On October 2, 1955, at 11:45 p.m., the power was finally shut off, and the ENIAC was retired. In 1996, precisely 50 years after ENIAC was publicly acknowledged by the government, the massive computer received its place in history. According to the Smithsonian, ENIAC was the center of attention in the city of Philadelphia as they celebrated being the birthplace of computation. ENIAC was ultimately dismantled, with sections of the massive machine on display at both Penn and the Smithsonian.

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Bellis, Mary. "The History of the ENIAC Computer." ThoughtCo, Apr. 5, 2023, Bellis, Mary. (2023, April 5). The History of the ENIAC Computer. Retrieved from Bellis, Mary. "The History of the ENIAC Computer." ThoughtCo. (accessed June 7, 2023).