What Is ENIAC?

The Giant Brain made history in many ways

ENIAC is the world's first electronic computer. As a stand-alone device, it didn't support networking, although it facilitated a network of humans who used it for years to aid the effort of World War II. It depended on a suite of vacuum tubes, transistors, and other typical electronics tools, rather than today's integrated circuits. Although it dates back to the 1940s, it's had a profound and lasting influence on the technology we rely on today.

Network administrator working on a massive main frame and one working on a laptop
Lifewire / Mary McLain 

What Is ENIAC?

ENIAC is an acronym for Electronic Numerical Integrator and Computer. Also known as The Giant Brain, it was the first programmable general-purpose electronic digital computer. In the 1940s, physicist John Mauchly began working on his concept for an electronic calculating machine while teaching at the Moore School of Electrical Engineering at the University of Pennsylvania, which was a center for wartime computing. The U.S. Army needed a faster computer to calculate the trajectory of artillery shells during World War II, and funded his work to develop such a machine.

With the help of his partner, J. Presper Ekert Jr., Mauchly completed ENIAC shortly after the war's end. ENIAC is distinct from the mechanical computers that went before it, which could perform calculations but were difficult to program. ENIAC did not have a single moving mechanical part. Instead, it was a machine comprised of several units, featuring approximately 18,000 vacuum tubes, several miles of wiring, and 40 black eight-foot panels. It was enormous, weighing 30 tons and occupying the 50-by-30-foot basement of the Moore School.

Along with subsequent computers that also used vacuum tubes, ENIAC was known as a first-generation computer. ENIAC could execute up to 5,000 additions per second, multiple orders of magnitude faster than its predecessors. And, unlike its predecessors, it could be reprogrammed for different tasks.

Programmers input a program into ENIAC
Public Domain

How ENIAC Worked

Even with its advanced level of technological sophistication, ENIAC required programmers to fulfill its function. At the time, more than 80 women worked at the University of Pennsylvania as programmers, or computers as they were called, calculating ballistic trajectories—complex differential equations—by hand. Six of these women were selected to be ENIAC's first programmers: Fran Bilas, Betty Jennings, Ruth Lichterman, Kay McNulty, Betty Snyder, and Marlyn Wescoff.

These programmers physically configured the U.S. Army's ballistics program on ENIAC using 3,000 switches, dozens of cables, and digit trays to physically route the data and program pulses throughout the machine. They would input a program into ENIAC using a combination of plugboard wiring and three portable function tables. Each function table included 1200 ten-way switches for entering tables of numbers. To the layperson's eye, the process for programming ENIAC looked like that of patching phone calls in a telephone exchange, though it was more complex and could take weeks.

Once the instructions were programmed, ENIAC computed the program at electronic speed—an improvement over card reader technology that typically delivered instructions to computers more slowly. ENIAC's inventors claimed that their electronic computer could compute mathematical problems 1,000 times faster than was possible before. It's estimated that by the end of World War II, ENIAC had performed more computations than had been successfully completed in human history up to that point.

ENIAC as seen at the Moore School
Public Domain

ENIAC's Lasting Influence

Because of its classified and strategic nature, the U.S. government kept the existence of ENIAC a closely guarded secret until the end of World War II. The public learned about the computer in 1946 when the War Department revealed ENIAC in a press release and the New York Times published a story about it.

ENIAC was later used to solve problems in nuclear physics, including calculating instructions for the first hydrogen bomb. Mauchly and Eckert went on to found the Eckert-Mauchly Computer Corporation, the first computer company. Today, a portion of ENIAC is on exhibit at the Smithsonian Institution in Washington, D.C.