What Is ENIAC?

The Giant Brain made history in many ways

ENIAC, the first electronic computer
Female programmers operating ENIAC.

ENIAC is the world's first electronic computer. Although it dates back to the 1940s, it's had a profound and lasting influence on the technology upon which we rely today. Here's the story of ENIAC, how it worked, and the important role it plays in our 21st century world.

The creators of ENIAC, John Mauchly and J. Presper Eckert, Jr.
John Mauchly and J. Presper Eckert, Jr.

What Is ENIAC?

So what does ENIAC stand for, you might ask? 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, a physicist named 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 US Army, needing a faster computer to calculate the trajectory of their artillery shells during World War II, began funding his work with the goal of developing 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. Rather, it was a machine comprised of multiple units, featuring approximately 18,000 vacuum tubes, several miles of 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.
Programming the ENIAC computer.

How ENIAC Worked

Even with its advanced level of technological sophistication, ENIAC still required programmers in order to fulfill its function. At the time, over 80 women were working at the University of Pennsylvania as programmers, or 'computers' as they were called back then, 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 US 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 that were used for entering tables of numbers. To the lay person's eye, the process for programming ENIAC looked not unlike that of patching phone calls in a telephone exchange, though it was actually far more complex and could take weeks.

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

ENIAC as seen at the Moore School

ENIAC's Lasting Influence

Due to its classified and strategic nature, the US government kept the existence of ENIAC computer a closely guarded secret until the end of World War II. The public finally learned about the computer in 1946, when the War Department revealed ENIAC in a momentous 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 (EMCC), the first computer company. Today, you can see a portion of ENIAC on exhibit at the Smithsonian Institution in Washington, D.C.

Although it may be easy to forget as we tap away on our smartphones and begin issuing voice commands to virtual assistants using smart speakers, the first computers were once complicated pieces of machinery that were enlisted to help defend democracy worldwide before giving rise to an incredible era of technological innovation that continues to this day. The next time you reach for your gadget of choice, it's worth remembering ENIAC's pivotal role in making our convenient modern lifestyles possible.