ENIAC, the First All-Purpose Digital Computer

Seventy-five years ago, in February 1946, the Electronic Numerical Integrator and Computer — ENIAC — was publicly demonstrated as the world’s first large-scale general-purpose digital computer. It was designed by John Mauchly (1907–80) and J. Presper Eckert (1919–95) at the University of Pennsylvania’s Moore School of Electrical Engineering in Philadelphia.

Research began during World War II in 1943. The U.S. Army’s Ballistic Research Laboratory expressed the need for calculations of artillery shell trajectories to be performed more quickly and accurately. Because of the military implications, ENIAC’s development was a top-secret mission, and the U.S. government invested more than $450,000 in this critical project. Although it was not completed in time to be used during the war, it launched the computer age. A 1946 Philadelphia Inquirer article announcing the machine described it as “a new epoch in the scope of human thought.” No modern-day invention has touched, and continues to touch, so many aspects of everyday life.

At the time ENIAC was introduced to the public, its computational abilities were astonishing. Considering the size and capacity of today’s computers, it is hard to imagine some of the limitations of this first innovative machine. ENIAC was 10 feet high and took up 18,000 square feet of space. It required 1 million IBM computer punch cards to input data for a complicated ballistics problem, could only calculate numbers up to 10 digits, and had a memory capacity of only about 20 words. Still, it could calculate trajectories in 30 seconds, a task that would have taken hours or days for humans with mechanical devices, the previous method for performing the computations.

Those human “computers,” as they were called, were primarily women. Six of the women were chosen to be programmers for ENIAC: Kathleen McNulty Mauchly Antonelli (1921–2006), Jean Jennings Bartik (1924–2011), Frances “Betty” Snyder Holberton (1917–2001), Marlyn Wescoff Meltzer (1922–2008), Frances Bilas Spence (1922–2012), and Ruth Lichterman Teitelbaum (1924–1986). With minimal training, they had to figure out how to connect thousands of circuits, cables and switches that would allow ENIAC to compute. ENIAC’s operation relied upon the ingenuity of these six pioneering women.

ENIAC and programmers Frances Bilas (later Spence) and Jean Jennings (later Bartik).
University Archives and Records Center, University of Pennsylvania

Mauchly and Eckert continued their research and founded their own company, Eckert–Mauchly Computer Corp. In 1949 they introduced BINAC (Binary Automatic Computer), developed for the Northrup Aircraft Co. By 1951 the team announced the completion of the world’s first commercial digital computer, UNIVAC (Universal Automatic Computer). Soon after UNIVAC I machines started coming off the assembly line, the general public was exposed to the computer’s abilities when CBS News used one of its specially designated programs to predict the results of the 1952 presidential election. Ironically, CBS withheld the results initially, fearing the machine had malfunctioned when UNIVAC I predicted Eisenhower’s landslide victory. Many pollsters were calling for a victory for Democrat Adlai Stevenson. The traditional result announcement late in the evening confirmed the accuracy of the computer’s figures, within an error margin of 1 percent.

In June 2000 the Pennsylvania Historical Marker for ENIAC was installed and dedicated on Chancellor Street between 33rd and 34th streets at the University of Pennsylvania in Philadelphia. Six years later, in September 2006, a marker titled Commercial Digital Computer Birthplace, commemorating BINAC and UNIVAC I, was unveiled at 3747 Ridge Avenue in the city, where BINAC passed its verification tests in 1949.

Karen Galle is on the staff of PHMC’s State Historic Preservation Office and has been the coordinator of the Pennsylvania Historical Marker Program since 2005.