On December 7, 1941, Japan attacked Pearl Harbor, drawing the United States into the conflagration known as World War II. One problem every country at war had was creating artillery ballistic tables for each type of artillery they produced. This was a huge undertaking, being both a very slow and tedious process. So, the U.S. army granted funds to the Moore School of Electrical Engineering at the University of Pennsylvania to build an electronic computer to facilitate this work. You might have guessed from the last page that our friend John Mauchly just happened to be there, and he then took on this project with a gifted graduate student named J. Presper Eckert.
However, World War II ended before the machine was completed. When finished in 1946, this 30-ton monstrosity consisted of 49-ft. high cabinets, 18,000 vacuum tubes, 1,500 relays, 70,000 resistors, 10,000 capacitors, and 6,000 manual switches, and it consumed 200 kilowatts. Although finished after the war, it hardly proved useless. Capable of 5,000 additions, 357 multiplications, or 38 divisions per second, the performance of this machine was incredible. Problems that took a human mathematician 20 hours to solve, took only 30 seconds for the ENIAC.
The main problem with the machine, aside from the unreliability inherent in all vacuum tube machines, was that it was not programmable in the conventional sense. "Programs" were entered by the "ENIAC girls" working on plug boards and banks of switches. This generally took from a few hours to a few days. Also, in a backward step from the ABC computer, the ENIAC worked with decimal and not binary numbers.
Nevertheless, the ENIAC was an extremely useful machine for the U.S., particularly with the enhancements that were later added on, until it was retired in 1955. During its lifetime, it worked on problems ranging from weather forecasts, random-number studies, thermal ignition, wind-tunnel design, artillery trajectory calculations, and even development of the hydrogen bomb. In fact, by the time it was retired in 1955, it was estimated that the ENIAC by itself did more calculations than all of humankind did up to 1945.
While the story of the ENIAC trails off in 1955, our two heroes, Mauchly and Eckert, still have much to accomplish before their stories end.