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Inventing the Computer: Mauchly and Eckert


Inventing the Computer: Mauchly and Eckert

Building the world’s first digital computer—at the University of Pennsylvania’s Moore School of Engineering from 1943–1945—wasn’t easy. 

For one, mice kept gnawing away at the circuitry of the thousand-square-foot machine. So, the project’s leader, Dr. John Mauchly, put mice in cages, fed them little, then unleashed them on assorted brands of wires. Only wires that survived the nibbling were bought.

Another problem was the 17,000-plus vacuum tubes in the device, the Electronic Numerical Integrator and Computer, or ENIAC. ENIAC would make a calculation error if any of the tubes failed, and the tubes were error-prone.

Mauchly’s upbringing had prepared him for such challenging work. Born in 1907, he was raised in Chevy Chase, Maryland, while his physicist father did research on electrical fields at nearby Washington, DC’s Carnegie Institute. As a child, to read past bedtime, Mauchly planted sensors outside his bedroom to warn of his parents’ approach. He also tapped into telephone poles to get phone service for his pals.

After a doctoral program in physics and engineering from Baltimore’s Johns Hopkins University, Mauchly got a job doing research on sunspots. Frustrated at sifting through vast amounts of solar data by hand, he tinkered with ways of automating the information. Buying up packs of GE neon bulbs, he wired together digitized switches. After obtaining a professorship at the Moore School, he spent further long hours poring through technical magazines and  soldering circuits. Using a now-familiar binary system of ones and zeros, he added up numbers with pulses of electricity, then stored the numbers electronically without having to laboriously re-enter the data.

In 1941, Mauchly began working with a 22-year-old Moore School engineering student, John Presper Eckert, Jr. The laid-back Mauchly excelled at theory—the eager Eckert at putting theory to practice and schematics to machine: The duo proved perfect complements.

By 1943, the United States had entered the Second World War. A pressing military need was faster ways of making “calculator tables,” which contained the many factors, like wind speed and shell velocity, for accurately firing artillery. The people using the guns,” noted Eckert, “were having to make guesswork corrections on the tables to hit anything.”

Mauchly claimed he could build a “computor” that would figure out a shell’s trajectory in 100 seconds, by performing 1,000 calculations a second. The Army’s Ballistic Research Laboratory, at Maryland’s Aberdeen Proving Ground, told him to try.

Mauchly, Eckert, and 12 engineers built their complex machine at the Moore School over two-and-half years, at a cost of $486,804. The 10-foot-tall ENIAC had 70,000 resistors, 10,000 capacitors, and 6,000 switches. Eckert got the 17,486 vacuum tubes to work, mostly without error, by fiddling with their voltage.

Card readers and card punches were employed for data entry and output. Manipulating the switches and cards were the first programmers—all of them women. One noted, “Most of the men were away fighting, so we were left in charge.”

The war-time team worked seven days a week, nicknaming their construction the “MANIAC,” but took out time for pranks. One night, after Eckert fell asleep next to the computer, two assistants carried him into an identical but empty room. When he awoke, he was certain ENIAC had been stolen.

The completed machine worked better than Mauchly had predicted, making 5,000 calculations in under a second, and figuring out a shell’s arc in 20 seconds. When journalists assembled for a demonstration, they asked an engineer running ENIAC when the test calculation would take place—then realized it already had.

Mauchly and Eckert went on to found the first computer firm, invent the first usable programming language, and design the first commercial computer, the UNIVAC.

The giant, cumbersome machine they patched together in the mid-1940s was the progenitor of all the tiny, elegant processors of today.


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