A few weeks after Kay McNulty graduated from Philadelphia's Chestnut Hill College in 1942 with a degree in mathematics, she got a job at the Army's Ballistic Research Laboratory as a human "computer," calculating artillery trajectories. For three years she did the kind of mind-numbing mathematical drudgery--punching numbers into a mechanical calculator and copying down the results--that in those days was measured in "girl hours." Then she was invited by the University of Pennsylvania's Moore School of Electrical Engineering to help J. Presper Eckert and John Mauchly put the finishing touches on a new kind of computing device called ENIAC (for Electronic Numerical Integrator and Computer). That machine and its descendants were destined not only to make her old job obsolete but to change the world profoundly.
One day last week McNulty (now the widowed Mrs. John Mauchly), Eckert and 500 computer enthusiasts gathered at a "black-tie optional and hackerwear essential" party at Boston's Computer Museum to celebrate the 40th anniversary of the dedication of the first all-electronic digital computer. On that day in 1946, ENIAC in 20 seconds performed a mathematical calculation that would otherwise have required 40 girl hours to complete. Newspapers headlined the performance. It "solves the unsolvable," reported the Philadelphia Inquirer. Indeed, many experts mark ENIAC's feat as the beginning of the modern computer age.
By every measure, ENIAC was an imposing machine. It weighed 30 tons and occupied a space as large as a boxcar. Its 40 modular memory and processing units, each housed in a 9-ft.-high black metal cabinet and bristling with dials, wires and indicator lights, filled a room the size of a small gymnasium. Its 18,000 vacuum tubes radiated so much heat that industrial cooling fans were needed to keep its circuitry from melting down.
ENIAC was the technological wonder of its day. Programming the machine could take as long as two days as "coders" armed with detailed instructions fanned out among the panels, setting dials and plugging in patch cords in an arrangement that resembled an old-fashioned telephone switchboard. Data were fed into ENIAC in the form of IBM punch cards; a million cards were required for the monster's first assignment, a top-secret numerical simulation for the still untested hydrogen bomb. Every time a tube burned out, which happened twice a day at the start, a technician had to rummage among the tangle of wires to locate and replace the dead component. To prevent rodents from nibbling at ENIAC and destroying vital parts, Eckert recalled at the anniversary party, the scientists captured some mice, starved them for several days and then fed them bits of the insulating materials used in the machine. Any pieces the mice seemed to favor were removed from ENIAC and replaced with less tasty parts.