Fifty years ago this month, a machine in the University of Pennsylvania’s Moore School of Electrical Engineering solved in 20 seconds an equation that would have required a human mathematician using a desk calculator 40 hours. The feat astounded the world, and launched the age of computers. The machine was the Electronic Numerical Integrator and Computer: ENIAC, for short.
Not that ENIAC was the first computer. Computers date back to at least 1839, when Englishman Charles Babbage developed his “difference engine,” a mechanical digital computer that could solve mathematical problems, including simple differential equations (hence the name).
ENIAC wasn’t even the first electronic computing device. Physicists were already using radiation counters and other specialized machines such as Colossus, which helped the British crack Germany’s Enigma code. What made ENIAC special was the fact it was a general-purpose computer: it could be programmed to compute any kind of equation.
ENIAC was the brainchild of John Mauchly, a meteorologist interested in developing high-speed computing devices to help predict the weather, and J. Presper Eckert, the brightest graduate student in the Moore School. Mauchly and Eckert met during a special war-time course, and began discussing ways to make Mauchly’s ideas a reality, culminating in a five-page memo written by Mauchly in 1942, called “The Use of Vacuum Tubes in Calculating.”
At any other time, Mauchly and Eckert’s ideas would have been considered too expensive, but the Army desperately needed a faster way to make ballistic calculations for artillery firing tables. At the time, they were using “human computers”–mostly young women with mathematics degrees–to perform the calculations on desk-top calculators. Calculating one ballistic trajectory could take up to 40 “girl-hours” (the Army’s term), and hundreds of such calculations were needed. Mauchly’s proposed machine would be able to compute ballistic trajectories in mere minutes.
The Army still took a lot of convincing, but on June 5, 1942, contract No. W-670-ORD-4926 was signed by the Trustees of the University of Pennsylvania and the U.S. Army Ordnance Department to build ENIAC.
The biggest problem was the unreliability of vacuum tubes. ENIAC’s 17,468 tubes operated at a rate of 100,000 pulses per second, which meant there were 1.8 billion chances of a failure occurring every second. But by designing ENIAC to treat its tubes as gently as possible, using a system of preventive maintenance that ensured only tubes in peak condition were installed, and instituting rigid requirements for design and construction, Eckert made ENIAC so reliable it consistently operated for more than 12 hours at a time.
In November, 1945, the first set of calculations were executed on ENIAC, proving wrong the critics who had said it was far too complicated to every work properly. By then the war was over–ENIAC never was used to calculate ballistic trajectories. Its first calculations were related to hydrogen-bomb research, instead. But that just proved the flexibility of a general-purpose computer and helped convince the government to keep funding it.
ENIAC introduced many fundamental elements of computer design, including one we could do without: by the time it was built, it was already obsolete–its designers had already come up with better ways of doing things.
ENIAC weighed 30 tons, and was housed in 40 nine-foot-tall black metal cabinets that bristled with dials, wires and indicator lights and filled a room the size of a small gymnasium. It took a whopping 174 kilowatts to operate; industrial cooling fans had to run constantly to keep its circuitry from melting down.
But ENIAC’s biggest shortcoming was that it couldn’t store a program in its own memory. Instead, programming was carried out by men and women called “coders,” who fanned out among the panels, setting dials and plugging in patch cords like so many old-fashioned telephone operators. It could take two days to program ENIAC.
Data was fed into it in the form of IBM punch cards: its first assignment required a million of them.
ENIAC didn’t suffer from viruses, but it did suffer from mice: they kept nibbling at the insulation. Finally the scientists captured some mice, starved them, then fed them bits of insulating materials. Anything the mice liked was replaced with something less tasty.
For ENIAC’s public demonstration 50 years ago, Eckert and the others placed translucent spheres–ping pong balls cut in half–over the neon bulbs that displayed ENIAC’s data. That image has stayed with us for most of half a century, resurfacing time and time again in movies and TV shows.
The real legacy of ENIAC–the integration of computers into our society–will stay with us far longer.
