DATE: 1946.
WHAT IT IS: The first large-scale general-purpose electronic computer.
WHAT IT LOOKS LIKE: Only portions of ENIAC survive, including panels (units that performed various mathematical operations such as addition and multiplication) and function tables (devices which stored numeric constants that were used by ENIAC’s program). The panels are 10 feet tall and 3 feet wide, and are painted black. Prominent features include round knobs and cables with plugs on the ends (the cables are of the patch-cord kind, and the plugs are large).
Deftly pushing contemporary technology to its limits and working without any kind of manual to guide them with regard to design, components, circuitry, assembly, or any other detail, the inventors of the electronic computer built what is arguably the first modern “thinking machine” by creating an electronic version of the mechanical adding machines of the day. They produced a device that by later standards was immensely heavy and huge; it weighed thirty tons and was shaped like a giant U with the two parallel sides each running sixty feet long, the bottom measuring thirty feet, and the whole contraption rising ten feet off the ground. It was large and cumbersome, indeed, and with its flashing lights and immense tangled forest of vacuum tubes, knobs, lights, and wires it resembled a contraption worthy of an old science fiction novel. But the machine was a landmark invention. After centuries of dreaming about an automatic calculating device, humans created ENIAC, the first general-purpose electronic digital computer, and with it ushered in the information age.
The first computing device, simply enough, was the human hand. A primitive digital computing device, fingers could be counted to solve basic arithmetical problems. The Romans and the Chinese each developed an abacus, a wire frame containing rows of movable beads that made possible more complex mathematical operations.
In the mid-1830s, Charles Babbage, an English mathematician who had built mechanical calculation machines, began designing an analytical engine in which tabulating cards were used for the performance of operations. Babbage, who through the years lost government support for his inventions, never finished building this forerunner of the modern automatic computer.
In 1944, Harvard professor Howard Aiken demonstrated a general-purpose electromechanical machine. Called the Automatic Sequence Controlled Calculator, it had moving parts—principally, electromagnetic relays—that were powered by electricity, but it was still essentially a mechanical device. ASCC contained some three-quarters of a million parts in total and was a huge punch card machine. An electronic computer had yet to be built.
Thanks to the U.S. Army, one was actually on its way. During World War II the army employed “computers” (people, typically women) to prepare firing tables for its guns. Using calculators, the workers—many of whom were Women’s Auxiliary Corps mathematicians—took between ten and forty hours to compute just one trajectory. But the tables contained up to four thousand trajectories each, and there simply weren’t enough people available to grind out the calculations. Some kind of device that could do the math much more quickly was needed.
ENIAC, the first modern general-purpose electronic digital computer. Could the inventors of the large-scale thinking machine ever have envisioned the laptop?
John Mauchly, a physics professor at Ursinus College in Collegeville, Pennsylvania, who was interested in using mathematics to predict weather, had proposed in a memo an electronic computer for making faster calculations. His idea caught the attention of Herman H. Goldstine of the Ballistic Research Lab in Aberdeen, Maryland. Goldstine, who was seeking an efficient way to calculate artillery trajectories, requested that Mauchly develop a proposal. Mauchly was practical about funding and understood that, at least at the time, ballistics took priority over weather. He undertook to write the proposal with a gifted electronic engineering graduate student named J. Presper Eckert. They submitted a proposal on April 2, 1943, for a machine called ENIAC, the Electronic Numerical Integrator and Calculator, and two months later they were awarded a contract.
A team of engineers headed by Eckert, with Mauchly the principal consultant, secretly built ENIAC in the Moore building at the University of Pennsylvania in Philadelphia; because it was wartime, and the output of ENIAC was needed to operate large guns, the project was kept under wraps. The machine, in which over 17,000 vacuum tubes, 6,000 switches, 10,000 capacitors, and 70,000 resistors were encased in black steel, occupied 1,800 square feet.
Unlike Howard Aiken’s Automatic Sequence Controlled Calculator, ENIAC was an electronic device in that it was based not on mobile metal parts but moving electrons; it did not have moving mechanical parts but electrons moving in a vacuum. ENIAC’s main components were the panels, which numbered forty in total. Numerous cables plugged into each panel. The other ends of the cables plugged into digit trays, which connected the panels. The panels had numerous rotary switches, or knobs, that indicated a particular number or function.
ENIAC worked in base ten, as opposed to modern computers, which work in base two. The foundation of the entire ENIAC was the accumulator, which was essentially an electronic version of an adding machine. The accumulator added ten-digit decimal numbers, and kept them in base ten. A panel would have the capability to display one decimal number ten digits long by using an array of lights, going from top to bottom, so it would have ten columns of ten lights each. These lights would signify numbers. The accumulators would be connected together to perform mathematical calculations. Essentially, Eckert, Mauchly, and their team of engineers strung together decimal adding machines, or mechanical accumulating calculators, of their day and made them electronic.
Unveiled in a ceremony on February 14, 1946, ENIAC, which punched results onto cards, performed high-speed calculations not feasible on other computing devices.
But its operation was delicate. Vacuum tubes were not always reliable, and with more than seventeen thousand of them emitting a hundred thousand pulses per second, there were almost two billion chances every second that ENIAC could fail. Furthermore, the complexity and interdependence of ENIAC’s circuits meant that a failure of just one of the thousands of solder joints could render the whole electronic brain unusable.
But the marvel was that ENIAC worked, and it was unquestionably a major improvement over the computing devices of the day—indeed, the inventors of ENIAC successfully harnessed the power of the vacuum tube to create a machine that worked more than a thousand times faster than these devices. Although the war was by this time over, ENIAC could compute a firing trajectory in just half a minute.
Despite its immense size and cost (over $486,000), ENIAC convinced an array of professionals of the potential of electronic computing, launching the modern computing era. The rest, as they say, is history: the FORTRAN language, magnetic disks for storage, transistors replacing vacuum tubes, keyboards and monitors replacing punched cards, minicomputers, microprocessors, silicon chips, personal computers, graphical user interfaces, Windows 95, laptops, the World Wide Web.
The programming capability of ENIAC can be approximated today with a small calculator that costs under $40. ENIAC’s clock speed was 100,000 pulses per second or 0.1 megahertz. This compares with modern computers that run at about 600 megahertz or more.
Today, the PC is the offspring of the computer revolution. A common household and office item, a PC can be purchased for under $1,000. But anyone who has ever clicked a mouse owes a debt to that monstrous hunk of metal and wires, ENIAC, which quietly sparked the revolution and forever changed the way we live.
LOCATION: National Museum of American History, Washington, D.C. This is the main repository of ENIAC’s panels. Of the sixteen panels the museum owns, some are on loan to other institutions, including the School of Engineering and Applied Science at the University of Pennsylvania in Philadelphia, the Computer Museum in Boston, and the Heinz-Nixdorf Museumsforum in Patterbom, Germany. Other panels and parts of ENIAC are located at other institutions.