ENIAC: Celebrating Penn Engineering History

ENIAC in Action: What it Was and How it Worked

When fully operational, ENIAC occupied a room 30 by 50 feet in size and weighed 30 tons. A total of 40 panels were arranged in a U-shape that measured 80 feet long at the front, and the 18,000 vacuum tubes required were more than 20 times as many as the total employed by all various systems aboard a wartime B-29 bomber. ENIAC's circuits included 500,000 soldered joints with 70,000 resistors and 10,000 capacitors. ENIAC also had its own dedicated power lines and used 150 kilowatts of electricity.

The operational characteristics of ENIAC included arithmetic, memory and control elements. Concerned with the arithmetic operations twenty accumulators for addition and subtraction, a multiplier and a combination divider and square rooter. The memory elements were composed of an "internal memory" consisting of two parts: the twenty ten-digit accumulators and the 6,000 switches and cables on the function tables, accumulators and "constant transmitters." The unlimited "external memory" was supplied from outside the machine in the form of punch cards.

The ENIAC now sits in the ground floor of the Moore Building, appropriately part of a computer lab. Now students sit within the shadow of its vacuum tubes and use descendants of ENIAC to accomplish their own tasks. In the lab, the parts of the ENIAC on display include the Cycling Unit, the Master Programmer Unit, a Function Table, an Accumulator and Digit Trays. Other parts of the original ENIAC were a Punch Card Reader, a Card Puncher, a Card Printer, a Division Unit, and a Square-root Unit.

After construction, the ENIAC was shipped to the military's Aberdeen Proving Ground in Aberdeen, Maryland. There, it produced firing tables used for the military to correctly fire weapons at specific trajectories to accurately hit targets. In addition to ballistics, the ENIAC's field of application included weather prediction, atomic-energy calculations, cosmic-ray studies, thermal ignition, random-number studies, wind-tunnel design, and other scientific uses. It is recalled that no electronic computers were being applied to commercial problems until about 1951.

With the ability to perform math at blinding speed, the ENIAC gave scientists a tool unlike any calculator that had come before. The ballistics calculation that previously took 12 hours on a hand calculator could be done in just 30 seconds. That means the ENIAC was faster by a factor of 1,440. Because of the associated drastic reduction in the cost of computing, calculation-intensive research proceeded in directions previously unavailable. This led to new consumer products and opened the vast new markets.