Technology History | Moore School, Philadelphia — ENIAC Had No Stored Program, and Six Women Wired It by Hand

Seventeen thousand four hundred and sixty-eight vacuum tubes, thirty tons, and a room of its own in the Moore School of Electrical Engineering.

ENIAC was shown to the press on 1 February 1946, unveiled publicly on the 14th, and formally dedicated on the 15th, which is the date Penn still keeps as ENIAC Day.

Anniversary coverage collapses those three into one and picks whichever suits. The distinction is worth holding onto, because it is the difference between a demonstration, a public claim and an institutional ceremony.

The qualifier is the fact here. ENIAC was the first programmable, general-purpose electronic computer, and every word in that phrase is load-bearing: the Atanasoff-Berry machine was electronic but special-purpose, Colossus was electronic and programmable but built for one cryptographic job, and Zuse's Z3 was programmable and automatic but ran on relays.

What ENIAC did not have was a stored program. Its instructions lived in the wiring, so changing the problem meant re-plugging cables and resetting switches by hand, which is where the other half of this story begins.

Six women did that work: Kay McNulty, Jean Jennings, Betty Snyder, Marlyn Wescoff, Frances Bilas and Ruth Lichterman.

They were selected from more than eighty women employed at the Moore School as computers, a job title that then meant a person who calculated ballistics trajectories by hand. For a period they lacked the clearance to enter the room at all and learned the machine from its wiring diagrams.

Two of them ran the public demonstration.

None of the six was invited to the celebratory dinner afterwards, and for decades researchers asking about the women in the ENIAC photographs were told they had been models. All six were inducted into the Women in Technology International Hall of Fame in 1997.

There is a legal coda as well. On 19 October 1973, in Honeywell v. Sperry Rand, Judge Earl R. Larson invalidated the ENIAC patent, finding that Eckert and Mauchly had not themselves first invented the automatic electronic digital computer but had "derived that subject matter from one Dr. John Vincent Atanasoff".

That settled a patent rather than the history. The court was answering a much narrower question than the one anniversary pieces ask.

The building still stands on South 33rd Street and still teaches engineering. Four original ENIAC panels are on display inside, which is a strange thing to walk past on the way to a lecture.

Cover: U.S. Army photograph, public domain, via Wikimedia Commons. Cpl. Irwin Goldstein sets the switches on a function table, and it is one of the few widely available images of the machine while it was still at the Moore School, since most circulated ENIAC photographs show it after its move to Aberdeen.