After six weeks of training, the women returned to Penn, where they were given poster-size diagrams and charts describing ENIAC. “Somebody gave us a whole stack of blueprints, and these were the wiring diagrams for all the panels, and they said, ‘Here, figure out how the machine works and then figure out how to program it,’” explained McNulty. That required analyzing the differential equations and then determining how to patch the cables to connect to the correct electronic circuits. “The biggest advantage of learning the ENIAC from the diagrams was that we began to understand what it could and could not do,” said Jennings. “As a result we could diagnose troubles almost down to the individual vacuum tube.” She and Snyder devised a system to figure out which of the 18,000 vacuum tubes had burned out. “Since we knew both the application and the machine, we learned to diagnose troubles as well as, if not better than, the engineers. I tell you, those engineers loved it. They could leave the debugging to us.”
Snyder described making careful diagrams and charts for each new configuration of cables and switches. “What we were doing then was the beginning of a program,” she said, though they did not yet have that word for it.
Photo: U.S. Army, Wikimedia Commons