ENIAC was modular. There were originally something like two dozen modules, each of which was roughly 8 feet high and 3 feet deep. The modules were then wired together with plugged cables; the cable configuration determined the program that was executed. In principle the modules could have been arranged in a line 100 feet long, but I doubt they ever were, because the room (just one room) was not that shape. Wikipedia has a picture. – Mark Dominus Jan 27 '19 at 6:37