ENIAC

ENIAC at the University of Pennsylvania's Moore School, photographed as two of its programmers, Betty Jennings and Frances Bilas, prepared it for its public demonstration in February 1946. Built by John Mauchly and J. Presper Eckert, it filled more than 1,000 square feet, weighed about 30 tons and ran on roughly 18,000 vacuum tubes. It was general purpose, but programming it meant setting switches and moving patch cables by hand, the panels and plugboards you can see here. That limitation is exactly what the stored-program machines that followed set out to fix.