1943- The Colossus, a programmable, digital machine also considered by some to be the first electronic computer, is operational in England .

1944- The relay-based Harvard-IBM MARK I, a program-controlled, large-scale calculating machine built by a team led by Howard Aiken, goes to work during World War II providing vital calculations for the U.S. Navy. Grace Hopper becomes its first programmer.

1946- J. Presper Eckert and John Maulchy unveil the ENIAC at the University of Pennsylvania ’s Moore School of Electrical Engineering. Later that same year, Eckert and Mauchly leave Moore School to found their own firm, Electronic Control Co., to design the UNIVAC.

F.C. Williams applies for a patent on his cathode-ray tube storing device, original form of random-access memory.