Short for Electronic Delay Storage Automatic Calculator, EDSAC is an early British computer considered to be the second stored program electronic computer, after the SSEM (Small Scale Experimental Machine). It was created at the University of Cambridge in England, performed its first calculation on May 6, 1949. It also has the distinction of being the first computer to run a graphical computer game, an implementation of tic-tac-toe called OXO. The picture is of the EDSAC I in June 1948, courtesy of the University of Cambridge.
Pictured below is an example of the original EDSAC displaying a game of OXO, and a software EDSAC emulator that simulates the way the computer would work.