OXO (also known as Noughts and Crosses) is a tic-tac-toe computer game made for the EDSAC computer in 1952. It was written by A.S. (Sandy) Douglas as an illustration for his Ph.D. thesis on human-computer interaction for the University of Cambridge. OXO is the first known (graphical) game to run on a computer. However, the first game to use a cathode ray tube display was a missile simulation game that was patented in 1947–1948.Thomas T. Goldsmith Jr. and Estle Ray Mann filed a United States patent application on January 25, 1947 and U.S. Patent #2 455 992 issued on December 14, 1948.

The player plays against the computer and output was displayed on the computer's 35×16 pixel cathode ray tube. The source code is short, yet plays a perfect game of noughts and crosses. OXO did not have widespread popularity because the EDSAC was a computer unique to Cambridge.

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