OXO is a video game created by A.S. Douglas in 1952. It copies the game of noughts and crosses, also known as tic-tac-toe. It was one of the first video games made during the early history of video games. Douglas created the game as part of his research on how people and computers interact at the University of Cambridge.

The program was written for a computer called the Electronic Delay Storage Automatic Calculator (EDSAC). EDSAC was one of the first computers that could store and run programs. It had three small screens made of cathode-ray tubes to show information in its memory. Douglas used one of these screens to display the game of noughts and crosses. After the game was no longer needed, it was removed from the original computer. However, it was later rebuilt.

OXO, along with a checkers game made by Christopher Strachey around the same time, is among the earliest games to show images on an electronic screen. Some definitions consider OXO the first video game, but others do not include it because it does not have moving or real-time graphics.

History

The Electronic Delay Storage Automatic Calculator (EDSAC) was built at the University of Cambridge’s Mathematical Laboratory between 1946 and May 6, 1949, when it ran its first program. It was used until July 11, 1958. The EDSAC was one of the first stored-program computers, meaning it could store and run programs in its memory. It filled an entire room and had three cathode-ray tubes (CRTs) that displayed the computer’s memory as a grid of dots.

Sandy Douglas, a doctoral student in mathematics, used one of these CRTs for a project about human-computer interaction. He displayed the state of a game of noughts and crosses (tic-tac-toe) on the screen. After Douglas completed his work, the game was no longer used. Douglas did not name the game; the name "OXO" was later added by computer historian Martin Campbell-Kelly when he created a simulation of the EDSAC.

Around the same time, Christopher Strachey adapted a checkers program he had written in 1951 and moved it to the Ferranti Mark 1 computer, which also used a CRT to show the game’s state. OXO and Strachey’s checkers program are the earliest known games to display visuals on an electronic screen. It is unclear which game appeared first. Some definitions consider OXO a contender for the first video game because it used a graphical display, while others do not, as it lacked moving images or continuous updates.

Interaction

Each game was played between one person and a computer-controlled opponent that could play perfectly. The player used a rotary dial controller to choose which of the nine squares on the board they wanted to select next. Their choice appeared on the screen, followed by the computer's move. The game display only changed when the game situation changed. OXO was not available to the public and could only be played in the University of Cambridge's Mathematical Laboratory with special permission. This was because the EDSAC computer could not be moved, and the game was created only for use in academic research.