Checkers (video game)

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Checkers, also known as Draughts, is a 1952 video game created by British computer scientist Christopher Strachey. It is one of the earliest computer games and may be the first to display visuals on an electronic screen using a general‑purpose computer. The game ran in July 1952 on the Ferranti Mark 1 at the University of Manchester.

Background and development
Strachey began work on Checkers in early 1951 while at the National Physical Laboratory (NPL), where the Pilot ACE computer was being developed. He was inspired by ideas in early articles about board games and by Charles Babbage’s analytical engine. Initial attempts were hampered by programming errors and limited memory. In spring 1952, Strachey learned that the Ferranti Mark 1 at Manchester offered more memory, so he ported the project there and met Alan Turing. With Turing’s encouragement, Strachey improved the program, and by July 1952 it ran at a playable speed.

How the game works
Checkers simulates English draughts on a monochrome display. It uses a simple artificial intelligence that looks ahead about three to four moves and chooses the strongest position it can reach. Kings are valued at three times a regular piece. The game uses a bitboard approach: three 32‑bit variables track the positions of pieces and kings for each player, with the playable squares numbered 1 to 31. Moves and game progress are recorded on a teleprinter. The player starts by flipping a coin to decide who goes first, then makes moves using switches and buttons. The computer alternates moves, prints its moves, and can show the player’s chosen move before finalizing it. The computer beeps to signal it is ready and may respond with pre‑written messages if the player delays or makes mistakes. When the game ends, the machine even plays a short tune, “God Save the King.”

Influence and legacy
Checkers helped demonstrate how a general‑purpose computer could run a game with visuals and a basic AI, predating other early efforts in computer games. It inspired Arthur Samuel, who saw Strachey describe the program at a conference in Toronto and created his own Checkers program for the IBM 701. Around the same period, other early games such as OXO (tic‑tac‑toe) and Turochamp (a chess program by Turing) appeared, though there is debate about which was first to display visuals.

Technical notes and preservation
The final version of Checkers consisted of over 1,000 instructions spread across more than 20 pages of code. It was the longest program then written for a computer. Five handwritten versions exist, and recordings of games played during tests are preserved on paper. The project established Strachey’s reputation as a talented programmer and contributed to the era’s exploration of machine intelligence. The program and its history are kept at the Bodleian Library at the University of Oxford.