Board representation (computer chess)

Board representation in computer chess is a data structure in a chess program representing the position on the chessboard and associated game state. Board representation is fundamental to all aspects of a chess program including move generation, the evaluation function, and making and unmaking moves (i.e. search) as well as maintaining the state of the game during play. Several different board representations exist. Chess programs often utilize more than one board representation at different times, for efficiency. Execution efficiency and memory footprint are the primary factors in choosing a board representation; secondary considerations are effort required to code, test and debug the application. Early programs used piece lists and square lists, both array based. Most modern implementations use a more elaborate but more efficient bit array approach called bitboards which map bits of a 64-bit word or double word to squares of the board.