Editing Bitboard (section)

==Description==
{{Further|Bit field}}
A bitboard, a specialized bit field, is a format that packs multiple related boolean variables into the same machine word, typically representing a position on a board game, or state of a game.  Each bit represents a space; when the bit is positive, a property of that space is true.  Bitboards allow the computer to answer some questions about game state with one bitwise operation.  For example, if a chess program wants to know if the white player has any pawns in the center of the board (center four squares) it can just compare a bitboard for the player's pawns with one for the center of the board using a bitwise AND operation.  If there are no center pawns then the result will be all zero bits (i.e. equal to zero).  Multiple bitboards may represent different properties of spaces over the board, and special or temporary bitboards (like temporary variables) may represent local properties or hold intermediate collated results.

The efficacy of bitboards is augmented by two other properties of the implementation. First, bitboards are fast to incrementally update, such as flipping the bits at the source and destination positions in a  bitboard for piece location when a piece is moved.  Second, bitmaps representing static properties like all spaces attacked by each piece type for every position on a chessboard can be pre-collated and stored in a table, so that answering a question like "what are the legal moves of a knight on space e4?" can be answered by a single memory fetch.

Bitfield implementations take advantage of the presence of fullword (32-bit or 64-bit) bitwise logical operations like AND, OR, NOT and others on modern CPU architectures in order to be efficient. Bitboards may not be effective on earlier 8- and 16-bit minicomputer and microprocessor architectures.