The game of chess is played by two opponents by moving pieces on a square board. The chess board is made up of 64 equal squares in color alternately light (the "white" squares) and dark (the "black" squares). The chess board is positioned between the players so that the square in the corner to the right of each player is white. The 8 rows of squares running between the edges of the chess board nearest the two players are called "ranks". The 8 rows of squares running at right angles to the ranks are called "files". The rows of squares of the same color touching at the corners are called "diagonals".
At the start of the game one player has 16 light colored pieces (the "White" pieces) and the other player has 16 dark colored pieces (the "Black" pieces). The pieces consist of one King, one Queen, two Rooks, two Knights, two Bishops and eight Pawns. Each player’s pieces are initially positioned on the board to cover the two ranks nearest the player. The Rooks occupy the two corner squares in the first rank, the Knights occupy the two squares next to the Rooks on the first rank, the Bishops occupy the two squares next to the Knights on the first rank, the King and Queen occupy the two centre squares on the first rank such that the King is on a square of the opposite color to itself, and the Pawns occupy the whole of the second rank.
The two players move pieces alternately, each player making one move at a time. The player who has the White pieces makes the first move. Except for castling, a move is the transfer of a piece from one square to another square which is either vacant or occupied by an opponent’s piece. No piece, except the Rook when castling or the Knight, can cross a square occupied by another piece. A piece played to a square occupied by an opponent’s piece takes the opponent’s piece as part of the same move, and removes it from the board.
The King, except for castling, can move to any adjacent square that is not attacked by an opponent’s piece.
Castling is a move of the King and Rook, counted as a single move, in which the King is transferred from it’s original square to either of the nearest squares of the same color in the same rank, then the rook towards which the King has moved is transferred over the King to the square the King has just crossed. Castling may not be performed if the King has already been moved, or with a Rook that has already been moved. Castling may not be performed if there is any piece between the King and the Rook involved, or if the squares that the King is on or that it must cross or that it will occupy is being attacked by an opponent’s piece.
The Queen can move to any square on the rank, file or diagonal on which it is placed. It may not jump over any other piece. The Rook can move to any square on the rank or file on which it is placed. It may not jump over any other piece.
The Knight can move one square along the rank or file plus one square along a diagonal moving away from the square it left.
The Bishop can move to any square on the diagonal on which it is placed. It may not jump over any other piece. By definition, a bishop will always remain on the same colored square throughout the game.
The Pawn can move only forward. Except when making a capture, it may advance on it’s first move one or two vacant squares along the file on which it is placed, and on subsequent moves one vacant square along the file on which it is placed. When making a capture it advances on one square along either of the diagonals on which it is placed. A Pawn attacking a square crossed by an opponent’s Pawn which has advanced two squares on the previous move can capture the pawn as though the latter had only advanced one square. This capture can only be made on the move immediately following such advance, and is known as "en passant". On reaching the end of a file a Pawn is immediately exchanged, as part of the same move, for a Queen, Rook, Knight or Bishop of the same colour at the player’s choice. This is called "Pawn promotion".
The King is in check when it’s square is attacked by an opponent’s piece. The check must be averted on the move immediately following, otherwise it is "mate". Check can be averted either by taking the attacking piece, moving a piece between the attacking piece (unless the attacking piece is a Knight), or moving the King.
The End of the Game
The game is won for the player who has mated the opponent’s King. The game is considered won for the player whose opponent resigns. When using clocks, the game is won by the player whose opponent exceeds their allotted time. The game is drawn under any of the following circumstances:
- When the King of the player whose turn it is to move is not in check, but such player cannot make a legal move. This is called "stalemate".
- On demand by either player when the same position appears three times, the same player having the move each time. The position is considered the same if pieces of the same kind and color occupy the same squares, and the possible moves of all pieces are the same.
- On demand by the player who’s turn it is to move if at least fifty moves have been made by each player without a capture of a piece and without a Pawn move having been made.
- By agreement between the two players.