Chess is the classic game of manoeuvre and control. It is played on an 8x8 board between two players, each with initial armies of 16 pieces set up as shown in figure 1:
The players take turns, starting with White, each moving one piece per turn with the goal of capturing the enemy king. Only one piece can occupy a square at a time, and an emery piece may be captured by occupying its square and removing it from the game.
The eight columns or files of the board are lettered A-H and the eight rows or ranks are numbered 1-8 as shown. Each square is identified by its file and rank; thus the Black King is initially on square E8.
There are six kinds of pieces as shown, each with its own pattern of movement:The Pawn, represented by an arrowhead, can advance along its file in the direction of its arrowhead one square per turn onto an unoccupied square, as shown by the solid arrow in Figure 2. It is, however, able to capture an emery piece diagonally ahead of it, as shown by the dotted arrows, and is the only chess piece to move and capture differently. The pawn is the foot soldier of chess, needing support from the other pieces to advance safely, but vital in holding territory. See also Double Advance, En Passant, and Queening below.
The Knight, represented by a horse, moves obliquely, 2 squares laterally and 1 to either side, as shown in Figure 2. It does not travel directly over any other squares and therefore cannot be blocked, making the Knight idea for behind-the-lines raids. It is worth about three pawns.
The Bishop, represented by a miter, moves diagonally any number of empty squares as shown in figure 2. It may capture an enemy encountered on the diagonal, but cannot continue beyond an occupied square. A Bishop can never encounter its brother since they are confined to squares of opposite colour, but it is a nimble piece, able to cross the board in a single move. It is worth about three pawns.
The Rook, represented by a castle, moves laterally any number of empty squares as shown in figure 3. It may capture any enemy encountered, but cannot continue beyond an occupied square. Although too valuable and confined to risk in the opening game, it is a powerful piece, able to force checkmate of a lone enemy king. It is worth about five pawns. See Castling below.
The Queen, represented by a diadem, moves diagonally or laterally any number of empty squares as shown in Figure 3. It combines the moves of Bishop and Rook and is the most powerful piece by far, but must be used carefully since its uncompensated loss is generally fatal. It is worth about nine pawns.
The King, represented by a crown, moves one square in any direction as shown in figure 3. It is vulnerable to attack if exposed, but must nonetheless be ready to play an active role once the major pieces have been captured. It is of course invaluable; any other piece must be sacrificed if necessary to save the King. See Castling below.
If a player moves so that he could capture the enemy king with his next move, the king is said to be in check, and it is customary to warn the opponent of this. It is illegal for a player to expose his own king to check, or to leave it in check when it can be saved. If it cannot be saved, the check is checkmate, and the game is then ended before the king is actually captured. A game is considered a draw if neither player can proceed to checkmate. A player must move when it is his turn, but if every move would expose his king to capture and thus be illegal, the game is considered a stalemate or draw; achieving this may be the stratagem of last resort for a losing side.
To improve the pace of the game, the following special moves have been added:
Double Advance and En Passant. For faster development, a pawn may advance two squares, provided they are unoccupied, from its initial position. However, this is not intended as a move to bypass an enemy pawn that would have been able to capture had a single advance been made. In such a situation (Figure 4), the double advance is permitted, but the opponent has the en passant option, for his next turn only, of returning the pawn to single advance and capturing it there.
Queening. If a pawn successfully reaches the opposite edge of the board, it is promoted to any other piece, except a duplicate king. The choice is usually a queen, and this dramatic increase of power makes the advance and queening of a pawn the critical feature of the end of many games.
Castling safeguards the king while centralising the rook. It a previously unmoved rook can move next to the previously unmoved king and be unattached there, the player may place the king on the other side of the rook (Figure 5). Castling out of check is not permitted.
Source: Boris Electronic Chess Computer