What is o-o in chess

Also 0-0. The move notation for kingside castling. (PGN format uses Os; FIDE uses 0s.)

Table of Contents Show

Pawn Promotion
Check and Checkmate
Ambiguous Moves
End of the Game
Other Symbols
A Full Game

Castling is a move in the game of chess involving a player's king and either of the player's original rooks. It is the only move in chess in which a player moves two pieces in the same move, and it is the only move aside from the knight's move where a piece can be said to "jump over" another.

Castling consists of moving the king two squares towards a rook on the player's first rank, then moving the rook to the square over which the king crossed.Castling may only be done if the king has never moved, the rook involved has never moved, the squares between the king and the rook involved are unoccupied, the king is not in check, and the king does not cross over or end on a square attacked by an enemy piece. Castling is one of the rules of chess and is technically a king move (Hooper & Whyld 1992:71).

The notation for castling, in both the descriptive and the algebraic systems, is 0-0 with the kingside rook and 0-0-0 with the queenside rook; in PGN, O-O and O-O-O are used instead. Castling on the kingside is sometimes called castling short (the rook moves a short distance, i.e. two squares) while castling on the queenside is called castling long (the rook moves a long distance, i.e. three squares) (Hooper & Whyld 1992).

Castling was added to European chess in the 14th or 15th century and did not develop into its present form until the 17th century. The Asian versions of chess do not have such a move.

Castling is represented by the following symbols:

O-O = Kingside castle
O-O-O = Queenside castle

Pawn Promotion

When a Pawn moves to the last rank it is promoted. The symbol for the chosen promotion piece is placed after the move.

Example: c8Q. This means that a Pawn was moved to c8, and the Pawn was promoted to a Queen.

Check and Checkmate

When check or checkmate is given, a symbol is placed after the move.

+ = check
# = checkmate.

Example: Qb3+. This means that the Queen has moved to the b3 square and placed the enemy King in check.

Another example: Qb3#. This means that the Queen has moved to the b3 square and checkmated the enemy King.

Ambiguous Moves

Occasionally, two or more pieces of the same type are able to move to the same square. Take the move Re5 for example. If there was a rook at d5 and another rook at f5, then we need to show which one made the move. This is done by placing a character after the piece symbol.

The file of the moving piece can be used. Example: Rde5. This indicates that the rook on the d file moved to e5.

The rank can be used. Example: N1f3. This indicates that a knight on the first row moved to f3.

The file method is the preferred choice, but sometimes the rank method must be used. In rare circumstances, the file and rank can both be used if required.

End of the Game

At the end of the game, a sign is given to indicate the winner.

1-0 = White wins
0-1 = Black wins
1/2-1/2 = Draw

Other Symbols

! = Good move
? = Mistake
!? = An interesting move that is probably good.
?! = An interesting move that is probably bad.

A Full Game

A famous game described with algebraic notation is presented below. Try playing the game out for yourself!

The Opera Game - Paul Morphy vs. Duke of Braunschweig and Count Isouard, Paris, 1858

The game was played in a Paris opera theatre between American Master Paul Morphy and two strong amateurs. The game is considered to be a must-read for chess enthusiasts and students.