Some moves require special notation.
Castling is denoted by O-O for castling Kingside and O-O-O for castling Queenside. Some writers prefer 0-0 and 0-0-0, but this causes no confusion.
Pawn promotion is handled by adding the promoting piece to the move. The move 'e8Q' means that the Pawn is being promoted to a Queen. Some writers use 'e8/Q' or 'e8=Q', but this causes no confusion.
Ambiguous moves are moves where two pieces of the same type can move to the same square. Suppose, for example, that White's Knights can both move to f3. The move is rendered unambiguous by inserting the file of the moving piece immediately after the letter denoting the piece. Instead of 'Nf3', we write 'Ndf3' or 'Ngf3' to show which Knight is moving. Where the file is the same for both pieces, we use the rank. The notation 'R8a4' means that the Rook on the 8th rank is moving to a4 rather than, say, the Rook on the 1st rank.
