ICCF numeric notation

ICCF numeric notation belongs to correspondence chess, a form in which players exchange moves remotely, traditionally by post. ICCF stands for the International Correspondence Chess Federation. The system avoids language-dependent piece initials by assigning every square a two-digit code.

Building the code

1. The first digit gives the file from White's viewpoint: a is 1, b is 2, and so on through h as 8.
2. The second digit gives the rank: 1 is nearest White and 8 is nearest Black.
3. A move joins the two digits for the origin to the two for the destination. Thus e2 is 52, e4 is 54, and e2-e4 becomes 5254.

The code does not name the piece or add a capture or check sign; the position supplies that information. Promotion adds a fifth digit: 1 for queen, 2 for rook, 3 for bishop, and 4 for knight. Castling records the king's initial and final squares, so White's kingside castling is 5171.

The ICCF rules document that defines the system assigns it to postal or email games outside the server, while server play uses algebraic notation. It resembles coordinate notation because both give origin and destination, but ICCF replaces the file letter with a number as well.