(FEN) is a standard notation for describing a particular board position of a chess game. The purpose of FEN is to provide all the necessary information to restart a game from a particular position.

 

FEN is based on a system developed by Scottish newspaper journalist David Forsyth. Forsyth's system became popular in the 19th century; Steven J. Edwards extended it to support use by computers. FEN is defined[2] in the "Portable Game Notation Specification and Implementation Guide".[1] In the Portable Game Notation for chess games, FEN is used to define initial positions other than the standard one.[3] FEN does not provide sufficient information to decide whether a draw by threefold repetition may be legally claimed or a draw offer may be accepted; for that, a different format such as Extended Position Description is needed.

 

A FEN record defines a particular game position, all in one text line and using only the ASCII character set. A text file with only FEN data records should use the filename extension *.fen