FEN (Forsyth-Edwards Notation)

Forsyth-Edwards Notation (FEN) – or X-FEN in extended form – 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. In fact this notation has one weakness: it is not describing how many times the described position was repeated. A detailed description is available online:

• ForsythEdwards Notation - Wikipedia 
• X-FEN - Wikipedia 

Also, it should be noted that Scidb can handle the Shredder FEN.

For other chess variants Scidb is using some required extensions:

• Drop Chess
• Three-check Chess

Drop Chess

Scidb is using an extended FEN (X-FEN, or Shredder FEN) for Drop Chess, derived from BPGN standard (⇒ BPGN - Bughouse Portable Game Notation ). The pieces in holding will be added at the end of first field; for example:

r2q1rk1/ppp2ppp/5p2/b7/8/P1NPB2b/1PP1QP1P/R3R1K1/NNPPbnp b - - 0 16

NNPPbnp is describing that the white player has two knights, and two pawns in holding; and the black player has one bishop, one knight, and one pawn in holding.

For pieces resulted from a pawn promotion the character tilde is tagging this piece. Example:

rkn2Q~N1/pppq4/5P2/8/1P1P1n2/5B1P/PPPN1PpP/R3K1R1/RBBBPPq b Q - 0 43

The white queen (Q~) was originated from a pawn promotion.

Three-check Chess

For this chess variant an additional field will be appended to the FEN (X-FEN, or Shredder FEN) for a description of the given checks. Example:

rnb1k1nr/pppp1ppp/8/4p3/3PP2q/2N5/PP3PPP/R1BQKBNR w KQkq - 1 5 +0+2

+0+2 means: the white player does not gave check at all to black, and the black player gave check to white king exactly two times.