is a code (named after the persons Guy / Blandford / Roycroft) concisely denotes chessboard forces/pieces in at most 6 digits.
Examples: two white knights and one black pawn codes into 0002.01; whiteQueen blackQueen whiteRook codes as 4100; white two Bishops vs blackKnight codes as 0023; The full complement of 32 chessmen codes as 4888.88.
The key to encoding is to compute the sum '1-for-White-and-3-for-Black' for each piece type in QRBN sequence, with white pawns and black pawns uncoded following the 'decimal point'. The key for decoding is to divide each QRBN digit by 3, when the quotient and remainder are in each of the 4 cases the numbers of Bl and W pieces respectively.
The GBR code permits unique sequencing, which, together with the fact that a computer sort of several thousand codes and the reference attached to each is a matter of a second or two, enormously facilitates the construction of look-up directories.
A consequence of the foregoing is the code's greatest overall advantage: its user-friendliness. The GBR code has the unique characteristic of equally suiting humans and computers. No special skill or translation process is required whether the code is encountered on a computer printout or whether it is to be created (for any purpose, including input to a computer) from a chess diagram.
White forces Stalemate.
A natural extension of the GBR code is to use it to represent a complete position.
Another convention is to precede the GBR code with the squares of the kings, and follow the code with the squares of the pieces, in W-before-Bl within code digit sequence, preserving the 'decimal point' to separate the pieces from the pawns, if any (where all W pawns precede all Bl).
The 223-move optimal play solution position in the endgame wR wB bN bN would be represented: a7d3 0116.00 b2b3c6d6 3/3+.
The '3/3' is a control indicating 3 W and 3 Bl men, with '+' meaning W wins, while '=' would mean White draws.
The win/draw indicators are optional. Note that although in this example there are no pawns the GBR code decimal point and immediately following pair of zeroes are obligatory (enabling a scan of a text file searching for encoded chess positions) but the absence of a decimal point in the list of squares confirms that there are no pawns.
A position with pawns but no pieces would be coded in this manner: a2c4 0000.32 .d4e3f2e4f3 4/3 WTM.
To indicate Black to move (but still with the implied win or draw for White) it is suggested that '-+' and '-=' be employed. Where the position result is unknown or undecided or unknowable it is suggested that the computer chess convention 'WTM' (White to move) and 'BTM' be followed.
The redundancy check piece-count (including the '/' separator) and terminating full stop are both obligatory.
Another explanation of the position code of endgamestudies.
If you see an endgamestudy in a database or elsewhere documented there often a coding like [+0020.42c1a1].
This coding is useful to find a startposition in a database e.g. to find if it is already in there, double or who did compose it.
Here an explanation of this coding about what this all means. Between the brackets [ and ] there are 5 characters before the dot and six after the dot.
The first character tells what the result of the study is.
+ means "White wins"
= means "White makes a draw"
The second character tells how many queens are on the chessboard.
0 (no Queens on the board)
1 (1 white Queen)
2 (2 white Queens)
3 (1 black Queens)
4 (1 white, 1 black Queen)
5 (2 white cs + 1 black Queen)
6 (2 black Queens)
7 (2 black Queens + 1 white Queen)
8 (2 white + 2 black Queens)
9 (one side has at least 3 Queens)
The third character tells how many rooks are on the chessboard analogous to 2nd character.
The fourth character tells how many bishops are on the chessboard analogous to 2nd character.
The fifth character tells how many knights are on the chessboard analogous to 2nd character.
The seventh character (first after the dot '.') tells us how many white pawns there are.
The eight character counts the amount of black pawns.
The last 4 characters (2 pairs) tell us where the white and black king are.
So the above example [+0020.42c1a1] means:
white wins, no queens, no rooks, white has 2 bishops (black none), no knights, white has 4 pawns, black has two pawns, white's king is on c1 and black's king is on a1.