The GBR-code
GBR code (after
the persons Guy/Blandford/Roycroft) concisely
denotes chessboard force in at most 6 digits. Examples: two white knights and
one black pawn codes into 0002.01; wQ bQ wR codes as 4100; wBB vs
bN codes as 0023; the full complement of 32 chessmen codes as 4888.88.
The key to encoding is to compute the sum '1-for-W-and-3-for-Bl' 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.
Bent,C 1993.
White forces Stalemate.
A natural extension of the GBR
code is to use it to represent a complete position. A good 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.