bitboards

Array of Long integers used as Bitboards. The index in the array is equal to the ordinal value minus one of the corresponding piece (e.g., Black Knight distribution is at index Piece.BN.ordinal - 1).

Each Long has 64 bits, where each bit represents a square in the board, following the Square enum order (A1 is bit 0, B1 is bit 1, up to H8 which is bit 63). A bit set to 1 indicates the presence of the piece corresponding to the array index, and 0 indicates absence.