Bit mask

A word selecting specified binary positions under a bitwise operation. To extract a stored bit at position $b$, logically shift by $b$ and combine with the mask 1. Grouping thirty-two cells into one Java integer permits a compact representation of a Conway Game of Life board.

// Destination: computer-science.bigb

For a bit mask $m$, the update $s\leftarrow (s-1)\&m$ visits its nonzero submasks in decreasing order. Every submask uses only positions set in $m$, so a mask with $k$ set bits has $2^k$ submasks including zero.

A bitboard represents occupied positions on a finite board by the bits of an integer. Bitwise operations combine occupancy masks and test whether pieces overlap.

Bitwise OR combines binary representations position by position: an output bit is one exactly when at least one input bit is one. On bit masks representing sets, it computes their union.