Bitmasks

Bitmasks are values used to encode multiple Boolean flags within a single binary quantity, typically an integer. Each bit position in the mask represents a separate condition or option, which allows compact storage and fast manipulation of large sets of binary states.

Common operations rely on bitwise operators. To turn on a flag, you OR the value with a mask: value = value | mask. To turn off, AND with the complement: value = value & ~mask. To toggle, use XOR: value = value ^ mask. To check, test with AND: if (value & mask) != 0 then the flag is set.

Mask creation and composition: a single-bit mask is produced by shifting 1 left by k positions, such as mask = 1 << k. Multi-flag masks combine via OR: maskA | maskB. You can also express ranges of bits with shifts, and use masks to clear or clear ranges.

Common applications: storing configuration flags, feature toggles, permissions, file modes, and protocol fields. They enable fast checks and minimal memory usage, and are widely supported across languages. In some systems, bitmasks are used for bitfields in structs.

Notes: be mindful of integer width and sign in different languages; bit shifts may have different semantics; use named constants; prefer explicit masks for readability. Debugging tip: isolate masking operations and test with representative values.