Bitfeld

Bitfeld is a term used in computer science to describe a structure or concept that stores information as a sequence of bits. The word combines bit, the basic unit of digital information, with feld (the German word for field), reflecting its origin in German technical literature. Bitfelds are typically used to represent multiple boolean flags or small-range values in a compact form.

In practice, a bitfeld can be implemented in two main ways. Some programming languages support native bit fields within data structures, such as a struct where each field is declared with a small width, for example unsigned int flag1:1; flag2:2;. In other scenarios, bitfeld-like behavior is achieved by using ordinary integer types together with bitwise operators to set, clear, and test individual bits or groups of bits. The latter approach is more portable across languages, while native bit fields may offer concise syntax and potential performance benefits on specific compilers.

Applications of bitfelds include representing sets of boolean options, status flags, or small numeric values within limited memory, which is important in embedded systems, network protocols, and file formats. They can improve cache efficiency by reducing the size of data structures, but at the cost of portability and readability. Endianness, padding, and bit-order are common sources of portability concerns when relying on native bit fields.

Related concepts include bitmaps, bitsets, and bitmasks, which also use bits to encode information but differ in structure and typical usage.