biendian

Biendian, or bi-endian, refers to the capability of a computing system to operate in both big-endian and little-endian byte orders. Endianness describes how multibyte values are laid out in memory: in big-endian order the most significant byte comes first, while in little-endian order the least significant byte comes first. A bi-endian system can switch between these orders, either globally or on a per-thread or per-process basis, allowing software to run in a chosen order or to interpret data from external sources that use a different order.

The mode switch can be supported by hardware, software, or a combination. In hardware-enabled bi-endian designs, the processor and memory subsystem can interpret and store data in either order and can switch at runtime. In other setups, the operating system or application libraries provide endianness conversion routines and ABI conventions to keep data correctly formed when exchanging with other systems. Care is required when sharing data structures or memory images across endiannesses, and when using network protocols that have a fixed endianness.

Applications and implications: Bi-endian capability is mainly valuable for software portability and interoperability in heterogeneous environments, such as systems that must interoperate with devices or networks using different byte orders. It can reduce the amount of manual byte-swapping, though mode switching incurs complexity and potential performance costs.

Examples: Several ARM implementations and some POWER and SPARC variants have supported bi-endian operation at various times, though most contemporary mainstream platforms favor a single endianness for performance and simplicity.