endian

Endianness, often called endian, is a property of computer architectures that determines how multi-byte values are stored in memory and transmitted over networks. It specifies the byte order used to represent data types larger than one byte.

The two most common schemes are big-endian and little-endian. In big-endian representations, the most significant byte of a multi-byte value is stored at the lowest memory address; in little-endian representations, the least significant byte is stored first. For example, the 32-bit value 0x01020304 would be stored as 01 02 03 04 in big-endian and 04 03 02 01 in little-endian.

The terms originated as metaphors from the Gulliver's Travels story, later adopted in computing to describe endianness. In networks, the standard byte order is big-endian, often called network byte order. Many processors use little-endian memory layout (for example x86); some architectures historically used big-endian or supported multiple modes, such as ARM and PowerPC. Some systems can operate in either mode (bi-endian or mixed-endian configurations), which can complicate binary data sharing.

Endianness has practical implications for data interchange, file formats, and network protocols. Software must correctly translate values when writing or reading data on systems with different byte orders, using host-to-network and network-to-host conversions or explicit serialization routines. Understanding endianness helps ensure cross-platform compatibility in low-level programming, data serialization, and network communications.

See also: byte order, network byte order.