Endianness-字节序

Endianness-字节序#

https://helpful.knobs-dials.com/index.php/Endianness

  • Little-endian (LSB) means we start with the least significant part in the lowest address.

  • Big-endian (MSB) means we start with the most significant part.

For example, 16-bit integer 0x1234 would be stored in bytes as

  • 0x12 0x34 (LSB)

  • 0x34 0x12 (MSB).

Little-endian, Big-endian, LSB, MSB#

Little-endian: lowest value first, or leftmost/lowest in memory, increasing numeric significance with increasing memory addresses (or, in networking, time)

  • Little-endian architectures store the least significant part first (in the lowest memory location)

  • They include the x86 line of processors (x86, AMD64 a.k.a. x86-64)

  • In byte architectures, little-endian is also known as LSB, referring to the Least Significant Byte coming first.

Examples: consider a 32-bit integer

  • 12345 = hex:0x12345 would, shown in hexidecimal, be 0x39 0x30 0x00 0x00

  • 287454020 would be 0x44 0x33 0x22 0x11

Big-endian: highest value first, decreasing significance

  • Big-endian architectures store the most significant part first (in the lowest memory location).

  • Includes the Motorola 68000 line of processors (e.g. pre-Intel Macintosh), PowerPC G5 a.k.a. PowerPC 970

  • In byte architectures, big-endian is also known as MSB, referring to the Most Significant Byte coming first.

Examples: consider a 32-bit integer

  • 12345 would, shown in hexidecimal, be 0x00 0x00 0x30 0x39

  • 287454020 would be 0x11 0x22 0x33 0x44

Network byte order is a term used by various RFCs, and refers to big-endian (with a few exceptions?[1])