Endianness

Byte Level

32bit Integer  0x5A5B5C5D
MemoryAddress  0x01  0x02  0x03  0x04
Big-Endian      5A    5B    5C    5D
Little-Endian   5D    5C    5B    5A

Big-Endian, IP Protocols, IBM z
Little-Endian, x86

Bit Level (bit numbering)

MSB 7 6 5 4 3 2 1 0 LSB
Big-Endian 7 6 5 4 3 2 1 0
Little-Endian 0 1 2 3 4 5 6 7
MSB, Most Significant Bit
LSB, Least Significant Bit

Big-Endian, I2C, SMBus, SONET, SDH
Little-Endian, RS-232, HDLC, Ethernet, USB