NETWORK NUMBERS (IP VERSION 4)
Internet network numbers may be specified in one of the following forms:
When four parts are specified, each is interpreted as a byte of data and assigned, from left to right, to the four bytes of an Internet network number. Note that when an Internet network number is viewed as a 32-bit integer quantity on a system that uses little-endian byte order (such as the Intel 386, 486, and Pentium processors) the bytes referred to above appear as "d.c.b.a". That is, little-endian bytes are ordered from right to left.
When a three part number is specified, the last part is interpreted as a 16-bit quantity and placed in the rightmost two bytes of the Internet network number. This makes the three part number format convenient for specifying Class B network numbers as "128.net.host".
When a two part number is supplied, the last part is interpreted as a 24-bit quantity and placed in the rightmost three bytes of the Internet network number. This makes the two part number format convenient for specifying Class A network numbers as "net.host".
When only one part is given, the value is stored directly in the Internet network number without any byte rearrangement.
All numbers supplied as "parts" in a . notation may be decimal, octal, or hexadecimal, as specified in the C language (i.e., a leading 0x or 0X implies hexadecimal; otherwise, a leading 0 implies octal; otherwise, the number is interpreted as decimal).
byteorder(3), inet(3), networks(5)