Internet protocol (IP) uses 'network byte order' (big-endian) because it was agreed that it would do so (see RFC 1700. IP 139.156.32.45 in big-endian binary is 10001011.10011100.00100000.00101101
(.
added for legibility), and this is how it would be transferred over the network.
Depending on your architecture this address can be stored in a big-endian or little-endian format. If you are using X86 architecture (little endian), the bits (per byte) would be reverted, so they would end up being stored as 11010001.00111001.00000100.10110100
. In a SPARC CPU, which uses big-endianness the bits would be stored like the IP protocol uses them.