Why does an 8-bit field have endianness?

Question

See the definition of TCP header in /netinet/tcp.h:

struct tcphdr
  {
    u_int16_t th_sport;         /* source port */
    u_int16_t th_dport;         /* destin         


        

Answer 1

There are two kind of order. One is byte order, one is bitfield order. There is no standard order about the bitfield order in C language. It depends on the compiler. Typically, the order of bitfields are reversed between big and little endian.