Q: How can I determine whether a machine's byte order is big-endian or little-endian?
A: The usual techniques are to use a pointer:
int x = 1;
if(*(char *)&x == 1)
printf("little-endian\n");
else printf("big-endian\n");
or a union:
union {
int i;
char c[sizeof(int)];
} x;
x.i = 1;
if(x.c[0] == 1)
printf("little-endian\n");
else printf("big-endian\n");
(Note that there are also byte order possibilities beyond simple big-endian and little-endian[footnote] .)
See also questions 10.16 and 20.9b.
References:
H&S Sec. 6.1.2 pp. 163-4