#include <stdio.h>

union
{
    unsigned short num;
    unsigned char c[2];
} data;

int main(int argc, char const *argv[])
{
    data.num = 0x0102;

    if (data.c[0] == 1)
    {
        printf("大端字节序\n");
    }
    else
    {
        printf("小端字节序\n");
    }

    return 0;
}