大端模式和小端模式

 #include     "unp.h"

  int
  main(int argc, char **argv)
  {
      union {
          short   s;
          char    c[sizeof(short)];
      } un;

      un.s = 0x0102;
     printf("%s: ", CPU_VENDOR_OS);
     if (sizeof(short) == 2) {
         if (un.c[0] == 1 && un.c[1] == 2)
             printf("big-endian\n");
         else if (un.c[0] == 2 && un.c[1] == 1)
             printf("little-endian\n");
         else
             printf("unknown\n");
     } else
         printf("sizeof(short) = %d\n", sizeof(short));

     exit(0);
 }