char s1[] = "Upper/LOWER.";
char s2[] = "mIXeD CaSe..";


/* exchanges and flips case of s2 */
 dostr (ptr1,ptr2)
 char *ptr1,*ptr2;
{
 unsigned char c, tmp;
   
 while (*ptr1 != 0) {
   tmp = *ptr1;
   c = *ptr2;
   if (c > 0x2F) {
     /* make sure it is not a special char */
     *ptr1 = c ^ 0x20; /* flip case of s2 */
   } else {
     /* leave special chars alone */
     *ptr1 = c;
   }
   *ptr2 = tmp;
   ptr1++;ptr2++;
  }

}

main()
{
 char c;


  printf("Before...\n");
  printf("s1: '%s'\n",s1);
  printf("s2: '%s'\n",s2);

  dostr(s1,s2);

  printf("After...\n");
  printf("s1: '%s'\n",s1);
  printf("s2: '%s'\n",s2);

}

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