#include "str.h"int str_diff(s,t)register char *s;register char *t;{  register char x;  for (;;) {    x = *s; if (x != *t) break; if (!x) break; ++s; ++t;    x = *s; if (x != *t) break; if (!x) break; ++s; ++t;    x = *s; if (x != *t) break; if (!x) break; ++s; ++t;    x = *s; if (x != *t) break; if (!x) break; ++s; ++t;  }  return ((int)(unsigned int)(unsigned char) x)       - ((int)(unsigned int)(unsigned char) *t);}