unsigned int strlen(const char *s) {
  register unsigned int i;
  if (!s) return 0;
  for (i=0; *s; ++s) ++i;
  return i;
}

char* strcat(register char* s, register const char* t) {
  char *dest=s;
  s+=strlen(s);
  for (;;) {
    if (!(*s = *t)) break; ++s; ++t;
  }
  return dest;
}

char* strcpy(register char* s,register const char* t)
{
  char *dest=s;

  while ((*dest++=*t++));
  return s;
}