rem: print_char (size_t n_bytes, const char *block, const char *fmt_string)
add: print_char (size_t n_bytes, void const *block, char const *fmt_string)
context: print_char (size_t n_bytes, const char *block, const char *fmt_string){  size_t i;  for (i = n_bytes; i > 0; i--)    {      unsigned int tmp = *(const unsigned char *) block;      printf (fmt_string, tmp);      block += sizeof (unsigned char);    }}