rem: sprintf (filename_space+strlen(prefix), "%0*d", digits, num);
add: sprintf (filename_space+strlen(prefix), "%0*u", digits, num);
context: make_filename (unsigned int num){  strcpy (filename_space, prefix);  if (suffix)    sprintf (filename_space+strlen(prefix), suffix, num);  else    sprintf (filename_space+strlen(prefix), "%0*d", digits, num);  return filename_space;}