The filename argument passed to fopen() specified syntax ((x)), where x is an unsigned integer, indicating a generated memory file name or perhaps a UNIX file. The application is either running POSIX(OFF) or the filename was prefixed with exactly two '/' characters, indicating that the file is not a UNIX file. The file name does not exist on the file chain, meaning that there is no such memory file. You cannot open a memory file using a generated memory file name when the memory file does not exist.