But sometimes you want to just "open" a file. The fact that your computer may choose to save it is an implementation detail. In fact, most systems don't actually 'save' it in many senses of the word. Instead they write it to the file system in a way that indicates that it may be removed at any time without notifying the user. In fact, on Linux (I can't speak to any other OS), it is common for these temporary files never to actually be saved to the disk. Instead they are loaded into a RAM based file-system (tmpfs), usually found at "/dev/shm"