How Linux can play a song, access a file, shows a movie if I delete the file during the process? I just discover I can move a mp3 and still listen to the song. Just a question: How?

You can move the MP3 file and it still plays (in xmms?) because the whole file has been dumped to memory and it's being played from there. Let's say, however, that you load a playlist (.m3u or whatever) and move one of the individual files (one that hasn't been played yet) in the list... when the player reaches that particular file, it'll throw a wobbly (or at least skip the file(s) and move onto the next valid file location).

Hope this helps.

Another observation, let say you have a huge mp3 file and you are playing it, memory gets filled with as much it can fit, lets say you removed the file after it started to play, the next page swap that occures in memory to free up/release unused pages and brin the new ones in you can have unpredictable outcome - you'd consider yourself lucky if it stops playing - I believe with linux memory management this is the case, in windows you'll get BSOD in the best case scenario.

Another possibility is when you move a file to another location in the same partition, you're not actually moving the file, you're just changing the directory information about that file. The operating system doesn't refer to that file by the directory name e.g. "/usr/data/mymusic/whatever.mp3", it refers to its inode. When you move a file, you don't change the inode, so when you move the file, the application that is currently reading the file has no idea about it because it doesn't track what the name, or directory location, of the file is (it only cares about the inode).