Keystroke: Ctrl + F4
Unless you have changed the content of a file, it will simply be closed and disappear from the screen. Otherwise, the above window will appear. This contains three buttons, which from left to right are:
Yes (or y): Your document changes will be saved. If your document has not previously been saved, then you will be shown a second
No (or n): Any changes you have made will be discarded.
Cancel (or c): This will take you back to the editing screen.