File menu
Compare files… leads to a file open dialog for each of two files to be compared
Compare directories…leads to dialog to allow entry of two directory names for comparison
Abort will be greyed unless an operation is in progress. Then allows that operation to be terminated before completion. When this is not greyed, there is also an Abort button at the top right of the window which has the same function.
Save File List allows the list of files which are (the same, different, only in left or only in right) to be saved. In addition, a checksum for each file can be saved.
Copy Files… leads to a dialog allowing you to write the files to a disk. This can be useful if you are trying to synchronise two directories.
Print prints the current view (either outline or expanded)