Normally the tewo file windows each contain the files of one directory. However, the contents of the directory may be filtered to include/exclude files matching the current window filter or the window(s) may contain multiple directories. Thus, the function actually compares the files shown in the two windows.

The master window is the left window and the right window contents are compared with the left window. The windows may swapped which swaps the master directory. The comparison does not start until 'Compare ' is pressed.

Comparison criteria is set by the user using the options shown in the bottom area of the dialog prior to starting a comparison.