Sample Prolog code from the slides and the whiteboard.

To load two files into SWI Prolog, use the following command at
the prompt:

	['file1.pl', 'file2.pl'].

For example, to load the list example, make sure that you are in the
the "list" subdirectory and issue the command:

	['sample.pl', 'list.pl'].
	
Once the files have been loaded, you can issue queries at the prompt.
For example, try this:

	['family.pl', 'windsor.pl'].
	cousin(X, Y).
	
Keep pressing ';' to see all matches. Press '.' to terminate the search.
