What's Up, Doc? provides a skeletal example of how you might manage multiple documents in an applicaton.  The actual documents are of little utility (they contain one line of text in a text field), but the functionality of What's Up, Doc?  provides a basis for a full-fledged application.

Some of the functions demonstrated in What's Up Doc? include:

		A full compliment of Save, SaveAs, SaveTo functions.
		A Revert function to restore a document from the last saved version.
		Methods for reading and writing the document that only saves the variable parts of the document (not the entire document window).
		If a user closes a window that has been edited, What's Up, Doc? will query if they wish to save the window before it's closed.
		If the user quits the application with edited documents, What's Up, Doc? will offer the chance to review unsaved documents.

What's Up Doc? maintains the notion of an "active document" which receives most of the actions initiated by the user.