I have made a simple application already, and I now realize that it would be best to have documents. I have been reading through http://developer.apple.com/document...sNSDocument.html#//apple_ref/doc/uid/20000028 , and I started to wonder about how a document structure would fit into my code. First of all, is it possible to have only one window, open, thus allowing only one document to be open at a time? If that is not possible or not recommended, should I separate my window that displays the document from the nib that has the mainmenu data? I have a NSObject subclass that controls about everything in a window. Other than simply saying it is a subclass of NSWindowController, are there any methods I need to subclass? What kind of data can be stored? Is it possible to have a .plist kind of thing, with an array and a few numbers? Any advice for switching to an NSDocument Application is welcomed!