Can anybody explain to me where the meat of the application code is? For example, when I look at GeoDraw under Appl/GeoDraw I see .def files containing definiti

Can anybody explain to me where the meat of the application code is? For example, when I look at GeoDraw under Appl/GeoDraw I see .def files containing definitions, declarative looking .ui files in the UI subdirectory and some .asm files containing only a few very short functions. That surely can't be everything? I remember it being quite a complex application.