The following figure shows the typical Smalltalk DDE architecture. Either one of these objects could be any other application that supports the DDE protocol for either a DDE server or a DDE client.

The classes depicted in the figure are described in the following sections. Their hierarchy is as follows:
Object
DdeClass
DdeClient
DdeServer
DdeServerManager

This hierarchy is not part of the windowing system (such as PM or Windows) but it does use the windowing system of the underlying platform.