Comparing OLE & DDE Message Protocols and Libraries

• Microsoft OLE version 1.0

At the Windows operating system level, both OLE and dynamic data exchange (DDE) are protocols for exchanging data and sending commands between applications. For Windows versions 3.0 and 3.1, neither the OLE libraries nor the Dynamic Data Exchange Management Library (DDEML) depend on special interprocess communications (IPC) mechanisms provided by the operating system. Rather, both OLE and DDE depend on the Windows messaging facility.

At the Windows operating system level, the OLE protocol is built on top of the DDE protocol. More specifically, the OLE protocol is largely a set of DDE Execute command strings that follow a conventional syntax.

At the application level, a function-based application program interface (API) is available for both OLE and DDE. For OLE, this API is provided to clients by the OLECLI.DLL file and to servers by the OLESVR.DLL file. For DDE, this API is provided by the DDEML.DLL file.

Despite the fact that OLE uses DDE as its transport mechanism, the present implementation of OLE is independent of the DDEML. This does not signify any functional or performance deficiencies of DDEML. Because the OLE libraries and DDEML were implemented in parallel, the schedule did not allow for this version of the OLE libraries to use DDEML.

It is quite likely that future versions of the OLE libraries will use DDEML rather than directly coding DDE messages.