OLEâ€™s predecessor, Dynamic Data Exchange, is a method of dynamically moving data among applications in the Microsoft Win32 Application Programming Interface (API).
The DDE protocols send messages between applications that share data and use shared memory to exchange data.
Applications can use the DDE protocol for one-time data transfer and for continuous exchanges in which applications send updates to one another as new data become available.
Prior to OPC, hardware manufacturers that recognized the need for software connectivity to their hardware was limited in their ability to develop driversâ€”the choice was between DDE and a list of proprietary DDE derivatives. Selecting any of these had possible
effects of limiting the userâ€™s choice of software or preventing the acceptance of the hardware.
Due to OPC data exchange popularity, DDE is becoming less popular.