How DDE Works

Dynamic Data Exchange (DDE) is used to transfer data between Windows applications.

Two applications that participate in DDE engage in what is known as a DDE conversation. The application that initiates the conversation is known as the client application, and the application that responds to the client is known as the server application.

Any Windows product that supports DDE as a server application must have a server name. For example, the server name for Word for Windows is WINWORD and for Quattro Pro it is QPW. To initiate a DDE link with a server application, you would normally use the server name and this would return a channel number. Using this channel number you would then send commands (normally in the format of the macro language supported by that server application) and finally close the link with that channel number when all processing is completed.

When communicating with a server you must also always specify a topic. Server applications can support many topics depending on which part of that application you want to communicate with. For instance, if you want to request information from Quattro Pro on a specific spreadsheet, the server name would be QPW and the topic name would be the spreadsheet name.

DDE was designed to form a standard way of communicating between Windows applications. However, the fact that each Windows application supports DDE differently (or sometimes not at all) makes it more difficult for the novice to understand it or become involved with it.

If you want to program using DDE, you will have to learn as much, if not more about the server application that you want to talk to, rather than if you were a direct user of the product itself.