Progress
External Program
Interfaces


Exchanging Data In Conversations

Once you have opened a DDE conversation, you can converse on the topic using four types of exchanges. These exchange types include:

Execute, request, and send exchanges are each demand-driven. When you invoke the exchange, Progress waits for the exchange to complete. A demand-driven exchange works like a FIND statement, which waits until Progress retrieves the desired record from the database. Advise exchanges are event-driven. Once an advise link is created for a data item, the Progress client continues execution and retrieves the data item value “automatically” as it changes. You can invoke both demand, and event-driven exchanges in the same conversation and for the same data item. The following sections describe how to implement these exchanges.


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