The following figure shows a series of IPC exchanges between an OpenEdge application and another Windows application using DDE.
Figure 36. ABL exchanging data using DDE
Note: Both OpenEdge graphical and character applications can use DDE in Windows.
In this example, the OpenEdge application sets the value of ABL ItemA from Server Item1; sets the value of Server Item2 from ABL ItemB; and executes a command on the Server, possibly returning a data value or error condition.
ABL supports DDE as a client only. This allows OpenEdge database clients to communicate with any other Windows application with DDE server capability. Examples of Windows applications with DDE server capability include the Windows Program Manager, Microsoft Excel for Windows, and Visual Basic applications. As a DDE client, ABL can, for example, create and modify worksheets in Excel, and at the same time automatically receive notification of updates to worksheet cells (data items) from Excel. Excel, as the DDE server, provides this notification by sending an event that ABL can handle in a trigger.
