Dynamic Data Exchange

In computing, Dynamic Data Exchange (DDE) is a method of interprocess communication under Microsoft Windows or OS/2. It allows one program to subscribe to items made available by another program, for example a cell in a Microsoft Excel spreadsheet, and be notified whenever that item changes. DDE was partially superseded by Object Linking and Embedding (OLE), but remains used for simple interprocess communication tasks.

Dynamic Data Exchange was first introduced in 1987 with the release of Windows 2.0 as a method of interprocess communication so that one program could communicate with or control another program, somewhat like Sun's RPC (Remote Procedure Call). It used the "Windows Messaging Layer" functionality within Windows. DDE continues to work even in modern versions of Windows, but has been superseded by newer technologies. Windows for Workgroups introduced a remoting version called NetDDE.

OLE and OLE Automation are more advanced than DDE, but have proven to be bulky and difficult to code. OLE is far more sophisticated and capable than DDE because it is built on top of Microsoft's Component Object Model, but also suffers from COM's problems of a higher performance penalty and a much steeper learning curve. COM that works between networked machines is known as DCOM (Distributed COM). .NET Remoting provides a layered architecture for interprocess communication in the .NET Framework. However, legacy DDE is still used in several places inside Windows, e.g. for Shell file associations and for the copy, cut and paste functions.

...
Wikipedia