Dynamic Data Exchange

Dynamic Data Exchange (English, abbreviation DDE) means dynamic data exchange.

Is a protocol for the exchange of data between various application programs, so an inter-process communications according to the client -server model.

Details

This protocol is local and within networks in the operating systems Windows available (version 2.0) and OS / 2.

Commands can be issued so that data exchanged or both applications have to run simultaneously. If necessary, the DDE client must start the necessary server process. The data exchange is always in complete units of data in Windows clipboard formats ( including binary data); continuous data streams are usually not supported. Since two label programs can define new clipboard formats is also the exchange of arbitrary large amounts of data, such as matrices in MATLAB, no problem. As a special DDE offers a " Advise " called hot-tracking (data change notification ) to, with which the client is automatically notified of changes to the server dataset.

Typical of DDE and also determined the three-level addressing of data elements, divided server ( service), topic ( topic) and item ( element). A deeper addressing, such as certain rows and columns of a spreadsheet page, must be made by an optional, non- enumerable item.

Implements DDE is through messages via the Windows typical thread queues, and by means of shared memory for the actual data.

The performance of DDE is roughly at 1000 transfers per second when the communication takes place via a GUI thread, and can be significantly higher when using separate threads. The 3.1 introduced with Windows DDE functions, first packed in DDEML.DLL are practically just wrappers, but easier to use bring no speed advantage.

DDE overcomes " bit boundaries " relatively easily. Thus it is possible that a 16 -bit and 32- bit Windows application designed to communicate, including a 32 -bit and a 64 bit program. Communication between 16- bit and 64- bit is regularly only by Network DDE feasible, because the 64 -bit versions of Windows do not have 16 -bit support.

Current status

DDE is today still use, such as for passing command line to already running processes, typically at MDI applications. Such a document, the Windows Explorer with suitable set shortcuts "Send " to an already ongoing editing process, without an unnecessary process copy.

Due to its simplicity Network DDE is common in machine and plant control systems.

DDE was supplemented by the OLE protocol and expanded.

As an alternative, especially for continuous data streams to sockets offer.

• Programming