.. highlightlang:: us

.. index:: Overview DDE, DDE 

.. _overview-dde:

Overview DDE
============

DDE is the abbreviation for Dynamic Data Exchange. DDE is a method of 
interprocess communication between programs to exchange data or control another 
program. Examples for DDE are querying a database, or sending data to a 
spreadsheet program. The application that intiates the conversation is the
DDE client application; the application that responds to the client is the 
DDE server application. UniPlot can be used as a DDE server or client.

UniPlot as a Client
-------------------

UniScript provides the following 6 functions for the client side.
The user must define the functions.

.. us.indexlist UniPlotasaClientDdeInitiateDdeExecuteDde,UniPlot as a Client,DdeInitiate,DdeExecute,DdePoke,DdeRequest,DdeTerminate,DdeTerminateAll,

.. include:: ../ftab/UniPlotasaClientDdeInitiateDdeExecuteDde.ftab

.. us.example

**Example**

Here is an example for UniPlot as client. The server is Excel:

::

   system("c:/msoffice/excel/excel.exe", SW_HIDE, 1);
   hConv = DdeInitiate("Excel", "System");
   ssFile = GetRootDirectory() + "samples\map-data.xls";
   DdeExecute(hConv, "[OPEN(\"" + ssFile + "\")]")
   hConvTab = DdeInitiate("Excel", "map-data.xls");
   ssData = DdeRequest(hConvTab, "z1s1:z16384s255");
   DdeExecute(hConv, "[QUIT()]");
   DdeTerminateAll();
   hedit = EdCreate();
   EdSetText(hedit, ssData);

The program excutes the following commands:

*  Excel will be started.

*  Excel will load the :file:`Samples\\map-data.xls` file.

*  Excel will send the sheet data to a UniPlot variable.

*  Teh content will be displayed in an UniPlot editor.

.. _uniplot-als-server:

UniPlot as a Server
-------------------

UniScript provides the following 6 functions calls for the server side. 
The user must define the functions.

.. us.indexlist UniPlotasaServerDdeCallback_ConnectDdeCa,UniPlot as a Server,DdeCallback_Connect,DdeCallback_ConnectConfirm,DdeCallback_Execute,DdeCallback_Poke,DdeCallback_Request,DdeCallback_Disconnect,

.. include:: ../ftab/UniPlotasaServerDdeCallback_ConnectDdeCa.ftab

.. us.example

**Example**

As an example we will write a Basic program for Microsoft Word. The 
Basic program will be used to create plots with UniPlot.

Lets start with the UniPlot side (Server). Copy the following code into 
a program editor in UniPlot and save the file on your computer. Press F4
to compile the function.

::

   def DdeCallback_Poke(hConv, ssItem, ssTopic, ssData)
   {
       ss = strtok(ssData, ",");
       rvData = strtod(ss);
       plot(1:len(rvData), rvData);
       return TRUE;
   }

To keep the function short we have not checked and function parameters
or return values.

Now lets start on the client side. Start Word and type in the following
macro (Execute: **Tools=>Macro=>Create Makro**): 

::

   Sub Main
       chan = DDEInitiate("UniPlotSL", "xydata")
       DDEPoke chan, "xydata", "1, 5, 3, 4, 8, 12"
       DDETerminate(chan)
   End Sub

If you execute the Basic function ``Main`` in Word, UniPlot will create 
a plot.

.. seealso::
   :ref:`functions-by-categories`

:sub:`id-1535155`