Advanced MFC Programming

Chapter 16. Context Sensitive Help
Summary
1) To support DDE in an application, function ::DdeInitialize(…) must be called to initialize it; also,
before the application exits, function ::DdeUninitialize(…) must be called to uninitialize the DDE.
1) The server must register DDE service by calling function ::DdeNameService(…). Before the server
exits, it must call the same function to unregister the service.
1) Before DDE client initiates any transaction, it must call function ::DdeConnect(…) to obtain a
conversation handle that can be used to identify the server in the following transactions.
1) A server can support several topics, under each topic there may be several items supported. When
initiating a transaction, the client need to specify both of them.
5) Data can not be exchanged directly between two processes. Instead, it must be sent either by data
handle or by DDE object. In the former case, the data can be accessed by calling functions
::DdeAccessData(…). Function ::DdeUnaccessData(…) can be used to unaccess data and
::DdeFreeDataHandle(…) can be used to free data. In the later case, the data can be retrieved by
calling function ::DdeGetData(…). To create a data handle, we can use function
::DdeCreateDataHandle(…).
1) In DDE model, two strings can be compared by their handles. In order to do this, we need to call
function ::DdeCmpStringHandles(…).
1) Data request transaction can be used to request data from the server.
1) Advise transaction can be used to let the client monitor the changes on the data stored on the server
side.
1) Poke transaction can be used by the client to update the data stored on the server side.
1) Execute transaction can be used by the client to let commands be executed on the server side.
1) There are two types of transmission modes: synchronous and asynchronous. Synchronous transaction
is easy to implement, but asynchronous transaction is more efficient under certain conditions.
1) Program Manager is a DDE server that supports execute transaction.
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