Automation Clients and Automation Components

A clearly defined "master-slave" relationship is always present in an Automation communication dialog. The master is the Automation client and the slave is the Automation component (server). The client initiates the interaction by constructing a component object (it might have to load the component program) or by attaching to an existing object in a component program that is already running. The client then calls interface functions in the component and releases those interfaces when it's finished.

Here are some interaction scenarios:

• A C++ Automation client uses a Microsoft or third-party application as a component. The interaction could trigger the execution of VBA code in the component application.

• A C++ Automation component is used from inside a Microsoft application (or a Visual Basic application), which acts as the Automation client. Thus, VBA code can construct and use C++ objects.

• A C++ Automation client uses a C++ Automation component.

• A Visual Basic program uses an Automation-aware application such as Excel. In this case, Visual Basic is the client and Excel is the component.