A composite control is a type of ActiveX control that can contain (similar to a dialog box) other ActiveX controls or Windows controls. Once the composite control is built, it can be inserted anywhere an ActiveX control can be hosted.
Visual C++ provides two tools, ATL COM AppWizard and ATL Object Wizard, that automate the process of creating and implementing a composite control project, similar to the result of running AppWizard to create an MFC application framework. Basically the development process consists of five steps: