The primary responsibility of any Control Panel application is to display
a dialog box and to carry out any tasks specified by the user.
Despite this responsibility, Control Panel applications do not provide menus
or other direct means for users to access their dialog boxes. Instead, these
applications operate under the control of another application and display
their dialog boxes only when requested by the controlling application.
Control Panel applications are usually controlled by a Windows system utility
specifically designed to give users access to these applications. However,
any application can load and manage Control Panel applications, as long as
the controlling application sends messages and processes return values in the
way that the Control Panel applications expect.
Most Control Panel applications display and manage a single dialog box,
giving the user control of the settings and operational modes of a single
system component. However, any given Control Panel application can provide
any number of dialog boxes to control any number of system components.
(These individual dialog boxes are sometimes called applets.) To distinguish
between dialog boxes, a Control Panel application typically supplies the
controlling application with a unique icon for each dialog box. The controlling
application displays these icons and the user can choose a dialog box by
choosing the corresponding icon.
Win32 Programming