Entry Points and Advertisements

Ever wonder how Windows Installer knows to get involved with repairing or installing an
application? Entry points allow Windows Installer to proxy the startup of an application and
perform application management tasks before the user is allowed to access the application. In
other words, when you double-click the icon for a Windows Installer packaged software
application, it does not actually attempt to start the application directly. The icon is a special icon
that asks Windows Installer to find the software application and start it. This is when Windows
Installer can use the MSI repository information, the installed application resources (files,
registry keys, and so on), and the original package file to perform the magic of self-healing and
install on demand.




An entry point turns into an advertised interface when any Feature that its Component belongs to
is advertised or installed on a target computer system. When a Windows Installer package is
advertised, advertised interfaces make it appear as though the application is installed and ready
to use. When a Windows Installer package is installed, advertised interfaces trigger Windows
Installer for self-healing and user profile fix-up checking. An entry point/advertised interface can
be:


• A shortcut (special Windows Installer shortcut)
• A document extension (association)
• A MIME type (Internet document types)
• A Class ID (CLSID)—Programmatic identities used for sharing software within and
between various applications