Windows Shell

Your applications can use the shell interfaces and functions to enhance various aspects of the Windows shell.

A namespace is a collection of symbols, such as file and directory names or database keys. The shell uses a single hierarchical namespace to organize all objects of interest to the user, including files, storage devices, printers, and network resources. The namespace is similar to the directory structure of a file system, except that the namespace contains objects other than files and directories.

A shortcut (also called a shell link) is a data object that contains information used to access another object located anywhere in the shell's namespace. A shortcut allows an application to access an object without having to know the current name and location of the object. Objects that are accessible through shortcuts include files, folders, disk drives, printers, and network resources.

There are several ways to extend the shell. The system uses icons to represent files in the shell's namespace. By default, the system displays the same icon for all files that have the same file name extension. An icon handler can override the default and set the icon for a particular file. A context menu handler is a shell extension that modifies the contents of a context menu. The system displays a context menu when the user clicks or drags an object using mouse button 2. The context menu contains commands that apply specifically to the object that was clicked or dragged. Most context menus have a Properties command that displays the property sheet for the selected item. A property sheet contains information about an object in a set of overlapping windows called pages. A property sheet handler is a shell extension that adds pages to a system-defined property sheet or replaces pages in a Control Panel application's property sheet. A copy hook handler is a shell extension that approves or disapproves the moving, copying, deleting, or renaming of a file object.

The shell includes a Quick View command that allows the user to view the contents of a file without having to run the application that created it. A file viewer provides a user interface for viewing a file. The shell uses the file name extension to determine which viewer to run. You can provide file viewers for new file formats or replace an existing viewer with one that includes more functionality. A file viewer works in conjunction with a file parser, which provides the parsing needed to generate the Quick View of a file of a specified type. You can provide additional file parsers to support new file types.

For more information, see Shell Basics