Your application uses the Window Manager to create and manage windows; for example, to create and display a new window when the user creates a new document or opens an existing document. When the user clicks or holds down the mouse button while the cursor is in a window created by your application, you use the Window Manager to determine the location of the mouse action and to alter the window display as appropriate. When the user closes a window, you use the Window Manager to remove the window from the screen
A Macintosh application uses windows for most communication with the user, from discrete interactions like presenting and acknowledging alert boxes to open-ended interactions like creating and editing documents. Users generally type words and formulas, draw pictures, or otherwise enter data in a window on the screen. Your application typically lets the user save this data in a file, open saved files, and view the saved data in a window.
A window can be any size or shape, and the user can display any number of windows, within the limits of available memory, on the screen at once.
The Window Manager defines a set of standard windows and provides a set of routines for managing them. The Window Manager helps your application display windows that are consistent with the Macintosh user interface.