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Inside Macintosh: Processes
Chapter 8 - Shutdown Manager

About the Shutdown Manager

The Shutdown Manager gives applications and other software a chance to perform any necessary shutdown processing before the computer is turned off or restarted. It also shuts down or restarts Macintosh computers, providing a consistent human interface for shutting down and restarting different models. Before restarting a computer or turning off the power, the Shutdown Manager checks for open device drivers and desk accessories and allows them to perform any necessary housekeeping.

The Shutdown Manager does not notify open applications that they are about to be shut down. This notification is handled by the Process Manager, as explained in "Using the Shutdown Manager" beginning on page 8-7. The Shutdown Manager provides two procedures that allow you to shut down or restart a Macintosh computer. However, these procedures do not perform the preliminary tasks that the Finder initiates when a user chooses Shut Down or Restart from the Finder's Special menu. Accordingly, your application should not call these procedures directly because all open applications will terminate abruptly without the opportunity to save their current states and exit gracefully. Instead, your application should send a Shutdown or Restart event to the Finder, as described in "Sending a Shutdown or Restart Event" on page 8-7.

The main function of the Shutdown Manager is to execute a custom shutdown procedure that lets your application perform some additional tasks before the computer shuts down. The types of software most likely to install shutdown procedures are device drivers and system extensions. For example, drivers of early hard disk drives that use stepper motors usually need to park the drive heads in a safe zone before the power is turned off. A shutdown procedure could notify a driver to park the head. In another case, a user could install a system extension that displays an alert box asking whether to back up the hard disk before the computer shuts down.

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© Apple Computer, Inc.
17 JUN 1996