If the Shut Down Warning option was active, a warning would appear when the Macintosh was restarted using the following methods:
- The plug was removed
- The system was forced to restart by means of clicking the Restart button on a system error dialog box
- A restart or shut down command was ordered by means of typing commands after invoking the interrupt switch or MacsBug
- The reset switch was pressed, or the user performed a "three-finger salute"
Beginning with Mac OS 8.5, the hard drive would additionally be checked for any defects.
The phrase Shut Down Warning was altered to read Check Disk in the General Controls control panel beginning with Mac OS 9.1.