Prohibitory symbol

The prohibitory sign is a sign of trouble on a Macintosh running Mac OS X. It has the same meaning as a Sad Mac icon and the Chimes of Death in classic Mac OS, meaning that it signifies trouble (the Mac is unable to boot normally).

The prohibitory sign is a large grey circle with a diagonal line across the middle of it, on a lighter grey screen. The prohibitory sign appears white on a black screen on newer versions of macOS. Under Mac OS X, normal booting would display a grey Apple logo with an animation of progress beneath it, or on later versions a white Apple logo with a progress bar underneath.