Normally you can restart your Mac by choosing Apple menu > Restart. However, in some cases—for example, if the pointer freezes on the screen or the Mac becomes unresponsive—you may have to use one of the startup methods listed here. You can use these key combinations when you start up your Mac. Unless otherwise specified, hold down the specified key immediately after you hear the startup tone (while the screen is still black). Action Shortcut…
OS X Mavericks: Methods for Starting up Your Mac
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