This is in the upper left corner of the screen.;
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For Mac laptops, the options displayed here will have two separate tabs for Battery and Power Adapter. You will have to set them both if you want the behavior to be the same when using your computer connected to power or on battery., Numbers under the slider indicate how much time must pass without any activity on the computer before it puts itself to sleep.
 Numbers under the slider indicate how much time must pass without any activity on the computer before the screen goes to sleep (the hard disks will remain active).


This option may instead appear as “Display Sleep” on some older versions of Mac OS.
 This option will stop the computer from entering a full sleep when only the display is asleep.


This option will appear in the Power Adapter tab for laptops.
 Preventing the hard disks from sleeping means the computer will not enter a full sleep. When in regular display sleep, the computer will react more quickly to a waking action.
Click the Apple menu.
Click System Preferences.

,
Click Energy Saver.
Drag the “Computer sleep” slider.
Drag the “Turn display off after” slider.
Click the “Prevent computer from sleeping automatically when the display is off” checkbox.
Uncheck the “Put hard disks to sleep when possible” checkbox.
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