From the Apple menu, choose Shut Down (or if the computer is not responding, hold the power button until it turns off).

If the computer still exhibits these types of issues after you've restarted the computer, try resetting the SMC by removing AC power: Resetting the SMC can resolve some computer issues such as not starting up, not displaying video, sleep issues, fan noise issues, and so forth. Force Shut Down (press the power button for 10 seconds).If the computer isn't responding, perform these steps one at a time, in the following order, until the issue has been resolved: Resetting the SMC will not resolve issues in which the computer is unresponsive-in these situations, restarting the computer will generally suffice. Note that resetting the SMC does not reset the PRAM. It is also recommended that the SMC be reset after a logic board, ambient board, or ambient board cable is replaced as part of a repair. Handling system resets from various commands.Telling the computer when to turn on, turn off, sleep, wake, idle, and so forth.The SMC controls several functions, including: If the computer is experiencing any power issue, resetting the SMC may resolve it. The System Management Controller (SMC) is a chip on the logic board that controls all power functions for the computer.

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