You need to turn off power to all system devices when you do the following:
Replace or add hardware.
Move the system from one location to another.
Prepare for an expected power outage or natural disaster such as an approaching electrical storm.
Turn off the power to system devices, including the CPU, the monitor, and external devices such as disks, tapes, and printers.
Before you turn off the power to all system devices, shut down the system cleanly, as described in the preceding sections.