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A CDE Definition

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power down

To turn off an electric or electronic device. For various computer power-down modes, see hibernate.


A power-off mode that preserves the last state of the computer. Turning the computer on after hibernating eliminates booting the operating system and reloading all the applications and data.

When hibernate is activated, the contents of memory (RAM) are written to storage (hard disk, SSD) and the computer is turned off. When turned back on again, the previous memory state is read from storage, and all applications appear exactly as they did the moment hibernate was triggered.

Hibernate Vs. Sleep Mode
Hibernate is power off, whereas sleep mode is power on with the screen and hard disks turned off. In sleep mode, the RAM chips are constantly refreshed in order to retain their content, and the CPU is placed into a low-power state. Although restoring from hibernate is faster than a cold start, coming out of sleep is immediate. Turning the computer back on from either mode eliminates having to reload all applications and data.

Hybrid Modes
Some laptop computers invoke both modes automatically. When put into sleep mode by the user, the computer may automatically go into hibernate mode when the battery reaches a low level. An alternative hybrid mode activates hibernate when the computer enters sleep mode, but the computer is not turned off. If the battery runs out while in sleep mode, the contents of memory have already been saved. See memory.

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