On switching the computer back on, the computer is restored to its state prior to hibernation, with all programs and files open, and unsaved data intact. Hibernation, also called Suspend to Disk on Linux, saves all computer operational data on the fixed disk before turning the computer off completely. In addition to a wake-up press of the power button, PCs can also respond to other wake cues, such as from keyboard, mouse, incoming telephone call on a modem, or local area network signal.

A sleeping PC is on standby power, and this is covered by regulations in many countries, for example in the United States limiting such power under the One Watt Initiative, from 2010. If undesired, the behavior can be altered in the operating system settings of the computer.Ī computer must consume some energy while sleeping in order to power the RAM and to be able to respond to a wake-up event. Because of the large power saving, most laptops automatically enter this mode when the computer is running on batteries and the lid is closed. Machine state is held in RAM and, when placed in sleep mode, the computer cuts power to unneeded subsystems and places the RAM into a minimum power state, just sufficient to retain its data. Sleep mode has gone by various names, including Stand By, Suspend and Suspend to RAM. When restored, the operation continues from the same point, having the same applications and files open. In computers, entering a sleep state is roughly equivalent to 'pausing' the state of the machine. Main article: Advanced Configuration and Power Interface

How to wake up mac from sleep mode