A computer may operate in four modes: On, Off, Standby and Hibernate. The first two modes are available to any normally functioning computer, the standby mode is activated if the APM standard is connected, and hibernate mode is available to portable computers (notebooks) with Windows XP/2000 only in the ACPI mode. Besides, in case of a particular signal, the suspend mode and low frequency mode (doze) can be automatically set, allowing the working capacity to be restored.
What is the difference between the standby and hibernate modes? All computer devices, except memory, are disconnected or go to the power saving mode in the standby mode. A monitor also “sleeps”. But all fans on a processor and in the power supply are still working. This allows returning a computer into its normal state either by pressing any button on a keyboard (mouse moving) or in case of some system event, for example when retrieving e-mail.