What is the meaning of ‘Hibernate’ in Windows XP/Windows 7?

Concept

Windows power options differ in one decisive respect: what happens to the contents of RAM. A state that first copies the entire memory image — every open program and document — to a file on disk and only then removes power is called hibernation, because that saved image can be loaded back into RAM at the next start so the session continues exactly where it stopped. A state that removes power after asking every process to exit discards RAM, and a restart re-boots the machine rather than preserving anything.

Applying it here

In Windows XP and Windows 7, choosing Hibernate writes the RAM image to the reserved file hiberfil.sys on the system drive and then powers the machine off completely. Because that image already holds the memory of every running application, no application is asked to close and none is terminated. When the machine is switched on again the image is read back into RAM and the open windows, documents and program state are exactly as they were left. So the machine is genuinely shut down — it draws no power — and yet the running applications were never closed.

Contrasting the four described behaviours

Result

‘Hibernate’ means shutting the computer down without closing the running applications: the session is saved to disk, the machine is powered off, and the session is restored on the next start.