Have you ever thought about this, Unlike humans they have more options than us, they can Sleep, Standby, Hibernate, Restart and the last one Shutdown !! !
These things is available at both softaware (OS) level and hardware level. In your desktop or laptop u must have used all these options
In this article I will explain both for general computer user and the embedded developers.
In Operating Systems:
Lets first see what happens in MS Windows OS.
StandBy: This option sets the screen off and harddisk stops. All other services continues except those dedicated to the user.
Sleep: This is a bit more than standby useful for power saving. This stops the hard disk, switch off the screen, switch off most of the parts and sets the clock speed low so as to lower power consumption.
Hibernate: Hibernate its very useful if u need your system to start from the last files u r working with as it is, and quick mode. What it does is
As you click hibernate it saves all the Data in RAM into a file Hiberfile.sys (which has size same as RAM size) and write an extra line in the Master Boot Record.
Next you start your PC it starts from MBR as normal but the extra line written in the previous session tells the system that it was hibernated in the previous session. So it searches for hyberfile.sys and loads that data onto RAM, while showing a screen message System Resuming ….
N.B.:There was a similar option in RHEL linux which was very similar to hibernate but not same in bachground. It saves all the session information(which files opened what edited….) and on next start it resumes according to that data, so it is a bit slower and some processes like games videos will not supports this.
In Microcontrollers and Microprocessors:
After dinner…. wait