Sleep 'vs' Hibernate...!!

You Have Seen Sleep & Hibernate In Your Power Button In Windows Where Shut Down, Log Off And Restart Buttons Are also given....
What is the Differences Between Sleep (Standby) and Hibernate...??
Do you Ever Think..??
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Both commands provide an easy and quick way to leave your computer in existing last state and come back to work on it at exactly the same state later without waiting too long to system to restore itself.. However fundamentally there is some difference between them...

SLEEP :- Sleep is commonly known as Standby in Windows system or S3 in ACPI.. In Sleep mode, the power supply to non-essential and non-critical component is withheld, and most system operation is shutdown and stopped. All data in physical memory (RAM module) is still kept in internal memory, and whole system is place in stand-by mode, which can be woke up and used almost immediately..Otherwise system will have to start again just like a newly boot computer just started from power off state..

Disadvantage:-> The power must not be cut off, and must be continue to supply to the computer..

HIBERNATE:- Hibernate, or S4 in ACPI, meanwhile will save the data in physical memory to hard disk drive (HDD), and then power off the computer. In Hibernate mode, a file named hiberfil.sys which has the same file size as the amount of system memory will be created on the local disk. When user wants to use the computer again, the computer will boot up and load back the state at the last hibernation..

Disadvantage:-> The disadvantage of Hibernate is that after a period of time, there may have fragmentation of file. Users will need to defragment the volume that stores the hibernation file frequently..