If an average person is asked to explain the activities that happen inside the brain, he/she will not dare to even open his eyes. The brain provides a convenient highly sophisticated abstraction. It merely provides the image of an object without letting people know about the activities that happen inside the brain. In this case eye is an interface between the object and the part of the brain that processes visual data. In a similar fashion the Operating System hides from a person know the complexity of the hardware and allow the user to use the name of the files for reading and writing. The Operating System adds extended capabilities to a machine with which it is easier to program than the underlying hardware. The Operating System manages the resource. Modern computers are highly complex machines. They get more complex day by day. So it is very difficult to manage such a complex system but the Operating System manages the complex system in an efficient way.