The software makes the hardware useful and can be divided into two classes system software to manage the operation of the computer and software application that performs useful actions to users.
Among the programs of the system include operating systems compilers interpreters editors, etc. The operating system is the first layer of software that sits on the raw hardware separating the users of it.
Attempting to give a formal definition of operating system is not an easy task and is more convenient to do this after viewing functions to fill. Every operating system has two main functions
The role of extended or virtual machine is to provide facilities to users by separating them from having to know the dark and complex internals of the hardware. For example a user who operates a machine with files that are opened read write, and close down rather than having to operate with a number of records time position engine off or on etc.
The resource manager function is to provide a way to assign in an orderly and controlled the various resources available to the computer system among several programs competing for them. This view of the operating system assumes the use of computer hardware in an efficient manner.
The first function indicated above is the primary reason for the existence of operating systems and this is most evident when it comes to computers for personal use.
The goal of efficiency is important for large computer systems and shared systems of multiple users . In this case it is meant that machine vision extended not remain an essential function.
As is past, efficiency considerations were often more important than the ease of use and therefore the operating systems theory focuses on the optimal use of resources. Today, with the widespread use of personal computers there is a greater emphasis on customer satisfaction and that is why the development of environments GUI .