An operating system is a program which establishes an interface between the user and hardware. It is basically used for application programs. Operating system has several layers. A computer system can be further classified into four parts. The parts are hardware, an operating system, an application programs and the users. Hardware contains the CPU (Central Processing Unit), the memory and input/output devices which is capable of providing the basic computing resources for the system. The application program defines the behavior by which these resources are used to solve user’s computing problems like word processors, spreadsheets, compliers, and web browser. The operating system controls hardware and provides the means for proper use of resources in operation. An operating system works like a government; it may provide an environmental within which programs can do useful work. It manages the resources of computer system implicitly. The resources are like memory, files, and I/O devices.
Two type of view’s in operating system: