OPERATING SYSTEM:

An operating system is a set of programs that make the hardware useable. In brief, an operating system is the set of programs that controls a computer. Some examples of operating systems are UNIX, Mach, MS-DOS, MS-Windows, Windows/NT, Chicago, OS/2, MacOS, VMS, MVS, and VM.

Modern Operating systems generally have following three major goals:\

• To hide details of hardware by creating abstraction
• To allocate resources to processes (Manage resources)
• Provide a pleasant and effective user interface

Operating systems generally accomplish these goals by running processes in low privilege and providing service calls that invoke the operating system kernel in high-privilege state.