Operating System is a system software. Operating system is the software that manages all the computerâ€™s resource. Operating system performs basic tasks, such as recognizing input from the keyboard, sending output to the display screen, keeping track of files and directories on the disk and controlling the peripheral devices. In another word we can say, it provides interface between hardware and software. There are so many operating systems available like WIN 95, 98, 2000, XP, Vista, Win 7, WIN NT. There are two types of platform available on which operating system works i.e. GUI and CUI.