There are two major classifications of an operating system. These are single tasking operating systems and multi-tasking operating systems.
An operating system controls the CPU processes and the input/output processes and manages the memory. Input/Output handling is related to interrupt handling and device drivers, which act as translators between the I/O devices and the application.
Interrupts are signals that inform the operating system that some activity has taken place.
The communication between the user and system is handled by the operating system. Command line, menu driven, and graphical user interfaces are used to facilitate interactions between the user and hardware. There are several operating systems like UNIX, MS-DOS, Mac OS, Windows 3.X, Windows 95, Windows 98, Windows Me, Windows CE, Windows NT, Novell’s NetWare, Linux, and Windows Vista.