Functions and Types of Operating Systems

What is an Operating System (O.S.)?
It is the heart and soul of a computer. It is the basis on which all software applications rest. It takes care of little details, such as reading a data from a disk, interpreting the keystrokes and so on.
An amazing aspect of operating systems is how varied they are in accomplishing these tasks. Mainframe operating systems are designed primarily to optimize utilization of hardware. Personal computer (PC) operating systems support complex games, business applications, and everything in between. Operating systems for handheld computers are designed to provide an environment in which a user can easily interface with the computer to execute programs. Thus, some operating systems are designed to be convenient, others to be efficient, and others some combination of the two.
A computer system can be divided into four components: the hardware, the operating system, the application programs and the users. An operating system is similar to a government, it simply provides an environment within which other programs can do useful work.