“An Operating system is a program that controls the execution of application programs and acts as an interface between the user of a computer and the computer hardware.”
A more common definition is that the operating system is the one program running at all times on the computer (usually called the kernel), with all else being applications programs.
An Operating system is concerned with the allocation of resources and services, such as memory, processors, devices and information. The Operating System correspondingly includes programs to manage these resources, such as a traffic controller, a scheduler, memory management module, I/O programs, and a file system.
Some of the popular operating systems used in personal computers are DOS, Windows,Unix, Linux, Solaris, etc.
Need for an Operating System
Operating system provides a platform, on top of which, other programs, called application programs can run. As discussed before, it acts as an interface between the computer and the user. It is designed in such a manner that it operates, controls and executes various applications on the computer. It also allows the computer to manage its own resources such as memory, monitor, keyboard, printer etc.
Our choice of operating system, therefore, depends to a great extent on the CPU and the other attached devices and the applications we want to run. The operating system controls the various system hardware and software resources and allocates them to the users or programs as per their requirement.