An operating system is the software that provides the basic functionality required to run the applications programs on your computer. It provides an interface between the applications programs and the computer hardware and makes the programs independent of the specific hardware that your computer contains.
Modern operating systems also provide a graphical interface. This interface is accessed by programs via an Application Programming Interface (API) that provide all of the standard functions that all programs require in order to interact with the screen, keyboard, and mouse. This ensures that all programs behave the same way with regard to these standard functions meaning that once you know how one program works on the operating system that you can reasonably expect other programs to behave similarly. It also reduces the requirement for programmers to provide their own versions of these standard functions.
Current versions of operating systems that run on PCS include Windows 7 (previous versions were OS/2v1, Windows NT, 2000, XP and Vista), eComstation (previous versions were called OS/2), Linux, and Mac OSX. Past operating systems that used to be used on PCs used names such as Windows ME (originally called MS/DOS), CP/M (from Digital Research this was the most popular operating system before IBM entered the market), MS-xenix, Apple DOS, and USCD-p. Mainframe computers generally run completely different operating systems that are designed to allow a large number of people to share the resources simultaneously.
This article written by Stephen Chapman, Felgall Pty Ltd.