There are two types of software running on a computer: software applications and system software. A software application is a program designed for end users, while system software consists of low-level programs belonging to the operating system, compilers and utilities for managing resources.
An operating system is software that enables services for software applications to run on a computer. An important task of an operating system is taking care of the communication between the software applications and hardware devices attached to your computer. For example, a word processor communicates with devices such as a keyboard and mouse.
Operating systems are large programs consisting of thousands of functions, which provide services of various kinds. Often called by events in the system, the functions perform a service when needed. To make operating systems fast and most effective, the functions are often written in C or C++, but also low-level programming languages such as Assembly has occasionally been used.
