Chapter I

Introduction to operating system

I-1 Introduction

A computer system is roughly divided into four parts:

• hardware,
• operating system,
• application programs and
• users

Figure 1 : Components of a computer system

Hardware: provides basic computing resources: central processing unit (CPU), central memory (MC) and input/output devices.

Application programs such as compilers, database systems, management programs, and games: define how resources are used to solve users' computing problems.

Users: people, machines, other computers; try to solve different problems using application programs.

The operating system controls and coordinates the use of hardware among various application programs for various users.

I-2 What is an operating system ?

An operating system (OS) is a program that acts as the interface between a user and the hardware; the purpose of an OS is to provide an environment in which the user can run their programs. The objective of an SE is therefore:

• ensure that the computer system is practical (convenient) to use,
• enable efficient use of computer hardware.

Another more well-known definition is to explain that the OS is the only program running at any time in the computer (usually called the kernel), all the rest of the software being application programs.