The Operating System

The computer is a very "stupid" piece of hardware. It is incapable of doing anything without "instructions". These instructions are called "Software".

Your computer does several things when you turn it on:

1. It performs a self test on its components and memory.

2. It loads up a software program called the OPERATING SYSTEM.

The OPERATING SYSTEM is the most important program that runs on a computer. Every general-purpose computer must have an operating system to run other programs. Operating systems perform basic tasks, such as accepting input from the keyboard, sending output to the display screen, keeping track of files and directories on the disk, and controlling peripheral devices such as disk drives and printers.

Operating systems provide a platform on top of which other programs, called APPLICATION PROGRAMS can run. Most of the programs we are familiar with are APPLICATION PROGRAMS. ( Quicken, WORD, TurbTax, Printshop, Internet Explorer, AIM, etc.) The application programs must be written to run on top of a particular operating system. Your choice of operating system, therefore, determines to a great extent the applications you can run. For PCs, the most popular operating systems are DOS, OS/2, and Windows, but others are available, such as Linux.

As a user, you normally interact with the operating system through a set of commands. Graphical user interfaces allow you to enter commands by pointing and clicking at objects that appear on the screen rather than typing in commands.