PC Hardware

Lesson 1: Operating System Basics

The term software refers to any program (set of instructions) that directs a computer to carry out a task or function. Software can be divided into two categories: operating systems and applications. Operating-system software is used to manage hardware, data, and application software. No computer can run without an operating system. MS-DOS, Windows 3.x, Windows 95, Windows 98, Windows NT, Windows 2000, OS/2, and UNIX are examples of operating systems.

Applications are the tools employed by users. Application software programs (such as Microsoft Word, Access, Excel, and so forth) use the operating-system software enabling users to create, manipulate, and present data. This tutorial focuses on the earlier operating-system software-MS-DOS and Windows 3.x. Although MS-DOS and Windows 3.x are somewhat outdated, they remain the foundation from which the newer 32-bit operating systems like Windows 95, Windows 98, and Windows 2000 evolved. Many fundamental concepts and conventions used with today's operating systems stem from these beginnings. As an A+ technician aspirant, you will find some questions regarding MS-DOS and Windows 3.x on the exam.

After this lesson, you will be able to:
  • Define an operating system.

  • Describe the difference between MS-DOS, Windows, and Windows NT.

Estimated lesson time: 20 minutes

An operating system is a special software program that is loaded into a computer at startup and is responsible for running the computer. It manages all the hardware, and provides an interface between the computer's hardware and the user.

Before You Begin

Some experience using MS-DOS and Windows is recommended before studying this tutorial; intermediate or expert level experience is not required. However, you should be able to perform the basic tasks of operating a computer, using a mouse, and navigating through screens.


DOS stands for disk operating system. The full proper name is preceded by the name of the manufacturer-for example, MS-DOS (for Microsoft and also used by "clone" makers) or PC-DOS (for versions specific to the IBM Personal Computer). This version was also sometimes referred to as IBM-DOS. All versions of DOS are actually the product of Microsoft development. The modern computer professional must be familiar with MS-DOS because MS-DOS remains at the heart of Windows. Although increasingly more configuration can be done through the Windows interface, there comes a time when every computer professional is faced with a screen of MS-DOS commands. Windows 98-the most current operating system-is more independent of MS-DOS than prior versions of Windows. However, every PC still requires AUTOEXEC.BAT, CONFIG.SYS, and various initialization files. So there remains a need for the computer professional to be familiar with MS-DOS.

DOS has been produced by three suppliers, and the versions are so similar that they are considered as one operating system. The three brands of DOS are:

  • MS-DOS, produced by Microsoft-the most popular

  • PC-DOS, produced by IBM

  • DR-DOS, produced by Novell