The Role of the Operating System

This section explains what an operating system is, what it does, and what its relationship is to your hardware and to the applications installed in it.

Note 

This book focuses mostly on systems running the Windows operating system for one simple reason: 85–90% of PCs run Windows in one or more versions.

What an Operating System Is

An operating system is a sophisticated piece of software designed to create and control the environment in which you and your PC work. An operating system serves three major functions:

• The operating system understands the needs of the various components of the PC and communicates with them, the PC’s BIOS services, and the hardware controls.

• The operating system provides a way for you, as a user, to enter input to the system by typing commands or clicking on an icon to perform a specific function.

• The operating system communicates information to you in the form of error messages, on-screen prompts (for example, Press <this button> to Perform this Function), and other important information.

  Operating systems tend to fall into two major categories:

Command-line  A command-line operating system is where commands are typed at a command prompt as you see with the Windows Recovery Console discussed in Chapter 7 and with Windows’ predecessor, the DOS operating system.

Graphical user interface (GUI)  In a GUI-based operating system, a pointing device such as a mouse is used to select options by pointing to and clicking icons, filenames, or other objects.

Windows is a GUI.

What an Operating System Does

Only one piece of software is needed universally by almost every computing device in the world: an operating system. It is so named because its job is to control and operate your PC as a total system, from taking information about your PC from BIOS to managing the PC’s hardware operations and the other software installed on it to starting up and shutting down your PC.

Since the birth of the first IBM PC in 1981, when the operating system was limited to a few commands typed at a black screen containing only a prompt and could easily fit on a floppy disk (and had to, since hard drives hit the scene much later), the operating system has been growing in power, complexity, and size.

To appreciate how things have changed, let’s look at an example. In the early days of the PC, printing was a much tougher job to accomplish for a number of reasons. For one, the PC processor was very slow (under 25MHz). There was no way to print in the background, so once you decided to print, everything on your desktop froze until the slow, clunky process of printing the page or document was done.

But more importantly, printing support wasn’t integrated into the operating system as it is today when you go to Windows Control Panel and see the Printers icon sitting there waiting for you. If you had five applications installed on your system and you needed to print from each one, you had to install your printer to each different application rather than just install your printer to Windows, as you do now, and have it automatically available from each Windows application that allows printing.

Tip 

The operating system produces some logs—some by default, some that you can turn on—to help diagnose problems during the bootup process or with the initialization of hardware. You’ll learn more about these in Chapter 7.

How the Operating System Works in Connection with Hardware and Applications

From the moment you begin to load an operating system on a PC, it becomes heavily involved in understanding and working with everything already attached or installed to a PC. For example, there are three major phases to a Windows Setup, regardless of the version of consumer Windows being used. These phases are:

1. Collection of data about the system on which it is to install (including detailed information about the attached hardware).

2. Physical copying of the new Windows files to the designated hard drive.

3. PC restarts and the configuration of the new operating system is complete from an installation perspective.

Windows—and its subsystems such as the Windows graphics subsystem described in the section “Video System”—takes its initial information about your hardware from the BIOS and then configures the hardware resources needed for the PNP hardware from those left after the BIOS makes assignments for the non-PNP hardware.

Once a device is properly installed, Windows and its subsystems work through the device drivers for the various pieces of hardware attached to your system to help control the hardware’s behavior and its communication with the other PC components.

The Role of the Windows Registry

A core component of the Windows operating system is something called the Windows Registry. This serves as a central index file or database of all the specifics of your system, storing information such as:

• What hardware is attached

• What settings are enabled/disabled for that hardware

• User-configured settings for how the operating system looks and feels to each user authorized to use the PC

• Product ID and software registration numbers

• What applications are installed

• What kinds of files the operating system and its applications can open and work with

Notice that the Registry is keeping track of far more than basic Windows information because it also includes details about hardware and applications. If Windows is operating properly, there is not much you can install, remove, or change about your system that won’t be reflected in your Windows Registry.

Did you ever delete a file you thought you didn’t need, only to find Windows giving you a warning about the file being missing next time you loaded Windows? It’s another example of the integration and interconnectedness of everything on your PC and a reminder that Windows effectively monitors all that you do. You must be aware that each action you take can have effects throughout the system.

You’ll learn more about the Registry as you go through this book. This is necessary because you’ll see situations in which a piece of hardware or application that you have removed may remain listed in the Registry and potentially interfere with your ability to install other hardware or applications.