Unit 3. Operating System

Operating System

An operating system (OS) is a software program that provides you with the tools (commands) that enable you to interact with the PC.

Most modern operating systems employ a graphical user interface (GUI) with which users control the system by pointing and clicking graphical objects on the screen. A GUI is based on the desktop metaphor. Icons, windows, menus, dialog boxes, and other graphical objects appear on the desktop for the user to manipulate. Applications designed to run under a specific operating system use the same interface elements, so users can see a familiar interface no matter what programs they are using. Some older operating systems, such as DOS and UNIX, use command-line interfaces, which the user controls by typing commands at a prompt.

The operating system manages all the other programs that run on the PC. The operating system also provides system-level services, including file management, memory management, printing, and others, to those programs. Some operating systems, such as Windows, enable programs to share information. This capability enables you to create data in one program and use it again in other programs without recreating it. Modern operating systems support multitasking, which is the capability of running multiple processes simultaneously.

The operating system keeps track of all the files on each disk. To track the location of each file, the operating system maintains a running list of information on each file, in a table that is typically called the file allocation table (FAT). Users can make their own file management easier by creating a hierarchical file system that includes folders and subfolders arranged in a logical order.

The operating system uses interrupt requests (IRQs) to maintain organized communication with the CPU and other pieces of hardware. Each of the hardware devices is controlled by another piece of software, called a driver, which allows the operating system to activate and use the device.

The operating system also provides the software necessary to link computers and form a network.

Types of Operating Systems

UNIX was the first multi-user, multiprocessor, multitasking operating system available for use on PCs. In many ways, UNIX served as the model for other PC operating systems.

DOS is a single-user OS that supports only 640 KB of memory. It features a command-line interface and does not support multitasking or multiprocessing.

The Macintosh operating system supports the graphical nature of the Macintosh computer. The Mac OS brought the first truly graphical user interface to consumers. It also brought interface conformity to the desktop.

Windows 3.0, 3.1, and 3.11 brought a graphical user interface and multitasking capabilities to PCs that ran DOS. Windows 3.x is an operating environment.

IBM's OS/2 Warp was the first true GUI-based operating system for Intel-based PCs. OS/2 is a multitasking operating system that provides support for networking and multiple users.

Microsoft's Windows NT was originally meant as a replacement for DOS but was too resource-intensive to work on most PCs at the time of its release. Microsoft issued two versions-Windows NT Workstation and Windows NT Server.

Windows 95 was Microsoft's first true GUI-based, 32-bit operating system for Intel PCs. Its strengths include multitasking and the capability to run older DOS and Windows 3.x programs.

The features of Windows 98 include advanced Internet capabilities, an improved user interface, and enhanced file system performance, among others.

Linux is a version of UNIX and is available free or at a low cost from various sources. Despite its low cost, it is a powerful 32-bit OS that supports multitasking, multiple users, networking, and almost any application.

Windows 2000 includes the same interface and features of Windows 98, with the file system, networking, power, and stability of Windows NT. Several versions of Windows 2000 are available, each targeting a specific user or computing environment.