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Operating System Basics

Role of Operating System

It is a software program which is the computers master control.

It provides you with the tools that enable you to interact withthe PC.

It performs the following functions:

Displays the on-screen elements with which you interact.These elements are collectively called User Interface.Loads programs in computers memory.Coordinates how programs work with hardware and other software.Manages the way information is stored on and retrievedfrom disks.

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Graphical User Interface (GUI)

An operating system provides a set of items on the screenwith which user interacts, called the User Interface.

Most modern Operating Systems provide a Graphical User Interface.

A GUI allows system control by clicking graphical objectson screen with a mouse.

A GUI is based on the desktop metaphor. Graphical objectsappear on desktop representing resources that can be used.

GUI Tools

Windows Operating System offers two unique tools calledTaskbar and Start Button. These help run and manage

programs.

Icons are pictures that represent computer resources and double

clicking an icon activates that program.

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Applications & InterfaceApplications designed to run under one operating system usesimilar interface elements.

Windows uses similar interface for all programs.

In a GUI, each program opens and runs in a separate windowcalled Frame.

In a GUI, multiple programs run at the same time each in aseparate window. The application in use is said to be theActive Window.

MenusGUI based programs let users issue commands by choosingthem from Menus.

A menu is a group of related commands.

Menus let you avoid memorizing and typing command names.

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Dialog Boxes

A Dialog box is a special window that appears when a programor Operating System needs more information beforecompleting a task.

They are so called because they conduct a dialog with the user for providing more information or making choices.

Command Line InterfacesIn Command Line Interface, commands are typed at a prompt.

DOS and Unix used Command Line Interface.

Under Command Line Interfaces, individual applications donot need to look or function the same way, so different

programs look different.

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Basic Services

The Operating System manages all the programs that run on thePC.

Operating System provides services to programs and users,including file management, memory management and printing.

In order to provide services to programs, the operating systemmakes system calls requesting other hardware and softwareresources to perform tasks.

MultitaskingMultitasking is the capability of running multiple processessimultaneously.

A multitasking operating system lets you run multiple programs at the same time.

Through multitasking, you can do several chores at one time,such as printing a document while downloading a file from theinternet.

There are two types of multitaskingCooperativePreemptive.

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Managing Hardware

The operating system is an intermediary between the

programs and hardware.The operating system uses interrupt requests (IRQs) tomaintain organized communication with the CPU andother pieces of hardware.Each hardware device is controlled by a piece of software, called a Driver , which allows theOperating System to activate and use the device.

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

Utility Software

A utility is a program that performs a task that is nottypically handled by the operating system.

Some utilities enhance the functionality of operatingsystem.

Some major categories of utilities include:File de-fragmentationData compressionBackupAntivirusScreen Saver