INTRODUCTION TO COMPUTINGCHAPTER NO. 03

Operating Systems and Utility Programs

Functions of Operating SystemsTypes of Operating Systems (Standalone OS,

Network OS, Embedded OS etc)Utility Programs (File Viewer, File

Compressor, Disk Scanner, Antivirus, Disk Defragmenter, Backup Utility, Data Recovery, Task Manager, Disk Cleanup, Uninstall etc)

Operating SystemsAn operating System is a set of programs

that manages all computer components and operations.

Users interact with computer through operating system.

When computer is turned on the OS runs and checks that all parts of the computer are functioning properly.

OS manages all operations on computer after loading.

Operating Systems

Operating Systems

Computer

Operating System

User

User Interaction with Computer through Operating system

Categories of Operating SystemsMulti-user OS – Allows multiple users to use

same computer at the same time. (eg; Linux, UNIX, Windows 2000)

Multiprocessor OS – Supports two or more processors that running programs at the same time. (eg; Linux, UNIX, Windows 2000)

Multitasking OS – It can execute more than one program at the same time. (eg; UNIX, Windows 2000)

Multithreading OS – Allows different parts of a program to run concurrently. (eg; Linux, UNIX, Windows 2000)

Categories of Operating SystemsTime Sharing OS – Allows many users to share

the computer simultaneously, it is used when several users are linked through communication networks to a single computer .

The computer first works on one user’s task for a fraction of time and then goes to the next user’s task.

The computer operates very quickly and can distribute time to various tasks, the computer rapidly switches back and forth among different tasks.

Functions of Operating SystemsBooting It is a process of starting the computer, OS

checks the computer and makes it ready to work, booting is of two types:Cold Boot: When computer is turned on

after it has been powered off completely.Warm Boot: When computer is restarted.

When booting process takes place, the kernel and important instructions of OS are copied from hard disk to main memory (RAM).

Kernel is the most important part of OS that manages memory and devices, maintains computer clock, starts applications and assigns computer resources like devices, programs, data, and information etc.

Kernel remains in memory permanently while the computer is turned on.

The step by step booting process is as follows:Step 1: BIOS and Setup ProgramROM: Permanent and unchanging memory.BIOS: The part of the system software that includes

the instructions to accept input and output.

Functions of Operating Systems

Load: To transfer from a storage device to memory, ROM loads BIOS into the computer’s memory..

Setup Program: A special program containing settings to control hardware, that can be accessed while the BIOS information is visible.

Step 2: Power-On-Shelf-Test (POST)A series of tests conducted on the computer’s

main memory, input/output devices, disk drives and the hard disk.

BIOS conducts POST to check the input/output system for operability.

Functions of Operating Systems

The computer will produce a beeping sound and an error message will appear on the screen if any problem is encountered.

Step 3: The Operating System (OS) LoadsBIOS searches for the OS.Settings in CMOS: Complementary Metal-Oxide

Semiconductor determine where to look for the OS.

The OS’s kernel is loaded into the computer’s memory.

The OS takes control of the computer and begins loading system configuration information.

Functions of Operating Systems

Step 4: System ConfigurationRegistry: Database to store information

about peripherals and software.Peripheral: Device connected to a computer.Driver: A utility program that makes

peripheral devices function properly.The system is configured from the OS’s

registry.Drivers are loaded into memory.

Functions of Operating Systems

Step 5: System Utilities LoadsSystem utilities are loaded into memory.Volume controlAntivirus softwarePC card unplugging utilityStep 6: Users AuthenticationAuthentication or user login occursUser name & PasswordThe user interface starts enabling user

interaction with computer programs.

Functions of Operating Systems

Memory ManagementIt is a process of optimizing the use of main

memory, OS allocates memory area to different programs, which is then deallocated when program finishes.

Some OS allocates a part of storage medium like hard disk as additional RAM.

A part of running program can be in RAM and the remaining part may be on the hard disk, this is known as Virtual Memory.

The area of the hard disk for the virtual memory is called swap file.

Functions of Operating Systems

It is used to exchange data, information, and instructions between memory and hard disk.

The amount of data and program instructions that can swap at a given time is called page.

The process of swapping items between memory and hard disk is called paging.

A situation in which most of the time of OS is wasted in paging instead of executing the program is called thrashing.

Functions of Operating Systems

Job SchedulingAny operation managed by processor is

called Job, eg; executing instructions, getting input or displaying result to the user etc.

OS determines the order in which these jobs are processed, many scheduling mechanisms are used by OS to execute these jobs.

Sometimes, jobs are executed in first-come-first-serve basis, but in some situations, the new coming job is given more priority.

Functions of Operating Systems

Functions of Operating SystemsIf a device is already busy in executing some

instructions, then a new job is stored in a memory area called Buffer.

Device ControllingThe hardware devices are controlled with a

small software called device drivers, that is a program to tell the OS how to communicate with a device.

The OS loads the drivers of all devices when computer boots, the devices cannot function properly without device drivers.

Functions of Operating SystemsIn latest Windows OS, when a new hardware device

is attached to the computer it automatically detects the device and install its driver if it is available.

This is known as Plug and Play.If the driver is not available, the OS guides the user

to install it manually from CD or floppy disk.Accessing the WebOS provides the facility to connect to the web, it

guides user to set up a connection between computer and ISP.

Some OS also provide the facilities of web browser and email program.

Functions of Operating SystemsMonitoring performanceA performance monitor is a program that checks

and reports information about different system resources and devices.

Example, it monitors the processor, disks, memory, and network etc.

Controlling NetworkSome OS are Network OS, that support network.A Network OS organizes how multiple users

access and share resources on network, resources include programs, files and hardware devices etc.

Functions of Operating SystemsHousekeeping ServicesOS performs different functions related to storage

and file management by using a special program known as File manager, these include:Formatting and copying disks - Formatting is a

process of preparing disk for reading and writing.

Displaying a list of files on a storage medium.Checking the amount of used or free space on a

storage medium.Organizing, Copying, renaming, deleting,

moving and storing files.Creating shortcuts.

Functions of Operating SystemsAdministrating SecurityOS manages the security of computer

system as well as data and programs stored on it, that is maintained by using user ID and Passwords.

The network administrator can also defines different levels of access to all for different users, some users may have full access to all resources but some may be restricted to only specific resources.

Functions of Operating SystemsProviding User InterfaceUser interface controls how user enters the

data and instructions and how information is displayed on the screen, types of user interface are:

Command-Line-Interface : The user enters data and instructions by typing keywords or pressing special keys on keyboard.

A set of commands used to interact with computer is called Command language.

Example: DOS

Functions of Operating SystemsMenu-Driven-Interface : The user enters

data and instructions by using menus, commands are not used.

Example: C language environmentGraphical-User-Interface : It is a visual

environment that is used by user to communicate with computer.

It uses windows, icons, menus, and other graphical objects to issue commands.

Example: MS Windows

Types of Operating SystemsStand-alone Operating SystemIt works on a desktop or notebook computer, it is

located on the computer’s hard disk. A stand-alone OS that works with a network OS is

called Client OS. Example: DOS, Windows 95, Windows NT

workstation, Windows Me, Windows XP Home Edition etc.

Network Operating SystemIt supports network and normally works on a Server. Example: Windows NT Server, Windows 2000

Server, NetWare, UNIX, Linux, Solaris etc.

Types of Operating SystemsEmbedded Operating SystemIt is used in most handheld computers and

small devices. It resides on a ROM chip. Example: Windows CE, Pocket PC 2000,

Palm OS etc.

Utility ProgramsIt is a type of system software that is used to

solve a particular problem.Many OS provide different types of utility

programs to solve the common problems of Software and Hardware .

File Viewer - Used to view and manage files in computer system, eg. Windows Explorer

File Compressor - Used to shrink the size of files, a large volume of data can be transferred by using file compressor, eg. WinZip

Utility ProgramsDisk Scanner - Used to detect physical and logical

problems of the disk, all OS provide disk scanners to manage compute disks.

Antivirus - A type of software that is used to detect and remove viruses, it also prevents new virus from entering into the computer, eg. Norton, McAfee etc.

Disk Defragmenter - Used to recognize the files on the disk, it manages the unused space on the disk so that OS may use data more quickly.

Backup Utility - Used to make backup of data and files, backup is used when data is lost or deleted unexpectedly.

Utility ProgramsData Recovery Utility - Used to restore the data

that has been damaged or corrupted, data can be damaged by hardware failure, power fluctuation, viruses, bad software etc.

Task Manager Utility - It appears when the user presses CTRL+ALT+DEL key, which displays information about programs and processes running on the computer, it also displays information about CPU and memory usage and user information.

Task Scheduler Utility - Used to schedule different types of tasks, it is automatically started when Windows is started, it runs in background.

Utility ProgramsDisk Cleanup - It scans hard drive to

determine the folders with files to be deleted, it also calculates the amount of hard drive space that will be freed after running disk cleanup, it can free hard disk by:Deleting temporary internet filesDeleting downloaded program filesEmpty recycle binDeleting files from temporary folderRemoving installed programs that are no

more required

Utility ProgramsPersonal Firewall - Used to detect and

protect a personal computer from unauthorized intrusions, the latest update to Windows XP automatically enables the built-in personal firewall when Windows is installed.

Spyware Remover - It detects and deletes spyware, that is a program placed on a computer without user’s knowledge, it secretly collects information about the user, it often enters a computer when the user installs new program.

Utility ProgramsUninstall Utility - It is a program that removes an

installed program from computer properly.When programs are uninstalled, small pieces of

program can be left behind on the hard drive or in system files.

A huge amount of extra data can be left behind if a program is removed by deleting its folder without using uninstall utility.

Uninstall utility removes the programs along with all references to the program in system files.

Occasionally, uninstall utilities can remove the files that are used by other programs remaining on the system.