Functions of OS. Detailed explanatoin of OS.

1. System and Network
Administration Windows Based
Lecture 3- Functions of OS
Week 3

2. Computer Operating System
User Interaction with Computer through
Operating system
 Categories of Operating Systems
 Multi-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)

3. Categories of Operating Systems
 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)

4.  Time 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.
Categories of Operating Systems

5. Functions of Operating Systems
 Booting: It is a process of starting the
computer, OS checks the computer and makes
it ready to work.
Types of Booting:
There are two types of booting process
 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).

6.  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.
Functions of Operating Systems

7. The step by step booting process is as follows:
Step 1:
 BIOS and Setup Program ROM: Permanent and
unchanging memory.
 BIOS: The part of the system software that
includes the instructions to accept input and output.
 Load: 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.
Functions of Operating Systems

8. Step 2:
 Power-On-Self-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.
 The computer will produce a beeping sound
and an error message will appear on the
screen if any problem is encountered.
Functions of Operating Systems

9. Step 3:
 The Operating System (OS) Loads BIOS
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

10. Step 4:
 System Configuration Registry: 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

11. Step 5:
 System Utilities Loads: System utilities are
loaded into memory. Volume control Antivirus
software PC card unplugging utility
Step 6:
 Users Authentication: Authentication or user
login occurs User name & Password The user
interface starts enabling user interaction with
computer programs.
Functions of Operating Systems

12. Functions of Operating Systems
Monitoring performance:
 A 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 Network
Some 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.

13. Housekeeping Services:
 OS performs different functions related to storage
and file management by using a special program
known as File manager.
 It includes: 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.
Functions of Operating Systems

14.  Administrating Security OS 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 Systems

15. Providing User Interface
User 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 Systems

16.  Menu-Driven-Interface :
 The user enters data and instructions by
using menus, commands are not used.
Example: C language environment
Graphical-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
Functions of Operating Systems

17.  Embedded Operating System: It is
used in most handheld computers
and small devices. It resides on a
ROM chip. Example: Pocket PC 2000,
Palm OS etc.
Functions of Operating Systems

18. 18
System Software
Operating
systems
 Control computer
functions:
 Hardware
 Memory
 Application
programs
 System
maintenance
 Provide user
interface
System utilities
 Programs that
perform computer
housekeeping tasks:
 Manage system
resources
 Improve efficiency
 Virus prevention

19. Utility Programs
 It 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

20.  Disk 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.
Utility Programs

21.  Data 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.
Utility Programs

22.  Disk 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 files, Deleting downloaded program
files, Empty recycle bin Deleting files from
temporary, folder Removing installed
programs that are no more required
Utility Programs

23.  Personal 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 Programs

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Utility Programs
 Small application programs that
perform special functions:
 Manage system
resources
 Create a pleasant
environment
 Improve efficiency

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Display Utilities
 Change the appearance of:
 Desktop
 Windows colors
 Font sizes
 Screen savers
 Screen resolution

26. 26
Add or Remove Programs
 Installation wizard
 Uninstall wizard:
 Do not just delete program files to remove
programs

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System Maintenance Utilities
 Disk cleanup
 Deletes
unnecessary files

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System Maintenance Utilities
 Disk defragmenter
 Tidies up a disk to
make it run faster
 ScanDisk:
 Error-checker

29. 29
System Maintenance Utilities
 Task manager
 Allows you to see
and control the
processes on your
machine
 Can be used to
find spyware

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System Restore
 System
Restore:
 Restores the
system settings
back to a
specific date

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System Backup
 Backup:
 Creates a copy of
the hard drive to
another storage
device

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Accessibility Utilities
 Utility manager:
 Magnify screen
image
 Screen contents
narration
 On-screen keyboard

33.  End of the lecture
 Ref: Introduction to Operating
System Chapter