INTRODUCTION TO

COMPUTER

NETWORKING AND

OPERATING SYSTEM

Chapter No. ONE

By

Dr. Yasir Zafar Khan

Computer Science Faculty

AMU Girl’s School, AMU

iec.ice@gmail.com

INTRODUCTION

Networking refers the inte-connection of various devices to share their resources.

A network is an inter-connection of machines or people.

A network is a group of devices connected with one another.

Cable television networks and telephone networks are examples of networks.

When we create a network of different devices, it is called networking.

COMPUTER NETRWORK

A computer network is a collection of computers and

peripheral devices such as printer connected communication

links.

To establish a computer network, we need at least two

computers and some other devices.

These devices are interconnected using a communication

medium such as wire.

The communication media or links allow the network

components to work together.

The network components may be located at remote locations

or within the same building.

NEYWROK BENEFITS

Many companies and individual

have discovered that there are several

benefits of connecting computers

together.

Network can improve the work by

increasing productivity, lowering costs

etc.

Ease of Access

Work from Home

Sharing Resources

Sharing Information

Productivity

Programs

Cost

Administration

Security

HARDWARE REQUIRED

TO

ESTABLISHED NETWORK

COMPUTERS

IBM-Compatible and Macintosh

Computers connected to a network need not to be

of the same type.

CABLE

Ethernet, twisted pair, Co-axial Cable and Optical

fiber.

Cables are wires that connect computers and

resources on a network.

CONNECTORS

RJ-45 connectors

A connector is a device that joins two computers

or networks together.

NETWORK

Network Interface Card (NIC)

Is a Device that join a cable to a computer.

TYPES OF NETWORK

PERSONAL AREA NETWORK (PAN)

A PAN is a computer network used for

communication among various electronic devices

such PDA’s (Personal Digital Assistants),

Mobile Phones in close proximity.

The area of PAN is typically a few meters.

<<

PAN can be used for communication among the

devices or for connecting to the internet.

A PAN may use wireless connection as well

Example of PAN: Home and School

LOCAL AREA NETWORK(LAN)

A LAN is the most common type of network.

A LAN connects computers and devices located

close to one another, such as in one building.

Usually LAN has not more than 100 computers.

Example of LAN: Computer Lab of your

school, CCTV Network

CAMPUS AREA NETWORK (CAN)

A CAN is a computer network made of an interconnection of two or more LAN’s within a limited area.

A CAN is larger than a LAN but smaller than

WAN.

Example of CAN: A University, College,

School or Shopping Mall

METROPOLITAN AREA NETWORK (MAN)

A MAN is also a collection of LAN.

MAN connects computers located in the same geographical area such as city or town.

Example of MAN: Cable network, Banks

WIDE AREA NETWORK (WAN)

A WAN connects local and metropolitan are network together.

The Networks that make up a WAN, may be

located throughout a country or even around the

world.

Example of WAN: Internet

NATURE OF COMPUTER NETWORK

Two types of nature of computer network are:

PERMANENT NETWORK

Most companies use a permanent network to transfer information.

A permanent network uses cables to link computers together.

The computers and cables on a permanent network stay connected and in place at all times.

TEMPORARY NETWORK

A temporary network is a network connection that is

established for a brief period of time and disconnected.

The most common type of temporary network

occurs when a n employee connects a computer at

home to a computer at work in the office using a

modem.

NETWORK TOPOLOGY

The art of connecting different

computers in a network is known as

topology.

The term network topology refers to

the way in which the nodes of a

network are linked together.

There are three basic topologies are:

STAR TOPOLOGY

All nodes are connected to a central system called

switch, which forwards data towards its final

destination.

The switch controls the communication on the

network.

Star topology has minimal line cost (Advantage)

If any of the local computers fails, the remaining

portion of the network is unaffected. (Advantage)

The system crucially depends on the central

switch. (Disadvantage)

If it fails, the entire network goes down.

(Disadvantage)

RING TOPOLOGY

The nodes are connected in a closed loop so that

each devices is connected to two others, one

either.

The computers in a ring topology are connected in

the shape of closed ring.

Data are simple passed from one machine to

another.

Data travel only in one direction in a ring.

Each computer passes the data to the next one on

the line automatically.

The ring works well where there is no central-site

computer system (Advantage)

It is more reliable than a star network. (Advantage)

The ring network requires more complicate

control software. (Disadvantage)

BUS TOPOLOGY

All of the nodes are connected to central cable

called bus.

A bus is single continuous cable.

Transmission from any node travels the length of

the bus in both directions and can be received by

all other nodes.

The bus has terminators at either ends which

absorbs the signal, removing it from the bus.

It is quit easy to set.

Failure of one node does not affect the rest of the

network.

It offers limited flexibility for change.

A signal on the bus must be strong enough to

reach the receiver.

OPERATING SYSTEM

The operating system, also referred to as the OS,

is a computer program that manages all the other

programs on your computer, stores files in an

organized manner, and coordinates the use of the

computer hardware such as the keyboard and

mouse

• The operating system frees one from having

to interact directly with the hardware—other

than clicking the mouse button or pressing

keys on the keyboard— to complete tasks.

VARIOUS FUNCTIONS OF OPERATING

SYSTEM

MEMORY MANAGEMENT FUNCTION

Operating System manages the primary memory of the

system.

It allocates the memory, on the request of process,

which is being run @ that time.

It also keeps a check @ a particular time, how many

bytes of memory are in use and which process is using

it.

It also keeps track of what part of it is free.

In case of multi-user system, it decides on the propriety

basis, that which user will have access to memory &

when.

How much of it is used depends on the requirements.

File Management Function

Writing & retrieving the information on/from the

secondary storage device is the function of an

Operating system.

It follows a complete methodology for maintaining the

files, so that different sets of information do not get

mixed up and exactly the same set of information is

supplied, which is required by the user.

Processor Management Functions

Operating System also takes care of the

processor

It allocates the processor.

In case of multi-user system, it allocates the

processor time to different users as and when

needed & in such a way that every user has a

minimum time.

Device Management Function

It keeps track of all the devices i.e. peripherals

attached to the computer such as I/O devices etc.

When needed, it allocates the devices in such

a way that can be efficiently used.

It initiates the I/O operations & allocates

them along with other devices to the user.

It initiates the I/O operations & allocates

them alongwith other devices to the user.

TYPES OF OPERATING SYSTEM

SINGLE USE OPERATING SYSTEM

These Operating Systems allows only user

to work on a computer at a time.

Example: MS-DOS, CP/M

MULTIUSER OPERATING SYSTEM

These Operating system allow more than one

user to work on the computer at the same

time.

These operating systems allocates memory in

such a way that different users can work

simultaneously without disturbing each other.

It also allocates the processing time in such a

way that every user gets a very quick response

from the machine.

These are also known as Time Sharing

Operating System.

Example: UNIX, XENIX, VMS and

Windows NT

MULTITASKING OPERATING SYSTEM

The ability to execute more than one task at the

same time, a task being a program.

The terms multitasking & multiprocessing are

often used interchangeably, although multiprocessing

sometimes implies that more than one CPU is

involved.

In multitasking sometimes, only one CPU is

involved, but it switches from one program to another

so quickly that it gives the appearance of executing all

of the programs at the same time.

There are two basic type of

multi-tasking:

Preemptive

The Operating system parcels out CPU time slices to

each program.

OS/2, Windows 95, Windows NT, the Amiga operating system

and UNIX use preemptive multitasking

Cooperative

Each program can control the CPU for as long as it needs it.

If a program is not using the CPU, however, it can allow

another program to use it temporarily.

MS-Windows 3.x and the MultiFinder

(for Macintosh computers) use cooperative multitasking)

SINGLE USER OPERATING SYSTEM

These Operating System allow execution of

only one task at a time

E.g.: MS-DOS

NETWORK OPERATING SYSTEM

An Operating System that includes special

functions for connecting computer & devices into

a local network (LAN).

Some Operating systems, such as UNIX &

Mac OS, have built-in networking functions.

The term network operating system, however,

is generally reserved for S/w that enhances a

basic operating system by adding networking

features.

Example: some popular NOS’s for DOS

& Windows systems include: Novell Netware,

Airsoft's, LANtastic, MS-LAN Manager and

Windows NT.