JBD Computer Studies Book 8

Chapter 6

Computer
Network

Objectives

After completing this chapter, you will be able to:

y Define computer network.
y Explain the hardware and software components required to interconnect network

nodes.
y Classify computers on the basis of geographical spread of network and services in a

network.
y Define network topology and explain the different types of network topology.
y Define network media and explain the different types of network media.
y Explain how to search educational materials through Web.

C Ooncept verview

Communication is the process of sharing a message. A conversation between
two people is an example of communication. Data communication refers to
the sharing of a virtual message. Electronic communications, like emails and
instant messages, as well as phone calls are examples of data communications.
The basic components of data communications are the same as the typical
communication process. You need a sender (transmitter), message (data) and
receiver (destination). Take the simple electronic communication method of
email for example. The computer in which you type the email is the sender,
known in data communications as the transmitter. The typed message is the data
being communicated. The computer the email is opened on is the destination,
the equivalent to the receiver in ordinary communication. Data communications
gives you the ability to easily stay in touch with others. Phones, instant messaging,
emails and social networking sites all utilize data communications.

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Computer Network

Networks are changing the computing
paradigm from “number-crunching” to
communicating. They have spawned
industries such as the online industry,
a collection of organizations providing
information and communication
services to remote customers via dial-up
modems. Computer network is a group
of computers and peripheral devices
connected through data communication
system. The computers on a network may
be linked through cables, telephone lines,
radio waves, satellites or infrared light.

Advantages of Computer Network

The advantages of computer network are explained below:
File Sharing
The major advantage of a computer network is that is allows file sharing and
remote file access. A person sitting at one workstation of a network can easily see
the files present on the other workstation, provided he is authorized to do so. It
saves the time which is wasted in copying a file from one system to another, by
using a storage device. In addition to that, many people can access or update the
information stored in a database, making it up-to-date and accurate.

Resource Sharing
Resource sharing is also an important benefit of a computer network. A computer
network provides a cheaper alternative by the provision of resource sharing.

Increased Storage Capacity
As there is more than one computer on a network which can easily share files, the
issue of storage capacity gets resolved to a great extent. A standalone computer
might fall short of storage memory, but when many computers are on a network,
memory of different computers can be used in such case. One can also design a
storage server on the network in order to have a huge storage capacity.

Increased Cost Efficiency
There are many software available in the market which are costly and take time for
installation. Computer networks resolve this issue as the software can be stored
or installed on a system or a server and can be used by the different workstations.

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Disadvantages of Computer Network
The disadvantages of computer network are explained below:
Security Issues
One of the major drawbacks of computer networks is the security issues involved.
If a computer is a standalone, physical access becomes necessary for any kind of
data theft. However, if a computer is on a network, a computer hacker can get
unauthorized access by using different tools. In case of big organizations, various
network security software are used to prevent the theft of any confidential and
classified data.

Rapid Spread of Computer Viruses
If any computer system in a network gets affected by computer virus, there is
a possible threat of other systems getting affected too. Viruses get spread on a
network easily because of the inter connectivity of workstations. Such spread can
be dangerous if the computers have important database which can get corrupted
by the virus.

Expensive Set Up
The initial set up cost of a computer network can be high depending on the
number of computers to be connected. Costly devices like routers, switches,
hubs, etc., can add up to the bills of a person trying to install a computer network.

Dependency on the Main File Server
In case the main file server of a computer network breaks down, the system
becomes useless.

Network Components

All computer networks are made up of basic hardware and software components
to interconnect network nodes.

Hardware Components
The hardware components in a network are:

Servers or Clients
A server is a network computer, computer program, or device that processes
requests from a client. The function of a computer server is to store, retrieve and
send or “serve” files and data to other computers on its network. A client is an
application or system that accesses a remote service on another computer system,
known as a server, by way of a network.

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Connectors
The connectors are used to connect network cables to terminals or other devices.
The type of connector depends on the cable types or devices used in the network.

Network cables
Networking cables are used to connect one
network device to other or to connect two or
more computers to share printer, scanner, etc.
The devices can be separated by a few meters
or nearly unlimited distances. Different types of
network cables like twisted pair cables, coaxial
cables and fiber optic cables are used depending
on the network’s topology, protocol and size.

Network Interface Card (NIC)
A network interface card is a computer component that will slot into a socket
on a PC motherboard with the back of the card providing one or more Ethernet
connection sockets. It allows computers to communicate over a computer
network. Modern PCs can also connect to the Internet wirelessly via a PC bus
card or a USB device connection - these devices could also be called network
interface cards.

Software Components

The software components required to run a computer network are of two types.
These are:
Network Operating System
A networking operating system (NOS) is an operating system (OS) designed
to allow shared file and printer access among computers in a network. It
provides printer sharing, common file system and database sharing, application
sharing, and the ability to manage a network name directory, security, and other
housekeeping aspects of a network. Unix, Linux and the server versions of
Windows are common network operating systems.

Communications Protocol
Communications protocol defines the rules for sending blocks of data (each
known as a Protocol Data Unit (PDU)) from one node in a network to another
node. It is necessary for all computers on a network to use the same protocol
in order to communicate. Protocols may include signaling, authentication and
error detection and correction capabilities. Some of the popular protocols are
TCP/IP, SMTP and POP3.

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Classification based on Geographical Spread of Network

A computer network refers to a group of networked computer i.e., computers
that are linked by means of a communication system. A network can mean a small
group of linked computers to a chain of a few hundred computers of different
types spread around the world. Thus, networks vary in size, complexity and
geographical spread. Mostly, computer are classified on the basis of geographical
spread and on this basis, there can be three types of networks. They are: Local
Area Network (LAN), Metropolitan Area Network (MAN) and Wide Area
Network (WAN)

Local Area Network (LAN)

Local Area Network is a combination of hardware, software and communication
channels that connect two or more computers within a limited area. It consists of
just two or more personal computers connected together by a cable, an infrared
link or a small radio transmitter. This network may be in one room or group
of buildings. It consists of a communications channel, networked computers
and devices, a network interface card and a network operating system. The key
purpose of LAN is to serve its users in resource sharing. The hardware as well as
software resources are shared through LANs. For instance, LAN user can share
data, information, programs, printers, hard disks and modem.

Metropolitan Area Network (MAN)

Metropolitan Area Network (MAN) is a network that interconnects users with
computer resources in a geographic area or region larger than that covered by
even a large Local Area Network (LAN) but smaller than the area covered by
Wide Area Network (WAN). For example, Cable TV networks that are spread
over a city, can be termed as Metropolitan Area Network.

Wide Area Network (WAN)

Wide Area Network is a geographically
dispersed telecommunications network. It
is a telecommunications network, usually
used for connecting computers, that spans a
wide geographical area. WANs can be used
to connect cities, states, or even countries.
Computers connected to a Wide Area
Network are often connected through public
networks such as the telephone system.
Sometimes they can be connected through
leased lines.

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Classification based on services in a Network
Network can be classified as one of the following two types based on their services
in a network. They are Client/Server Network and Peer-to-Peer Network.
Client/Server Network
Client/Server network is a network in which servers provide services to clients.
Typically, there is at least one server providing central authentication services.
Servers also provide access to shared files, printers, hardware, and applications.
In client/server networks, processing power, management services and
administrative functions can be concentrated where needed, while clients can
still perform many basic end–user tasks on their own.

Peer-to-Peer Network
Peer-to-peer network is a network in which resource sharing processing and
communications control are completely decentralized. All clients on the network
are equal in terms of providing and using resources and users are authenticated
by each individual workstation. Computers in a peer to peer network run the
same networking protocols and software. Peer networks are also often situated
physically near each other, typically in homes, small businesses or schools. Peer-
to-Peer networks are easy and inexpensive to implement.

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Physical Topology

The configuration or physical arrangement, of the devices in a communications
network is called the network topology or network architecture. Network
architecture is similar to the architecture of a building. Like a blueprint, which
shows the physical layout of the building, a drawing of a network architecture
provides a pictorial representation of the physical layout of the network. The
commonly used physical network topologies are bus, ring and star.

Bus or Linear Topology

A bus network comprises a continuous
length of cable that connects the device. A bus
network is also called a backbone network.
Bus networks are often used on local area
networks that contain only two or three
computers, such as a home network. On a
bus network, only one computer can transfer
information at a time. When a computer
sends information, the information moves through the entire length of the cable.
The destination computer retrieves the information from the cable.

Ring Topology

A ring network structure consists of computer
connected to a single length of cable
arranged in a ring. The information on a ring
network travels in one direction only. When
a computer transfers information, it sends
the information to the computer located next
to it. If a computer receives information that
is not addressed to it, the computer passes
the information to the next computer in the
ring. The computers continue to pass the
information until it reaches the intended
destination.

Star Topology

A star network consists of computers connected to a central network connector,
which is usually a hub or a switch. All information that transfers from one
computer to another on the network passes through the hub or switch. Devices
typically connect to the hub with Unshielded Twisted Pair (UTP) or Shielded
Twisted Pair (STP).

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Network Media

Network media, the conduit through which networking communications flow,
can be either guided or unguided. Guided transmission media uses a “cabling”
system that guides the data signals along a specific path. Guided media is also
known as bounded media, since the data signals are bounded by the cabling
system. Cable can be physical or conductive media like wires, coaxial cables or
fibre optics. Unguided media consists of a means (e.g. air, space) for the data
signals to travel, however there is nothing to guide them along a specific path,
like in wires. In such cases, the data signals are not bounded to a cabling media.
Unbounded media is electromagnetic waves in the form of radio, microwave,
infra-red or others.

Copper Media

Copper cable is a type of bounded media that uses one or more copper conductors
rounded by a non – conductive insulated coating. The conductors can be made of
a wire or built from braided strands of wire.

Twisted Pair Cable
Twisted pair cable is the oldest and most
common medium of transmission. It consists
of two pairs of copper wires twisted together
in an insulated cable, to minimize electrical
noise. The twisted pair cable are easy to install
and inexpensive. The two types of twisted
pair cable are Unshielded Twisted Pair and
Shielded Twisted Pair.

Fibre Optic Cable
Fibre optic cable consists of a centre glass core
surrounded by several layers of protective
materials. It transfers data in the form of light
rather than electrical signals, thus there isn’t
any electrical or electromagnetic inference
to such cable. This makes it ideal for certain
environment that contain a large amount of
electrical interference. It has also made it the
standard for connecting networks between
buildings, due to its immunity to the effects of
moisture and lightning.

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Wireless Communication

Wireless communication is a type of communication in which signals are
transmitted without using bounded media of any sort. Instead signals are
transmitted as electromagnetic energy, such as radio, microwave, or light
pulses. Wireless communication enables users to move around while remaining
connected to the network

Radio Networking

Radio networking is a form of wireless communications in which signals are
sent via radio frequency (RF) waves in the 10 KHz and 1 GHz range. It is used
for private communication with devices like portable phones. It is subject to
electrical interference from power lines, a building’s metal structural components
and atmospheric conditions.

Infrared Transmission

Infrared transmission allows computing
devices to communicate via short-range
wireless signals. With the help of infra-
red, computers can transfer files and
other digital data between each other.
Infra-red transmission requires line-
of-sight transmissions. That means the
sender and receiver must be aligned so
that nothing obstructs the path of the
infra-red wave. Infra-red communication
is usually used over short distance. Today
most of the consumer devices like mobile
phones, Personal Digital Assistant (PDA),
Computer and laptop have built in infra-
red port for infra-red communication.

Microwave Transmission

Microwavetransmissionisusedextensivelyinsituationswhenphysicaltransmission
media is impractical or difficult to install, for example between high building,
across rivers, mountains, jungles and remote areas. Microwaves are transmitted
via earth atmosphere between two stations. It can be used for only short distance
up to 50km. Repeater station is needed if transmission distance is more than 50km.
Microwave transmission is line of sight transmission, the transmit station must
be in visible contact with the receive station. Such type of communication can be
easily affected by atmospheric changes for example weather.

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Searching Education Materials through Web
A search engine is a tool
designed to search for
information on the World
Wide Web. The search results
are usually presented in a list
of results and are commonly
called hits. The information
may consist of web page,
images, information and
other types of files. There
are many search engines
available on the web. Some
of the popular search engines
are Yahoo, Excite, Altavista
and Infoseek.

The search engines work in the following manner:

• The searcher types a query into a search engine.

• Search engine software quickly sorts through literally millions of pages in its
database to find matches to this query.

• The search engine’s results are ranked in order of relevancy.

For those just starting to learn the search process, this segment is recommended
to help you understand how the process works. The following is the general
procedure:

• Connect to the Internet via your browser (e.g. Firefox or Internet Explorer)

• In the browser’s location box, type the address (i.e. URL) of your search tool
choice. Press Enter. The Home Page of the search tool appears on your screen.

• Type your query in the address box at the top of the screen. Press Enter.

• Your search request travels via phone lines and the electronic backbone of the
Internet to search the tool’s Web site. There, your query terms are matched
against the index terms in the site’s database. The matching references are
returned to your computer by the reverse process and displayed on your
screen.

• The references returned are called “hits” and are ranked according to how
well they match your query.

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C Dompu- ictionary

Computer network : An interconnected collection of autonomous
computers.

Node : A networking device, such as a client computer,
a server, or a shared printer, that is connected to
the network and is capable of communicating with
other network devices.

Client : A network computer that utilizes the resources of
other network computers, including other clients.

Peer : A network computer that acts both as a server and
a client to other similar computers on the network.

LAN : A combination of hardware, software, and
communications channels that connect two or
more computers within a limited area.

Recap

• Computer network refers to a group of networked computer i.e., computers
that are linked by means of a communication system.

• Local Area Network is a combination of hardware, software, and
communications channels that connect two or more computers within a
limited area.

• Metropolitan area network (MAN) is a network that interconnects users with
computer resources in a geographic area or region larger than that covered by
even a large local area network (LAN) but smaller than the area covered by a
wide area network (WAN).

• A client / server network is a network in which servers provide services to
clients.

• A peer-to-peer network is a network in which resource sharing processing and
communications control are completely decentralized.

• The configuration or physical arrangement, of the devices in a communications
network is called the network topology or network architecture.

• A bus network comprises a continuous length of cable that connects the device.

• A ring network structure consists of computer connected to a single length of
cable arranged in a ring.

• Network media, the conduit through which networking communications flow,
can be either guided or unguided.

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Review Yourself

1. State whether the following statements are true or false.

a. Two computers are said to be interconnected if they are capable of
exchanging information.

b. A server is a network computer that utilizes the resources of other
network computers, including other client.

c. The largest WAN in existence is the Internet.

d. A peer-to-peer network is a network in which servers provide services
to clients.

e. A bus network comprises a continuous length of cable that connects the
device usually a hub or a switch.

2. Fill in the blanks.

a. A ____________ is a network computer that facilitates the sharing of
data, software, and hardware resources on the network.

b. A ____________ is a network computer that acts both as a server and a
client to other similar computers on the network.

c. ____________ is a combination of hardware, software, and
communications channels that connect two or more computers within a
limited area.

d. A ____________ network is a network in which resource sharing
processing and communications control are completely decentralized.

e. A ____________ consists of computers connected to a central network
connector, which is usually a hub or a switch.

3. Match the following. A networking device, such as a client computer, a
Client server, or a shared printer, that is connected to the
network and is capable of communicating with other
Peer network devices.
Node
A network computer that utilizes the resources of
Server other network computers, including other clients.

A network computer that facilitates the sharing
of data, software, and hardware resources on the
network.

A network computer that acts both as a server and a
client to other similar computers on the network.

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4. Give one word answer for each of the following.

a. An interconnected collection of autonomous computers.

b. A networking device, such as a client computer, a server, or a
shared printer, that is connected to the network and is capable of
communicating with other network devices.

c. A network computer that utilizes the resources of other network
computers, including other clients.

d. A network computer that facilitates the sharing of data, software, and
hardware resources on the network.

e. A network computer that acts both as a server and a client to other
similar computers on the network.

5. Answer the following questions.

a. What is a computer network?

b. What are the advantages of computer network.

c. Define the following terms:

i. Node ii. Client iii. Peer

d. What is Local Area Network? List the components of a typical LAN.

e. What is Metropolitan Area Network?

f. What is Wide Area Network?

g. What are the main differences between LAN and WAN?

h. What is client/server network?

i. What is peer-to-peer network?

j. What is a physical topology? List some of the commonly used physical
topologies.

k. What is star topology? Draw a neat diagram of star topology.

l. Differentiate between bounded media and unbounded media.

m. What is fiber optic cable?

n. What is the difference between radio networking and infrared
transmission?

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Chapter 7

Computer
Viruses

Objectives

After completing this chapter, you will be able to:

y Define computer virus and list its features.
y Explain how does computer virus work.
y Explain the different types of computer viruses.
y List the symptoms of a computer virus infection.
y Define antivirus and list the popular anti-virus.

C Ooncept verview

A computer virus is a program or piece of code that is loaded onto your computer
without your knowledge and runs against your wishes. Viruses can also replicate
themselves. All computer viruses are man-made. There are different types of
viruses and they range from being a nuisance that constantly displays pop-ups to
being a real severe danger that deletes system files, attaches to registries, destroys
ability to log into the Internet and even destroying the computer’s operating
system along with all the data that is on it. Unless you have completely backed-
up the data on your laptop, recovering that data will be impossible if you have to
re-install the operating system after a virus infection. The best protection against
computer viruses is prevention, early detection and removal. A good anti-virus
or Malware removal program can protect computers and provide peace of mind
when surfing the net.
Some of the features of a computer virus are listed below:
• The computer virus may cause problems immediately.
• It may reproduce itself and then cause damage.
• It may look at the computer’s clock and cause damage on a specific date.

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How does a computer viruses work?

Computer virus is a computer program designed to copy itself into other
programs, with the intention of causing mischief or damage. A virus will usually
execute when it is loaded into a computer’s memory. On execution, it instructs
its host program to copy the viral code into any number of other programs and
files stored in the computer. The corrupted programs may continue to perform
their intended functions while also executing the virus’s instructions, thus further
propagating it.
Infections spread from machine to machine, and from organization to organization,
in a number of ways.
Viruses can be transmitted by:
• Booting a PC from an infected medium
• Executing an infected program
• Opening an infected file
Common routes for virus infiltration include:
• Floppy disks or other media that users can exchange
• E-mail attachments
• Pirated software
• Shareware

Types of Computer Viruses

There are many kinds of viruses. Viruses come in a wide variety. The level
of destructiveness of viruses varies widely. Virus behaviour can range from
annoying to destructive. They are of the following types:

Boot Sector Viruses
A boot sector virus infects diskettes and hard drives. All disks and hard drives
contain smaller sections called sectors. The first sector is called the boot. The
boot carries the Mater Boot Record (MBR). MBR functions to read and load the
operating system. So, if a virus infects the boot or MBR of a disk, such as a floppy
disk, your hard drive can become infected if you re-boot your computer while the
infected disk is in the drive. Once your hard drive is infected all diskettes that you
use in your computer will be infected. Boot sector viruses often spread to other
computers by the use of shared infected disks and pirated software applications.
The best way to disinfect your computer of the boot sector virus is by using
antivirus software. The examples of boot sector viruses are Disk Killer, Stoned
and Michelangelo.

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Program Viruses

Program virus becomes active when the program file (usually with extensions
.BIN, .COM, .EXE, .OVL, .DRV) carrying the virus is opened. Once active, the
virus will make copies of itself and will infect other programs on the computer.
This type of virus targets a large range of operating systems, including Macintosh,
UNIX, DOS, and Windows. Friday the 13th, Enigma and Nemesis are examples
of this type of virus.

Symptoms of virus infection

Different viruses can affect a computer system in different ways. In order to
detect a virus attack on the computer, you must observe the computer for signs of
changes or strange behaviour that may be the symptoms of a virus attack. Some
of the symptoms of virus infection are discussed below:
• Slow performance
• Takes long to load programs
• Shows a sudden decrease in the free space on your disk
• Data files become corrupt or missing
• Programs do not run
• A disk drive light flashes constantly
• Shows an unusual display on the screen

Safe Computing

Computer virus attacks have become one of the biggest threats to an organization.
The organizations spend large amount of money to prevent, detect and recover
from computer virus attacks. The spreading of computer virus infections can be
stopped through the practice of safe computing. The following are a list of some
recommendations for safe computing:
• Install the latest updates from Microsoft Update on the computer.
• Update the antivirus software on the computer. Then, perform a thorough

scan of the computer by using the antivirus software.
• Do not load illegal software on your computer. The illegal software contains

viruses.
• Allow only genuine users to use the computer under supervision.
• Never load unknown disks into your system unless you make sure they are

virus free.
• Back up your files on a regular basis. If a virus destroys your files, at least you

can replace them with your backup copy.

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AntiVirus
Antivirus software is a program designed to prevent, detect and remove
computer viruses from computer system. Antivirus program is memory resident.
Whenever the computer system is booted, the anti virus program starts. It checks
for viruses in all files of the computer system. Virus authors are continually
releasing new and updated viruses, so it is important that you have the latest
definitions installed on your computer.
Once you have installed an anti-virus package, you should scan your entire
computer periodically.
• Automatic scans
Depending what software you choose, you may be able to configure it to

automatically scan specific files or directories and prompt you at set intervals
to perform complete scans.
• Manual scans
It is also a good idea to manually scan files you receive from an outside source
before opening them. This includes
• saving and scanning email attachments or web downloads rather than

selecting the option to open them directly from the source
• scanning media, including CDs and DVDs, for viruses before opening any

of the files
Some popular antivirus software available are PC Tools, Kaspersky, Norton Anti-
virus, Mcafee Anti-virus and AVG Anti-virus.

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C Dompu- ictionary

Antivirus : A program designed to detect and remove viruses from
computer system.

Boot sector virus : A computer virus designed to infect the boot sector of the disk.

Program virus : A computer virus designed to infect executable program
files having an extension .exe, .com, or .dll.

Kaspersky : An antivirus program developed by Kaspersky Lab
designed to protect users from malware and is primarily
designed for computers running Microsoft Windows and
Mac OS X.

Norton AntiVirus : AntiVirus developed and distributed by Symantec
Corporation.

Recap

• A computer virus is a program or piece of code that is loaded onto your
computer without your knowledge and runs against your wishes.

• The best protection against computer viruses is prevention, early detection
and removal.

• A good anti-virus or Malware removal program can protect computers and
provide peace of mind when surfing the net.

• Viruses can be transmitted by:
• Booting a PC from an infected medium
• Executing an infected program
• Opening an infected file
• Common routes for virus infiltration include:
• Floppy disks or other media that users can exchange
• Email attachments
• Pirated software
• Shareware
• A boot sector virus infects diskettes and hard drives.
• The examples of boot sector viruses are Disk Killer, Stoned and Michelangelo.
• Program virus becomes active when the program file (usually with extensions

.BIN, .COM, .EXE, .OVL, .DRV) carrying the virus is opened.
• Friday the 13th, Enigma and Nemesis are examples of this type of virus.
• Antivirus software is a program designed to prevent, detect and remove

computer viruses from computer system.

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Review Yourself

1. State whether the following statements are true or false.

a. A computer virus is a program or piece of code that is loaded onto your
computer without your knowledge and runs against your wishes.

b. Viruses can be transmitted by booting a PC from an infected medium,
executing an infected program and opening an infected file.

c. Program viruses often spread to other computers by the use of shared
infected disks and pirated software applications.

d. Friday the 13th, Enigma and Nemesis are examples of boot sector virus.

e. Antivirus software is a program designed to prevent, detect and remove
computer viruses from computer system.

2. Fill in the blanks.

a. A __________________ is a program or piece of code that is loaded onto
your computer without your knowledge and runs against your wishes.

b. A _________________ virus infects diskettes and hard drives.

c. _________________ virus becomes active when the program file (usually
with extensions .BIN, .COM, .EXE, .OVL, .DRV) carrying the virus is
opened.

d. _________________ is a program designed to prevent, detect and remove
computer viruses from computer system.

e. Antivirus program is _________________________.

3. Match the following.

Program virus A program designed to detect and remove viruses
from computer system.

Norton AntiVirus A computer virus designed to infect the boot sector
of the disk.

Antivirus A computer virus designed to infect executable
program files having an extension .exe, .com, or .dll.

Boot sector virus An antivirus program developed by Kaspersky
Lab designed to protect users from malware and is
primarily designed for computers running Microsoft
Windows and Mac OS X.

Kaspersky AntiVirus developed and distributed by Symantec
Corporation.

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4. Give one word answer for each of the following.
a. A program designed to detect and remove viruses from computer
system.
b. A computer virus designed to infect the boot sector of the disk.
c. A computer virus designed to infect executable program files having
an extension .exe, .com, or .dll.
d. An antivirus program developed by Kaspersky Lab designed to protect
users from malware and is primarily designed for computers running
Microsoft Windows and Mac OS X.
e. AntiVirus developed and distributed by Symantec Corporation.

5. Answer the following questions.
a. What is a computer virus?
b. How do computer viruses spread? Explain in brief.
c. What is a boot sector virus? Give any two examples of boot sector
viruses.
d. What is a program virus? Give any two examples of program viruses.
e. List some symptoms of a virus infection.
f. List some precautions that must be observed to avoid virus infection.
g. What are antivirus software? Give examples.

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Chapter 8

ICT, Computer
Ethics,

Cyber Law

Objectives

After completing this chapter, you will be able to:

y Define Information and Communication Technologies.
y Explain the usages of ICT tools.
y Define Cyber Law and explain the objectives of Cyber Law of Nepal.
y Define Cyber Ethics and list the ten commandments of Cyber Ethics.

C Ooncept verview

ICT stands for “Information and Communication Technologies.” ICT refers to
technologies that provide access to information through telecommunications. It is
similar to Information Technology (IT), but focuses primarily on communication
technologies. This includes the Internet, wireless networks, cell phones, and other
communication mediums.
In the past few decades, information and communication technologies have
provided society with a vast array of new communication capabilities. For
example, people can communicate in real-time with others in different countries
using technologies such as instant messaging, voice over IP (VoIP), and video-
conferencing. Social networking websites like Facebook allow users from all over
the world to remain in contact and communicate on a regular basis.
Modern information and communication technologies have created a “global
village,” in which people can communicate with others across the world as if
they were living next door.

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Usages of ICT tools

ICT stand for information and communication technologies and is defined, as a
“diverse set of technological tools and resources used to communicate, and to
create, disseminate, store, and manage information.” “ICT implies the technology
which consists of electronic devices and associated human interactive materials
that enable the user to employ them for a wide range of teaching - learning
processes in addition to personal use.” These technologies include computer
peripheral devices, the Internet, broadcasting technologies (radio and television),
and telephony.

Peripheral Devices
The peripheral devices such as multimedia projector, digital camera and scanner
are used in information and communication technology.

Multimedia Projector
A multimedia projector is a tool that is used in
ICT to deliver audiovisual media to entertain,
educate, or communicate with people. Using
a multimedia projector, you can show a DVD,
video, slide show or television program on a
large screen with color and sound. Multimedia
projectors allow for presentations that can be
used for work functions, classroom instruction
or enjoyment of films and television at home.

Digital Camera
A digital camera records and stores photographic images in digital form. Many
current models are also able to capture sound or video, in addition to still images.
Capture is usually accomplished by use of a photosensor, using a charged coupled
device (CCD).These stored images can be uploaded to a computer immediately
or stored in the camera for to be uploaded into a computer or printer later. Images
may also be archived on a photographic compact disk or external hard disk.

Scanner

Scanner is a computer peripheral or a stand-alone device that converts a
document, film, graphic, or photograph to a digital image, manipulable through
an appropriate software. When used with an optical character recognition (OCR)
software, a scanner can convert printed, typewritten (and, with some devices,
handwritten) text into a digital file that can be read by a word processor.

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Internet Services
The Internet is widely used in almost every walk of life. It offers access to data,
graphics, sound, text and people through a variety of services and tools for
communication and data exchange. Various web sites on the WWW provide
different kinds of facilities such as email, chat rooms and blog. Some of the useful
online services provided on the Internet are discussed below:

Electronic Mail
Electronic mail, or e-mail (and mail) is sending and receiving messages through
computer. Messages through e-mail can be in different forms such as text, image,
sound, database, spreadsheet or an application. All online services and Internet
Service Providers (ISPs) offer e-mail account promptly after you sign up. The
most popular Web-based email services are Gmail from Google, Outlook.com
(formerly hotmail.com) from Microsoft, and Yahoo! Mail from Yahoo.

Chat room
Chat room is a Web site, part of a Web site, or part of an online service such
as America Online, that provides a venue for communities of users with a
common interest to communicate in real time. Forums and discussion groups,
in comparison, allow users to post messages but do not have the capacity for
interactive messaging. Most chat rooms do not require users to have any special
software; those that do, such as Internet Relay Chat allow users to download
it from the Internet. Chat room users register for the chat room of their choice,
choose a user name and password, and log into a particular room (most sites
have multiple chat rooms). Inside the chat room, generally there is a list of the
people currently online, who also are alerted that another person has entered
the chat room. To chat, users type a message into a text box. The message is
almost immediately visible in the larger communal message area and other users
respond.

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Blog

A blog is a discussion or information site published on the World Wide Web
consisting of discrete entries (“posts”) typically displayed in reverse chronological
order so the most recent post appears first. Many blogs provide commentary
on a particular subject; others function as more personal online diaries; yet still
others function more as online brand advertising of a particular individual or
company. In education blogs can be used as instructional resources. These blogs
are referred to as an Edublog. A typical blog combines text, images, and links
to other blogs, Web pages, and other media related to its topic. The ability of
readers to leave comments in an interactive format is an important part of many
blogs. Most blogs are primarily textual, although some focus on art (art blogs),
photographs (photoblogs), videos (video blogs or “vlogs”), music (MP3 blogs),
and audio (podcasts).

Broadcasting Technologies

Broadcasting is the distribution of audio and video content to a dispersed
audience via any audio or visual mass communications medium, but usually one
using electromagnetic radiation (radio waves). The receiving parties may include
the general public or a relatively large subset thereof. Broadcasting has been
used for purposes of private recreation, non-commercial exchange of messages,
experimentation, self-training, and emergency communication such as amateur
(ham) radio and amateur television (ATV) in addition to commercial purposes
like popular radio or TV stations with advertisements.

Radio broadcasting
Radio broadcasting (experimentally from 1906, commercially from 1920): radio
broadcasting is an audio (sound) broadcasting service, broadcast through the
air as radio waves from a transmitter to a radio antenna and, thus, to a receiver.
Stations can be linked in radio networks to broadcast common radio programs,
either in broadcast syndication, simulcast or sub-channels.

Cable television
Cable television is a system of providing television programs to consumers via
radio frequency (RF) signals transmitted to televisions through coaxial cables
or digital light pulses through fixed optical fibers located on the subscriber’s
property. This can be compared to over-the-air method used in traditional
broadcast television (via radio waves) in which a television antenna is required.
FM radio programming, high-speed Internet, telephony, and similar non-
television services may also be provided through these cables.

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Telephony

Telephony is a term denoting the technology that allows people to have long
distance voice communication. It comes from the word ‘telephone’ which, in
turn, is derived from the two greek words tele which means far and phone which
means speak, hence the idea of speaking from far. The term’s scope has been
broadened with the advent of the different new communication technologies.
In its broadest sense, the terms encompasses phone communication, Internet
calling, mobile communication, faxing, voicemail and even video conferencing.

Cyber Law

Cyber crime refers to any crime that involves a computer and a network, where the
computers may or may not have played an instrumental part in the commission
of a crime. Cybercrime involve illegal access to company information. Just as
with individuals, criminals can steal financial information and make purchases
using the data. The criminal may also withdraw funds from company reserves,
transferring the stolen funds through a variety of accounts and making it
virtually impossible to locate the stolen assets. In other cases, it is not money or
credit information the criminal seeks; obtaining proprietary client information
and selling it to competitors is another example of this type of high tech criminal
activity. As a growing problem around the world, many countries are beginning
to implement laws and other regulatory mechanisms in an attempt to minimize
the incidence of cybercrime.

Cyber Law of Nepal

Cyber law of Nepal commonly known as the Electronic Transaction and Digital
Signature Act-Ordinance was enacted in Nepal in 2061 BS (2004). The cyber
law in Nepal was formulated after making a thorough discussion of the IT Acts
already implemented in other countries. It was formulated mainly to legalize the
different trading activities through the global computer network and to give a
boost to the e-governance activities. It contains a strong provision of punishment
against cyber crimes according to the nature of the crime. The different cyber
crimes mentioned in the law include hacking, damage to computer source code,
breach of privacy and faking digital signatures. As per the provisions

of law, the government is fully authorized to punish cyber criminals - both an
individual or an institution with imprisonment and fine.

The Act provides for:

• Legal Recognition of Electronic Documents

• Legal recognition of Electronic commerce Transactions

• Admissibility of Electronic data/evidence in Court of Law

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• Legal Acceptance of digital signatures
• Punishment for Cyber obscenity and crimes
• Establishment of Cyber regulations advisory
• Committee and the Cyber Regulations Appellate Tribunal
• Facilitation of electronic filing maintenance of electronic records
The major objectives are:
• To provide legal recognition for transactions
• Other means of electronic communication, commonly referred to as “electronic

commerce”, involving the use of alternatives to paper-based methods of
communication and storage of information
• To facilitate electronic filing of documents with the Government agencies
• Aims to provide for the legal framework so that legal sanctity is accorded to
all electronic records and other activities carried out by electronic means

Cyber Ethics

Computers are capable of doing many things as per the instructions given to it.
This quality makes computers a very useful (and powerful also) tool. Because the
capabilities of computers offer such strong temptations we must be especially
careful to use them wisely. It is not the computers we should be concerned about,
but rather the people whose lives we can affect by our actions. Cyber ethics refer
in general, to the behaviour and ways of thinking of computer users in situations
where a choice can affect the dignity and well being of others.The computer
ethics institute in Washington DC, has proposed the ten commandments of cyber
ethics. They are:
• Do not use a computer to harm other people.
• Do not interfere with other people’s computer work.
• Do not snoop around in other people’s computer files.
• Do not use a computer to steal.
• Do not use a computer to bear false witness.
• Do not copy or use proprietary software for which you have not paid.
• Do not use other people’s computer resources without authorization or proper

compensation.
• Do not use other people’s intellectual output.
• Always think about the social consequences of the program you are writing

or the system you are designing.
• Always use a computer in ways that demonstrate consideration and respect

for your fellow humans.

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C Dompu- ictionary

ICT : The technology that provide access to information
Digital camera through telecommunications.
Chat room
: A device that records and stores photographic images
Blog in digital form.

E-Mail : A Web site, part of a Web site, or part of an online
service such as America Online, that provides a venue
for communities of users with a common interest to
communicate in real time.

: A discussion or information site published on the
World Wide Web consisting of discrete entries
(“posts”) typically displayed in reverse chronological
order so the most recent post appears first.

: The sending and receiving messages through
computer.

Recap

• Information and Communication Technologies refers to technologies that
provide access to information through telecommunications.

• A multimedia projector is a tool that is used in ICT to deliver audiovisual
media to entertain, educate, or communicate with people.

• A digital camera records and stores photographic images in digital form.

• Scanner is a computer peripheral or a stand-alone device that converts a
document, film, graphic, or photograph to a digital image, manipulable
through an appropriate software.

• Electronic mail, or e-mail (and mail) is sending and receiving messages
through computer. Messages through e-mail can be in different forms such as
text, image, sound, database, spreadsheet or an application.

• Chat room is a Web site, part of a Web site, or part of an online service such
as America Online, that provides a venue for communities of users with a
common interest to communicate in real time.

• A blog is a discussion or information site published on the World Wide
Web consisting of discrete entries (“posts”) typically displayed in reverse
chronological order so the most recent post appears first.

• Broadcasting is the distribution of audio and video content to a dispersed
audience via any audio or visual mass communications medium, but usually
one using electromagnetic radiation (radio waves).

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Review Yourself

1. State whether the following statements are true or false.
a. Modern information and communication technologies have created a
“global village,” in which people can communicate with others across
the world as if they were living next door.
b. Multimedia projectors allow for presentations that can be used for work
functions, classroom instruction or enjoyment of films and television at home.
c. Blog is the distribution of audio and video content to a dispersed
audience via any audio or visual mass communications medium.
d. Cyber law of Nepal commonly known as the Electronic Transaction and
Digital Signature Act-Ordinance was enacted in Nepal in 2061 BS (2004).
e. Computers are capable of doing many things as per the instructions
given to it.

2. Match the following.
Digital camera The technology that provide access to information

through telecommunications.
ICT A device that records and stores photographic images

in digital form.
E-Mail A Web site, part of a Web site, or part of an online

service such as America Online, that provides a venue
for communities of users with a common interest to
communicate in real time.
Chat room A discussion or information site published on the
World Wide Web consisting of discrete entries
(“posts”) typically displayed in reverse chronological
order so the most recent post appears first.
Blog The sending and receiving messages through
computer.

3. Fill in the blanks.
a. __________________ refers to technologies that provide access to
information through telecommunications.
b. ___________________ is a computer peripheral or a stand-alone
device that converts a, film, graphic, or photograph to a digital image,
manipulable through an appropriate software.

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c. __________________ is a Web site, part of a Web site, or part of an online
service such as America Online, that provides a venue for communities
of users with a common interest to communicate in real time.

d. A __________________ is a discussion or information site published on
the World Wide Web consisting of discrete entries (“posts”) typically
displayed in reverse chronological order so the most recent post
appears first.

e. __________________ refers to any crime that involves a computer
and a network, where the computers may or may not have played an
instrumental part in the commission of a crime.

4. Give one word answer for each of the following.
a. A computer peripheral or a stand-alone device that converts a
document, film, graphic, or photograph to a digital image, manipulable
through an appropriate software.
b. The sending and receiving messages through computer.
c. A Web site, part of a Web site, or part of an online service such as
America Online, that provides a venue for communities of users with
a common interest to communicate in real time.
d. The distribution of audio and video content to a dispersed audience
via any audio or visual mass communications medium, but usually
one using electromagnetic radiation (radio waves).
e. A term denoting the technology that allows people to have long
distance voice communication.

5. Answer the following questions.
a. What is information and communication technology?
b. What is the role of multimedia projector in information and
communication technology?
c. What is a digital signature?
d. What is chat room?
e. What is a blog?
f. What do you understand by broadcasting?
g. What is meant by cyber law?
h. What are the main objectives of Cyber law of Nepal 2061 BS (2004)?
i. What is cyber ethics? What are the ten commandments of cyber ethics?

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Chapter 9

Operating System
Software

Objectives

After completing this chapter, you will be able to:

y Define operating system and list the role of an operating system.
y Explain the different types of operating system.
y Explain how to manage files and folders in Windows 7.
y Explain different types of internal commands and external commands.

C Ooncept verview

An operating system is the most important software
that runs on a computer. It is considered the
backbone of a computer, managing both software and
hardware resources. Operating system is responsible
for everything from the control and allocation of
memory to recognizing input from external devices
and transmitting output to computer display. It also
manages files on computer hard drives and controls
peripherals, like printers and scanners. Without it, the
system cannot function. There is a close relationship
between the power of computer hardware and the
power of its operating system. The faster and more
powerful the CPU and the greater the amount of
memory, better the operating system can function.
Better the operating system can function, the more
useful it can make a computer for its users. The
most popular operating systems include MS-DOS,
Windows 98, Windows NT, Windows XP/Vista/2007,
Mac OS and Linux.

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Need for Operating System

An operating system is a software component that acts as the core of a computer
system. It is the primarily a manager of a computer’s resources. An operating
system is needed because of its following jobs.
• The operating system assists in the execution of user programs. The operating

system provides an environment in which particular software packages can
execute.
• A user submits job to the operating system. Once the operating system accepts
a user’s job, it create several processes and execute them to accomplish the
jobs.
• When a job is submitted by the user, operating system ensures that it gets
the required system resources like memory, processor time, devices, etc. to
accomplish the job. If any of the resources are unavailable, it makes them
available. Similarly, it declaims resources when the job is over.

Role of an Operating System

An operating system is a software component that acts as the core of a computer
system. It is the primarily a manager of a computer’s resources. The major
functions of an operating system are:
• As a resource manager, the operating system keeps track of all the resources

of a computer system. The memory, CPU, data, input, output devices, etc. are
the resources of the computer system.
• It keeps track as to how much memory is free and how much is in use.
• It monitors the status of the input and output devices, i.e., which devices are
in use and in which job.
• It keeps track of the information stored in memory of the computer.
• It keeps track whether the processor is busy or not.

Types of Operating System

Within the broad family of operating systems, there are generally different
categories based on the types of computers they control and the sort of applications
they support. The categories are:

Single-user, single task
Single-user, single tasking operating system is designed to manage the computer
so that one user can effectively do one thing at a time. The Palm OS for Palm
handheld computers is a good example of a modern single-user, single-task
operating system.

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Single-user, multi-tasking
Single-user, multi-tasking operating system support execution of more than one
job at a time on a computer. Microsoft’s Windows and Apple’s Mac OS platforms
are the examples single-user, multi-tasking operating system.

Multi-user
Multi-user operating system allows many different users to take advantage of the
computer’s resources simultaneously. The operating system must make sure that
the requirements of the various users are balanced and that each of the programs
they are using has sufficient and separate resources so that a problem with one
user doesn’t affect the entire community of users. Unix and MVS are examples of
multi-user operating systems.

User Interface

User interface is a program that controls a display for the user and allows the
user to interact with the system. A good user interface makes a computer easy to
use. Through the user interface, the computer accepts your input and presents
you with output.
The most common types of user interfaces are:
• Character User Interface (CUI)
• Graphical User Interface (GUI)

Character User Interface
Character User Interface (CUI) is a mechanism for interacting with a computer
operating system or software by typing commands to perform specific tasks.
The method of instructing a computer to perform a given task is referred to as
“entering” a command. The system waits for the user to conclude the submitting
of the text command by pressing the “Enter” key. MS-DOS is a character user
interface operating system.

Graphical User Interface
Graphical User Interface (GUI) is an
interface for issuing commands to a
computer utilizing a pointing device,
such as a mouse, that manipulates and
activates graphical images on a monitor.
Microsoft Windows is a Graphical User
Interface operating system.

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Microsoft Windows 7
Microsoft Windows 7 is the most widely used operating system for desktop and
laptop computers. It is a GUI-style operating system produced by US-based
Microsoft, the world’s largest software company. When you switch ON your
computer having Windows as the operating system, Windows gets loaded
automatically. The display that appears on your monitor screen is called the
Windows Desktop. It is the background image of a display screen, on which
windows, icons, and other graphical items appear. The Windows Desktop has
various components as shown below:

Icons

Start Menu
Taskbar

My Documents
My Documents provides a default storage location for data files you create in
applications such as WordPad. Double-click the My Documents icon on the
desktop and then double-click the name of the file you want to open.

My Computer
My Computer is a system folder that appears as an icon on the desktop. It allows
you to browse all the disks that are physically attached to your computer. The
contents of the My Computer window depend on the disk drives on your PC and
the network support that is installed.

Recycle Bin
Recycle Bin is a system folder in which Windows 7 stores the items you delete.
Windows 7 puts the deleted objects in the Recycle Bin. These deleted files still
occupy as much disk space as they did before you delete them. The space does
not become available until you empty the Recycle Bin.

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My Network Places
My Network Places is a system folder that displays and allows you to browse
shared resources on other computers. Choosing this object displays the computer
and shared printers in your network.
Taskbar
Taskbar is a long horizontal bar located at the bottom of the screen when you start
Windows for the first time. The taskbar contains three elements: the Start menu
button, buttons for open windows and the time of day indicator at the right end
of the taskbar.
Windows Explorer to View Files
Windows Explorer is a program that helps in managing files/folders. In the
Windows Explorer window, the Folders bar (left pane) shows the hierarchy of
folders in your computer, while the right pane shows the content for the folder
selected in the left pane.
To view files using Windows Explorer, follow these steps:
• Click on the Start button to see the Start menu.
• Choose Programs|Accessories| Windows Explorer.

• On the left side of the Windows Explorer window, click the plus sign (+) to
see the folders it contains.

• Click the minus sign (-) of a folder to hide the folders.
• In Folder bar, click the desired folder to view its contents in the right pane.

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Creating a Folder
A folder is a location on some storage medium in which you can store files and
other folders. You can create a new folder to organize the information stored on
your computer.
To create a folder on the desktop, follow these steps:
• Right-click a blank area on your desktop. A menu appears:
• Point to New on the shortcut menu.
• Click on Folder on the submenu.
• Type a new folder name and then press Enter key.
Creating a File
A file is a collection of related information. You can instantly create, name and
store a new file in the location you want.
To create a file on the desktop, follow these steps:
• Open the folder in which to create new file.
• Right-click an empty area of the desktop or folder. A menu appears:
• Point to New on the shortcut menu.
• Click desired file type on the submenu. A file icon appears with a temporary

file name.
• Type new file name and then press Enter key.

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Renaming Files/Folders
You can rename both files and folders. You can give the file a new name to describe
the contents. This makes it easier to find the file.

To change the file’s/folder’s name, follow these steps:
• Open folder containing file or folder to rename.
• Right-click the file/folder which you want to rename. A menu will pop up.
• Click on Rename.
• Type a new name for the file or folder.
• Press Enter key.

Moving Files/Folders
You can reorganize the files stored on your computer by placing them in different
folders. Moving files is similar to rearranging documents in a filing cabinet to
make them easier to find.

To move a file to a folder, follow these steps:
• Place your mouse pointer over the file that you want to move.
• Press and hold down the left button as you drag the mouse to where you

want to place the file.
• Release the button and the file moves to the new location.

Note:
You can make an exact copy of a file and then place the copy in a new folder. This
lets you to store the file in two different locations. To copy a file, press and hold
down the CTRL key as you drag the file to a new location.

Deleting Files/Folders
Except for files deleted from removable disks, such as pen drives, Microsoft
Windows stores items you delete in the Recycle Bin, where they can be restored
to their original locations, if needed.

To delete a file or a folder, follow these steps:
• Open folder containing files or folders to delete.
• Select files or folders to delete. Windows highlight selected items.
• Drag the selection onto the Recycle Bin.

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MS-DOS

MS-DOS is an acronym that stands for “Microsoft Disk Operating System. It is a
single-user, single tasking operating system. It was developed for the IBM range
of computers at Microsoft Inc, USA. The development of MS-DOS originally
started in 1981 and was first released as MS-DOS 1.0 in 1982. MS-DOS, like other
operating systems, oversees operations such as disk input and output, video
support, keyboard control and many internal functions related to program
execution and file maintenance.
The main features of MS-DOS are:
• It can interpret your keyboard and mouse input.
• It can display information on the monitor.
• It can store and retrieve information from the disk drive.
• It can control a printer.
• It can work with other hardware attached to the computer.

Booting a System

Booting is a bootstrapping process that starts operating systems when the user
turns on a computer system. A boot sequence is the initial set of operations that
the computer performs when power is switched on. The bootloader typically
loads the main operating system for the computer. Once the operating system is
loaded, it is ready for users to run applications.

Types of Booting
The computer can be booted in one of the two ways:
• Cold booting
• Warm booting

Cold booting
Booting a system by switching on the power, the computer reads its RAM space
and searches for the DOS system files from the disk drives. As soon as it finds the
system files, the DOS system files are loaded from the secondary media into the
main memory of the computer. This is known as cold booting.

Warm booting
Booting a system by pressing CTRL+ALT+DEL key at the same time is called
warm booting. The program in RAM gets deleted, searches for DOS system files
and loads the system files into the main memory of the computer.

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Main Files for Booting
The main files necessary to start up a computer are:

IO.SYS
IO.SYS is an essential part of MS-DOS. It contains device drivers for computer
peripherals such as the keyboard, hard disk, serial port and real-time clock.

MSDOS.SYS
MSDOS.SYS is an important system file on MS-DOS and Windows 9x systems.
It is run after IO.SYS. In MS-DOS, it contains the core operating system code, the
kernel. By default, the file is located in the root directory of the bootable drive/
partition (normally C:\) and has the hidden, read-only and system file attributes
set.

COMMAND.COM
COMMAND.COM is the command interpreter for MS-DOS.

Directory

A directory is a catalog for files stored on the disk of a personal computer. It is
used to organize your data by grouping related files in one area of your disk. It
contains the name of the file, the size of the file, date and time of file creation or
modification.
There are two types of directories:

Root directory
A root directory is the top-level directory on a disk. It is created automatically
when you format a disk and start storing files on it.

Sub-directory
A sub-directory is a directory within another directory. The directory that contains
sub-directories is called a parent directory.
The rules for writing the directory names are:
• Directory name must not exceed eight characters.
• The extension can be up to three characters. They generally do not have an

extension for simplicity.
• Blank spaces are not allowed.
• Both the uppercase and lowercase letters are accepted.

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File

A file is a collection of logically related information. It may be a program, a
document, a database or some other collection of bytes. Each file must have its
own unique name. This name has two parts: a filename and an extension.
• Filename is the identifier of a file on a disk.
• Extension is a set of characters added to a filename that serves to extend or

clarify its meaning or to identify a file as a member of a category.
Let’s look at a typical file:
COMMAND . COM

Filename Extension
The rules that govern filenames in DOS are discussed below:
• Filenames can have a maximum of eight characters from A to Z or 1-9 or

special characters such as $ & # @ ! % ‘ ( ) - { } _ ~
• Filenames should not contain any blank character (space) and any of the

following characters: ? / \ [ ] ÷ : | < > =
• Each extension can contain a maximum of three characters.
• Files with extensions .EXE, .COM and .BAT are called executable files and

should be used only for a very specific purpose.
• The character dot (.) is used to separate the filename from its extension.

Wildcard Characters

Wildcard characters are the special characters that can be used to represent any
character or series of characters in a statement. The wildcard characters are used
to restrict the scope of a DOS command to only those files which match the pattern
specified. There are two types of wildcard characters:

Asterisk (*) wildcard

The asterisk (*) wildcard is used to substitute a set of characters.

For example:

C:\>DIR green.*

Displays all the filenames having their file name as green, irrespective of the
extension.

C:\>DEL *.exe

Deletes a group of file ending with an extension .exe from drive C:

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Question mark (?) wildcard

The question mark (?) wildcard is used to substitute a single character at a
particular position.
For example:
C:\>DIR p?????.exe
Displays all the files having 6 characters long with the first character as p and the
extension as exe.

C:\>DEL B????.txt
Deletes all the files having 5 characters long with the first character as B and the
extension is .txt.

Command

Command is an instruction to a computer program that, when issued by the user,
causes an action to be carried out. Commands are usually either keywords typed
at the keyboard or chosen from a menu. MS-DOS command can have up to three
parts- a command name, parameter and switch. All the MS-DOS commands have
command names. MS-DOS command uses the following syntax:
COMMAND [option]

Command Types

The entire set of commands available in DOS can be divided into two types.
These are:
• Internal commands
• External commands

Internal commands
The commands that COMMAND.COM recognizes are called internal commands.
These commands reside in memory as long as the machine is at the system prompt
(C:\>) level.

External commands
The commands that are stored on the system disk as program files are called
external commands. They must be read from the disk before they are executed.
Any filename with an extension of .COM, .EXE, or .BAT is considered as an
external command.

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Date Command
Date command is used to display or set the system date. The syntax is:
DATE <mm-dd-yy>
Examples:
• C:\>DATE
Displays the current date and allows you to enter new date.
• C:\>DATE 02-04-2015
Sets the new date to 02-04-2015.

Time Command
Time command allows you to enter or change the time known to the system. The
syntax is:
TIME hh:mm [:ss] [:cc] [a|p]
Examples:
• C:\>TIME
Displays the current time and allows you to change the time.
• C:\>TIME 10:00P
Sets the system time to 10:00 P.M.

Type Command
Type command displays the contents of a text file on the screen. The syntax is:
TYPE [drive:] [path] filename
Examples:
• C:\>TYPE AUTOEXEC.BAT
Allows you to view the content of a file AUTOEXEC.BAT.
• C:\>TYPE ABC>PRN
Prints the contents of ABC file.

Ren (Rename) Command
Ren (Rename) command allows you to rename a file or group of files. The syntax
is:
RENAME [drive:][path][old filename][new filename]

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or
REN [drive:][path][old filename] [new filename]
Examples:
• C:\>REN *.COM *.EXE
Renames all the files having the extension .COM into the extension .EXE,
with the same corresponding primary names.

Copy Command
Copy command copies one or more files to another location. This command also
appends files. The syntax is:
To copy files
COPY [drive:] [source] [drive:] [destination]
To append files
COPY pathname1+pathname2 [...] pathname n
Examples:
• C:\>COPY red.txt B:
Copies the file red.txt from drive C: to drive B:
• C:\>COPY A:\red\*.exe B:
Copies all the files of A: having exe as an extension of the subdirectory red to

B: drive staying in C:

Del (Erase) Command

Del (Erase) command allows to delete one or more unwanted files. The syntax
is:
DEL [drive:][path]filename [/p]
or
ERASE [drive:][path]filename [/p]

Examples:
• C:\>DEL *.exe
Deletes a group of file ending with an extension .exe from drive C:.
• C:\>DEL B????.txt
Deletes all the files having 5 characters long with the first character as B and

the extension is .txt.
• C:\>DEL abcd??.txt
Deletes all the files whose name is 6 characters wide starting with abcd having

txt as an extension.

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Edit Command
Edit command starts the MS-DOS editor, a text editor used to create and edit
ASCII text files. The syntax is:
EDIT [/b] [/h] [/r] [/s] [/<nnn>] [/?] [file(s)]
Examples:
• C:\>EDIT abc.txt
Starts the MS-DOS editor and allows to edit text filenamed abc.txt.
• C:\>EDIT a:\abc.txt
Allows you to edit text filenamed abc.txt of drive A:.

Format Command
Format command formats the disk in the specified drive to accept MS-DOS files.
The syntax is:
FORMAT drive:[/v[:label]] [/q][/s][/f:size]
Examples:
• C:\>FORMAT A:
Formats a disk in drive A:
• C:\>FORMAT A:/S
Formats a disk in drive A: and copies the system files on to it.
• C:\>FORMAT A:/Q
Performs a quick format of a disk in drive A:
• C:/>FORMAT A:/V:Disk
Formats a disk in drive A: and assigns the volume label Disk.

Md (Mkdir) Command
Md (Mkdir) command allows you to create new sub-directories. The syntax
is:
MD [drive:] path
or
MKDIR [drive:] path
Examples:
• C:\>MD JBD
Creates a new sub-directory called JBD on drive C:
• C:\>MD A:\JBD
Creates a new sub-directory called JBD on drive A:

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Cd (Chdir) Command
Cd (Chdir) command displays working (current) directory and/or changes to a
different directory. The syntax is:
CHDIR [drive:] [path]
or
CD [drive:][path]
CHDIR [..] or CD [..]
CHDIR [\] or CD [\]
Where,
.. Specifies that you want to change to the parent directory.
\ Specifies that you want to change to the root directory.
Examples:
• C:\>CD JAY
Changes to a sub-directory called JAY of drive C:

Rd (Rmdir) Command
Rd (Rmdir) removes an existing sub-directory from a disk. The directory to be
removed must be empty. The syntax is:
RD [drive:] path

or
RMDIR [drive:] path
Examples:
• C:\>RD JAY
Removes a sub-directory called JAY from drive C:

Dir Command
Dir command displays list of files and subdirectories stored on the disk. The
syntax is:
DIR [drive:][path][filename] [/p][/w] [/a[[:]attributes]][/o[[:] sortorder]] [s] [/b] [/l]
Examples:
• C:\>DIR/P
Displays all the files and directories in pagewise of drive C:.

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C Dompu- ictionary

Operating system : The most important software that runs on a computer.

User interface : A program that controls a display for the user and
allows the user to interact with the system.

Booting : A bootstrapping process that starts operating systems
when the user turns on a computer system.

Directory : A catalog for files stored on the disk of a personal
computer.

File : A collection of logically related information.

Command : An instruction to a computer program that, when
issued by the user, causes an action to be carried out.

Windows 7 : A GUI-style operating system produced by US-based
Microsoft, the world’s largest software company.

Recap

• Operating Systems are responsible for everything from the control and
allocation of memory to recognizing input from external devices and
transmitting output to computer displays.

• Single-user, single tasking operating system is designed to manage the
computer so that one user can effectively do one thing at a time.

• Graphical User Interface (GUI) is an interface for issuing commands to a
computer utilizing a pointing device, such as a mouse, that manipulates and
activates graphical images on a monitor.

• Microsoft Disk Operating System is a single-user, single tasking operating
system.

• Booting is a bootstrapping process that starts operating systems when the user
turns on a computer system.

• A directory is a catalog for files stored on the disk of a personal computer.

• A file is a collection of logically related information.

• Wildcard characters are the special characters that can be used to represent
any character or series of characters in a statement.

• Command is an instruction to a computer program that, when issued by the
user, causes an action to be carried out.

• Microsoft Windows 7 is the most widely used operating system for desktop
and laptop computers.

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Review Yourself

1. State whether the following statements are true or false.

a. The faster and more powerful the CPU and the greater the amount of
memory, the better the operating system can function.

b. The Palm OS for Palm handheld computer is a good example of a modern
multi-user operating systems.

c. Graphical User Interface (GUI) is a mechanism for interacting with a
computer operating system or software by typing commands to perform
specific tasks.

d. My Documents provides a default storage location for data files you
create in applications such as WordPad.

e. My Network Places is a system folder that displays and allows you to
browse shared resources on other computers.

2. Match the following.

Windows Explorer A bootstrapping that starts operating systems
when the user turns on a computer system.

Command A catalog for files stored on the disk of a personal
computer.

Directory A collection of logically related information.

Booting A program that helps in managing files/folders.

File An instruction to a computer program that, when
issued by the user, causes an action to be carried
out.

3. Fill in the blanks.

a. An _______________ is a software component that acts as the core of a
computer system.

b. A _____________ is a mechanism for interacting with a computer
operating system or software by typing commands to perform specific
tasks.

c. A ________________ sequence is the initial set of operations that the
computer performs when power is switched on.

d. The commands that COMMAND.COM recognizes are called
______________ commands.

e. _____________ is a system folder in which Windows 7 stores the items
you delete.

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4. Answer the following questions.
a. What is an operating system?
b. List any four major functions of an operating system.
c. What does booting a system refer to? Name the essential files required
to boot a system.
d. What is a directory? What does it contain?
e. What is a file? What is file made up of?
f. What is a wildcard character?
g. What are the two wildcard characters used in DOS? Mention their uses.
h. What is an extension? List out some typical file extensions and their
meanings.
i. What is a command? Distinguish between internal command and
external command.
j. What is Microsoft Windows?
k. What is a desktop?

5. Write down the appropriate DOS command(s) to perform the following task.
a. Display the current date and allows you to enter new date.
b. Copy the file jay.txt from drive C: to drive B:
c. Delete a group of file ending with an extension ext from drive C:.
d. Format a disk in drive A: and copies the system files on to it.
e. Performs a quick format of a disk in drive A:
f. Formats a disk in drive A: and assigns the volume label Disk.
g. Display all the files having com as an extension.

6. Write the effects of the following MS-DOS commands.
a. C:\>TIME 10:00P
b. C:\>COPY A:\jay\*.exe
c. C:\>FORMAT A:/Q
d. C:\>RD jay
e. C:\>DIR/P
f. C:\>FORMAT A:/S
g. C:\>DIR r????.exe

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Hands-On Practice Time

(use MS-DOS)
SET A

1. Display date in your computer system.
2. Display time in your computer system.
3. Create a file called Earth in drive C: and type two lines about Earth.
4. Rename the file Earth to Universe.
5. Display the contents of a file Universe and add one more line to it.
6. Create a subdirectory called Life in drive C:
7. Change over to the newly created directory.
8. Copy the file Universe to your newly created directory.
9. Display the contents of your directory.
10. Delete the file from the directory.
11. Remove the directory you have created.

(use WINDOWS 7)
SET B

1. Switch on the computer and observe the screen while it boots.
2. Create a new sub-folder named as “JAY” on the desktop.
3. Copy any three files from the My Document folder and store them in

JAY.
4. Rename the sub-folder JAY as JBD.
5. Move the sub-folder named JBD to the Recycle Bin.
6. Restore the sub-folder named JBD from the Recycle Bin.
7. Delete the sub-folder JBD.
8. Empty the Recycle Bin.

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Chapter 10

More Features in
Word 2010

Objectives

After completing this chapter, you will be able to:

y Define Word processing and list the features of Microsoft Office Word.
y Explain the steps to display non-printing characters.
y Explain the formatting text with styles.
y Define tab and explain the different types of tab stops.
y Define mail merge and explain the steps to use mail merge.

C Ooncept verview

Word processing is one of the most widely used
applications installed on the computer for the
purpose of writing, editing and creating certain
reports or documents. It had been providing the
users with many benefits and this is found to be one
of the most famous computer applications which
are used by the people on regular basis. Different
sort of functions can also be performed in the
word processing unit. For the working of the word
processing it must be ensured by the users that they
have the word processor installed in the computer,
where they would be able to write the text and apart from this the computer is
another important thing that must be possessed by the users. In most of the cases
in word processing the users can also used a printer as well for the purpose of
taking the prints so that the entire document that had been created can be easily
read by the user. Some of the popular word processing software packages are
Microsoft Word, Notepad, WordPad and Atlantis Word Processor.

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Microsoft Word 2010
Microsoft Word is a full-featured word processing program created by Microsoft
and first released for Windows in 1995. Microsoft Office 2010 (also called Office
2010 and Office 14) is a version of the Microsoft Office productivity suite for
Microsoft Windows. It is the successor to Microsoft Office 2007 and the predecessor
to Microsoft Office 2013. Office 2010 includes extended file format support, user
interface updates, and a changed user experience.
To load Microsoft Office Word 2010, follow these steps:
• On the Windows task bar, click the Start button, then click All Programs. A

menu of installed programs appears.
• Click the Microsoft Office folder.
• Next click Microsoft Word 2010. Word opens and a new blank document

appears. When you start Microsoft Office Word, the default Word window
appears:

Creating A Document
When you start keying text at the insertion point in an open document, you have
begun to create a Word document. As you type, Word inserts the text to the left of
the insertion point and uses the program’s defaults for margins and line spacing.
Word also has a number of tools and automatic features to make creating a
document easier, including nonprinting characters,AutoComplete, and Word
Wrap. When you key text into a new document, it will be inserted to the left of
the insertion point and the document will be created using Word’s defaults for
margins and line spacing. The margin defaults are set to one-inch top, bottom,
left, and right margins; the line spacing is set to 1.15;and the spacing after is set
to 10 points.

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