Approved by the Government of Nepal, Ministry of Education, Curriculum Development
Centre (CDC), Sanothimi, Bhaktapur, Nepal as an additional material for schools.
JCBD omputer
Studies
10
Authors
Sushma Pradhan
Kiran Kumar Shrestha
JBD Publication Pvt. Ltd.
Bhotahity, Kathmandu, Nepal
Published By
JBD Publication Pvt. Ltd.
Bhotahity, Kathmandu, Nepal
P.O. Box 8897, Tel: 01 - 4252371, Fax: 01 - 4221880
Email: [email protected]
Web : www.jbdbooks.com
© Reserved with publishers
First Edition : 2010 (2068 BS)
Second Edition (Revised and Updated) : 2015 (2072 BS)
ISBN: 978-9937-544-81-8
Authors:
Mrs. Sushma Pradhan
Mr. Kiran Kumar Shrestha
Mahabir Offset Press, Tel: 025-521634
Preface
Progress in information technology is affecting our lives more than
ever. Computers have played a key role in this, and they too have
evolved at a fast pace. Today, they are used in almost every sphere of
life. It has become imperative for us to know the usage of computers.
Computer education makes a child understand computer and its basic
functions.
The ‘Computer Studies’ series is a set of computer books meant for
the students of Primary and Middle School levels. The books have
followed the guidelines prepared by CDC, Government of Nepal. The
book 10 of this series is recommended for use in Class 10.
The series ‘Computer Studies’ has been written to impart computer
skills to students at different school stages. It is well-focused on building
a strong foundation and achieving age-appropriate competency. Each
chapter in the book has a separate overview with plenty of illustrations
and text supported by screenshots on a Windows 7 platform. It is
written in a very simple language and chapters are presented in a user-
friendly format.
Suggestions for further improvement from the users of the series will
be whole-heartedly appreciated and gratefully acknowledged.
Authors
Contents 5
26
1. Computer Network and Telecommunications 40
2. The Internet and its Services 51
3. Computer Security System 59
4. Computer Viruses 68
5. Cyber Law and Computer Ethics 77
6. Multimedia and its Applications 91
7. Computer Number System 130
8. Database Management System 159
9. Modular Programming 178
10. File Handling in QBASIC 209
11. Introduction to C-Language 217
Solved Model Test Paper 218
Unsolved Practical Test Paper
Project Work
Chapter 1
COMPUTER
NETWORK
AND
TELECOMMUNICATIONS
Objectives
After completing this chapter, you will be able to:
y Define computer network.
y Identify and 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 Explain the different types of physical topologies.
y Explain the different types of communication media and networking devices.
C Ooncept verview
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 beams. Computer network
facilitates the sharing of hardware and software
resources among different users working on
different computers.
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Computer Network Defined
Computer network, often simply referred
to as a network, is a group of computers and
devices interconnected by communication
channels that facilitate communications
among users and allows users to share
resources. It includes network media, such
as a cable to carry network data; network
adapter card to translate the data between
the computer and the network media;
a network operating system to enable a
machine to participate in the network; and
a network protocol to control the network
communications.
Advantages of Computer Network
Computer networks can be used for several purposes:
Facilitating communications
Using a network, people can communicate efficiently and easily via e-mail,
instant messaging, chat rooms, telephone, video telephone calls and
videoconferencing.
Sharing files, data and information
In a network environment, any authorized user can access data and information
stored on other computers on the network. The capability of providing access to
data and information on shared storage devices is an important feature of many
networks.
Sharing hardware
In a network environment, each computer on a network can access and use
hardware on the network.
Sharing software
Users connected to a network can access application on the network.
Redundancy
Networks reduce the need for hard copies of all documents. By sharing files over
the network, the need to share paper copies of reports or any other information
can be eliminated or greatly reduced.
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Disadvantages of Computer Network
Security issues
One of the major drawbacks of computer network 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 interconnectivity of workstations. Such spread can
be dangerous if the computers have important database which can get corrupted
by the virus.
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. There are many different types of servers. For
example:
File server: a computer and storage device dedicated to
storing files. Print server: a computer that manages one
or more printers, and a network server is a computer that
manages network traffic. Database server: a computer
system that processes database queries.
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)
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. Some of the
features of network operating system are:
• Add, remove and manage users who wish to use resources on the network.
• Allow users to have access to the data on the network. This data commonly
resides on the server.
• Allow users to access data found on other network such as the internet.
• Allow users to access hardware connected to the network.
• Protect data and services located on the network.
• Enables the user to pass documents on the attached network.
Some of the popular network operating systems are: Novell Netware, Microsoft
Windows NT, Microsoft Windows Server 2008 and Linux.
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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
listed in the next page.
TCP/IP
Transmission Control Protocol/Internet Protocol is the standard internet
communication protocol that allows digital computers to communicate over long
distances. The Internet is a packet-switched network, in which information is
broken down into small packets, sent individually over many different routes at
the same time, and then reassembled at the receiving end. TCP is the component
that collects and reassembles the packets of data, while IP is responsible for
making sure the packets are sent to the right destination.
Simple Mail Transfer Protocol
SMTP (Simple Mail Transfer Protocol) is a protocol for sending email messages
across the Internet. It is a ‘push’ protocol and it cannot be used to ‘pull’ the
messages from the server. SMTP is used for outgoing mail while POP3 and IMAP
are used for incoming mail.
Post Office Protocol
Post Office Protocol is an Internet standard protocol used by local e-mail clients to
retrieve e-mail from a remote server over a TCP/IP connection. A POP-compatible
electronic mail program, which runs on your workstation or PC, establishes a
connection with the POP server, and detects that new mail has arrived. You can
then download the mail to the workstation or computer, and reply to it, print it,
or store it, as you prefer.
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. Different types of networks
are distinguished based on their size (in terms of the number of machines), their
data transfer speed, and their reach. The entire computer network can be clas-
sified into three categories depending on the company’s size and communica-
tion needs. They are: Local Area Network (LAN), Metropolitan Area Network
(MAN) and Wide Area Network (WAN).
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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 pur-
pose 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 connect-
ed through public networks such as the telephone system. Sometimes they can
be connected through leased lines. The largest WAN in existence is the Internet.
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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
• 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 network, 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.
The characteristics of client/server
network are:
• Reduced network traffic.
• The cabling scheme can range from the simplest to the most complicated
ones.
• Centralized data and security.
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. Some
peer networks, however, utilize the Internet and are geographically dispersed
worldwide.
You can configure computers in peer to peer workgroups to allow sharing of files,
printers and other resources across all of the devices. Peer networks allow data to
be shared easily in both directions, whether for downloads to your computer or
uploads from your computer.
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The characteristics of peer-to-peer network are:
• Covers small geographical area.
• Simple cabling scheme.
• No central administrator who sets the network policies.
• No extra investment in server hardware or software is required.
Physical Topology
The configuration or physical arrangement, of the devices in a communications
network is called the network topology or network architecture. Network archi-
tecture 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.
The advantages of the bus topology are:
• Simple architecture.
• Low installation cost.
• Easy to add a new node.
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The disadvantages of bus topology are:
• Fault diagnosis is difficult.
• If problem occurs on the backbone “cable”, the entire network will go down.
• All computers in the network must have good communication and decision-
making capability.
Ring Topology
A ring topology is a computer network topology in which each node (network
computer) and device are connected to each other forming a large circle. Each node
acts as a transmitter and a receiver, and data is transmitted in one direction only.
Data travels from node to node, with each node along the way handling every
packet. Each packet is sent around the ring until it reaches its final destination.
Since there is only one pathway in a ring topology, ring networks are generally
disrupted by the failure of a single link.
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The most well known example of a ring topology is Token Ring.
The advantages of ring topology are:
• Single cable connection between the devices.
• Short cable connection which causes an increase in network reliability.
• Can use the optical fiber to increase the speed and to reduce the problem of
electrical interference.
The disadvantages of ring topology are:
• Any node failure causes network failure.
• Difficult to diagnose faults.
• Network reconfiguration is difficult.
Star Topology
A star topology is a computer network topology. It is a common network setup
where the computers and other devices on the network are connected to a central
or master computer, also known as the hub. The hub, along with the leaf nodes
and the transmission lines connecting them form the topology of a star. The cen-
tral hub controls all the functions and transmissions of the networks that are con-
nected to it. The configuration of the star topology is done with the help of optical
fiber cable, twisted pair cable or a coaxial cable.
The advantages of star topology are:
• Easy to install and wire.
• Gives a better performance than any other network topology as there is no
clogging of nodes.
• The faulty and defective parts of the network can be easily replaced.
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The disadvantages of star topology are:
• If the central hub has some errors, then the communication between the
systems fail, as the nodes are highly dependent on the proper functioning of
the central hub.
• More cabling is needed as compared to bus or ring topologies.
• The traffic of the network is also disrupted if the node that occupies a major
portion in the processing capability of the central node is faulty.
Transmission Modes
When the node has data to send to another node in a network, it must establish
a connection to the other node. This connection will be used to send the packet.
If a connection cannot be established, the packet cannot be sent. There are three
ways of transmitting data from one point to another.
Simplex Transmission Mode
Simplex transmission mode is a mode of radio transmission in which
communication takes place between two stations in only one direction at a time.
A device using the simplex mode of transmission can either send or receive data,
but it cannot do both. Simplex mode are seldom used because a return path is
generally needed to send acknowledgment, control, or error signals. It resembles
listening to the radio-there is a one-way path from the transmitting station to
your radio.
Direction of Data
Terminal
Mainframe
Half Duplex Transmission Mode
Half duplex transmission mode is a mode of transmission in which data flows
in both directions, but only in one direction at a time. The transmitting and re-
ceiving ends take turns sending data. The transmitting end sends data while the
receiving end listens. Once the channel is clear, the receiving end sends any data
it has and the other nodes listen. This mode is commonly used for linking com-
puters together over telephone lines.
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Full Duplex Transmission Mode
Full duplex transmission mode is a mode of transmission in which data is
transmitted in both the directions simultaneously on the same channel. Commonly,
servers are connected to a full duplex device that enables them to receive data from
one node while sending data to another.
Both ways, simultaneously
Communication Channel Bandwidth
The bandwidth of communication channel determines the rate or speed at which
data can be transmitted over a channel. Bandwidth is the media’s total capabil-
ity to carry data at any given instance. Technically, bandwidth is the difference
between the highest and lowest frequencies the media can handle. It is measured
in bits per second.
There are three bandwidth for communication channels:
Narrow-Band Channels
Narrow band channels handle slow data volumes and their transmission rate is
between 40 to 100 bits per second (bps). Telegraph lines are examples of narrow
band channels.
Voice-Band Channels
Voice band channels handle moderate data volumes and their transmission rate
is between 110 to 9600 bps. Standard telephone lines are examples of voice band
channels.
Broad-Band Channels
A data transmission channel that can handle frequencies higher than the normal
voice-grade line limit of 3 to 4 kilohertz; it can carry many voice or data channels
simultaneously or can be used for high-speed single-channel data transmission.
Broad-band channel s handle large volumes of data and transmits data at high
speeds. Microwave, coaxial cables and fiber optics are examples of broad-band
channels.
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Media Types
Communication media are the electronic roadways along which the signals are
transferred. There are two types of communication media:
• Guided media
• Unguided media
Guided Media
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 conduc-
tive media like wires, coaxial cables or fibre optics.
Copper Media
Copper cable is a type of bounded media that uses one or more copper conduc-
tors 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 inexpen-
sive. Twisted pair cable can be:
• Unshielded Twisted Pair (UTP)
• Shielded Twisted Pair (STP)
• Unshielded Twisted Pair (UTP)
Unshielded Twisted Pair (UTP) consists of two unshielded wires twisted
around each other within the cable to carry a differential signal. Typically it
contains four pairs of stranded or solid conductors. It is inexpensive, reliable
and supports data transfer rates up to 1 Gbps. It supports distances of up to
100 meters.
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• Shielded Twisted Pair (STP)
Shielded Twisted Pair (STP) consists of wires wrapped in a metal sheath
to provide extra protection from external interfering signals. STP is more
difficult to install and is more expensive than UTP. STP has a shorter distance
than UTP (only 90 meters) but it has better noise rejection. STP cable grades
are called types and they range from type 1 to type 9 with types 1, 1A, 2A and
6A used in networks.
Coaxial Cable
Coaxial cable (Coax) known by its common name just “coax,” is so named
because of the physical relationship between the center conductor and the shield
where they share a COmmon AXis. It is a round, flexible, two conductor cable
consisting of a copper wire, a layer of protective insulation, a braided metal mesh
sleeve, and an outer shield, or jacket of polvinyl chloride.The shield prevents
signals transmitted on the centre wire from affecting nearby components and
prevents external interference from affecting the signal carried on the centre
wire. It supports a physical bus topology with a maximum transmission speed
of 10 Mbps.
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.
Coaxial cable (Coax) Fibre optic cable
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Unguided Media
Unguided media uses a transmission carrier to send data signals through the air
instead of cables. It is electromagnetic waves in the form of radio, microwave,
infra-red or others.Unguided media technologies have two distinct advantages
for businesses over guided media; first, they are generally easier to install and
reconfigure; and second; they afford client machines a lot of mobility.
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 infrared, computers can transfer files
and other digital data between each other. Infrared transmission requires line-
of-sight transmissions. That means the sender and receiver must be aligned so
that nothing obstructs the path of the infrared wave. Infrared 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 infrared port for infrared communication.
Microwave Transmission
Microwave transmission is used extensively in situations when physical
transmission media is impractical or difficult to install, for example between high
buildings, across rivers, mountains, jungles and remote areas. The microwave
transmission consists of a transmitter, receiver and the atmosphere. Microwaves
are transmitted via earth atmosphere between two stations. It can be used for only
short distances up to 50 km. 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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Network Devices
Network media, both bounded and unbounded carry the data across your
network. To move data around the network on the media, network connectivity
devices are needed. Network connectivity devices connect clients to the network
and assist in moving data around a network in the most efficient manner. Some
of the devices commonly used in network connectivity are network hub, network
switch, repeaters, bridges, routers, gateway and MODEM.
Ethernet hub
Ethernet hub is a small, simple, inexpensive
device that joins multiple computers together. A
cable connects the network cards on each device
to one of the ports on the hub. Many network
hubs available today support the Ethernet
standard. There are two types of hubs: passive
hub and active hub. Passive hub do not amplify
the electrical signal of incoming packets before
broadcasting them out to the network whereas
active hub can regenerate or amplify a signal.
Network Switch
Network switch is a small hardware device that joins multiple computers
together within one Local Area Network. Network switches appear nearly
identical to network hubs, but a switch generally contains more intelligence
(and a slightly higher price tag) than a hub. Unlike hubs, network switches are
capable of inspecting data packets as they are received, determining the source
and destination device of each packet, and forwarding them appropriately. By
delivering messages only to the connected device intended, a network switch
conserves network bandwidth and offers generally better performance than a
hub. Most consumer-grade network switches provide either 4 or 8 connections
for Ethernet devices.
Network Repeater
Network repeater is a device used to expand the boundaries of a wired or wireless
(WiFi) local area network (LAN). The repeaters would amplify the data signals
before sending them on to the up linked segment, thereby countering signal
decay that occurs over extended lengths of wire. Modern Ethernet networks use
more sophisticated switching devices, leaving the wireless flavour of the network
repeater a more popular device for use with wireless LANs (WLANs) at work
and home.
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Bridge
Bridge is a networking device that filters data traffic at a network boundary.
Bridges reduce the amount of traffic on a LAN by dividing it into two segments.
Bridges inspect incoming traffic and decide whether to forward or discard it.
Router
Router is a device in computer networking that forwards data packets to their
destinations, based on their addresses. It sends data between networks by
examining the network addresses contained in the packets they process. It extracts
the destination of a packet it receives, selects the best path to that destination, and
forwards data packets to the next device along this path.
Gateway
Gateways are the indispensable components in order to achieve communications
between terminals connected to heterogeneous networks that use different
protocols and have different network characteristics. It provides the connectivity
between remote systems at remote locations with the target systems of interest
to enable different network applications. It also manages its client devices,
aggregates their data, and performs other related tasks. It provides mutual
communication by performing communication protocol conversion between the
public communication network and the private communication network.
MODEM
Modem, short for modulator-demodulator is an electronic device that converts
a computer’s digital signals into specific frequencies to travel over telephone or
cable television lines. It converts the discrete stream of digital ON-OFF electrical
pulses used by computers into the continuously variable analog wave patterns over
existing telephone lines. Digital pulses cannot cover large distances effectively. A
modem is needed to modulate or convert the digital pulses to analog waves for
transmission. Another modem at the receiving end demodulates the signal i.e
recovers the digital signal from the analog signal. Thus, modems are needed at
both the sending and the receiving ends.
Wireless Access Points
Wireless Access Point is a device that allows wireless communication devices to
connect to a wireless network using Wi-Fi, Bluetooth or related standards. The
WAP usually connects to a router, and can relay data between the wireless de-
vices (such as computers or printers) and wired devices on the network. With the
advent of the Wireless Access Point, network users are now able to add devices
that access the network with few or no cables.
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C Dompu- ictionary
Client : A network computer that utilizes the resources of
Peer other network computers.
Protocol : A communications model in which each party has
Server the same capabilities and either party can initiate a
communication session.
Hub
Modem : A set of rules by which computers communicate with
each other over a network.
: A computer designed to process requests and deliver
data to other (client) computers over a local network
the Internet.
: A device with multiple ports that allow network
devices to be connected together.
: An electronic device that converts a computer’s
digital signals into specific frequencies to travel over
telephone or cable television lines.
Recap
• Computer network is a group of computers and peripheral devices connected
through data communication system.
• Local Area Network is a combination of hardware, software and
communications channels that connect two or more computers within a
limited area.
• Wide Area Network is a geographically dispersed telecommunications
network.
• Client/Server network is a network in which servers provide services to
clients.
• 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.
• A star topology is a common network setup where the computers and other
devices on the network are connected to a central or master computer, also
known as the hub.
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Review Yourself
1. State whether the following statements are true or false:
a. The function of a computer server is to store, retrieve and send or “serve”
files and data to other computers on its network.
b. TCP/IP is a ‘push’ protocol and it cannot be used to ‘pull’ the messages
from the server.
c. LAN is a telecommunications network, usually used for connecting
computers, that spans a wide geographical area.
d. A ring network structure consists of computer connected to a single
length of cable arranged in a ring.
e. Unbounded media uses a transmission carrier to send data signals
through the air instead of cables.
2. Fill in the blanks.
a. A _______________ is an operating system (OS) designed to allow shared
file and printer access among computers in a network.
b. ______________ is a Internet standard protocol used by local e-mail clients
to retrieve e-mail from a remote server over a TCP/IP connection.
c. ______________ is a network in which resource sharing, processing and
communications control are completely decentralized.
d. The configuration or physical arrangement, of the devices in a
communications network is called the_______________.
e. ______________ is a common network setup where the computers
and other devices on the network are connected to a central or master
computer, also known as the hub.
3. Match the following.
Router An electronic device that converts a computer’s digital
signals into specific frequencies to travel over telephone or
cable television lines.
Modem A device that connects multiple networks that use the same
protocol.
LAN An operating system (OS) designed to allow shared file and
printer access among computers in a network.
WAN A combination of hardware, software and communications
channels that connect two or more computers within a
limited area.
NOS A geographically dispersed telecommunications network.
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4. Select the best answer from the list of choices:.
a. _________________ provide centralized access and storage for resources
that can include applications, files, printers or other hardware, and
specialized services such as email.
i. Node ii. Client iii. Server
b. The native protocol of the Internet and is required for Internet connectivity.
i. TCP/IP ii. HTTP iii. AppleTalk
c. A computer component that allows computers to communicate over a
computer network.
i. NIC ii. Connector iii. Modem
d. A text based protocol in which message text is specified along with the
recipients of the message.
i. TCP/IP ii. POP iii. SMTP
e. A combination of hardware, software and communication channels that
connect two or more computers within a limited area.
i. LAN ii. MAN iii. WAN
f. A computer network topology in which each node (network computer)
and device are connected to each other forming a large circle.
i. Bus ii. Ring iii. Star
5. Give the appropriate technical term for the following.
a. A set of rules by which computers communicate with each other over a
network.
b. A computer designed to process requests and deliver data to other (client)
computers over a local network or the Internet.
c. The difference between the highest and lowest frequencies of a
transmission channel.
d. A device with multiple ports that allow network devices to be connected
together.
e. A device that allows computers to be joined together in a LAN, or local
area network.
f. An operating system (OS) designed to allow shared file and printer access
among computers in a network.
g. A combination of hardware, software and communications channels that
connect two or more computers within a limited area.
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24 Computer Studies-10
6. Give the full forms of the following abbreviation. b. WAN
a. LAN d. STP
c. UTP f. MODEM
e. NIC
7. Answer the following questions.
a. What is a computer network? How is it useful?
b. What are the advantages and disadvantages of computer network?
c. What are the hardware and software components of computer network?
d. Define the following terms:
i. Server ii. Client
iii. Network Operating System
e. What is a network interface card? Explain its usage in a computer system.
f. What is a communication protocol? What are the normal functions
performed by these protocols?
g. What is local area network? What are its main objectives?
h. What is WAN? How does if differ from MAN?
i. What is a client/server network? State any three characteristics of client/
server network.
j. What is a network topology? Name the different types of network
topology.
k. What is a star topology? Draw a neat diagram of bus topology.
l. What is bandwidth, and how is it measured?
m. Differentiate between half duplex mode and full duplex mode.
n. What is a communication media? Differentiate between guided media
and unguided media.
o. What is a coaxial cable?
p. What are modems? What purpose do they serve in data communication
systems?
q. What is wireless access point?
8. Identify the following communication media.
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Chapter 2
THE INTERNET
AND
ITS SERVICES
Objectives
After completing this chapter, you will be able to:
y Define the Internet and list the services provided by the Internet.
y Explain the origin and growth of the Internet.
y Explain the different types of Internet connections.
y Identify the hardware and software requirements for the Internet connection.
y Explain how the Internet works.
y Explain the useful services provided on the Internet.
C Ooncept verview
Internet has perhaps been the most outstanding
innovation in the field of communication in
the history of mankind. It also became the
best business tool of modern scenario. It has
brought a globe in a single room. Right from
news across the corner of the world, wealth
of knowledge to shopping, purchasing the
tickets of your favourite movie-everything is at
your finger tips. The Internet is a world-wide
network of computer networks joined together
by communication lines, wireless connections
and satellite connections. It connects millions
of computers around the world in a non-
hierarchical manner unprecedented in the
history of communications.
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The Internet Defined
The Internet is a world-wide network of
computer networks joined together by
communication lines, wireless connections
and satellite connections. It connects
millions of computers around the world in
a non-hierarchical manner unprecedented
in the history of communications. It is a
combination of several media technologies
and an electronic version of newspapers,
magazines, books, catalogues, bulletin
boards, and much more. This versatility
gives the Internet its power. The Internet’s
technological success depends on its
principal communication tools, the
Transmission Control Protocol (TCP) and
the Internet Protocol (IP). It can be called
network of networks or mother of all
networks.
The major services provided by the Internet are listed below:
• Serves as a communication channel for anybody who requires a quick and
reliable communication.
• The Internet is a virtual treasure trove of information. Any kind of information
on any topic under the sun is available on the Internet.
• Cheapest and fastest means to access and provide information.
• Allows people on one computer to connect to a remote computer.
• Many services are now provided on the internet such as online banking, job
seeking, purchasing tickets for your favourite movies, guidance services on
array of topics engulfing the every aspect of life, and hotel reservations.
• Allows you to complete your business transactions in the market place.
Origin and Growth of the Internet
The Internet grew out of a U.S. Defence Department program called ARPANET
(Advanced Research Projects Agency Network), established in 1969 with connec-
tions between computers at the University of California at Los Angeles, Stanford
Research Institute, the University of California-Santa Barbara, and the University
of Utah. ARPANET’s purpose was to conduct research into computer networking
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in order to provide a secure and survivable communications system in case of
war. As the network quickly expanded, academics and researchers in other fields
began to use it as well. In 1986, the National Science Foundation established the
NSFNET, a distributed network of networks capable of handling far greater traf-
fic, and within a year more than 10,000 hosts were connected to the Internet. This
led to the formation of interconnected networks. In course of time the network
spread throughout the world, giving birth to Internet.
Who Controls the Internet
“The Internet, a loosely-organized international collaboration of autonomous, in-
terconnected networks, supports host-to-host communication through voluntary
adherence to open protocols and procedures defined by Internet standards.”
Although the above definition is fundamentally correct, it conveys that no one is
at the helm of the Internet. But in real sense, some protocols, and the parameters
required for their usage, are essential in order to work on the Internet. A number
of bodies are responsible for maintaining those protocol standards and param-
eters and these bodies steer the Internet in a significant sense. Brief descriptions
of these bodies are as follows:
International Council For Assigned Names and Numbers (ICANN)
ICANN (Internet Corporation for Assigned Names and Numbers) oversees the
distribution of Internet domain names, or site addresses, and other identifiers
that distinguish one Internet site from another. The non-profit entity handles the
assignment of IP addresses, which identify computers that are connected to a
TCP/IP network; port numbers, which identify the type of port being used to en-
sure that data is connected to the proper service; and other protocol parameters
that allow the Internet to operate as it does.
Internet Engineering Task Force
The Internet Engineering Task Force (IETF) was created in 1986 by the Internet
Architecture Board. It consists of Internet administrators, designers, vendors, re-
searchers, and individuals interested in the evolution of the Internet architec-
ture, and is responsible for improvement of the Internet technology protocols
and standards.
Internet Architecture Board (IAB)
The IAB (Internet Architecture Board) is the Internet Society overseer of the tech-
nical evolution of the Internet. The IAB supervises the Internet Engineering Task
Force (IETF), which oversees the evolution of TCP/IP and the Internet Research
Task Force (IRTF), which works on network technology.
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World Wide Web Consortium
The World Wide Web Consortium (W3C), is an international community that
develops standards to ensure the long-term growth of the Web. Founded and
headed by Sir Tim Berners-Lee, the consortium is made up of member organiza-
tions which maintain full-time staff for the purpose of working together in the
development of standards for the World Wide Web. It is also engaged in educa-
tion and outreach, develops software and serves as an open forum for discussion
about the Web.
How does the Internet work?
A message travels across the network with the help of networking protocol.
Transmission Control Protocol/Internet Protocol (TCP/IP) is the native protocol
of the Internet and is required for Internet connectivity. When using this pro-
tocol, data is transmitted through networks in the form of small packets. Each
data packet transmitted contains different details such as the portion of the data
transmitted, sequence number of the packet, address of the sender as well as the
address of the recipient. A code for error correction will also be included along
with the data. These packets are passed from one network to another until they
reach the destination. At the receiving end, these packets are collected and joined
in the correct order to get the original data file. Before joining different packets,
it is ensured that data packets received are free from errors. If any packets are
missing or damaged, protocol software on the receiving computer requests that
the source resend them. Only when the data has arrived correctly, the protocol
software makes it available to the receiving application program, and therefore
to the user.
Internet Connections
Internet can be connected in one of the following basic ways:
• Dial-up connections
Dial-up connections are one type of internet connection available from ISPs,
they are the slowest and the most inexpensive. A dial-up connection allows
you to connect to the internet via a local server using a standard 56k modem.
Your PC literally dials a phone number (provided by your ISP) and connects
to the server and therefore the internet.
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• ADSL connections
ADSL (Asymmetric Digital Subscribers Line) connections are becoming more
and more widely available and can provide an excellent internet connection.
The connections work by splitting your phone line into two separate channels,
one for data (internet) and one for voice (phone calls), which means you can
talk on the phone and be connected to the internet at the same time.
• Cable connections
Cable connections are considered one of the best types of internet connection
available to the home user, they offer very fast and reliable connections with
a fixed monthly fee. Cable companies usually offer different packages to suit
different internet subscribers, your choice of package, as with all internet
connections, will depend on how you intend to use the internet.
Internet Requirements
The most important requirements for getting online are explained below:
An Internet access account from an ISP
Now, more and more people are accessing the Internet from home or from stand-
alone computers at work. Internet Service Providers (ISPs) worldwide offer
various options and packages to the general public for Internet access. ISP is a
company which gives us the facility to gain access to the Internet against a fee.
Computer
All kinds of computers from PCs to Macintosh, desktop computers and note-
books, can be used to connect to the Internet. The main requirement is that you
connect your computer to a modem. The minimum requirement to access a TCP/
IP account is a PC having a 80486, 40 GB hard disk with minimum 64 MB RAM.
However, the recommended configuration for TCP/IP access would be a Pentium
processor with 128 MB RAM.
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Modem connected to a telephone line
To connect a computer to the Internet over a telephone line, it is necessary to
convert the digital information, as you wish to send or receive into electrical im-
pulses or analog currents, that can be sent over the connection. The device that
makes this happen is known as modem-which is short form for Modulator/De-
modulator. A modem converts the digital signals of the sending computer to ana-
log signals that can be transmitted over telephone lines. When the signal reaches
its destination, another modem reconstructs the original digital signal, which is
processed by the receiving computer. Thus, a modem is the primary link between
the computer and Internet Service Provider.
There are two types of software required for the Internet connection. They
are:
a. Internet Access Software
Internet Access Software is a system software necessary for setting up and
controlling the connection from your computer’s operating system to the
Internet. This set of software has two key components: dialer and TCP/IP.
Dialer is used to instruct the modem to dial the right phone number, and to
identify your machine to the access provider’s system. TCP/IP allows cooper-
ating computers to share resources across a network.
b. Internet Application Software
Internet Application Software is a special program used for communicat-
ing with Web servers and it enables us to surf the Internet, send and receive
mails and read news. Some of the common Internet Application Software are
Google Chrome, Internet Explorer, Mozilla Firefox, Opera, etc.
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World Wide Web
The World Wide Web (usually referred to as “the Web”) is a collection of millions
of files stored on thousands of computers (called Web servers) all over the
world. These files represent text documents, pictures, videos, sounds, programs,
interactive environment and just about any other kind of information that has
ever been recorded in computer files.
The advantages of WWW are listed below:
• The Web has presented a comprehensible online library, a decentralised
information resource that via internet search engines, such as Google and
Yahoo!, offers instant access to a vast amount of information.
• The Web opens up new communication possibilities for personalized
messages to be delivered to targeted individuals.
• Online advertising has the capability to reach a global audience at a fast rate.
• The Web provides file to download and also upload.
Components of Web
Web uses the following components:
Website
Website is a collection of Web pages belonging to a particular person or
organization. Each document on the Website, which may contain only text or a
combination of text, images and multimedia, is called Web pages. Examples of
some Web sites are www.google.com and www.yahoo.com.
Web Server
Web server is simply a computer with an Internet connection that runs software
designed to send out HTML pages and other file formats (such as multimedia
files). The server computer should have a relatively high-speed connection on
the Internet and are powerful enough to deal with a number of simultaneous
connections from the Internet. Some examples of Web servers are Apache Web
Server and Webstar.
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Web browser
Web browser provides you an interface
to interact with the Internet. Browsers
are also called clients. Any software that
allows you to browse the Web is called
a Web client. A browser is a software
program that allows users to access and
navigate the World Wide Web. Examples
of Web browsers are Internet Explorer,
Netscape Navigator and Mozilla.
HyperText Transfer Protocol (HTTP)
The hypertext transfer protocol is an access method (method to access web pages)
used on Internet. It is the primary access method for interacting with Internet.
The http generally works in combination with www. The http is responsible for
accessing hypertext documents on World Wide Web.
Uniform Resources Locator (URL)
URL stands for Uniform Resource Locator, which means it is a uniform way to
locate a resource (file or document) on the Internet. The URL specifies the address
of a file, and every file on the Internet has a unique address. Web software use the
URL to retrieve a file from the computer on which it resides. The URL provides an
addressing scheme which allows the browser to request just about any document
or Web page, located anywhere on the Internet.
TCP/IP
TCP/IP (Transmission Control Protocol/ Internet Protocol is a protocol used to
exchange information between clients and Web servers. It is also known as the
standard set of protocols used for conducting communication on the Internet.
TCP/IP is the most popular and widely accepted protocol available on the Internet
today.
Home Page
The first page of a Web site is called the home page. This is the most important
page of any web site. The home page contains number of hyperlinks to other web
pages. A home page of a web site can be used to provide a dashboard-like view
to the rest of the pages-directing visitors to key areas of the web site. It is often
viewed as a chance to market products or promote an image. A web site’s home
page will typically be used to explain what the web site does and who it aims to
serve.
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Online Resources
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 business forums. Some
of the useful online services provided on the Internet are discussed below:
Information Retrieval
Internet is world’s largest computer
network spread over the world. On the
Internet you can keep yourself informed
about the incidents taking place across
the world. You can get large amounts of
government, business and educational
information. Nowdays, you can also sell
your poducts and buy anything from
the world markets. You can handle your
bank account on the Internet. You can
also exchange your personal information
or messages across the world to your
relatives, friends or other family members.
You can also receive or send your business data worldwide within fraction of a
second. You can spread your own information all over the world, which can be
a global advertising. This is most inexpensive way to put about yourself, your
business, and your products to the world community.
E-mail Service
Electronic mail, or e-mail (and mail) for short, is one of the most popular uses of
the Internet. It 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 from Microsoft, Yahoo
Mail from Yahoo!
The advantages of an electronic mail are as follows:
• Electronic mail is extremely cost-effective way to move information around.
• Electronic mail can be delivered almost as fast as the wire can carry it.
• The image, sound, video and documents can be attached to e-mail messages.
• You can automatically maintain a record of communications with someone
else.
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Search Engines
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. A number of search engines are available on the Internet and
sometimes they are called Web crawlers or Web spiders. Some of the popular
search engines are: HotBot, WebCrawler, Yahoo! and AltaVista.
Electronic Commerce
Electronic commerce, commonly known as e-commerce or eCommerce, or
e-business consists of the buying and selling of products or services over electronic
systems such as the Internet and other computer networks. E-commerce can apply
to purchases made through the Web or business-to-business activities such as
inventory transfers. A customer can order items from a vendor’s Web site, paying
with a credit card (the customer enters account information via the computer) or
with a previously established “cybercash” account. The transaction information
is transmitted (usually by modem) to a financial institution for payment clearance
and to the vendor for order fulfillment.
Online Education
Online education is very popular nowadays.
Online education is teaching and learning
based on the same instructional principles
as those employed in classrooms, using
the Internet and computers to facilitate
instruction when the teacher and students
are at different locations and may be
on different time schedules. Content is
delivered via the Internet. It can be self
paced or instructor led and includes media
in the form of text, image, animation,
streaming video and audio.
Video Conferencing
Video conferencing or video conference (also known as a videoteleconference)
is a set of interactive telecommunication technologies which allow two or more
locations to interact via two-way video and audio transmissions simultaneously.
This can be accomplished through the use of cameras, video displays,
microphones, speakers, video conferencing software and internet connection.
Microsoft Internet has a built-in conferencing program, called NetMeeting.
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Chat Room
Chat room is a Web site that provides a venue for communities of users with a
common interest to communicate in real time. 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.
Telnet
One of the early services offered by the Internet is the remote working on
computers, referred to as Telnet (Terminal Emulation). This type of remote
working facility makes the Internet more fascinating and flexible. Telnet allows
users to login to remote computers. The user requires the login name and the
password to login to the remote computer. It sets up a rapid, error-free link between
the local computer and the remote computer. Utilizing Telnet, an Internet user
can establish connections with a multitude of bibliographic databases, campus
information systems of various universities, full-text databases, data files and
other online services.
Newsgroup
Newsgroup is a system of discussion group in the Internet which allows users
to indulge in discussion with people anywhere in the world on any subject.
Anybody can subscribe to newsgroups and can read the messages posted on
them. Users can also post their own message or articles to members in the group.
Topics for discussion for newsgroups are wide and varied. Usenet is a typical
discussion group. Special programs like Newsreader are available to read the
articles posted by the newsgroup members.
File Transfer Protocol
File Transfer Protocol (FTP), a standard Internet protocol, is the simplest way to
exchange files between computers on the Internet. There are several FTP servers
on the Internet that store different types of files. Different types of files - text,
image, audio, or a Web file can be transferred between computers. The process of
transferring a copy of a file from a remote computer to the requesting computer
is called downloading whereas the process of transferring a copy of a file from a
local computer to a remote computer is called uploading.
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C Dompu- ictionary
Internet : A world-wide network of computer networks joined
together by communication lines, wireless connections
WWW : and satellite connections.
Web search engine : A global medium that contains linked text, image,
sound and video documents.
Electronic commerce :
A tool designed to search for information on the World
Chatting : Wide Web.
The buying and selling of goods and services on the
Internet, especially the World Wide Web.
A real-time conversation among computer users in a
networked environment such as the Internet.
Recap
• The Internet is a world-wide network of computer networks joined together
by communication lines, wireless connections and satellite connections.
• World Wide Web (WWW) is a global medium that contains linked text,
image, sound and video documents.
• TCP/IP (Transmission Control Protocol/ Internet Protocol is a protocol used
to exchange information between clients and Web servers.
• Electronic mail, or e-mail (and mail) for short, is sending and recieving
messages through computer.
• A web search engine is a tool designed to search for information on the World
Wide Web.
• Electronic commerce refers to the buying and selling of goods and services
on the Internet, especially the World Wide Web.
• Video conferencing is a set of interactive telecommunication technologies
which allow two or more locations to interact via two-way video and audio
transmissions simultaneously.
• Chatting is a real-time conversation among computer users in a networked
environment such as the Internet.
• A newsgroup is a system of discussion group in the Internet which allows
users to indulge in discussion with people anywhere in the world on any
subject.
• File Transfer Protocol (FTP), a standard Internet protocol, is the simplest way
to exchange files between computers on the Internet.
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Review Yourself
1. State whether the following statements are true or false.
a. The Internet’s technological success depends on its principal
communication tools, the Transmission Control Protocol (TCP) and the
Internet Protocol (IP).
b. The Internet grew out of a U.S. Defense Department program called
ARPANET (Advanced Research Projects Agency Network), established
in 1699.
c. Electronic mail is extremely cost-effective way to move information
around.
d. The search results are usually presented in a list of results and are
commonly called hits.
e. Gopher is a real-time conversation among computer users in a networked
environment such as the Internet.
2. Fill in the blanks.
a. _____________ is a combination of several media technologies and an
electronic version of newspapers, magazines, books, catalogues, bulletin
boards and much more.
b. A ______________ is a tool designed to search for information on the
World Wide Web.
c. _______________ refers to the buying and selling of goods and services on
the Internet, especially the World Wide Web.
d. A ____________ is a system of discussion group in the Internet which
allows users to indulge in discussion with people anywhere in the world
on any subject.
e. ____________ is a system that helps you locate specific software and data
files stored at anonymous FTP sites.
3. Give the full forms of the following abbreviations.
ARPAnet, FTP, NSFNET, TCP/IP, Telnet
4. Give the appropriate technical term for the following.
a. A world-wide network of computer networks joined together by
communication lines, wireless connections and satellite connections.
b. A global medium that contains linked text, image, sound and video
documents.
c. A web search engine is a tool designed to search for information on the
World Wide Web.
d. A set of interactive telecommunication technologies which allow two or
more locations to interact via two-way video and audio transmissions
simultaneously.
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5. Match the following.
WWW A world-wide network of computer networks
joined together by communication lines, wireless
connections and satellite connections.
Internet A global medium that contains linked text, image,
sound and video documents.
Electronic commerce A tool designed to search for information on the
World Wide Web.
Chatting The buying and selling of goods and services on
the Internet, especially the World Wide Web.
Web search engine A real-time conversation among computer users in
a networked environment such as the Internet.
6. Answer the following questions.
a. What is the Internet? What are the major services provided by the Internet?
b. How did the Internet evolve?
c. What are the requirements for internet connection?
d. How does the Internet work?
e. What is World Wide Web? What are the advantages of World Wide
Web?
f. What is an electronic mail? What are the advantages of an electronic
mail?
g. What are search engines? Name few search engines.
h. What is chat room?
i. What is e-Commerce?
j. What is Telnet?
k. What is the difference between “downloading” and “uploading” of
information?
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Chapter 3
COMPUTER
SECURITY
SYSTEM
Objectives
After completing this chapter, you will be able to:
y Define computer security.
y Explain the hardware measures to protect computer system.
y Explain the software measures to protect computer system.
y Define defragmentation and scandisk.
C Ooncept verview
In the last few years, the use of computers
in the home and in business has increased
considerably. During this period, large
computer networks have been built
to connect these computer systems.
Computers connected to these networks
are often operated and owned by different
organizations, each with their own views of
security. In such a scenario, it is difficult to
define a secure system that fits the viewpoint
of each organization.
Computer security is the process of
preventing and detecting unauthorized use
of your computer.
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Computer Security Defined
Computer security is the process of preventing
and detecting unauthorized use of your computer.
Prevention measures help you to stop unauthorized
users from accessing any part of your computer
system. Detection helps you to determine whether
or not someone attempted to break into your system,
if they were successful, and what they may have
done. The objective of computer security includes
protection of information and property from theft,
corruption, or natural disaster, while allowing the
information and property to remain accessible and
productive to its intended users.
Hardware Security
Hardware security deals with protection of computer hardware and associated
equipment, such as, computers, servers, networks, connectivity and peripheral
equipment, etc. from external physical threats, such as tampering, theft,
earthquakes, water, etc.
There are three main components to hardware security. First, obstacles can be
placed in the way of potential attackers and sites can be hardened against accidents
and environmental disasters. Such measures can include multiple locks, fencing,
walls, fireproof safes and water sprinklers. Second, surveillance and notification
systems can be put in place, such as lighting, heat sensors, smoke detectors,
intrusion detectors, alarms, and cameras. Third, methods can be implemented
to apprehend attackers and to recover quickly from accidents, fires, or natural
disasters.
System Maintenance
System maintenance is a term used to describe
various forms of computer or server maintenance
required to keep a computer system running
properly. This sort of maintenance is typically
performed on a regular or semi-regular schedule,
often during non-peak usage hours. It keeps
equipment in good operating condition and to
find and correct problems before they develop
into severe malfunctions.
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Air Conditioner
Monitoring the environment conditions in a computer room or data center is
critical to ensuring uptime and system reliability. Maintaining recommended
temperature and humidity levels in the computer room can reduce unplanned
downtime caused by environment conditions and save companies thousands
or even millions of dollars per year. So, a good air-conditioner is required to
dehumidify and extract heat from an area. Maintaining an ambient temperature
range of 68° to 75°F (20° to 24° C) is optimal for system reliability. Relative humidity
(RH) is defined as the amount of moisture in the air at a given temperature in
relation to the maximum amount of moisture the air could hold at the same
temperature. In a data center or computer room, maintaining ambient relative
humidity levels between 45% and 55% is recommended for optimal performance
and reliability.
Power Protection Devices
In today’s electrical system environments, power disruptions are very common.
These disruptions can be due to various reasons like fault in the distribution
system, operations of the nearby equipment, lightning strikes, normal utility
operations, etc. In order to eliminate and reduce the loss of precious time and
resources, it is necessary to provide a proper level of power supply and power
protection. But there are some issues associated with power supply like the
matters relating power smoothing, preventing sudden surges or drops in supply,
and the supply itself. Blackouts and power dips can cause the computers to
shut down suddenly, losing any unsaved data that is only stored in temporary
memory or RAM. Sometimes sudden surges or drops in supply can also cause
physical damage to computer components. constant voltage transformers (CVTs).
The power protection devices can prevent damage, expensive data loss and
unnecessary down-time. There are several power conditioning devices available
in the market. They are:
• Uninterruptible Power Supply (UPS)
• Surge suppressors
• Spike busters
• Voltage regulators
• Uninterruptible Power Supply
An uninterruptible power supply (UPS) is primarily used to provide a backup
power source to the parts in the computer case, the monitor, and any other
device plugged into the computer. In addition to acting as a backup when
the power goes out, most UPS devices also act as power “conditioners” by
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ensuring that the electricity flowing to your computer and accessories is
free from drops or surges. If a computer is not receiving a consistent flow of
electricity, damage can and often does occur.
• Voltage Regulator
Voltage regulator is an electrical regulator designed to automatically maintain
a constant voltage level. Electronic components are often made to accept
only a low maximum voltage, and can be badly damaged by a power surge.
Likewise, a low voltage can fail to provide enough power for the component.
Voltage regulators are often responsible for maintaining a voltage within the
range that the elect ronic component can safely accept.
• Surge Suppressor
A surge suppressor (sometimes optimistically
called a “surge protector”) is a device
inserted in the alternating current utility line
and/or telephone line to prevent damage to
electronic equipment from voltage “spikes”
called transients. A typical surge suppressor
is a small box with several utility outlets, a
power switch, and a 3-wire cord for plugging
into a wall outlet.A surge suppressor prevents
the peak AC voltage from going above a
certain threshold such as plus-or-minus 200
volts. The effectiveness of a surge suppressor
is measured in joules.
Buildings with Restricted Access
Computer systems that store sensitive or valuable data is very important and
expensive for the business. If such computer systems are stolen then it may cost
more because they also involve the cost of replacing the lost data, the cost of
installing new machines and training people to use them. Such computers must
be kept in buildings with restricted access. Alarms, security lighting and closed-
circuit television cameras are some of the methods of hardware protection.
Biometrics
Theft or sabotage also poses a major threat to the security of data or information.
An intruder with malicious intentions may resort to theft or sabotage to destroy
critical data or information. To prevent identity theft, biometric devices can be
used. Biometrics is used as a form of identity access management and access
control. It is also used to identify individuals in groups that are under surveillance.
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Fire Alarms
An automatic fire alarm system is designed to
detect the unwanted presence of fire by monitoring
environmental changes associated with combustion.
In general, a fire alarm system is either classified as
automatically actuated, manually actuated, or both.
Automatic fire alarm systems can be used to notify
people to evacuate in the event of a fire or other
emergency, to summon emergency services, and
to prepare the structure and associated systems to
control the spread of fire and smoke.
Data Security
Data is the raw form of information stored as columns and rows in our databases,
network servers and personal computers. This may be a wide range of information
from personal files and intellectual property to market analytics and details
intended to top secret. Data could be anything of interest that can be read or
otherwise interpreted in human form. However, some of this information isn’t
intended to leave the system. The unauthorized access of this data could lead to
numerous problems for the larger corporation or even the personal home user.
Encryption
Encryption has become a critical security feature for thriving networks and
active home users alike. This security mechanism uses mathematical schemes
and algorithms to scramble data into unreadable text. It can only by decoded
or decrypted by the party that possesses the associated key. (FDE) Full-disk
encryption offers some of the best protection available. This technology enables
you to encrypt every piece of data on a disk or hard disk drive. Full disk encryption
is even more powerful when hardware solutions are used in conjunction with
software components. This combination is often referred to as end-based or end-
point full disk encryption.
Backup System
Backup is the act of copying files to a second medium such as a diskette, zip drive
or tape, as a precaution in case the first medium (hard disk) fails. A copy of files
maintained on a second medium (a disk or tape) as a precaution in case the first
medium fails. Data backup provides ways to protect data in case of a physical
problem with the computer system such as a hard disk failure or power failure. It
is vitally important to backup software and key files since even the most reliable
computer is apt to break down eventually.
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Password Security
Passwords are an important aspect of security in an organization. A high-quality
password is very important both in order to save your own documents and to
protect other accounts on the computers that you log in to. In case you think that
you personally do not have any files that a hacker might be interested in, once the
hackers are in through your account there is a greater chance that they will find
some way to access other accounts.
The numbers of factors that contribute to the difficulty of cracking a password
are in plenty. First and the foremost significant factor in password security is to
keep it secret. You are advised not to share your password with anyone and do
not leave it lying around on sticky notes or in desk drawers where others might
find it. Second important factor in password security is its length. The longer a
password is, the more difficult it becomes to crack. Another important factor is
the character set by which a password is being created. Finally, the period of the
password is important. This is the only reason you should change your password
every two months and do not allow you to reuse recent passwords.
Virus Prevention and Protection Policy
With the broader use of computers and increasing connectivity, online
communication has grown tremendously. But as it is said that everything comes
with a price, it is also true in the case of online communication. The increased
and effective connectivity has made it easier for malicious virus writers to create
viruses and worms that spread faster and further. Security problems from these
viruses have generated some of the most costly mistakes in the computer industry
in the last few years. When a virus infects your computer, it may produce strange
sounds or music plays from the speakers unexpectedly, the computer runs very
slowly and it takes a long time to start, new programs do not install properly,
Windows spontaneously restarts unexpectedly. Protection from virus attacks is
one of the most important security aspects of an organization. The chances of a
virus getting onto a computer system can be reduced if certain rules are always
obeyed.
• Installation of antivirus software on all workstations.
• Do not allow any software to be installed beyond those provided with their
system.
• Restricting downloads and software installation only to the system
administrator or the IT department.
• Restriction on downloading and installation of shareware (games,
screensavers, etc) by users.
• Avoid using data and program disks received from unknown sources.
• System administrators should regularly update virus signature files on
workstations and servers. Most vendors offer updates on regular basis.
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Defragmentation
Over time and with regular use, files and folders on a computer’s hard drive break
down or become fragmented. This can cause the system to run slowly and to
experience processing problems. Defragmenting the computer generally improves
retrieval time and overall performance. For example, a computer program must
access various files on the hard drive every time it is run. If those files are spread
out on hard drive, the computer will have to work extra hard and take extra time
to access the information it needs. In some cases, severe defragmenting may even
cause a program to stop running entirely. Defragmenting reorganizes the hard
drive by putting pieces of related data back together so that files are organized
in a contiguous fashion. As a result, the computer system can access files more
efficiently.
Scandisk
Computer system stores valuable files. If the file is lost due to any error, it entails
loss of productivity in the normal business operation. Scandisk is one of the tools
used to maintain performance and error-free file management. ScanDisk is found
in System Tools with the Defrag utility. It searches the disk drive for disconnected
file clusters and converts them into a form that can be checked and manipulated.
This way, the user can determine whether any information in the lost cluster can
be restored. In addition to locating and converting lost clusters on the disk drive,
the ScanDisk utility can detect and delete cross-linked files from the drive. It
can also make corrections to file and disk errors that it detects. ScanDisk can be
run from the command line or as a Windows utility program. To run ScanDisk
in Microsoft Windows, click the Start button, select Programs, then Accessories,
then System Tools and then Scandisk.
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C Dompu- ictionary
Computer security : The process of preventing and detecting unauthorized
use of your computer.
Voltage regulator : An electrical regulator designed to automatically
maintain a constant voltage level.
UPS : A device primarily used to provide a backup power
source to the parts in the computer case, the monitor,
and any other device plugged into the computer.
Surge suppressor : A device inserted in the alternating current utility line
and/or telephone line to prevent damage to electronic
equipment from voltage “spikes” called transients.
Backup : The act of copying files to a second medium such as a
diskette, zip drive or tape, as a precaution in case the
first medium (hard disk) fails.
Recap
• Computer security is the process of preventing and detecting unauthorized
use of your computer.
• Hardware security deals with protection of computer hardware and
associated equipment.
• Routine servicing of hardware is a must to keep equipment in good operating
condition and to find and correct problems before they develop into severe
malfunctions.
• The temperature in the computer system should be maintained between 21°C
to 24°C.
• The power protection devices can prevent damage, expensive data loss and
unnecessary down-time.
• Voltage regulator is an electrical regulator designed to automatically maintain
a constant voltage level.
• A surge suppressor is a device inserted in the alternating current utility
line and/or telephone line to prevent damage to electronic equipment from
voltage “spikes” called transients.
• An automatic fire alarm system is designed to detect the unwanted presence
of fire by monitoring environmental changes associated with combustion.
• Encryption uses mathematical schemes and algorithms to scramble data into
unreadable text.
• Backup is the act of copying files to a second medium such as a diskette, zip
drive or tape, as a precaution in case the first medium (hard disk) fails.
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Review Yourself
1. State whether the following statements are true or false.
a. The first benefit of doing the regular computer maintenance is the longer
computer life.
b. The temperature in the computer system should be maintained between
21°C to 42°C.
c. Excessive heat can cause premature aging and failure of the computer
components.
d. Voltage regulator is an electrical regulator designed to automatically
maintain a constant voltage level
e. A high-quality password is very important both in order to save your own
documents and to protect other accounts on the computers that you log into.
2. Fill in the blanks.
a. An _______________ is primarily used to provide a backup power source
to the parts in the computer case.
b. A _______________ is a device inserted in the alternating current utility
line and/or telephone line to prevent damage to electronic equipment
from voltage “spikes” called transients.
c. An ________________ is designed to detect the unwanted presence of
fire by monitoring environmental changes associated with combustion.
d. ____________ is the act of copying files to a second medium such as a
diskette, zip drive or tape, as a precaution in case the first medium (hard
disk) fails.
e. ____________ is one of the tools used to maintain performance and error-
free file management.
3. Match the following. The process of preventing and detecting unauthorized
Voltage regulator use of your computer.
Backup A power supply that includes a battery to maintain
power in the event of a power outage.
Computer security
An electrical regulator designed to automatically
UPS maintain a constant voltage level.
The act of copying files to a second medium such as a
diskette, zip drive or tape, as a precaution in case the
first medium (hard disk) fails.
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4. Select the best answer from the list of choices.
a. _____________ deals with protection of computer hardware and associated
equipment,
i. Internet security ii. Hardware security iii. Software security
b. _______________ is defined as the amount of moisture in the air at a given
temperature in relation to the maximum amount of moisture the air could
hold at the same temperature.
i. Temperature ii. Relative humidity iii. None of the above
c. A device that protects your PC against power surges and spikes.
i. UPS ii. Voltage regulator iii. Surge suppressor
d. An automatic ____________ system is designed to detect the unwanted
presence of fire by monitoring
environmental changes associated with combustion.
i. Fire alarm ii. Password iii. Scandisk
e. The type of security that provides protection against programs, files, and
the information flow to and from a computer.
i. Computer security ii. Hardware security iii. Software security
f. _______________ is the act of copying files to a second medium such as a
diskette, zip drive or tape, as a precaution in case the first medium (hard
disk) fails.
i. Copy ii. Backup iii. Move
g. The ______________________ process optimizes the read/write process
by realigning the positions of related file clusters to speed up the overall
operation of the drive.
i. Fragmentation ii. Defragmentation iii. Scan disk
h. _____________ is one of the tools used to maintain performance and error-
free file management.
i. Fragmentation ii. Defragmentation iii. Scan disk
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5. Give the appropriate technical term for the following.
a. The process of preventing and detecting unauthorized use of your
computer.
b. A device primarily used to provide a backup power source to the parts in
the computer case.
c. An electrical regulator designed to automatically maintain a constant
voltage level.
d. The act of copying files to a second medium such as a diskette, zip drive
or tape, as a precaution in case the first medium (hard disk) fails.
e. The tool used to maintain performance and error-free file management.
6. Answer the following questions.
a. What is meant by computer security?
b. What do you mean by hardware security?
c. What are the three main hardware security measures?
d. What are power protection devices? Give examples.
e. What is UPS? What are the functions of UPS in computer security?
f. What is a voltage regulator?
g. What is surge supressor?
h. What is meant by data security?
i. What is encryption?
j. What is data backup system?
k. What is a password policy? How can the user password help in data
security?
l. What is meant by defragmentation?
m. What is scandisk?
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