XII IP CBSE 1-3

1 Puzzle
After learning this chapter the students will be able to:
Define what a Computer Network is
List the benefits of networking
List different wired and wireless media for communication
Identify different network devices
Identify the type of network on the basis of area covered
Describe various terms associated with computer networks.
List various security threats to computer networks
List the preventive and corrective measures against these threats
Have you ever worked on Internet? Have you ever used an ATM? Have you ever
given the print command on a computer to get the printout on a printer attached
to some other computer? Have you ever transferred songs from your computer to a
cell phone or vice-versa? If the answer to any of these questions is YES, then you
have experienced and utilized the services of a computer network. In this chapter
you will study about various types of computer networks, their benefits, and what
is required to create computer networks.
Can you place 10 coins in such a way that they lie in 5 straight lines and on each line there
are exactly 4 coins?
Such situations are faced by the designers of computer networks. They have to think of
various ways of interconnecting the computers so that the specific goals of network setup
are achieved.

1 COMPUTER NETWORKING
2
Networking – a brief overview

A computer network is a collection of interconnected computers and other devices which
are able to communicate with each other. In this context, the term interconnected means
that there exists a path through which data can be transmitted from one
computer/device to another.
A computer network is a collection of interconnected computers and other
devices which are able to communicate with each other and share hardware
and software resources.
Why do we have computer networks? Are there any advantages of networked computers
over stand alone computers? Yes, there are many. A few of these advantages are:
Resource Sharing
Cost saving
Collaborative user interaction
Time saving
Increased storage
Let us discuss these advantages in some details.
In a networked computer lab when print command is given on one computer the
document may be printed by the printer which is attached to some other computer. This
printer is able to print documents from multiple users on the network. It means that the
printer is being shared by more than one users. This is an example of resource sharing,
and this is possible only when the computers are interconnected to form a network.
Similarly other resources like Hard Disk, DVD Drive, and Scanner etc. can also be shared
on a computer network. Software resources like Application Softwares, Anti-Virus tools
etc. can also be shared on computer networks. You can very easily conclude that this
resource sharing also leads to cost-saving.
Resource Sharing:
COMPUTER NETWORKING
3
Collaborative User Interaction:
Increased Storage:
Let us take one more example of a school. Here we assume that all the computers in the
school are connected to one main computer (called server). After the exams, teachers
have to exchange marks with each other for result preparation. So all the teachers enter
the marks class wise for their respective subjects at one centralized location and from
there the class teachers can copy the marks of their classes and can prepare the result.
This way data is shared on a computer network. Similar is the case with other
computerized organizations also.
Let us take another example of collaborative user interaction. If we are working on a
computer which is a part of a computer network, we can communicate with any other
user of the network through e-mail or chatting. It takes negligible time to send and
receive messages and watch live videos of one another irrespective of terrestrial
distances. If the e-mail or chatting is done for some useful purpose, it leads to increased
productivity, cost-saving as well as time-saving.
On a network, same data may be replicated on multiple computers to ensure the
availability of data in the case of some computer getting faulty. For example, when you
save your java applications on your computer, you can also store their copies on some
other networked computers in your lab. This way your work will be available even if your
computer develops some fault or somehow your programs are deleted from your
computer. Similarly, on large networks also the data is replicated on multiple computers
as if a huge storage area is available to store multiple copies of the data.
All these advantages are there for a small organization like a school as well as for big
business organizations and for governments. Today, small as well as big organizations,
and governments keep their data on secured large scale computers called servers. They
share this data with authorized users. This ensures security. Customer care cells of
companies share the resources and data and they also communicate among themselves as
well as with customers with the help of computer networks only.
COMPUTER NETWORKING
4
Networking Hardware
Transmission Media
To form a computer network a lot of hardware devices are required. Some of these
devices along with their functionalities are mentioned below :
Computers on a network are able to share data and other resources. They are also able to
communicate among themselves. To make all this possible there must be some medium
over which the data can travel from one computer to another. A medium of data
transmission over a computer network is called a channel or a transmission medium.
Channels may be guided (wired) or unguided (wireless).
A transmission medium is a medium of data transfer over a network. It can be wired
or wireless.
A number of various types of cables are used to transfer data over computer networks.
These are Twisted Pair Cable, Co-axial Cable, and Optical Fiber Cable. Let us know about
these in some details.
This is probably the most widely used cable for creating small
computer networks. It contains four twisted pairs covered in an outer shield. These pairs
are colour coded. An RJ-45 connecter is used to connect this cable to a computer. It is of
two types:
UTP (Unshielded Twisted Pair): As the name suggests in UTP cables individual pairs are
not shielded.
Wired Media
Twisted Pair Cable –
COMPUTER NETWORKING
UTP Cable UTP Cable
With RJ-45 Connector
5
Characteristics of UTP cable:
It is a low-cost cable available for setting up small networks.
It is a thin (External diameter app. 0.43cm) and flexible cable and therefore it
offers ease of installation.
It can carry data upto a length of 100m at a stretch.
STP (Shielded Twisted pair): It is the same cable as the UTP, but with each pair shielded
individually. An outer shield then covers all the pairs like in UTP. STP data connectors are
used to connect STP cable to the computer. RJ-45 connectors can also be used to connect
this cable to a computer.
Characteristics of STP cable:
As compared to UTP, STP offers better immunity against internal and external
electromagnetic interferences.
It is expensive than UTP cable.
As compared to UTP cable, STP cable is difficult to install.
A coaxial
cable consists of two conductors that
share a common axis. The inner
conductor is a straight wire and the
outer conductor is a shield that might be
braided or a foil.
Characteristics of Co-axial cable:
It can carry data for a larger distance (185m – 500m) at a stretch.
Less susceptible to electromagnetic fields
Bulkier and less flexible than twisted pair.
Due to its thickness (1cm diameter) and less flexibility, it is difficult to install as
compared to twisted pair cable.
Earlier coaxial cable was also used for connecting computers in small networks but now
UTP/STP cables are more commonly used for this purpose.

Co-axial cable (or coax) –
COMPUTER NETWORKING
Copper Wire
Insulation
Wire Mesh
Insulation
6
Optical Fiber cable –
Comparison of wired media
Cable Twisted Pair Coaxial Cable Optical Fiber
Paramater Cable Cable
Optical Fibers are long, thin
strands of glass about the thickness of a human
hair. They are arranged in bundles called optical
fiber cables and used to transmit data through
light signals over long distances.
An optical fiber has following parts:
Core – It is the thin glass rod at the center through which the light travels
Cladding – It is the outer optical material surrounding the core that reflects the
light back into the core
Buffer coating – It is the plastic coating that protects the cable from damage
and moisture
These optical fibers are arranged in bundles of hundreds and thousands and are protected
by the cable’s outer covering, called jacket.
Characteristics of Optical Fiber Cable:
It can carry data for a very large distance at a stretch.
Not susceptible to electromagnetic fields
Specially skilled people are required to install optical fiber cables.
Till date it is the most expensive and at the same time the most efficient cable
available for computer networks.
Data Transfer Rate 10Mbps-10Gbps 100 Mbps More than100 Gbps
Data Transfer Range 100 m 185m-500 m –
Interference More Less than NIL
Susceptibility Ethernet cable
Cost of Cable Least Cost More than Ethernet Very Expensive

COMPUTER NETWORKING
Jacket
Buffer
Cladding
Core
7
Wireless Media
Electromagnetic Spectrum
Radio Waves –
Electromagnetic waves are used for wireless communication over computer networks.
Frequencies of waves are measured in Hertz (Hz). As the frequencies of electromagnetic
waves change, their properties also change. Based on their frequencies, electromagnetic
waves are categorized into various categories. These categories are (in increasing order
of frequencies): radio waves, microwaves, infrared radiation, visible light, ultraviolet
radiation, X-rays, and Gamma rays.
Out of these only radio waves, microwaves, and infrared rays are used for wireless
communication. Let us now study about these waves in some details.
Radio waves have a frequency range of
3 KHz to 3GHz. Radio waves are used for
communication over distances ranging from a few
meters (in walkie-talkies) upto covering an entire
city. These waves are easy to generate, can travel
long distances and can penetrate buildings easily.
That’s why they are widely used for communication,
both indoors and outdoors. Cordless phones, AM and
FM radio broadcast, Garage door openers etc. are
examples of radio wave transmission.
COMPUTER NETWORKING
Category Long Radio Radiowaves Microwaves Infrared Ultraviolet X-Rays Gamma
Rays Visible Light Rays Rays
Omni Directional Radio Waves
R O Y G B I V
3 8 11 14 14 Frequency Less than 3 x 10 to 3 x 10 to 3 x 10 to 4.3×10 to More than 10
3 9 11 14 14 (Hz) 3×10 3 x 10 3 x 10 4 x 10 7.5×10
8
Characteristics of Radio Wave Transmission:
These waves are omni-directional, so the transmitting and receiving antennas
need not be aligned.
(Recall when you throw a stone in a pond, circular waves are generated and
spread outwards. Similarly, radio waves are generated by the transmitter and
spread in all the directions.)
Relatively inexpensive than wired media.
It offers ease of communication over difficult terrain
The transmission can be interfered by motors or other electrical equipment
Permission from concerned authorities is required for use of radio wave
transmission
Less secure mode of transmission
Micro waves have a frequency range of 300MHz (0.3 GHz) to 300 GHz. This
range has some overlapping portion (0.3GHz – 3GHz) with radio waves as there is no clearcut
demarcation between radio waves and micro waves. Microwaves travel in straight
lines and cannot penetrate any solid object. Therefore for long distance microwave
communication, high towers are built and microwave antennas are put on their tops.
Distance between two microwave towers depends on many factors including frequency of
the waves being used and heights of the towers. These waves travel in straight lines and
therefore the sending and receiving antennas have to be aligned with each other.
An example of usage of microwaves for communication is as follows:
In the big cities where land is very costly and a lot of formalities have to be completed to
get permission to dig land for cabling, microwave antennas can be put on top of high rise
buildings and communication can be started in a short time.

Micro Waves –
COMPUTER NETWORKING
9
Characteristics of Micro Wave Transmission:
Free from land acquisition rights
Relatively inexpensive than wired media
Offers ease of communication over difficult terrain
The transmission is in straight lines so the transmitting and receiving antennas
need to be properly aligned ( line of sight transmission)
Infrared waves have a frequency range of 300 GHz to 400 THz. If you
recall VIBGYOR spectrum of light, you will also recall that red light has the lowest
frequency (400THz – 484THz) in this spectrum. Infrared waves are so called because they
have a frequency range of just less than that of red light. These waves are used for short
range communication (approx. 5m) in a variety of wireless communications, monitoring,
and control applications. Home-entertainment remote-control devices, Cordless mouse,
and Intrusion detectors are some of the devices that utilize infrared communication.
These waves are easy to build but have a major drawback- they do not pass through solid
objects (try standing between your remote control and your television and see if it still
works). On the other hand, these waves do not pass through solid walls is a plus point also.
Because of this, infrared system in one room of a building will not interfere with a similar
system in adjacent rooms (you cannot control TV in another room with the remote in your
hand in a room).

Infrared Waves –
COMPUTER NETWORKING
Micro Wave Communication
Micro Wave
Tower
Office 1 Office 2
Micro Wave
Micro Wave
10
Characteristics of Infrared Wave Transmission:
It is a line of sight transmission; therefore information passed to one device is
not leaked to another device.
No government license is required for their use
It is a line of sight transmission, therefore at a time only two devices can
communicate.
The waves do not cross any solid object in between
Performance drops with longer distances
Bluetooth technology uses radio waves in the frequency range of 2.402 GHz
to 2.480 GHz. This technology is used for short range communication (approx. 10m) in a
variety of devices for wireless communication. Baby monitors, door openers, and cell
phones are some of the devices that utilize Bluetooth communication.
Characteristics of Bluetooth Transmission:
Line of sight between communicating devices is not required. (Think Why?)
Bluetooth can connect upto eight devices simultaneously.
Slow data transfer rate (upto 1Mbps).
Satellite links are used for very long distance wireless communication
which may range from intercity to intercontinental. Transmission from the earth to a
satellite is known as uplink. Transmission from a satellite to the earth is known as
downlink. There are multiple micro wave frequency bands which are used for satellites
links. Frequency used for uplink varies from 1.6 GHz to 30.0 GHz and that for downlink
varies from 1.5GHz to 20.0GHz. Downlink frequency is always lower than the uplink
frequency. For example, the uplink frequency is 6.0GHz, and the corresponding downlink
frequency is 4.0 GHz. A communications satellite is a relay station in orbit above the earth
that receives, regenerates, and redirects signals carried on a specific frequency. The
satellite system is very expensive but its area coverage and fringe benefits compensate
for the expenses. Communication satellites are normally owned by governments or by
government approved organizations of various countries

Bluetooth –
Satellite Link –
COMPUTER NETWORKING
11
Communication using Satellite Link
Characteristics of Transmission using satellite link:
Satellites cover large area of earth
Since communication over very long distances is possible, this becomes a
commercially attractive option.
This system is expensive
Requires legal permissions.

COMPUTER NETWORKING
Earth
Station
Europe
Downlink
Uplink
Orbit
Uplink
Downlink
Communication
Satellite
Earth
Station
Asia
Communication
Medium
Guided
(Wired)
Unguided
(Wireless)
Twisted Pair
Cable
Co-axial
Cable
Optical Fiber
Cable
Radio
Waves
Micro
Waves
Infrared
Waves
12
Network Devices
Other than the transmission media many other devices are required to form computer
networks. Some of these devices are:
Any computer which has to be a part of a computer network must have an NIC
(Network Interface Card / Unit) installed in it. A computer communicates with other
computers on a network with the help of an NIC only. Now a days, in most of the PCs and
the laptops, NIC is an integral part of the motherboard.
A Network Interface Card
An NIC (Network Interface Card) is a device that enables a computer to connect to
a network and communicate.
Hub is a device that allows us to connect multiple computers/devices together in a
network. A hub has ports into which the cables from individual computers’ NICs are
inserted. This way each computer’s NIC is connected to hub and hence all the computers
are connected together. Whenever a computer has to send some information to some
other computer(s), the information is sent by the NIC to the hub. Then the hub retransmits
this information to the other computers attached to it. The computer(s) for
which the information is intended receive(s) this information and accept(s) it. Other
computers on the network simply reject this information.
NIC:
Hub:
COMPUTER NETWORKING
Socket for
RJ-45
Connector
Hub/Switch
13
A Hub is an electronic device that connects several nodes to form a network and
redirects the received information to all the connected nodes in broadcast mode.
A switch is an intelligent hub. It looks exactly like a hub. It has the same function
as that of a hub: to connect multiple computers/devices in a network. But the difference
between the two is in the way they re-transmit the received information. Unlike a hub,
instead of broadcasting (sending to each device attached to it) the received information,
a switch sends the information selectively only to those computers for which it is
intended. This makes a switch more efficient than a hub.
A Switch is an intelligent device that connects several nodes to form a network
and redirects the received information only to the intended node(s).
When the data is transmitted over a network for long distances, the data
signal gets weak after certain distance. This distance depends on the data transfer range
of transmission channel being used and can be from a few meters to a few kilometers. If
the signal becomes weak, it cannot reach its destination. Therefore, some device is
required which can re-strengthen the data signal before it gets too weak. Repeater is
such a device. A repeater regenerates the received signal and re-transmits it to its
destination
A Repeater is a device that is used to regenerate a signal which is on its way
through a communication channel. A repeater regenerates the received signal
and re-transmits it to its destination.
There are a large number of computer networks in this world. As common
examples you can consider your school’s computer network, ATM network of a bank, a big
company’s computer network spread over a city, etc. There are thousands of computer
networks that exist. These networks use different hardware and software. Many times
these networks need to communicate with each other. For example, companies X, Y, and
Z do business with each other and therefore they want to interconnect their computer
networks. Another example is the internet which contains a large number of different
types of networks spread over the globe. Different networks are sometimes incompatible
Switch:
Repeater:
Gateway:
COMPUTER NETWORKING
14
with each other. It is like a group of persons using different languages for conversation.
When two or more networks using different hardware and software have to be
connected, some device is needed which can translate one network’s language into the
other’s. A gateway is a device, which is used to connect different types of networks. A
gateway is capable of understanding address architectures used in different networks
and seamlessly translate between these address architectures.
A Gateway is a device, which is used to connect different types of networks and
perform the necessary translation so that the connected networks can
communicate properly.
Before we start discussion on network topologies, let us understand the term ‘NODE’.
Any device (Computer, Scanner, Printer, etc.) which is directly connected to a computer
network is called a node. Suppose you are working on a PC at your home and then you
connect it to internet. As soon as it becomes a part of internet (which is a computer
network), it becomes a node. Similarly, in your school, all the computers which are linked
to school’s computer network are nodes.
A Node is a device, which is directly connected to a computer network. It can be a
computer or any other device like printer, scanner etc.
Once we know about different communication media and devices to form a computer
network, we can procure these media and devices and start constructing a computer
network. Suppose we have 10 computers and we want to interconnect them to form a
network. How can we interconnect them?
Recall the puzzle given in the beginning of this lesson. Is that not similar to the problem of
connecting nodes in a network?
Similarly, when we have to connect computers/devices in a network, there may be
certain conditions which have to be satisfied. Depending upon these conditions, there
may be different ways of interconnecting the computers/devices. The way in which the
Network Topologies
COMPUTER NETWORKING
15
computers/devices are physically interconnected to form a network is called a Topology.
A Topology is an arrangement of physical connections among nodes in a network.
There exist different network topologies. Let us discuss a few of them.
In bus topology all the nodes are connected to a main cable called
backbone. If any node has to send some information to any other node, it sends the signal
to the backbone. The signal travels through the entire length of the backbone and is
received by the node for which it is intended. A small device called terminator is attached
at each end of the backbone. When the signal reaches the end of backbone, it is absorbed
by the terminator and the backbone gets free to carry another signal. This prevents the
reflection of signal back on the cable and hence eliminates the chances of signal
interference.
Characteristics of Bus topology:
It is easy to install.
It requires less cable length and hence it is cost effective.
Failure of a node does not affect the network.
In case of cable (backbone) or terminator fault, the entire network breaks
down.
Fault diagnosis is difficult.
At a time only one node can transmit data.
Bus Topology:

COMPUTER NETWORKING
Bus Topology
Node
(Server)
Terminator Terminator
Backbone
Node Node
Node Node Node
Node-Printer
16
Star Topology:
Tree Topology:
In star topology each node is directly connected to a hub/switch. If any
node has to send some information to any other node, it sends the signal to the
hub/switch. This signal is then broadcast (in case of a hub) to all the nodes but is
accepted by the intended node(s). In the case of a switch the signal is sent only to the
intended node(s).
Bus Topology
Star topology generally requires more cable than bus topology.
Characteristics of Star topology:
It is more efficient topology as compared to bus topology.
It is easy to install
It is easy to diagnose the fault in Star topology.
It is easy to expand depending on the specifications of central hub/switch
Failure of hub/switch leads to failure of entire network
It requires more cable length as compared to bus topology.
Tree topology is a combination of bus and star topologies. It is used to
combine multiple star topology networks. All the stars are connected together like a bus.
This bus-star hybrid approach supports future expandability of the network

COMPUTER NETWORKING
Node Node
(Server) Node
Node Node
Hub/
Switch
Node-Printer
17
Tree Topology
Characteristics of Tree topology:
It offers easy way of network expansion
Even if one network (star) fails, the other networks remain connected and
working.
A computer network can be set up after procuring all the required hardware. But the
network devices will be able to communicate with each other only after they know the
rules of communication. Think of a group discussion session where all the participants can
speak. Each participant can speak a lot. But the group discussion can be started and can
be conducted well if each participant knows the rules of discussion. If all the participants
start speaking suddenly and suddenly they stop, or a person stands up randomly and starts
interrupting the discussion, or any such thing happens, the group discussion cannot be
conducted at all. A more complex situation exists in the case of computer networks where
the participating devices have no common sense and they follow each defined rule to the
T. So it is essential that the rules of communication are very well defined. A set of rules is
also known as a protocol.

Network Protocols
COMPUTER NETWORKING
18
A network protocol is a set of rules for communication among networked devices.
Protocols generally includes rules of how and when a device can send or receive the
data, how is the sent data packaged, and how it reaches its destination.
There are a number of protocols defined for computer networks. Here we discuss three of
them – HTTP, TCP/IP, PPP.
HTTP is used to transfer all files and other data
(collectively called resources) from one computer to another on the world wide web.
When an HTTP client (a browser) sends a request to an HTTP server (web server) , the
server sends responses back to the client. This transfer of requests and responses is done
following HTTP protocol.
It is the basic protocol of
the Internet. Communication between two computers on internet is done using TCP/IP
protocol. TCP/IP can also be used as a communications protocol in a private network.
TCP/IP is a two-layer protocol. When data is to be sent from one computer to another
over internet, it is first broken into smaller packets which are actually sent. When these
packets are received by the receiver computer, they are assembled into the original
message. This job of dividing the original message into packets and re-assembling the
received packets into the original message is done following TCP protocol. Internet
protocol is followed to ensure that each of these packets gets to the right destination.
Different packets from the same message may be routed differently, but they reach the
same destination and are reassembled there.
It is a protocol for direct communication between two
computers, typically a personal computer connected by phone line to a server. Most
Internet service providers (ISPs) use PPP for customer dial-up access to the Internet. PPP
is used over many types of physical networks including cellular telephone, serial cable,
phone line, trunk line, specialized radio links, and fiber optic links.
There are a lot of other communication protocols like SMTP, POP, UDP etc. You can
explore the net to find more about these protocols.
HTTP (Hyper Text Transfer Protocol):
TCP/IP (Transmission Control Protocol / Internet Protocol):
PPP (Point to Point Protocol):
Know More!
COMPUTER NETWORKING
19
COMPUTER NETWORKING
Types of Networks

A computer network may span any amount of geographical area. It can be on a table, in a
room, in a building, in a city, in a country, across continents or around the world. On the
basis of area covered computer networks are classified as:
PAN – Personal Area Network
LAN – Local Area Network
MAN – Metropolitan Area Network
WAN -Wide Area Network
A PAN is a network of Communicating devices (Computer,
Phone, MP3/MP4 Player, Camera etc.) in the proximity of an individual. It can cover an
area of a few meters radius.
When you have to transfer songs from one cell phone to another, you set up a PAN of two
phones. When files are transferred from a PC to an MP3 player, a PAN is set up between
the two. There can also be multiple devices in PAN. A PAN can be set up using guided
media (USB cable) or unguided media (Bluetooth, Infrared).
PAN (Personal Area Network):
A PAN
20
LAN (Local Area Network):
MAN (Metropolitan Area Network):
A LAN is a network
of computing/Communicating devices in a
room, building, or campus. It can cover an area
of a few meters to a few kilometers radius. A
networked office building, school, or home
usually contains a single LAN, though
sometimes one building can contain a few small
LANs (Like some schools have independent LANs
in each computer lab.). Occasionally a LAN can
span a group of nearby buildings.
In addition to operating in a limited space, a LAN is owned, controlled, and managed by a
single person or organization.
A LAN can be set up using wired media (UTP cables, Co-axial cables etc.) or wireless
media (Infrared, radio waves). If a LAN is setup using unguided media, it is known as
WLAN (wireless LAN).
A MAN is a network of computing/communicating
devices within a city. It can cover an area of a few kilometers to a few hundred kilometers
radius. A network of schools, or banks, or Government offices etc., within a city, are
examples of MANs. A MAN is usually formed by interconnecting a number of LANs and
individual computers. All types of communication media (guided and unguided) are used
to set up a MAN. A MAN is typically owned and operated by a single entity such as a
government body or a large corporation. A good example of a MAN is the interconnected
offices of a state government.
COMPUTER NETWORKING
Wireless LAN
Warehouse
Branch Office
Central Office
Factory
A Metropolitan Area Network
21
COMPUTER NETWORKING
WAN (Wide Area Network): A WAN is a network of computing/communicating devices
crossing the limits of a city, country, or continent. It can cover an area of over hundreds of
kilometer radius. A network of ATMs, BANKs, National Government Offices, International
Organizations’ Offices etc., spread over a country, continent, or covering many
continents are examples of WANs. WANs usually contain a number of interconnected
individual computers, LANs, MANs, and maybe other WANs. All types of communication
media (guided and unguided) are used to set up a WAN. The best known example of a WAN
is the internet.
A Wide Area Network
LAN
PC
PC PC
LAN
MAN
Devices and Protocols
for data transmission
22
The following table summarizes the characteristics of PANs, LANs, MANs, and WANs.
Area Covered Small Area A few meters A city and its Entire country,
(Upto 10m to a few vicinity continent, or
radius) kilometers (Upto 100Km globe
(Upto 10Km radius) (No upper limit)
radius)
Error Rates Lowest Lowest Moderate Highest
Transmission High Speed High Speed Moderate Low speed
Speed Speed
Networking Cost Negligible Inexpensive moderately Expensive
expensive
equipment
Once a network has been set up, the nodes can communicate among themselves. But for
proper communication, the nodes should be uniquely identifiable. If a node X sends some
information for node Y on a network, then it is mandatory that nodes X and Y are uniquely
identifiable on the network. Let us see how this is achieved.
Each NIC has a universally unique address assigned
to it by its manufacturer. This address is known as the MAC (Media Access Control) address
of the card. It means that a machine with an NIC can be identified uniquely through its
NIC’s MAC address. MAC address of an NIC is permanent and does never change.
MAC addresses are 12-digit hexadecimal (or 48 bit) numbers. By convention, MAC
addresses are usually written in one of the following two formats:
MM:MM:MM:SS:SS:SS
MM-MM-MM-SS-SS-SS
Network PAN LAN MAN WAN
Parameter
MAC (Media Access Control) address:
Identification of computers and users over a network
COMPUTER NETWORKING
23
COMPUTER NETWORKING
The first half (MM:MM:MM) of a MAC address contains the ID number of the adapter
manufacturer. The second half (SS:SS:SS) of a MAC address represents the serial number
assigned to the adapter (NIC) by its manufacturer.
For example, in the following MAC address,
00:A0:C9 : 14:C8:35
The prefix 00:A0:C9 indicates that the manufacturer is Intel Corporation. And the last
three numbers 14:C8:35 are given by the manufacturer (Intel in this example) to this NIC.
A MAC (Media Access Control) address is a unique 12 digit (6 digits for
manufacturer code and 6 digits for serial number) hexadecimal number assigned
to each NIC. MAC address of an NIC never changes.
Every machine in a network has another unique identifying number, called its
IP Address. An IP address is a group of four bytes (or 32 bits) each of which can be a number
from 0 to 255. A typical IP address looks like this:
59.177.134.72
To make it easier for us to remember, IP addresses are normally expressed in decimal
format as a “dotted decimal number” like the one above.
On a network, IP address of a machine, and not the MAC address of its NIC, is used to
identify it. Do you recall IP protocol? IP protocol identifies a machine with its IP address to
route the packets.
MAC address is used only when a specific machine is to be targeted. For example, suppose
we want to block a specific PC to access some network resource. If we use the PCs IP
address, then the PC is not blocked permanently as its IP address may change when it
connects to the network next time. Instead, if the PCs MAC address is used for the
purpose, then the job is done!
An IP (Internet Protocol) address is a unique 4 digit hexadecimal number assigned
to each node on a network. IP address settings of a node can be changed by the
user
IP Address:
24
Know More!
There are two versions of IP addresses: version 4 (IPv4) and version 6 (IPv6). IPv6
32 uses 128 bits (IPv4 uses 32 bits) for an IP address. Using IPv4 only 2 (approximately
4 billion) distinct devices can be addressed. In the current scenario and in the near
future, this is a small fraction of the number of objects which need to be allocated
IP addresses. As the human population and also the number of devices which need
to be online (mobile phones, home appliances, personal communication devices,
etc.) is increasing at a very fast pace, IPv4 addresses are being exhausted. To
address this problem IPv6 was developed and it is now being deployed. Using IPv6
128 2 (approximately 4 Bn x 4 Bn x 4 Bn x 4 Bn) distinct devices can be addressed. IPv6
also includes an important feature: a set of possible migration and transition plans
from IPv4.There are many other features of IPv6. You can explore the internet and
find more information about IPv6.
You might wonder how an IP address differs from a MAC
address. In fact, the IP address is assigned by the network administrator or the internet
service provider while the MAC address is assigned by the manufacturer. Thus if a
computer is transferred from one network to another, its IP address gets changed where
as the MAC address remains the same.
From the IP address it is usually possible to track the tentative location of the computer
but this is not the case with a MAC address.
So, whenever we have to communicate with a computer on internet, we
can do so by using its IP address. But it is practically impossible for a person to remember
the IP addresses of all the computers one may have to communicate with. Therefore, a
system has been developed which assigns names to some computers (web servers) and
maintains a database of these names and corresponding IP addresses. These names are
called Domain Names. Examples of some domain names are cbse.nic.in, sikkimipr.org,
indianrailway.gov.in etc. Domain names are used in URLs to identify particular Web
servers. For example, in the URL http://www.cbse.nic.in/welcome.htm, the domain
name is http://www.cbse.nic.in.
IP Address Vs MAC Address:
Domain Name:
COMPUTER NETWORKING
25
COMPUTER NETWORKING
A domain name usually has more than one parts: top level domain name or primary
domain name and sub-domain name(s). For example, in the domain name , in
is the primary domain name; nic is the sub-domain of in; cbse is the sub-domain of nic.
There are only a limited number of top level domains, and these are divided into two
categories: Generic Domain Names and Country-Specific Domain Names. For example:
Generic Domain Names:
·com – commercial business
·edu – Educational institutions
·gov – Government agencies
·mil – Military
·net – Network organizations
·org – Organizations (nonprofit)
Country Specific Domain Names:
.in – India
·au – Australia
·ca – Canada
.ch – China
.nz – New Zealand
.pk – Pakistan
.jp – Japan
.us – United States of America
In context of internet, a Domain Name is a name assigned to a server through
Domain Name System (DNS). A domain name usually has more than one parts: top
level domain name or primary domain name and sub-domain name(s).
cbse.nic.in
26
Domain Name Resolution: Domain Name Resolution is the process of getting the
corresponding IP address from a domain name. It happens as follows:
Suppose you mention a URL in the web-browser to visit a website. The browser first
checks your computer to find if the IP address of the server corresponding to the Domain
Name (embedded in the URL) is present. If this address is present then with the help of
this address, the corresponding server is contacted and then the website opens in your
browser. Otherwise the browser sends this domain name to some specific servers (called
domain name servers) to find the corresponding IP address. Once the IP address is known,
the server is contacted and then the website opens in your browser.
Domain Name Resolution is the process of getting corresponding IP address from
a domain name.
The Internet Corporation for Assigned Names and Numbers (ICANN) is an
internationally organized, non-profit corporation that has responsibility for
Internet Protocol (IP) address space allocation, protocol identifier assignment,
generic (gTLD) and country code (ccTLD) Top-Level Domain name system
management, and root server system management functions. These services were
originally performed under U.S. Government contract by the Internet Assigned
Numbers Authority (IANA) and other entities. ICANN now performs the IANA
function.
Computer networks are communication highways on which the data travels. Data travels
on a network when an e-mail is sent or received, any transaction is made using a credit or
a debit card, a web site is accessed, chatting is done, or any other work is done on a
network. Data travelling over a network is vulnerable to attacks and thefts. There are
some people who want to illegally access this data for any reason: using a credit/debit
card data for shopping, using a company’s data to sell it to some rival company, to find the
kind of web sites a person accesses, or may be hundreds of other reasons. These people
Know More!
Network Security
COMPUTER NETWORKING
27
COMPUTER NETWORKING
may sometimes also want to destroy the data on its way, or block the services of some
resources or sites. As the data goes from one point to another point on the Internet, for
example, it may pass through several points along the way, giving other users the
opportunity to access, and even alter it. Even other users on your system may maliciously
transform your data. Unauthorized access to your system may be obtained by intruders,
who then use advanced knowledge to impersonate you, steal information or even deny
your access to your own resources.
Therefore, there is always a threat of some kind of attacks on computer networks’
security. Some kinds of attacks on network security are as follows:
A Denial of Service (DoS) attack is an attempt to make one or
more network resources unavailable to their legitimate users. Examples of such attacks
are:
Denial of Access to Information: Corrupting, Encrypting, or changing the
status of information so that it is not accessible to its legitimate user.
Denial of Access to Application: Forced shutting of an application as soon as
the user opens it.
Denial of Access to Resources: Blocking a resource, may be a printer or
scanner or USB port, of a computer from proper working.
Denial of Access to a Website: Continuously sending bulk requests to a website
so that it is not available to any other user.
An Intrusion problem is an attempt to mischievously steal some
information from someone’s computer. Examples of Intrusion are:
Have you ever tried to read someone else’s slam book secretly? This is
snooping. Have you ever tried to read what someone else is writing in his/her
letter/email to someone else? This is snooping. Do you think your parents try to secretly
check your mobile phone to find its contents? If yes, then what your parents are doing is
snooping.
In context of network security, snooping refers to gaining unauthorised access to another
person’s or organization’s data. This may be done in a number of ways:
Denial of service attacks:
Intrusion Problems:
Snooping –

28
By getting someone’s login information by casually watching what he/she is
typing.
Reading the files on someone’s computer in an unauthorised manner
Using some softwares which keeps track of the activities and data being sent or
received on someone’s computer.
Snooping refers to gaining unauthorised access to another person’s or
organization’s data.
Do you ever find that when you are talking to someone else, another
person is secretly trying to listen to your talks? What that person is doing is
‘eavesdropping’. Have you ever tried to secretly listen to the conversation between two
teachers regarding your class? If yes, then what you have done is ‘eavesdropping’.
In context of network security Eavesdropping refers to unauthorised access to another
person’s or organization’s data while the data is on its way on the network.
This may be done in a number of ways:
By setting up parallel telephone lines.
By installing some software (spyware) in the target computer.
By installing some receiver which captures the data while on its way.
Eavesdropping refers to gaining unauthorised access to another person’s or
organization’s data while the data is on its way on the network
It is the responsibility of a person/organization to protect its network from such attacks.
The term Network Security refers to all activities undertaken to protect a computer
network from attacks to its security. This covers protection of computers in the premises
and data on the network from both internal and external attacks. To protect a network
from security attacks, a number of steps are taken. These steps include:
By assigning login names and strong passwords to the users of a system,
it can be ensured that only authorized people access a computer. This helps in increasing
the computer as well as network security. A strong password is the one which is easy to

Eavesdropping –
Login-Password:
COMPUTER NETWORKING
29
COMPUTER NETWORKING
remember for the user but difficult (almost impossible) for the others to guess
successfully. On the other hand a weak password is generally the name of a person or
organization, the registration number of a vehicle, year of birth of a person and so on. A
weak password can be cracked in a few attempts. Examples of strong passwords may be
raavanisdead (raavan is dead – with spaces removed), 2aur2paanch (name of an old Hindi
movie) or anything like that.
A firewall is a hardware device or a software that is installed to monitor the
data entering the computer/Network or leaving it. A firewall permits only that data to
enter or leave a computer/Network for which permissions have been granted by the
computer/network administrator.
These days anti-virus softwares work against not only the virus but
also against almost all kinds of malware. Therefore by installing a full version legal (not
the pirated one or freeware) anti-virus software network security can be increased.
A data file on a computer can be created, read, or modified. An
application file can be run or executed. Accordingly, different rights (privileges) can be
given to different users of a computer to perform one or more of these tasks. For
example, suppose there is a data file containing students’ marks in a school. The system
administrator has created that file. If there is a need to create another such file, then
again only the system administrator can create it. So, system administrator is given the
‘Create’ right. A teacher can read this file to go through the marks of the students. She can
also enter or alter the marks in this file. Therefore a teacher has ‘Read’, ‘Write’, and
‘Modify’ rights to this file. The students can only view their marks; therefore, the students
are given only the ‘Read’ right to this file. If report cards have to be printed for a class, the
class teacher makes a request to the computer operator, who can run a program to print
the report cards. This computer operator has been given the ‘Execute’ right to the
application program which prints the report cards. This way by giving appropriate rights
to respective users, computer security as well as network security can be increased.
Let us now take an example to see how can a computer network be setup.
Think of a hypothetical Educational Society (say XYZ Educational Society) with its head
Firewall:
Anti Virus Software:
File Permissions:
Setting up a computer network
30
office in Chennai (Tamil Nadu) and schools in various parts of the globe. The society is
setting up a new senior secondary school, ‘SF School’, in Bahadurgarh (Haryana).
The ‘SF School’ will have 3 computer labs with 30 computers in each, 1 Accounts office
with 3 computers, 1 Administrative block with 5 computers, and 1 Principal’s office with 1
computer. Let us see how a computer network can be set up in the school.
First of all we can draw a rough sketch of the school with computers at various locations
as follows:
Independent LANs can be set up in each of the following buildings:
Computer Lab1, Computer Lab2, Computer Lab3, Administrative Block, Accounts Office.
These LANs can be set up in STAR topology using UTP cable (economical, reliable, and
easily available). For this 1 switch (with suitable number of ports) will be required in
each of these buildings. More than one switches can be used in computer labs if a switch
with more than 30 ports is not available.
Two internet connections (broadband for high speed) can be procured in Administrative
Office. Two connections should be procured from two different ISPs so that
(i) Internet connection in Administrative office can be kept separate from the
other Computer labs where students may do a lot of experimentation.
(ii) If one internet connection is not working, the other can be used in case of
urgent requirements.
COMPUTER NETWORKING
Computer Lab 1
Administrative
Block
Principal’s
Office
Accounts
Office
Computer Lab 2 Computer Lab 3
31
COMPUTER NETWORKING
These buildings can then be connected as follows:
This interconnection will ensure that each building is directly connected to
Admisnistrative block. This way internet connection will be available in each building
irrespective of the status of the other building.
Server (if any) of the school may be placed in Administrative block so that it remains safe
(physically) and a firewall can be set up so that the whole network remains safe from any
kinds of virus or intrusion attacks.
There is no need to do any extra efforts or expenses to link the school to its head office.
This can be taken care of using the internet connections.
A computer network is a collection of interconnected computers and other
devices which are able to communicate with each other.
Communication Media are the links over which the data is sent from one node
to another over a network.
Hardware devices used to form a network are: Cables, NIC, Hub, Switch,
Repeater, and Gateway.
Repeaters are used to regenerate the signal which gets weakened during its
transmission. Repeater are generally used to connect two networks which are
more than 80 m apart.
Gateway is a device which connects two different types of networks.
On the basis of area covered by a network it is categorized as PAN, LAN, MAN, or
WAN.
SUMMARY

Principal’s
Office
Computer Lab 1 Computer Lab 2
Administrative
Block
Accounts
Office
Computer Lab 3
32
Physical arrangement of computers in a network is called network topology.
Basic network topologies are bus, star and tree.
Each machine on a network is identified by its IP address.
Conversion of domain name into IP address is done by DNS (Domain Name
Server)
Denial of service, snooping and intrusion are some common threats for network
security.
Network security can be increased by applying some preventive methods.
The scenario of how computers are networked is changing very fast. Before full
implementation of a technology, a new technology is visible at the horizon. One
such new technology is 4G. 4G stands for fourth generation of mobile technology.
Change from one generation to another involves a major advancement in the
technology used. 1G technology was used in the first mobile phones. 1G used
analog radio signals. 1G was introduced in 1980s and continued until 1992 when
2G was introduced. 2G technology used a digital format and introduced text
messaging. 2G also introduced data services for mobiles, starting with SMS. 3G
technology has introduced more efficient ways of carrying data, making it
possible to have faster web-services, live chat, fast downloading, video
conferencing etc. over mobile phones. Today we are living in the world of 3G.
Soon, 4G will rule the mobile market. Unlike previous generations of mobile
technology, 4G mobile technology will be used for internet access on computers
also, and it will be totally wireless! 4G will provide internet access, high quality
streaming video and “anytime, anywhere” voice and data transmission at a much
faster speed than 3G. The “anytime, anywhere” feature of 4G is also referred to
as “MAGIC” (Mobile multimedia; Anytime/anywhere; Global mobility support;
Integrated wireless solution; Customized personal services).
You can explore more about 4G technology on the internet.

Future Trends
4G Technology
COMPUTER NETWORKING
33
COMPUTER NETWORKING
This is an emerging area of demand based resource sharing, resulting into drastic
saving of energy and cost. This is also referred to as ‘Green IT’.
You can explore more about Cloud Computing on the internet.
1. Which of the following topologies is a combination of more than one topologies?
a. Bus b. Tree
c. Star d. None of these
2. Which of the following is used for wireless communication?
a. Optical Fiber b. UTP cable
c. Radio Waves d. Coaxial Cable
3. Which of the following is not a transmission medium?
a. Telephone Network b. Coaxial Cable
c. Modem d. Microwaves
4. IP addresses of two computers on a network:
a. Can be the same b. Cannot be the same
c. Are not defined d. Must match with a third computer
5. Bluetooth can be used for
a. Long distance communication b. Short distance communication
c. In mobile phones only d. None of the above
6. Micro waves are
a. Uni directional b. Omni directional
c. Guided media d. Not used for communication.
Cloud Computing
MULTIPLE CHOICE QUESTIONS
EXERCISES
34
7. Snooping is
a. A threat to data security b. Not a threat to data security
c. Good for laptops d. A topology
8. A repeater
a. Regenerates the received signal b. Destroys the received signal
c. Can be used as a hub d. None of the above
9. Satellite links are generally used for
a. PANs b. LANs
c. MANs d. All of the above
10. A domain name maps to
a. A URL b. An IP address
c. A website d. All of the above
1. What is a computer network? What are its advantages?
2. What is meant be communication channels? Give two examples of guided media and
two examples of unguided media.
3. Which communication channel(s) is/are suitable in each of the following situations:
a. Setting up a LAN
b. Transfer of data from a laptop to a mobile phone.
c. Transfer of data from one mobile phone to another.
d. Creating a remote control that can control multiple devices in a home.
e. Very fast communication between two offices in two different countries.
f. Communication in a hilly area
g. Communication within a city and its vicinity where cost of cabling is too high.
4. Why is a switch called an intelligent hub?
ANSWER THE FOLLOWING QUESTIONS
COMPUTER NETWORKING
35
COMPUTER NETWORKING
5. When is a repeater used in a computer network?
6. Diagramatically show how would you connect 6 PCs, 1 server, 1 printer, and 2
scanners in
a. Star topology b. Bus topology
7. Two engineers in the same room have connected their Palm-tops using bluetooth for
working on a Group presentation. Out of the following, what kind of Network have
they formed?
LAN, MAN, PAN, WAN
8. What is a MAC address? What is the difference between a MAC address and an IP
address?
9. Give some examples of domain names and URLs. How is a domain name different
from a URL?
10. What is domain name resolution?
11. Define Network security? What kind of attacks can be made on data and computer
networks?
12. List some methods which are used for network security.
13. Differentiate (with examples wherever possible) between :
a. LAN and MAN b. MAN and WAN
c. Hub and Switch d. Guided and Unguided media
14. Write one advantage of star topology over bus topology and one advantage of bus
topology over star topology.
15. Ishika Industries has set up its new production unit and sales office at Ranchi. The
company compound has 4 buildings as shown in the diagram below:
Administrative
Office
Factory A
Factory B
Sales Office
36
COMPUTER NETWORKING
Distances between these buildings are as follows:
Administrative Office to Factory A 150 m
Factory A to Factory B 50 m
Factory B to Sales Office 100m
Sales Office to Administrative office 200m
Administrative Office to Factory B 125 m
Number of Computers in each of the buildings is follows:
Administrative Office 15
Factory A 25
Factory B 18
Sales Office 15
1. Suggest a cable layout of connections between the buildings so that each building is
directly connected to Administrative Office.
2. Suggest the most suitable place (i.e. building) to house the server of this production
unit with a suitable reason.
3. Suggest the placement of the following devices with justification:
(i) Repeater
(ii) Hub/Switch
4. The Administrative office of this unit is to be linked with the head office situated in
Patiala (Punjab). What will be the most economical way to do this? Justify your
answer.
37
COMPUTER NETWORKING
LAB EXERCISES
TEAM BASED TIME BOUND EXERCISES
1. Find the IP addresses of at least five computers in your school.
2. Find the MAC addresses of at least 2 computers in your lab. Then verify their
manufacturer’s name on the net.
3. Find the layout of LAN in your school’s labs. If you think some modifications can be
done in the layout, note these down in your notebook.
4. Find the name of Internet Service Provider of your school.
5. Find the IP address of your school’s web site.
(Team size recommended: 3 students each team)
1. A school building is divided into 4 blocks (A, B, C, and D). Each block is at a distance
of 25m from its adjacent blocks. Each block has 1 computer lab with 15 computers
each. Each block also has some other rooms (maximum 10) with 1 computer each.
The school has only one internet connection. The computer network in the school
has to be restructured with the following goals in mind:
Each lab has to have an independent LAN.
All the computers in the school should have internet access. (The school does
not want to have any other new internet connection.)
For internet access a computer should be dependent only on one point and not
on multiple points. It means that if the internet connection is active, any
computer should be able to access it directly irrespective of whether some
other computer in the school is ON or OFF.
Any two computers in the school should be able to communicate with each
other irrespective of whether any other computer in the school is ON or OFF.
The job of each team is to design a layout for this new network structure. Each team
has to specify
The layout of the network structure diagrammatically.

38
COMPUTER NETWORKING
Topology/topologies is/are used in the layout.
How the design will be able to fulfill all the mentioned requirements.
2. Find the average price and specifications of each of the following network devices in
the market: Switch , Cable (UTP), LAN Card. Each team has to specify:
Different types of switches available in the market, their prices, and number of
ports.
Names of brands of UTP Cable available in the market, along with their prices.
Different types of LAN cards available in the market along with their prices.

39
OPEN SOURCE CONCEPTS
Learning objectives

2 Puzzle
Introduction
After learning this chapter the student will be able to:
Understand about OSS/FOSS/FLOSS
Cite different examples of OSS
Describe open document format
Understand character encoding in Indian languages
Know about open type/true type/static/dynamic fonts
Write the numbers 1 to 8 in the given circles so that no two numbers joined by a line differ
by 1.
Computers and internet have transformed our lives. Software is required to work on a
computer but the software that we buy or download only comes in the compiled ready-
PT
A
E
H
R
C
2
40
OPEN SOURCE CONCEPTS
to-run version. It is next to impossible to modify the compiled version of the software. At
times we feel the need to change certain features of the software but are unable to do so.
In this chapter we will study about software which are developed collaboratively and
they can be modified as well. Such software are available in many forms like Free
Software, Open Source Software (OSS), Free Open Source Software (FOSS) and
Free/Liberal Open Source Software (FLOSS).Well, have you noticed something common
in all these terms. That’s right! It is the word free. People often correlate this word with
the cost. They think that these software are available for free. Practically, these software
can be acquired at very little or no cost. But, here, “free” means freedom to use.
These software can be studied, copied, redistributed freely and even modified according
to one’s need without seeking any kind of permission. In order to modify such software the
developers also provide the source code to the users.
There do exist software which are actually “free” in the sense of price. These are known as
Freeware. Lots of freeware can be downloaded from the internet for various different
purposes such as currency converters, drawing graphs and charts etc. But freeware may
not come with the source code. Therefore freeware differ from free software. The focus
in this chapter is on free software rather than freeware.
The first formal definition of “free software” was given in 1983 by Richard Stallman, a long
time member of the hacker community at the MIT Artificial Intelligence Laboratory. He
insisted that a free software should give the following four freedoms to users:
Freedom 0: The freedom to run the program for any purpose.
Freedom 1: The freedom to study how the program works, and change it to
make it do what you wish.
Freedom 2: The freedom to redistribute copies so as to help your neighbour.
Freedom 3: The freedom to improve the program, and release your
improvements (and modified versions in general) to the public, so that the
whole community benefits.
Examples of free software include the Linux Kernel, MySQL Relational Database, Apache
web server, OpenOffice.org office suite and TeX and LaTeX typesetting systems.

41
OPEN SOURCE CONCEPTS
Later on, the term “free software” was recoined as “open source software (OSS)” and soon
after as “free open source software (FOSS)”. In order to avoid the ambiguity in the word
“free”, in 2001, FOSS was termed as FLOSS, short form of “free/liberal open source
software”.
You can get more information on open source software from opensource.org.
National Resource Centre for Free and Open Source Software (NRCFOSS) is an initiative of
the Department of Information Technology, Ministry of Communications & Information
Technology, Government of India. NRCFOSS contributes to the growth of FOSS in India
through Research & Development, Human Resource Development, Networking &
Entrepreneurship development, as well as serves as the reference point for all FOSS
related activities in the country.
Operating systems and Desktop environments
Linux – Operating system kernel
Ubuntu – Linux distribution with full complement of software for everyday
use.
Google Chrome OS – Lightweight operating system based around the web
browser
Android smart – phone operating system – by Google / Open Handset Alliance
Symbian smart – phone operating system – by Nokia
Graphics and multimedia
GIMP – Bitmap graphics editor, similar to Adobe Photoshop
Blender – Advanced 3D modelling and rendering application.
Songbird – similar to iTunes with built-in browser.
Know More!

NRCFOSS :
Examples of FLOSS/FOSS :
42
OPEN SOURCE CONCEPTS
Audacity – digital audio editor
Ardour – digital audio workstation
F-Spot – Photo manager
Office software
OpenOffice.org – office productivity software. Comparable to Microsoft
Office. It uses an open file format and can read and write Microsoft Office files
NeoOffice – Mac OS X version of OpenOffice
PDFCreator – creates PDFs from any Windows program.
Internet related software
Apache webserver – web server
Mozilla Foundation
Mozilla Firefox – web browser
Mozilla Thunderbird – mail client
Google Chrome – Google’s web browser
Other
Celestia – 3D space simulation software.
Flight Gear – flight simulator
Second life – virtual world viewer
Wine – a compatibility layer for computers running Linux that enables them to
run many applications that were originally written for MS Windows
Programming related
Eclipse – software framework and Java IDE
PHP – server-side programming language
PERL – Dynamic programming language

43
OPEN SOURCE CONCEPTS
Python – versatile, clean and powerful programming language used for crossplatform
desktop applications, server-side scripting for websites, and scripting
within java and .net environments
MySQL – Database management system
Java – Programming language
More comprehensive list of open-source software can be found at :
http://en.wikipedia.org/wiki/List_of_open_source_software_packages
The GNU Project was launched in 1983 by Richard
Stallman of Free Software Foundation (FSF) to develop a
complete Unix-like operating system which is free software:
the GNU operating system. Unix-like operating systems are
built from a collection of libraries, applications and developer
tools, plus a kernel to allocate resources and to talk to the
hardware. GNU is often used with the Linux kernel. The
combination of GNU and Linux is the GNU/Linux operating
system, now used by millions.
Firefox is a free and open source web browser
produced by Mozilla Foundation. Firefox runs on various
versions of GNU/Linux, Mac OS X, Microsoft Windows and many
other Unix-like operating systems.
Open Office is the leading open source office
suite for word processing, spreadsheets, presentations,
databases etc. It is available in many languages. It stores files in
open document format (ODF) for data interchange that is its
default file format.

GNU/Linux –
Firefox –
Open Office –
44
OPEN SOURCE CONCEPTS
NetBeans –
BOSS( Bharat Operating Systems Solutions) –
NetBeans began in 1996 as verify, a Java
Integrated Development Environment (IDE) student
project, under the guidance of the Faculty of
Mathematics and Physics at Charles University in
Prague. In 1999 it was bought by Sun Microsystem which open-sourced the NetBeans IDE
in June of the following year. The NetBeans community has since continued to grow,
thanks to individuals and companies using and contributing to the project. NetBeans
refers to both a platform framework for Java desktop applications, and an IDE for
developing applications with Java, JavaScript, PHP, Python, Ruby, C, C++, and others.
BOSS is
a free Indian Operating System based on GNU/LINUX
developed by C-DAC(Center for Development of
Advance Computing). BOSS makes it easier for a
Microsoft Windows user to shift to GNU/LINUX
platform which is there with variant features. Currently BOSS GNU/Linux Desktop is
available in many Indian Languages which also enables the non-English literate users in
the country to be exposed to Information and communication technology and to use the
computer more effectively.
A commonly voiced concern about open source software:
Open Source Software Security
“If anyone can contribute to open source software, doesn’t it become a free-for-all
full of loopholes?”
The Answer is while anyone can propose a contribution to an open source project, any
actual change must go through a small core group of maintainers first. Getting a change
incorporated into an open source project is thus rather like getting an article published in
a scientific journal.
Open source software is more heavily tested than their commercial counterparts as it can
be downloaded by anybody around the world and any one of them can discover a bug or
security flaw and submit those reports back to the project.
45
OPEN SOURCE CONCEPTS
Also since it’s an Open Source, if any bug or flaw is found, project’s core maintainers,
while potentially embarrassed, have no further reason to cover up the flaw like their
proprietary counterpart. Also the loop-hole or bug is available to every one and the
customer can take the preventive measure accordingly and fix comes faster.
The Open Document format (ODF) is a format for office documents, such as spreadsheets,
databases, presentations and word-processing documents. Open Document is a free and
open format. For governments, businesses, archivists and others, it’s critical to store
documents in a way that can be read for years to come. Proprietary digital file formats
are typically changing with every new version of the software, so there should be some
format which supports files created in any application. The data should be the center of
importance not the application. Office suite applications, as always, need a file format
that is designed to organize the data when it moves away from the application. People
with different machines in different places should be able to open and edit the data in a
file. ODF offers an open alternative to the formats used by all of the existing Office
application versions for text, spreadsheet, presentation, and other kinds of documents.
Open Document’s main file extensions are .odt (for text documents), .ods (for
spreadsheets), and .odp (for presentations). These will be more commonly recognized
when more people and organizations adopt Open Document-ready software.
Ogg Vorbis is a new audio compression format developed by Xiph.org. It is an open,
patent-free, professional audio encoding and streaming technology with all the benefits
of Open source. It is comparable to other formats such as MP3, VQF, AAC etc. used to store
and play digital music.
A character encoding system consists of a code that associates each character from a
given system with something else, such as a sequence of natural numbers, binary
numbers or electrical pulses, in order to facilitate the transmission of data (generally
numbers and/or text) through telecommunication networks or for storage of text in
Common open standards
Open Document Format
Ogg Vobris
Character Encoding
46
OPEN SOURCE CONCEPTS
computers. ASCII, EBCDIC, and UNICODE are the most widely used character encoding
systems for computers.
Let us recall from Annexure I of Class XI that in order to communicate with the computers
some kind of a binary code is required. In this regard, a detailed study was made on BCD
code which is a 4 bit code. However, BCD code is not sufficient enough to accommodate
even all the characters of English alphabet and digits. To accommodate all these, a higher
bit code is required. Among such codes, the most popular is the ASCII code (American
7 Standard Code for Information Interchange). It is a 7 bit code that can store 2 = 128
characters. In the earlier days most computers were using an 8 bit system. This extra bit
gave computer developers lot of empty spaces which was used for different purposes. In
order to work with Indian languages, these unspecified spaces were used for Indic
characters. The efforts were very creative and gave good results despite the fact that
there was no or very little support from the operating systems. Since no general rules and
methodologies were adopted in developing Indic characters, different developers
developed these characters in their own ways. This created compatibility issues across
different programs and across different operating systems. For example browsers like
Internet Explorer did not support all Indic characters and displayed distorted texts.
On one hand, more and more work had been undertaken to facilitate the use of Indian
languages on computers but on the other hand it was becoming difficult to maintain
consistency across different programs developed for the same set of Indic characters. In
such a scenario, it was important to have a common standard for coding Indian scripts. In
1991, the Bureau of Indian Standards (BIS) adopted the Indian Script Code for Information
Interchange (ISCII), the ISCII standard that was evolved by a standardization committee,
under Department of Electronics during 1986-88.
ISCII is an 8 bit encoding system as compared with the 7 bit ASCII. The lower 128 code
points are plain ASCII while the upper 128 code points are ISCII specific containing the
basic alphabets required for the 10 Indian scripts (Assamese, Bengali, Devanagari,
Gujarat, Gurmukhi, Kannada, Malayalam, Oriya, Tamil and Telugu) which have originated
from the Brahmi script.
Indian Language Computing
47
OPEN SOURCE CONCEPTS
Know More!

The Indic scripts are a family of abugida (alphabetic-syllabary) writing systems.
They are used throughout South Asia, Southeast Asia, and parts of Central and East
Asia, and are descended from the Brahmi script of the ancient Indian
subcontinent. They are used by languages of several linguistic families: Indo-
European, Dravidian, Tibeto-Burman, Mongolic, Austro-Asiatic, Austronesian, Tai,
and possibly Korean (hangul). They were also the source of the dictionary order of
Japanese kana.
For a long time ASCII has been the standard code used worldwide. ISCII was the Indian
contribution to work with Indian languages. Similarly, to work with other languages of the
world, people were making efforts to use ASCII along with the extra 8th bit. Efforts were
continued to conceive a single standard code which could cater to all world’s languages
and it was UNICODE.
Unicode was developed with the aim to conceive a single standard code which could
manage to represent all languages of the world.
Unicode characters are represented in one of the three encoding forms: a 32-bit form
(UTF-32), a 16-bit form (UTF-16), and an 8 bit form (UTF-8). The 8-bit, byte oriented
form, UTF-8, has been designed for ease of use with existing ASCII-based systems.
With the usage of Unicode, single versions of software were developed instead
of language-specific versions that reduced the complexity.
UNICODE is supported by most OS and application vendors. This ensures
platform, vendor and application independence.
Incorporating Unicode into applications and websites offers significant cost
savings than proprietary solutions.
It allows data to be transported through several different systems without
distortion.
UNICODE
Advantages of Unicode
48
OPEN SOURCE CONCEPTS
Since every number and character combination is unique, the representation
results in a true standard.
This font format was developed by Adobe in 1980’s. This font consists of two parts which
are both necessary for the font to be properly printed and displayed on screen. With most
operating systems, these fonts can be installed simply by being placed in the system’s
folder. However, for Micro Soft operating systems predating windows 2000, they need to
be installed using ATM (Adobe Type Manager) utility.
This format was jointly developed by Apple and Microsoft in the late 80s. These fonts
contain both the screen and printer font data in a single component, making the fonts
easier to install. And that is why these are a good choice for those who find the
installation of fonts difficult.
This is the latest font format which is a joint effort by Apple and Microsoft. Like True Type
fonts, this contains both the screen and printer font data in a single component. However,
open type fonts support multiple platforms and expanded character sets. Additionally,
open type format allows the storage of upto 65,000 characters. This additional space
provides freedom to include add-ons such as small caps, old style figures, alternate
characters and other extras that previously needed to be distributed as separate fonts.
However, not all open type fonts contain additional characters. Many fonts have been
converted from either PostScript or TrueType formats without expanded character sets to
take advantage of the cross-platform functionality benefits of Open Type. OpenType
fonts that do contain expanded character sets are referred to informally as OpenType Pro
fonts. Support for OpenType Pro fonts is increasing, but the format is yet to be fully
supported by all applications.

Different Types of Fonts
Post Script
True Type
Open Type
49
OPEN SOURCE CONCEPTS
Static and Dynamic fonts
Static fonts –
Dynamic fonts –
Phonetic Text Entry (Transliteration)
Keymap based Text Entry
In these types of fonts the characters are designed and digitized and then
stored in font files. Every time printing takes place, same character will appear with
same shape e.g. Times New Roman, Arial etc.
Dynamic font is a web browser technology used when visiting any
website that uses fonts which are not installed on client’s machine. The web browser
would not be able to display the page properly, but will select one of fonts available on
client machine. In this the characters are redefined at each occurrence (everytime they
are displayed or printed). All hand written fonts such as handwritten alphabets,
calligraphic letters, graffiti etc are dynamic fonts because of individual variations.
This technology is helpful in displaying multilingual websites.
Many tools have been developed to facilitate the typing of Indian language text. These
tools broadly support two types of text entries:
Phonetic Text Entry
Keymap based Text Entry
In this type of text entry, traditional keyboards with English keys are used. But while
typing, the Indian alphabets are written phonetically (i.e., the way they sound as per the
pronunciation) in English Script and then converted to corresponding language word. For
e.g. we will type “mera desh mahaan” from English keyboard and the relevent phonetic
key entry software will transliterate it in the language selected eg. Hindi.(“esjk ns’k egku”)
In this method the keyboard keys are mapped to specific characters using a keymap. The
whole arrangement of mapping the keyboard keys to specific language characters is
known as keymap. A keymap is internally stored as a table. Multiple keymaps are used to
store complete keymapping e.g. a table to represent the keymappings without any
additional key press(such as shift) ; a table representing keymappings along with Shift key
press; along with Ctrl key press and so on.
Entering Indian language text

50
OPEN SOURCE CONCEPTS
Indian language keymaps are known as INSCRIPT keymaps or Indian Script Keymaps.
The ASCII characters of a standard QWERTY keyboard are on the left half of a key. The INSCRIPT
(Indian Script) overlay characters are shown on the right half of a key. CAPS LOCK is used to select
the INSCRIPT overlay.
When Nukta “-” is typed after character, the character shown to its left on the
key, is obtained.
ENGLISH KEYBOARD WITH INSCRIPT OVERLAY
NUKTA CHARACTERS IN INSCRIPT OVERLAY
51
OPEN SOURCE CONCEPTS
INSCRIPT OVERLAY FOR ASSAMESE
Know More!
Future Trends
You can get more information on Indian script keymaps from
http://tdil.mit.gov.in/isciichart.pdf.
At present very few open source endeavors which involve few people are there and
are largely unstructured and undisciplined. But as this concept matures in future
more OSS projects will come up and will adopt more structured methodologies to
code, control and coordinate. In future this concept will be adopted at a big level
by private and government sector. This will force companies to embrace open
source and will force the open source community to innovate in line with more
complex need of government and business.
52
OPEN SOURCE CONCEPTS

Free and open source software, also OSS, FOSS, or FLOSS (free/libre open
source software) is software that is liberally licensed to grant the user right to
use, study, change, and improve its design through the availability of its source
code.
NRCFOSS – National Resource Centre for Free and Open Source Software.
ODF (Open Document Format) offers an open alternative to the formats used
by all of the existing software.
Ogg Vorbis is open audio compression format.
A character encoding system consists of a code that associates each character
from a given system with something else, such as a sequence of natural
numbers, binary numbers or electrical pulses, in order to facilitate the
transmission of data (generally numbers and/or text) through
telecommunication networks or for storage of text in computers
ISCII – Indian Script Code for Information Interchange is common standard for
coding Indian Scripts.
UNICODE – Universal Code is a single standard code which can cater to all the
world’s languages.
Post Script font consists of two parts which are both necessary for the font to be
properly printed and displayed on screen.
True type fonts contain both the screen and printer font data in a single
component.
Open type fonts support multiple platforms and expanded character sets.
On the basis of their configuration, fonts are categorized as static fonts and
dynamic fonts.
For entering text in Indian script keymap based or phonetic text based entry
can be done.
53
OPEN SOURCE CONCEPTS
EXERCISES
MULTIPLE CHOICE QUESTIONS
1) Open Document’s main file extensions are
(a) .odt (b) .ods
(c) .odp (d) All of these
2) Technology no longer protected by copyright, available to everyone, is considered
to be
(a) Proprietary (b) Open
(c) Experimental (d) in the public domain
3) Which of the following codes uses 7 bits to represent a character
(a) ISCII (b) ASCII
(c) UNICODE (d) All of the above
4) How many bits are used by UTF-8 to represent a character
(a) 7 (b) 8
(c) 16 (d) 32
5) ASCII stands for
(a) American System Code for Information Interchange
(b) American Standard Code for Information Interchange
(c) American Standard Code for Interchange Information
(d) American System Code for Interchange Information
6) ISCII stands for
(a) Indian System Code for Information Interchange
(b) Indian Standard Code for Information Interchange
(c) Indian Script Code for Interchange Information
(d) International Standard Code for Interchange Information
54
OPEN SOURCE CONCEPTS
7) ISCII is
(a) An 8 bit character code (b) A 16 bit character code
(c) A 7 bit character code (d) Same as ASCII
8) Which of the following is open source operating system
(a) DOS (b) Windows 2010
(c) BOSS (d) Mac
9) Following operations are possible with OSS
(a) Free download
(b) Source code is available
(c) You can redistribute the modified version
(d) All of the above
10) Platform independence is provided by
(a) ASCII (b) ISCII
(c) UNICODE (d) All of the above
1) Define Open source software. Give at least two examples of OSS. Justify that free
software is not open source software.
2) Give examples of two OSS in each of the following categories :
(a) OS (b) Graphics and animation
(c) Office software (d) Internet related software
(e) Programming related software.
3) What is a character encoding system?
4) Differentiate between true type font and open type font.
5) What do you understand by ODF?
ANSWER THE FOLLOWING QUESTIONS
55
OPEN SOURCE CONCEPTS
6) What is Ogg Vorbis?
7) Expand the following terms:
OSS, FLOSS, ISCII, ASCII, BOSS, NRCFOSS
8) What is UNICODE?
9) Write short notes on GNU, BOSS, ISCII
10) What is the difference between static and dynamic fonts?
1) Find out which software in your school lab are open source.
2) Note down the category of software (system software or application software) to
which they belong to.
3) If any of them is application software then specify its area of application.
4) Search on internet about the features of mySQL and Netbeans.
(Team size recommended: 3 students each team)
1) Download open office on your computer. Write down its components, their areas of
applications, their file extensions.
2) Procure BOSS and install it (with the permission of your teacher) on your computer
and write down the features which are similar to windows and also which are not
similar to windows.
LAB EXERCISES
TIME BOUND TEAM BASED EXERCISE
56
Puzzle
After studying this lesson the students will be able to:
Identify, name and state the usage of the different components of the
NetBeans IDE.
Identify and name the various methods and properties associated with the
various form controls
Create simple applications in Java using NetBeans IDE.
Create GUI applications using the concepts of variables and control
structures.
NetBeans IDE allows us to develop applications by dragging and positioning GUI
components from a palette onto a container. The GUI builder automatically takes
care of the correct spacing and alignment of the different components relative to
each other. The JFrame acts as a container for the elements like the JLabel,
JButton, JTextArea and allows direct editing of their associated properties at the
design time and run time. The related methods are used in the code to develop
applications for a specific task. The concept of variables and control structures
are used to simplify the code of the applications.
This group of phrases has something amazing hidden in it. Try and find out what is so
unusual about this group of phrases? Is there any specific pattern in each line? *
Bar crab
Borrow or rob
Straw warts
PT
A
E
H
R
C
3 GUI PROGRAMMING – A REVIEW
57
GUI PROGRAMMING – A REVIEW
Live evil
A man, a plan, a canal–Panama!
Delia failed.
Evil olive
Pull up if I pull up.
Step on no pets.
Ten animals I slam in a net.
Was it a bat I saw?
Was it a car or a cat I saw?
We found an interesting pattern in the puzzle and we will use this concept to develop an
application in netbeans.
Let us take a journey back in time and think as to what the world was like 15 years ago.
Amazon was a large river in South America. Yahoo was a term from Gulliver’s Travels. A
googol was a very large number (one followed by a hundred zeroes) and to get our tickets
booked we had to go to shops called ‘travel agents’. In case we fell sick and went to a
hospital, our records were maintained on paper. If the doctor wanted to refer to a
particular patient’s record, he had to instruct a assistant to hunt for information from the
pile of files.
Nowadays hospitals use computers to keep the records of patients – medical history,
details on what medication to give to a patient, the prescribed dosage and also personal
details that can be accessed at the click of a button. The entire information is entered
into a computer using a front end that accepts the different patient details. We learnt
how to design valid front end forms in class XI in Java using the NetBeans IDE. This chapter
will help us recapitulate all the concepts learnt in class XI.
Introduction
58
GUI PROGRAMMING – A REVIEW
NetBeans IDE
It can be used to create java applications very easily using the efficient GUI builder. Let us
quickly recap the different components of the NetBeans IDE:
Figure 3.1 NetBeans IDE
1. Title Bar
2. Menu Bar with pull down menus
3. Toolbars
4. GUI builder: It is an area to place components on the form visually. There are two
views of the GUI builder- the Design View and the Source View. We can switch over
from one view to another by simply clicking on the source and design tabs directly
above the Design Area.
5. Palette: Palette contains controls or components used to create GUI applications.
Inspector Window Design Area Properties Window Palette
59
GUI PROGRAMMING – A REVIEW
6. Inspector Window: This window is used to display a hierarchy of all the components
or controls placed on the current form.
7. Properties Window: Using this window we can make changes in the properties of
currently selected control on the form.
8. Code Editor Window: – It is the area where we write code for our java application.
Components (also known as “widgets”) are the basic interface elements the user interacts
with: jlabels, jbuttons, jtextfields etc. Components are placed on a container (like the
jFrame). There are two types of controls :
They act as a background for other controls. For
example-Frame. When we delete a parent control, all its child controls get
deleted. When we move a parent control all its child controls also move along
with it.
controls placed inside a container control are called child
controls. For example-Text Field, Label, Button etc.
Components
Parent or container controls:
Child controls:


Parent or container controls
Child controls
Figure 3.2 Parent and Child controls
60
GUI PROGRAMMING – A REVIEW
Creating a New Project
The steps to create a new project are:
1. Select New Project from the File menu. You can also click the New Project button in
the IDE toolbar.
2. In the Categories pane, select the General node. In the Projects pane, choose the
Java Application type. Click the Next button.
3. Enter the name of the project in the Project Name field and specify the project
location. Do not create a Main class here.
4. Click the Finish button.
Let us recap the relation between a Project, Form and Components. Each application is
treated as a Project in NetBeans and each project can have one or multiple forms and this
fact is clear from the Projects window as shown in Figure 3.3.
Figure 3.3 Project Window Showing Multiple Forms
Further each form can have one or more elements – some of which may be visible and
some invisible. The visible components are all shown under the Frame Component and
the non-visible components are part of Other components.
We use the drag and drop feature of NetBeans to place components on the form to design
an effective interface for our applications. The first step that we undertook while
designing our applications was adding a new jFrame form. The jFrame is a window with
Multiple Forms
under one Project
Project Name
61
GUI PROGRAMMING – A REVIEW
title, border, (optional) menu bar and is used to contain all other components placed by
the user on the form. Some of the properties of the jFrame form are
defaultCloseOperation and Title.
defaultCloseOperation Sets action to be performed when the user
attempts to close the form.
Title Sets the text to be displayed in the Title bar of the
form window.
Figure 3.4 Properties of the jFrame Form
Any component of GUI front-end (the form itself and the swing containers and controls
placed in the form) of an application is an object. Each of these objects belongs to its
corresponding class predefined in Java. For example, a form is an object of JFrame class,
all the textfields are objects of JTextField class, and so on. Each object has some
properties, methods, and events associated with it using which you can control the
object’s appearance and behaviour.
Properties of an object are used to specify its appearance on the form. For example to
set the background colour of a textfield you change its background property; to set its
font you change its font property; and so on.
Methods are used to perform some action on the object. For example to display
something in a textfield you can use its setText() method, to extract the contents of a
textfield you can use its getText() method. Methods can be divided into two categoriesgetters
and setters.
Getters are the methods which extract some information from the object and
return it to the program. Getters start with the word get. Examples of getters
are: getText(), getForeground(), getModel(), isEditable etc.
Setters are the methods which set some properties of the object so that the
object’s appearance changes. Setters start with the word set. Examples of
setters are: setText(), setForground(), setModel() etc.
Events are the actions which are performed on controls. Examples of events are:
mouseClick, mouseMoved,keyPressed etc. When the user performs any action on a
Property Description


62
GUI PROGRAMMING – A REVIEW
control, an event happens and that event invokes (sends a call to) the corresponding part
of the code and the application behaves accordingly.
After setting the properties of the jFrame we can start placing components like jButton
on the jFrame form. A button is a component that the user presses or pushes to trigger a
specific action. When the user clicks on the button at runtime, the code associated with
the click action gets executed. The various methods and properties associated with the
jButton are summarized in Figure 3.5.
Background Sets the background color.
Enabled Contains enabled state of component – true if enabled
else false.
Font Sets the font.
Foreground Sets the foreground color.
horizontal alignment Sets the horizontal alignment of text displayed on the
button.
Label Sets the display text.
Text Sets the display text
getText() Retrieves the text typed in jButton.
String result=<button-name>.getText( );
setEnabled Enables or disables the button.
<button-name>.setEnabled(boolean b);
setText() Changes the display text at runtime.
<button-name>.setText(String text);
setVisible Makes the component visible or invisible – true to make
the component visible; false to make it invisible.
<button-name>.setVisible(boolean aFlag);
Figure 3.5 Properties and Methods of the jButton
Property Description
Method Description
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GUI PROGRAMMING – A REVIEW
We developed simple real life applications wherein on the click of the button we
accepted the data from the user in the jTextField and after processing the data the result
was displayed in a jTextField or a jLabel. jTextField allows editing/displaying of a single
line of text. jTextField is an input area where the user can type in characters whereas a
jLabel provides text instructions or information. It displays a single line of read-only text,
an image or both text and image. The various methods and properties associated with the
jTextField and jLabel are summarized in Figure 3.6 and 3.7 respectively.
Background Sets the background color.
Border Sets the type of border that will surround the text field.
editable If set true user can edit textfield. Default is true.
enabled Contains enabled state of component- True if enabled
else false.
font Sets the font.
foreground Sets the foreground color.
horizontalAlignment Sets the horizontal alignment of text displayed in the
textField.
text Sets the display text
toolTipText Sets the text that will appear when cursor moves over
the component.
getText() Retrieves the text in typed in jTextField.
String result=<textfield-name>.getText( );
isEditable() Returns true if the component is editable else returns
false.
boolean b=<textfield-name>.isEditable( );
Property Description
Method Description
64
GUI PROGRAMMING – A REVIEW
isEnabled() Returns true if the component is enabled,else returns
false.
boolean b =<textfield-name>.isEnabled( );
setEditable Sets whether the user can edit the text in the textField.
true if editable else false.
<textfield-name>.setEditable(boolean b);
setText() Changes the display text at runtime.
<textfield-name>.setText(String t);
setVisible() Makes the component visible or invisible – true to make
the component visible; false to make it invisible.
<textfield-name>.setVisible(boolean b);
Figure 3.6 Properties and Methods of the jTextField
background Sets the background color.
enabled Contains enabled state of component- true if enabled
else false.
font Sets the font.
foreground Sets the foreground color.
horizontalAlignment Sets the horizontal alignment of text displayed in the
component.
text Sets the display text
Property Description
65
GUI PROGRAMMING – A REVIEW
Method Description
Property Description
getText() Retrieves the text in typed in jLabel.
String result=<label-name>.getText();
isEnabled() Returns true if the component is enabled,else returns
false.
boolean b=<label-name>.isEnabled();
setText() Changes the display text at runtime.
<label-name>.setText(String t);
setVisible() Makes the component visible or invisible – true to make
the component visible; false to make it invisible.
<label-name>.setVisible(boolean b);
Figure 3.7 Properties and Methods of the jLabel
When we had become familiar with the usage of jTextField and jLabel controls then we
developed an application in which we wanted to accept multiline input and display
multiline output. Well can you recall the name of the component. Exactly the component
is Text Area component. This component allows us to accept multiline input from the user
or display multiple lines of information. This component automatically adds vertical or
horizontal scroll bars as and when required during run time. The various methods and
properties associated with the jTextArea are summarized in Figure 3.8.
background Sets the background color.
columns Sets number of columns preferred for display.
editable If set true user can edit textfield. Default is true.
enabled Contains enabled state of component- true if enabled
else false.
font Sets the font.
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GUI PROGRAMMING – A REVIEW
foreground Sets the foreground color.
lineWrap Indicates whether line of text should wrap in case it
exceeds allocated width.(Default is false)
rows Sets number of rows preferred for display.
text Sets the display text
wrapStyleWord Sends word to next line in case lineWrap is true and it
results in breaking of a word, when lines are wrapped.
append() Adds data at the end.
<textarea-name>.append(String str);
getText() Retrieves the text in typed in jTextArea.
String str = <textarea-name>.getText();
isEditable() Returns true if the component is editable else returns
false.
boolean b = <textarea-name>.isEditable();
isEnabled() Returns true if the component is enabled, else returns
false.
boolean b = <textarea-name>.isEnabled();
setText() Changes the display text at runtime.
<textarea-name>.setText(String t);
Figure 3.8 Properties and Methods of the jTextArea
Let us try and recollect the name of the component which can be used to enter
confidential input like passwords which are single line. That’s right the component is
jPassword. We can suppress the display of input as this component allows us to input
confidential information like passwords. Each character entered can be replaced by an
echo character. By default, the echo character is the asterisk, *. The properties of
jPassword are summarized below:
Method Description
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GUI PROGRAMMING – A REVIEW
Property Description
Property Description
background Sets the background color.
font Sets the font.
foreground Sets the foreground color.
text Sets the display text
echoChar Sets the character that will be displayed instead of text.
Figure 3.9 Properties of jPassword
Well we used radio buttons when we wanted to provide the user several choices and
allowed him to select one of the choices (the radio buttons belong to a group allowing the
user to select single option). But radio buttons occupy a lot of space. Thus, in case of too
many options we used Combo boxes as they help save space and are less cumbersome to
design as compared to radio button. We used check box and list when we wanted to
display multiple options like selecting favourite sports or ordering multiple food items in
a restaurant. The list is a preferred option over check box in situations wherever multiple
options are required to be selected from a large number of known set of options as they
help save space and are less cumbersome to design as compared to check boxes. The
properties and methods of jRadioButton are summarized below:
background Sets the background color.
buttonGroup Specifies the name of the group of button to which the
jRadioButton belongs.
enabled Contains enabled state of component -true if enabled else false.
font Sets the font.
foreground Sets the foreground color.
label Sets the display text.
text Sets the display text.
Selected Sets the button as selected, if set to true, default is false.
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GUI PROGRAMMING – A REVIEW
Method Description
Property Description
getText() Retrieves the text displayed by radio button.
String str = <radiobutton-name>.getText();
isSelected() Returns true if the component is checked else returns
false.
boolean b = <radiobutton-name>.isSelected();
setText() Changes the display text at runtime.
<radiobutton-name>.setText(String t);
setSelected() Checks(true) or unchecks the radio button.
<radiobutton-name>.setSelected(boolean b);
Figure 3.10 Properties and methods of the jRadioButton
jCheckBox is a small box like component that is either marked or unmarked. When you
click on it, it changes from checked to unchecked or vice versa automatically. The
properties and methods of jCheckBox are summarized below:
background Sets the background color.
buttonGroup Specifies the name of the group of button to which the
jCheckBox belongs.
font Sets the font.
foreground Sets the foreground color.
label Sets the display text.
text Sets the display text
selected Sets the check box as selected if set to true, default is
false.
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Method Description
Property Description
getText() Retrieves the text typed in
String str = <checkbox-name>.getText();
isSelected() Returns true if the component is checked else returns
false.
boolean b = <checkbox-name>.isSelected();
setText() Changes the display text at runtime.
<checkbox-name>.setText(String t);
setSelected() Checks(true) or unchecks the checkbox.
<checkbox-name>.setSelected(boolean b);
Figure 3.11 Properties and methods of the jCheckBox
jComboBox is like a drop down box – you can click a drop-down arrow and select an option
from a list whereas jList provides a scrollable set of items from which one or more may be
selected. The properties and methods of jComboBox and jList are summarized below:
background Sets the background color.
buttongroup Specifies the name of the group of button to which the
jComboBox belongs.
editable If set true user can edit ComboBox. Default is true.
enabled Contains enabled state of component- True if enabled else false.
font Sets the font.
foreground Sets the foreground color.
model Contains the values to be displayed in the combobox.
text Sets the display text
selectedIndex Sets the index number of the element which should be selected
by default.
selectedItem Sets the selected item in the combobox. selectedItem and
selectedIndex are in synchronization with each other.
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Method Description
Property Description
getSelectedItem() Retrieves the selected item.
Object result =
<combobox-name>.getSelectedItem();
getSelectedIndex() Retrieves the index of the selected item.
int result =
<combobox-name>.getSelectedIndex();
setModel() Sets the data model that the combo box uses to get its
list of elements.
<combobox-name>.setModel
(ComboBoxModel aModel);
Figure 3.12 Properties and methods of the jComboBox
background Sets the background color.
enabled Contains enabled state of component- true if enabled
else false.
font Sets the font.
foreground Sets the foreground color.
model Contains the values to be displayed in the list.
selectedIndex Contains the index value of selected option of the
control.
selectionMode Describes the mode for selecting values.
– SINGLE (List box allows single selection only)
– SINGLE_INTERVAL (List box allows single continuous
selection of options using shift key of keyboard)
– MULTIPLE_INTERVAL (List box allows multiple
selections of options using ctrl key of keyboard)
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Method Description
Method Description
getSelectedValue() Returns the selected value when only a single item is
selected, if multiple items are selected then returns
first selected value. Returns null in case no item
selected
Object result=
<list-name>.getSelectedValue();
isSelectedIndex() Returns true if specified index is selected.
boolean b =
<list-name>.isSelectedIndex(int index);
Figure 3.13 Properties and methods of the jList
We used JOptionPane when we wanted to request information from the user, display
information to the user or a combination of both. It required an import statement at the
top of the program. Well can you recollect the import statement? That’s right it is:
import javax.swing.JOptionPane;
OR
import javax.swing.*;
Either of them is acceptable. The difference is that the latter will import the entire
library as denoted by the star whereas the first statement will just import the
JOptionPane library.
showMessageDialog() Shows a one-button, modal dialog box that gives the user
some information.
Example :
JOptionPane.showMessageDialog(this,”Java
and NetBeans”);
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showConfirmDialog() Shows a three-button modal dialog that asks the user a
question. User can respond by pressing any of the suitable
buttons.
Example:
Confirm=
JOptionPane.showConfirmDialog(null,”quit?”)
showInputDialog() Shows a modal dialog that prompts the user for input. It
prompts the user with a text box in which the user can enter
the relevant input.
Example :
name=
JOptionPane.showInputDialog(this,”Name:”);
Figure 3.14 Properties and methods of the JOptionPane
Let us try and recollect why the need for variables arose. Well, we used variables when
we required containers to store the values for some input, intermediate result or the final
result of an operation. The characteristics of a variable are:
It has a name.
It is capable of storing values.
It provides temporary storage.
It is capable of changing its value during program execution.
Variables help us to hold value for some input coming from the user or to
hold intermediate result of some calculation or the final result of an
operation. In other words, variables are like containers that can be used to
store whatever values are needed for a specific computation. However, as
different materials require different containers, and so we used different
data types to hold different values.
Variables




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Java programming language requires that all variables must first be declared
before they can be used.
When programming, we store the variables in our computer’s memory, but the computer
has to know what kind of data we want to store in them, since it is not going to occupy the
same amount of memory to store a simple number or to store a single letter or a large
number, and they are not going to be interpreted the same way so variables were used
along with datatypes. The data types supported by java are summarized as follows:
Data type states the way the values of that type are stored, the operations that can be
done on that type, and the range for that type.
These data types are used to store integer values only i.e. whole numbers only. The
storage size and range is listed below :
7 7 byte 1 byte(8 bits) -128 to 127(-2 to +(2 -1)) byte rollno;
15 15 short 2 bytes(16 bits) -32768 to 32767(-2 to +(2 -1)) short rate;
31 31 int 4 bytes(32 bits) -2 to +(2 -1) int num1;
63 63 long 8 bytes (64 bits) -2 to +(2 -1) long amount;
Figure 3.15 Storage size and range of numeric data types
These data types are used to store numbers having decimal points i.e. they can store
numbers having fractional values.
-38 38 float Single precision 4 bytes (3.4×10 ) to +(3.4×10 ) float
floating point (32 bits) average;
-308 308 double Double precision 8 bytes (1.8×10 ) to +(1.8×10 ) double
floating point (64 bits) principal;
Figure 3.16 Storage size and range of floating data types
Numeric Data Types :
Name Size Range Example
Floating Data Types:
Name Description Size Range Example
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The decision about which numeric data type to use should be based on the range of values
that a variable can take.
These data types are used to store characters. Character data types can store any type of
values – numbers, characters and special characters. When we want to store a single
character, we use char data type and when we want to store a group of characters we use
string data type. For example to store grades (A, B, C, D, E) of a student we will use char
type but to store name of a student, we will use string type. The char data type value is
always enclosed inside ‘ ‘ (single quotes), whereas a string data type value is enclosed in ” ”
(double quotes).
Operators are symbols that manipulate, combine or compare variables.
Character Data Types:
Operators
With the introduction of variables and constants there arose a need to perform certain
operations on them. We performed operations on variables and constants using
operators. The operators available in java are summarized below:
One of the most common operator is the assignment operator “=” which is used to assign a
value to a variable. We assign the value given on the right hand side to the variable
specified on the left hand side. The value on the right hand side can be a number or an
arithmetic expression. For example:
int sum = 0;
int prime = 4*5;
These operators perform addition, subtraction, multiplication, and division. These
symbols are similar to mathematical symbols. The only symbol that is different is “%”,
which divides one operand by another and returns the remainder as its result.
+ additive operator
– subtraction operator
Assignment Operator :
Arithmetic Operators :
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* multiplication operator
/ division operator
% remainder operator
A relational operator is used to test for some kind of relation between two entities. A
mathematical expression created using a relational operator forms a relational
expression or a condition. The following table lists the various relational operators and
their usage:
== equal to Tests whether two values are equal.
!= not equal to Tests whether two values are unequal.
> greater than Tests if the value of the left expression is greater
than that of the right.
< less than Tests if the value of the left expression is less than
that of the right.
>= greater than or Tests if the value of the left expression is greater
equal to than or equal to that of the right.
<= less than or Tests if the value of the left expression is less
equal to than or equal to that of the right.
Figure 3.17 Relational Operators
A logical operator denotes a logical operation. Logical operators and relational operators
are used together to form a complex condition. Logical operators are:
&& a>10 && b<8 a and b are both true
|| a>10 || b<8 Either a or b is true
! ! a a is false
Figure 3.18 Logical Operators
Relational Operator :
Operator Meaning Usage
Logical Operator :
Operator Use Meaning
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Unary Operators :
Symbol Name of the Operator Operation Example
Increment/Decrement Operators :
The unary operators perform different kind of operations on a single operand .The
operations performed are increasing/decreasing a value, negating a value/ expression,
or inverting a boolean value.
+ Unary plus operator indicates positive value num = +1;
– Unary minus operator negates an expression num = – num;
++ Increment operator increments a value by 1 num = ++ num;
— Decrement operator decrements a value by 1 num = — num;
Figure 3.19 Unary Operators
The increment/decrement (++,–) operators can be a prefix or a postfix. In a pre
increment/decrement expression (++ x or — x), an operator is applied before an operand
while in a post increment/decrement expression (x++ or x –) an operator is applied after
an operand. In both conditions 1 is added to the value of the variable and the result is
stored back to the variable. However, in a prefix expression, value is incremented first
then this new value is restored back to the variable. In postfix expression the current
value is assigned to a variable then it is incremented by 1 and restored back to the original
variable.
Let us now try and recollect the conversion methods that we have used in java. When a
Java program receives input data from a user, it must often convert it from one form
(e.g., String) into another (e.g., double or int) for processing.
To convert a string value to a number (For example, to convert the String value in a
text field(jTextField1) to an int, long, float or double), we can use parse methods.
Assume the following declarations:
String num1=jTextField1.getText();
int sum; long product;
float amount; double simple_int;
Conversion methods

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Type Example statement
int sum=Integer.parseInt(num1);
int sum=Integer.parseInt(jTextField1.getText());
long product=Long.parseLong(num1);
long product=Long.parseLong(jTextField1.getText());
float amount=Float.parseFloat(num1);
float amount=Float.parseFloat(jTextField1.getText());
double simple_int=Double.parseDouble(num1);
OR
simple_int=Double.parseDouble(jTextField1.getText());
Figure 3.20 Usage of Parse Methods
To convert a number to string we used valueOf method. Assume the following code:
int i = 100;
float f = (float) 200.0;
double d = 400.0;
long l = 100000;
string str1 = String.valueOf(i);
string str2 = String.valueOf(f);
string str3 = String.valueOf(d);
string str4 = String.valueOf(l);
jTextField1.setText(“Values of int, float, double and long
are “+str1+”, “+str2+”, “+str3+” and “+str4);
Figure 3.21 Usage of valueOf Method

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To convert a number to string, we also used toString method. Assume the following
code :
int i = 100;
float f = (float) 200.0;
double d = 400.0;
long l = 100000;
string str1 = Integer.toString(i);
string str2 = Float.toString(f);
string str3 = Double.toString(d);
string str4 = Long.toString(l);
jTextField1.setText(“Values of int, float, double and long
are “+str1+”, “+str2+”, “+str3+” and “+str4);
Figure 3.22 Usage of toString Method
To convert a number to string, we also used concatenation operator(+). If either
operand of a concatenation is a string, the other operand is converted to string.
Assume the following code :
int sum = 103;
String convertsum;
convertsum = “” + sum;
// Converts int 103 to String “103”
convertsum = sum + ” is a number”;
// Assigns “103 is a number” to convertsum.
convertsum = “” + 10.9;
// Assigns “10.9” to convertsum
convertsum = “” + 10.0/3.0;
// Assigns “3.3333333333333333” to convertsum
Figure 3.23 Concatenation operator
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Control Structures
We used control structures when we wanted to control the flow of the program. We learnt
two types of control structures in class XI namely, Selection statements and Iteration
statements.
Control structures allow us to control the flow of our program’s execution. If left
unchecked by control-flow statements, a program’s logic will flow through
statements from top to bottom. We can have some control on the flow of a
program by using operators to regulate precedence of operations, but control
structures provide the power to change statement order and govern the flow of
control in a program.
A selection statement selects among a set of statements depending on the value of a
controlling expression. The selection statements are the if statement and the switch
statement, which are discussed below:
The if statement allows selection (decision making) depending
upon the outcome of a condition. If the condition evaluates to true then the statement
immediately following if will be executed and otherwise if the condition evaluates to
false then the statements following the else clause will be executed. The selection
statements are also called conditional statements or decision statements.
The syntax of if statement is as shown below:
Syntax:
if (conditional expression)
{
Statement Block;
}
else
{
Statement Block;
}
Selection Statements:
Simple if Statement –
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Points to remember about if statement :
The conditional expression is always enclosed in parenthesis.
The conditional expression may be a simple expression or a compound
expression.
Each statement block may have a single or multiple statements to be
executed. In case there is a single statement to be executed then it is not
mandatory to enclose it in curly braces ({}) but if there are multiple statements
then they must be enclosed in curly braces ({}).
The else clause is optional and needs to be included only when some action is to
be taken if the test condition evaluates to false.
These control structures are used to test for multiple conditions as
against the simple if statement which can be used to test a single condition. The syntax of
nested if else is as follows:
Syntax:
if (conditional expression1)
{
statements1;
}
else if (conditional expression2)
{
statements2;
}
else if (conditional expression3)
{
statements3;
}
else
{
statements4;
}




Nested if . . . else –
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Now let us design a form as shown in figure 3.24
Figure 3.24 To check whether the given number is a multiple of 3,5 or 7
Follow the steps enumerated below to design the form:
1. Add a new JFrame Form and change its title property to Quick Multiple Checker.
2. Add a label set its Text as Enter Number
3. Add a jTextField and set its initial Text as “”
4. Add three radio buttons on the form – Set the text of each of them as “Multiple of 3”,
“Multiple of 5” and “Multiple of 7”.Group the radio buttons so that only one can be
selected.
In this application we ask the user to enter a number and then the user will select one of
the radio buttons and depending upon the button selected the multiple check for that
number will be performed. Let us now write the code for the above mentioned
application. Code to check for multiple of 3 is given. Try and write the code to perform a
similar check for multiple of 5 and multiple of 7.
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GUI PROGRAMMING – A REVIEW
private void
jRadioButton1ActionPerformed(java.awt.event.ActionEvent evt)
{
double Number=Double.parseDouble(jTextField1.getText());
if (Number%3==0)
JOptionPane.showMessageDialog(this,”It is multiple of 3″);
else
JOptionPane.showMessageDialog
(this,”It is NOT multiple of 3″);
}
Figure 3.25 Code for Multiple Checker
Let us now understand this code in detail.
Double.parseDouble(jTextField1.getText())
retrieves the value entered by the user in the text field using getText().This
value by default is treated as a string and not as a number so it needs to be
converted to a double type and this is achieved using the parseDouble()
method.The value is then stored in the variable Number.
if (Number%3=0)
check whether the number when divided by 3 gives 0 as the remainder.If the
remainder is zero then the number is divisible by 3 else it is not.
This selection statement allows us to test the value of an expression
with a series of character or integer values. On finding a matching value the control
jumps to the statement pertaining to that value and the statement is executed, till the
break statement is encountered or the end of switch is reached. The expression must
either evaluate to an integer value or a character value. It cannot be a string or a real
number. The syntax of the switch statement is as follows:


Switch Statement –
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GUI PROGRAMMING – A REVIEW
switch (Variable/Expression)
{
case Value1:statements1 ;
break ;
case Value2:statements2 ;
break ;
.
.
default:statements3 ;
}
Switch is used to select sections of code
depending on specific integer or character values. If we are handling specific coded
values (eg, the number of the button that was clicked in a JOptionPane), or processing
characters(whose codes are treated like numbers), then switch is useful. The limitations
of switch are as follows:
It doesn’t allow ranges, eg case 90-100.
It requires either integers or characters and doesn’t allow useful types like
String.
String comment; // The generated result.
int choice = Integer.ParseInt(jTextField.getText);
//Enter 0, 1, or 2.
switch (choice)
{
case 0: comment = “You look so much better than usual.”;
break;
case 1: comment = “Your work is up to its usual standards.”;
break;
Comparing Switch and If..else Statements –


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GUI PROGRAMMING – A REVIEW
case 2: comment =
“You’re quite competent for so little experience.”;
break;
default: comment =
“Oops — something is wrong with this code.”;
}
Equivalent if statement
String comment; // The generated result.
int choice= Integer.ParseInt(jTextField.getText);
//Enter is 0, 1,or 2.
if (choice == 0)
comment = “You look so much better than usual.”;
else if (choice == 1)
comment = “Your work is up to its usual standards.”;
else if (choice == 2)
comment=”You’re quite competent for so little experience”;
else
comment = “Oops — something is wrong with this code.”;
A switch statement can often be rewritten as an if statement. Let us look at the example
given above, when a selection is to be made based on a single value, the switch statement
is generally easier to read. The switch is useful when you need to manage a lot of if /else
if / else. It has a shorter syntax and is more appropriate in this case.
Let us now design an application in which we will calculate the selling price depending
upon the profit percent selected by the user. Design the application as shown in figure
3.26. Set the relevant properties of the components.
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GUI PROGRAMMING – A REVIEW
Figure 3.26 To calculate selling price depending upon profit margin
In this application depending upon the profit percent selected by the user we will
calculate the selling price .Let us now write the code.
//Business Calculator
private void
jButton1ActionPerformed(java.awt.event.ActionEvent evt)
{
double CP,Profit=0,SP;
CP=Double.parseDouble(jTextField1.getText());
Profit=jComboBox1.getSelectedIndex();
SP=CP+CP*(Profit/100);
jTextField2.setText(Double.toString(SP));
}
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GUI PROGRAMMING – A REVIEW
private void
jButton2ActionPerformed(java.awt.event.ActionEvent evt)
{
jTextField1.setText(“”);
jComboBox1.setSelectedIndex(0);
jTextField2.setText(“”);
}
Figure 3.27 Code to calculate selling price
Let us now understand the code in detail.
Double.parseDouble(jTextField1.getText())
retrieves the value entered by the user in the text field using getText().This
value by default is treated as a string and not as a number so it needs to be
converted to a double type and this is achieved using the parseDouble()
method. The value is then stored in the variable CP.
jComboBox.getSelectedIndex()
retrieves the index of the selected item so if the user selects 1st item profit is 0
and if the user selects 3rd, item profit is 2.This value is saved in a variable
profit.
SP=CP+CP*(Profit/100)
Formula to calculate selling Price.
jTextField2.setText(Double.toString(SP)
The variable SP is a numeric value so it is converted to a string using the
toString() method and then the value is displayed in the text field using the
setText() method.
In the above application the profit margin is obtained from the Index value of the
selected item of the combo box but what happens if the values in the combobox are as
shown in the figure 3.28.




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GUI PROGRAMMING – A REVIEW
Figure 3.28 Business Calculator version 1.2
We will use switch case to write the code. Only the code using switch case is given below
but it is recommended that you think and try writing the code on your own.
private void
jButton1ActionPerformed(java.awt.event.ActionEvent evt)
{
double CP,Profit=0,SP;
CP=Double.parseDouble(jTextField1.getText());
switch (jComboBox1.getSelectedIndex())
{
case 0:Profit=5;break;//if first item selected profit is 5
case 1:Profit=10;break;//if second item selected profit is 10
case 2:Profit=15;break;
case 3:Profit=20;break;
case 4:Profit=25;break;
default:Profit=0;break;
}
Figure 3.29 Code for Business Calculator version 1.2
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GUI PROGRAMMING – A REVIEW
Iteration Statements :
for loop –
These statements are used to perform a set of instructions repeatedly while the
condition is true. Iteration statements are also called looping statements.
The loop has four different elements that have different purposes. These
elements are:
a) Initialization expression: Before entering in a loop, its variables must be
initialized.
b) Test Expression: The test expression decides whether the loop body will be
executed or not. If the test condition is true, the loop body gets executed otherwise
the loop is terminated.
c) Increment/Decrement Expression: The Increment/Decrement expression changes
the value of the loop variable.
d) The Body of the loop: The statements, which are executed repeatedly while the
test expression evaluates to true form the body of the loop.
The syntax of the for loop is:
Syntax
for( initialization; test exp; increment/decrement exp)
{
statements;
}
The three expressions inside the round braces of for loop are optional. Using this fact an
infinite loop can be created as follows:
for (int I = 1 ;I <= 5 ;I++ )
{
jTextArea1.setText (jTextArea1.getText()+I);
//It will display 12345 in jTextArea1
}
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GUI PROGRAMMING – A REVIEW
While Loop –
Do..While Loop –
The while loop is an entry-controlled loop. It means that the loop condition
is tested before executing the loop body. If the loop condition is initially false, for the
first iteration, then loop may not execute even once. The main characteristic of the
while loop is that it can be used in both cases i.e. when the number of iterations is known
as well as when it is unknown. The syntax of the while loop is as follows:
Syntax
while(test expression)
{
loop body
}
Remember that in while loop, a loop control variable should be initialized before the loop
begins and the loop variable should be updated inside the body of the while loop (else it
will become an endless loop).
Do..While loop is an exit-controlled loop. In the do..while loop, the test
occurs at the end of the loop. This ensures that the do..while loop executes the
statements included in the loop body at least once. After the first execution of the
statement, it evaluates the test expression. If the expression evaluates to true, then it
executes the statements of the loop body again. Like if and while statements, the
condition being checked must be included between parenthesis. The while statement
must end with a semicolon. The syntax of the loop is as follows:
Syntax
do
{
loop body
}
while (test expression);
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GUI PROGRAMMING – A REVIEW
Comparing Do…While and While – The difference between do-while and while is that dowhile
evaluates its expression at the end of the loop instead of at the beginning.
Therefore, the statements within the do block are always executed at least once. Dowhile
is an exit controlled loop and while is an entry controlled loop.
int ctr;
ctr=0;
while (ctr < 5) // Test and Loop
{
JOptionPane.showMessageDialog(this,ctr);
// Display Number
ctr = ctr + 1;
// Increment LoopCounter
}
The same code is written using do while. In do while counter is checked at the end of loop
body,therefore loop body is executed at least once.
int ctr = 0;
do // Loop Begins
{
JOptionPane.showMessageDialog(this,ctr);
// Display Number
ctr = ctr + 1;
// Increment LoopCounter
}
while (ctr<5); // Testing the value of counter
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GUI PROGRAMMING – A REVIEW
Let us now develop a few applications which will help us to strengthen our programming
concepts learnt in class XI.
Let us now design an application in which we will generate the series and its sum. Design
the application as shown in figure 3.30. Set the relevant properties of the components.
Series and its Sum
1+2+3+4
2+4+6+8+10
2+7+12+17+22
Figure 3.30 Sum of Series Calculator
Let us now write the code as follows:
private void
jButton1ActionPerformed(java.awt.event.ActionEvent evt)
{
int Start,Step,Terms,Sum=0;
Start=Integer.parseInt(jTextField1.getText());
//Start point of series
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GUI PROGRAMMING – A REVIEW
Step =jComboBox1.getSelectedIndex()+1;
//step in the series
Terms=Integer.parseInt(jTextField2.getText());
// no of terms
for (int I=1;I<=Terms;I++)
{
Sum+=Start;
Start+=Step;
}
jTextField3.setText(Integer.toString(Sum));
}
private void
jButton2ActionPerformed(java.awt.event.ActionEvent evt)
{
jTextField1.setText(“”);
jTextField2.setText(“”);
jTextField3.setText(“”);
//Index -1 indicates no selection
jComboBox1.setSelectedIndex(-1);
}
Figure 3.31 Code to generate the series and the Sum of Series
Let us now understand the code in detail.
Integer.parseInt(jTextField1.getText())
retrieves the value entered by the user in the text field using getText().This
value by default is treated as a string and not as a number so it needs to be
converted to an integer type and this is achieved using the parseInt() method.
The value is then stored in the variable Start.

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GUI PROGRAMMING – A REVIEW
jComboBox.getSelectedIndex()+1
retrieves the index of the selected item so if the user selects 1st item as Step
then 1 is added to the index value of the 1st item. This value is saved in a
variable Step.
Integer.parseInt(jTextField1.getText())
retrieves the value entered by the user in the text field using getText().This
value by default is treated as a string and not as a number so it needs to be
converted to an integer type and this is achieved using the parseInt()
method.The value is then stored in the variable Terms.
Now we have the value from where the user wants to start the series, the terms in the
series and the step between numbers of the series.
for (int I=1;I<=Terms;I++)
{
Sum+=Start;
Start+=Step;
}
jTextField3.setText(Integer.toString(Sum));
the for loop is executed as many times as the Terms and the Step is added to
Start which in turn is added to Sum and finally the Sum of the numbers is
displayed.
jTextField1.setText(“”);
jTextField2.setText(“”);
jTextField3.setText(“”);
jComboBox1.setSelectedIndex(-1);
On clicking the reset button all the three textfields are set to “” and the
setselectedIndex value of combobox is set to -1. Index -1 indicates that no item
is selected.




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GUI PROGRAMMING – A REVIEW
Let us now develop an application to reverse the given number and also find out whether
the number is a palindrome or not.(The pattern that we found in the phrases was that
each line had a palindrome hidden in it.)
Figure 3.32 Reverse Number and Palindrome Check
Let us now write the code for reversing a given number and check whether the given
number is a palindrome or not.
//Reverse Number Program with Palindrome Check
private void
jButton1ActionPerformed(java.awt.event.ActionEvent evt)
{
long Number,Temp,RevNumber=0;
Number=Long.parseLong(jTextField1.getText());
Temp=Number;
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GUI PROGRAMMING – A REVIEW
while (Temp>0) // till temp > 0 continue to perform the loop
{
RevNumber=(RevNumber*10)+(Temp%10);
// RevNumber is multiplied by 10 and added to the
// remainder of temp divided by 100
Temp=Temp/10;
}
jTextField2.setText(Long.toString(RevNumber));
if (Number==RevNumber)
JOptionPane.showMessageDialog
(this,”Number is Palindrome”);
else
JOptionPane.showMessageDialog
(this,”Number is not a Palindrome”);
}
private void
jButton2ActionPerformed(java.awt.event.ActionEvent evt)
{
jTextField1.setText(“”);
jTextField2.setText(“”);
}
Figure 3.33 Code for Reverse Number and Palindrome Check
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GUI PROGRAMMING – A REVIEW
Let us now understand the code in detail :
Long.parseLong(jTextField1.getText())
retrieves the value entered by the user in the text field using getText().This
value by default is treated as a string and not as a number so it needs to be
converted to long type and this is achieved using the parsetLog() method. The
value is then stored in the variable Number.
Temp=Number
the number is stored in another variable temp.
while (Temp>0)
{
RevNumber=(RevNumber*10)+(Temp%10);
Temp=Temp/10;
}
while loop will continue as long as temp is greater than zero. In this loop we
divide temp by 10 and obtain the remainder. The remainder is then added to
the value in the variable RevNumber multiplied by 10.Initially
RevNumber=0.The value of variable temp is divided by 10 every time the loop
is executed. The loop is executed as long as temp is greater than 0.
if (Number==RevNumber)
JOptionPane.showMessageDialog
(this,”Number is Palindrome”);
else
JOptionPane.showMessageDialog
(this,”Number is not Palindrome”);
If the reverse of the number, which is stored in variable RevNumber and the
number entered by the user which is stored in Number are the same then the
number is a palindrome otherwise it is not a palindrome.




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GUI PROGRAMMING – A REVIEW
We have revised the concepts learnt in class XI. Now in the next few chapters we will
enhance our knowledge of NetBeans and delve further into programming concepts.
NetBeans is an IDE using which we can develop GUI applications in Java.
NetBeans provides various components used to create a GUI front-end
interface.
GUI components’ appearance and behaviour is controlled by their properties
and methods.
We should use meaningful names for controls on the form and variables in the
code. It makes programming convenient.
Some useful Data Types supported in Java are: int, double, char and boolean.
String is an Object (reference) type supported in Java.
A variable must be declared before it can be used.
Different types of operators are available in Java. Operators are used to
perform various operations on data.
Control Statements available in java are: if..else, switch..case, for, while,
do..while.
1. What will be the output of the program given below. Which number is printed twice?
int sum1 = 3;
sum1++;
jTextField1.setText(“”+sum1);
++sum1;
jTextField2.setText(“”+sum1);
jTextField3.setText(“”+(++sum1));
Summary









EXERCISES
MULTIPLE CHOICE QUESTIONS
98
GUI PROGRAMMING – A REVIEW
jTextField4.setText(“”+sum1++);
jTextField5.setText(“”+sum1);
a. 5 b. 6
c. 4 d. 7
2. Consider the following code snippet :
int anumber=14;
if (anumber >=10){
if (anumber == 10)
jLabel1.setText(“first string”);
else jLabel1.setText(“second string”);
jLabel2.setText(“third string”);
What will be the output when anumber=14
a. first string b. second string
c. first string d. second string
third string third string
3. What value for X above will print EXACTLY 20 lines to standard output :
int count = 0;
while(count++ < X ) {
jTextField1.setText(“Line ” + count);
}
a. 0 b. 5
c. 10 d. 11
4. What will be the value of total after the loop finishes execution.
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GUI PROGRAMMING – A REVIEW
int total = 0; // must be initialized before the for (int count =
5; count <=10; count++ )
{
total += count;
}
jTextField1.setText(“The total is ” + total);
a. 10 b. 16
c. 45 d. 36
5. What’s wrong with the while statement?
while( (ctr < 5) && (ctr > 30))
a the logical operator && cannot be used in a test condition.
b the while loop is an exit-condition loop.
c the test condition is always false.
d the test condition is always true.
6. If there is more than one statement in the block of a for loop, which of the
following must be placed at the beginning and the ending of the loop block?
a parentheses () b French curly braces { }
c brackets [ ] d arrows < >
7. Given the following information:
int a = 11;
int b = 22;
int c = 33;
int d = 11;
Which of the following statements are true :
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GUI PROGRAMMING – A REVIEW
i) a = = b ii) b != d iii) c <= b
iv) a < c v) a = = d vi) c > a
vii) a >= c
a i),iv) & vii) b ii),iv), v) & vi)
c ii),iv), vi) & vii) d iii),v),vi) & vii)
8. The statement i++; is equivalent to
a i = i + i; b i = i + 1;
c i = i – 1; d i – – ;
1. Explain the following terms:
a) IDE
b) Inspector Window
c) Form
2. Differentiate between :
a) TextField and TextArea
b) ComboBox and ListBox
c) getText() and setText()
3. What is the significance of the following properties in TextArea ?
LineWrap WrapStyleWord
4. What are list type controls used for ?
5. How would you determine whether a combo box is editable or not ?
6. List different selection modes of a list.
7. What is a button group? Which control is generally used with a buttongroup.
8. Write and explain two methods each of check box and radio button.
ANSWER THE FOLLOWING QUESTIONS
101
GUI PROGRAMMING – A REVIEW
LAB EXERCISES
1. Design a GUI application in which the user enters a number in the text field and on
clicking the button the sum of the digits of the number should be displayed in a
label.
Hint : Suppose user enters 123 the output should be 6(1+2+3).
2. Design a GUI application to accept a String from the user in a text field and print
using option pane whether it is a palindrome or not.
Hint ABBA is a palindrome.
3. Design a GUI application to accept the cost price and selling price form the user in
two text fields then calculate the profit or loss incurred.
4. Design a GUI application to accept a character in a text field and print in a label if
that character is a vowel: a, e, i, o, or u. The application should be case sensitive.
5. Design a GUI application that repeatedly accepts numbers in a option pane and once
the typed number is 0 the maximum and minimum of all numbers typed are
displayed.
6. Design a GUI application in java to convert temperature from Celsius to Fahrenheit
or vice versa using radio buttons and two text fields
7. Design a GUI application in java to convert kilograms into grams, litres into
milliliters, rupees into paisa using combobox and text fields.
8. A book publishing house decided to go in for computerization. The database will be
maintained at the back end but you have to design the front end for the company.
You have to accept book code, Title, Author and Quantity sold from the user. The
Price will be generated depending upon the book code. Net price should be
calculated on the basis of the discount given.
Bookseller – 25%
School – 20%
Customer – 5%
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GUI PROGRAMMING – A REVIEW
9. A networking company decided to computerize its employee salary . Develop an
application to store employee’s personal data which will be saved in the back end.
The front end should accept Name, Father’s Name, Mother’s Name, Address, Gender,
Basic Salary, Medical and Conveyance. Calculate gross and net salary.
>=40000 35% 37%
>=20000 25% 32%
>=10000 25% 30%
(Team size recommended : 3 students in each team)
1. Students will visualize the details that have to be provided while creating a member
registration for an e-reservation site. Each team has to design a layout for the form.
The form has to be designed using NetBeans IDE. The team has to specify the
following:
Controls that will be used to develop the application.
Data types of variables to be used.
Validations to be performed while accepting the data.
2. Students will visualize the details that have to be provided while developing a
domicile certificate for a student of class XII. Each team has to design the form using
NetBeans IDE. The team has to specify the following:
Controls that will be used to develop the application
Data types of variables to be used.
Validations to be performed while accepting the data.
Basic DA HRA
TEAM BASED TIME BOUND EXERCISE

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