this captures only the following: definition of computer networks, functional relationships, communcation channels, internet, emails and so on.

1. COMPUTER NETWORKS
What is a computer network?

2. What is a Computer Network ?
• A network consists of two or more
computers that are linked together
in order to share resources e.g
printers, memory , exchange files
and folders, allow electronic
communication e.g Email etc. It is a
system for communication among
two or more computers.

3. Requirements for a computer
network.
• Network Interface Card (NIC)
• Network Operating System
• Communication channel(Media)

4. The communication channel.
• Communicating data from one
location(computer) to another requires
some form of pathway or medium. These
pathways, called communication channels
use two types of media:
• (i)Cable e.g Twisted-pair cable and fiber-
optic cable. Cable or wireline media use
physical wires to transmit data and
information.

5. data comm continued
• Twisted-pair wire and coaxial cables are
made of copper, and fiber-optic cable is
made of glass.
• (ii) Broadcast(wireless) e.g This media
uses radio waves ,microwaves and
infrared

6. TYPES OF COMPUTER NETWORKS
Computer networks are categorized into four
major types.
1. Personal area network (PAN):
A personal area network (PAN) is a computer
network used for communication among
computer devices (including telephones and
Personal Digital Assistants (PDAs) close to one
person. The devices may or may not belong to
the person in question.

7. TYPES OF COMPUTER NETWORKS(….)
2. Local Area Network (LAN):
Is a computer network covering a
local area, like a home, office or
small group of buildings such as a
college. The topology (physical lay
out)of a network dictates its
physical structure. The generally
accepted maximum size for a LAN is
1000m2.

8. TYPES OF COMPUTER NETWORKS(….)
3. Metropolitan Area Network
(MAN).
•Is a large computer network
usually spanning a campus or
a city. It typically uses optical
fiber connections to link its
sites.

9. Wide Area Network (WAN)
• Is a computer network covering a wide
geographical area, involving vast array of
computers. This is different from personal
area networks (PANs), metropolitan area
networks (MANs) or local area networks
(LANs) that are usually limited to a room,
building or campus. The best example of a
WAN is the Internet. Using a WAN, schools in
Uganda can communicate with places like
Tokyo in a matter of minutes, without paying
enormous phone bills.

10. Functional relationship:
• In any given form of network, computers
communicate to each other depending on
the relationship that exists. The following
shows the relationship therein.
(i) Client / Server - Is a network application
architecture, which separates the client
from the server. Each instance of the
client software connects to a server or
application server.

11. • A client is a computer that accesses a
service made available by a server.
• A server is computer that shares its
resources with other computers called
clients on a net work.
• Server software generally but not always
runs on powerful computers dedicated for
exclusive use to running the business
application.

12. • Client software on the other hand
generally runs on common PCs or
workstations. Clients get all or most of
their information and rely on the
application server for things such as
configuration files, business application
programs or to offload computer
intensive application tasks back the server
to keep the client computer free to
perform other tasks.

13. Advantages of a client/server
network:
• Centralization - In a client/server network there is
centralized control. Servers help in administering the whole
set-up. Access rights and resource allocation is done by
Servers.
• Security : Rules defining security and access rights can be
defined at the time of set-up of server
• Proper management- All the files are stored at the same
place. In this way, management of files becomes easy. Also
it becomes easier to find files.

14. • Back-up and Recovery possible : As all the data is
stored on server its easy to make a back-up of it. Also,
in case of a break-down if data is lost, it can be
recovered easily and efficiently. While in peer
computing we have to take back-up at every
workstation.
• Flexibility - New technology can be easily integrated
into system without having to work on individual
machines.
• Accessibility - Server can be accessed remotely and
across multiple platforms.

15. • Easy upgrade and scalability - Changes
can be made easily by just upgrading the
server. Also new resources and systems
can be added by making necessary
changes in server.
• Speed - The network will runs far better
as data and resources are handled by a
dedicated machine.

16. Disadvantages of a client/server
network:
• Cost - It is very expensive to install and
manage this type of network.
• Maintenance - Large networks will require
professional IT staff to maintain the servers
and ensure efficient operation of other
technical details of network.
• Dependence - When server goes down all
operations will cease across the network.

17. Disadvantages of a client/server
network:
• Congestion in Network : Too many requests from
the clients may lead to congestion and this
overload can lead to breaking-down of servers. In
peer-to-peer, the total bandwidth of the network
increases as the number of peers increase.
• It can the summarized that client-server model is
not used in small scale networks and networks
where security is not a big issue.

18. A peer-to-peer (or P2P)
• Refers to the network, where any
node(e.g computer) is able to initiate or
complete any supported transaction with
any other node. It is a network in which
resources and files are shared without a
centralized management source.

19. Advantages of a peer-to-peer
network:
• The over-all cost of building and
maintaining this type of network is
comparatively very small.
• It is easy to setup e.g an operating system
(such as Windows XP) already in place
may only need to be reconfigured for
peer-to-peer operations.
• In peer-to-peer, the total bandwidth of
the network increases as the number of
peers increase.

20. Advantages of a peer-to-peer
network:
• P2P is more reliable as central
dependency is eliminated. Failure of one
peer doesn’t affect the functioning of
other peers.
• There is no need for full-time System
Administrator. Every user is the
administrator of his/ her machine. Users
can control their shared resources.

21. Disadvantages of a peer-to-peer
network:
• The network is decentralized thus it is difficult
to administer. ie one person cannot
determine the whole accessibility setting of
whole network.
• Security - Does not provide the security
available on a client/server network.
• Data recovery or backup is very difficult. Each
computer should have its own back-up
system.

22. • Security in P2P is very limited, viruses,
spywares, trojans, etc malwares can easily
transmitted between clients.
• Note: Peer to peer networks are good to
connect small number (around 10) of
computer and places where high level of
security is not required.

23. Network Topology:
• The physical topology of a network refers to
the configuration of cables, computers, and
other peripherals.
• Physical topology should not be confused with
logical topology which is the method used to
pass information between workstations.

24. Bus Topology
• A bus network is such that there is a
single line /cable (the bus) to which all
nodes are connected, and the nodes
connect only to this bus.

25. Advantages of the bus topology.
• Easy to implement and extend.
• Well suited for temporary networks (quick
setup).
• Typically the cheapest topology to
implement.
• Failure of one station does not affect others.
• Easy to connect a computer or peripheral to a
linear bus.
• Requires less cable length than a star
topology.

26. Disadvantages of the Bus
Topology.
• Difficult to administer/troubleshoot
• Limited cable length and number of
stations
• The main cable break can disable the
entire network
• Maintenance costs may be higher in the
long run.
• Performance degrades as additional
computers are added

27. Disadvantages…..
• Terminators are required at both ends of
the backbone cable.
• Difficult to identify the problem if the
entire network shuts down.
• Not meant to be used as a stand-alone
solution in a large building.

28. Ring Topology
• A network topology in which every node
has exactly two branches connected to it.
These nodes and branches form a ring. If
one of the nodes on the ring fails then the
ring is broken and cannot work. A dual
ring topology has four branches
connected to it, and is more resistant to
failures.

29. Advantages of Ring Topology.
• Growth of the system has minimal impact
on performance
• All stations have equal access.
• Each node on the ring acts as a repeater,
allowing ring networks to span greater
distances than other physical topologies..

30. Disadvantages of Ring topology.
• Is often the most expensive topology.
• Failure of one computer may affect
others.

31. Star Topology
• A network topology in which peripheral
nodes are connected to a central node,
which rebroadcasts all transmissions
received from any peripheral node to all
peripheral nodes on the network,
including the originating node. All
peripheral nodes may thus communicate
with all others by transmitting to, and
receiving from the central node only.

32. Advantages of the Star Topology.
• Easy to implement and extend, even in
large networks.
• Well suited for temporary networks (quick
setup)
• Easy to detect network problems.

33. Disadvantages of Star Topology.
• Limited cable length and number of
stations
• Maintenance costs may be higher in the
long run
• Performance degrades as more
computers are added
• Failure of the central node can disable the
entire network.

34. Mesh Topology:
• Is a network topology in which there are
at least two nodes with two or more
paths between them.

35. Tree and hyper tree topologies :
• Are important special cases of star network
topologies.
• Advantages of a Tree Topology
(i) Point-to-point wiring for individual segments.
(ii) Supported by several hardware and software
venders.
Disadvantages of a Tree Topology
• Overall length of each segment is limited by the type
of cabling used.
• If the backbone line breaks, the entire segment goes
down.
• More difficult to configure and wire than other
topologies.

36. Networking Hardware
• Networking hardware includes all
computers, peripherals, interface cards
and other equipment needed to perform
data processing and communications
within the network.
• This section provides information on the
following components:

37. Networking Hardware....
• 1. File Server
A File server is a high capacity computer that
provides
various resources to the network.
The server requires;
(i) a very fast computer with a large amount of RAM
and storage space, a fast network interface card,
and a tape back-up device
(ii) network operating system such as Windows
2000, XP…, Novell Netware, Windows NT server,
or Apple Share

38. 2.Workstations: A computer in a network
is called a workstation or client. It
requires a network interface card, not
necessarily need floppy disk drives or
hard disks since files can be saved on the
file server.

39. Network Interface Cards (NICs) - NIC provides the link
between your computer and your network. It provides
the physical connection between the network and the
workstation.
Most NICS are internal, with the card fitting into an
expansion
slot inside the computer ,others are build on the
motherboard.
The type of NIC affects the speed and performance of a
network
Three common network interface connections exist;
Ethernet
Cards,LocalTalk connectors, Token Ring cards.

40. Hubs/Concentrators
A hub is a device whose primary function is to send
and receive signals along the network between
the nodes connected to it.
• It connect s multiple devices to the network,
• It serves as a central meeting place for cables
from
computers, servers and peripherals.
• It is usually configured with 4, 8, 12, or 24 RJ-45
ports.
• The entire network shuts down if there is a
problem
• on a hub

41. Repeaters.
• A repeater is a device that regenerates and
amplifies signals to create long-distance
networks.
• It simply receives, amplifies and rebroadcasts
the signals. Some repeaters provide basic
error-checking
• A repeater can be a separate device or it can
be incorporated into a concentrator. It is used
to overcome distance limitations.

42. A bridge
• A bridge is a device that links two homogenous packet-
broadcast local networks. It accepts all packets from
each network addressed to devices on the other,
buffers them, and retransmits them to the other
network.
• It connects two or more networks using the same
address method or protocol.
• It can provide some addressing information.
• Monitors and manages the traffic to maintain
optimum performance on both sides of the network
often used when LANs reach their capacity of
nodes

43. Switches
• A switch is a high-speed multi port bridge. Today,
switches are replacing multiport repeaters or
concentrators in a UTP environment. (Unshielded
Twisted Pair)
• It is an intelligent hub that maintains a bridging
table, keeping track of which hardware addresses
are located on which network segment.
• more efficient than any other type of hub
• It has ability to dedicate bandwidth to each port
on itself.

44. Routers
• Routers are similar to bridges in that they link
two or more physically separate network
segments. The network segments linked by a
router, however, remain logically separate and
can function as independent networks.
Routers;
• translate information from one network to
another; similar to a super-intelligent bridge. i.e
receive information from a cabled network and
transmit it wirelessly.
• maintain a map of the network, select the best
route for data.

45. • have information on source addresses,
destination addresses and path distances.
• segment bandwidth and segment status are
contained in the router's routing table
• can translate messages with different
addressing methods
• can act as firewalls (many ISP's block traffic at
the router level)
• direct signal traffic efficiently

46. • can route messages between linear bus,
star, and token ring topologies
• can route messages across fibre optic,
coaxial, and twisted-pair cabling

47. Network Media and cabling
What is a Network C able?
A Cable is the medium through which
information usually moves from one
network device to another. There are
several types of cables which are
commonly used with LANs. In some cases,
a network will utilize only one type of
cable, other networks will use a variety of
cable types.

48. The type of cable chosen for a network is
related
to the network's topology, protocol, and
size.
Understanding the characteristics of
different
types of cables and how they relate to other
aspects of a network is necessary for the
development of a successful network.

49. Types of Network cables.
• The following are some of the types of
cables used in networks .
1. Unshielded Twisted Pair (UTP) Cable
2. Shielded Twisted Pair (STP) Cable
3. Coaxial Cable
4. Fiber Optic Cable

50. Twisted pair cable.
• The twisted pair cable comes in two
varieties: Shielded and Unshielded.
Unshielded Twisted Pair (UTP) is the most
popular and is generally the best option
for school networks (See fig. below:

51. • The quality of UTP may vary from
telephone-grade wire to extremely high-
speed cable. The cable has four pairs of
wires inside the jacket. Each pair is
twisted with a different number of twists
per inch to help eliminate interference
from adjacent pairs and other electrical
devices. The tighter the twisting, the
higher the supported transmission rate
and the greater the cost per foot

52. Categories of Unshielded Twisted
Pair
Category Speed Use
A 1 Mbps
Voice Only (Telephone
Wire)
2 4 Mbps
LocalTalk &
Telephone (Rarely
used)
3 16 Mbps 10BaseT Ethernet
4 20 Mbps
Token Ring (Rarely
used)
5
100 Mbps (2 pair) 100BaseT Ethernet
1000 Mbps (4 pair) Gigabit Ethernet
5e 1,000 Mbps Gigabit Ethernet

53. • Unshielded Twisted Pair Connector.
• The standard connector for unshielded twisted
pair cabling is an RJ-45 connector. This is a plastic
connector that looks like a large telephone-style
connector . A slot allows the RJ-45 to be inserted
only one way. RJ stands for Registered Jack,
implying that the connector follows a standard
borrowed from the telephone industry. This
standard designates which wire goes with which
pin inside the connector.

54. • UTP cable is the least expensive cable, it
may be susceptible to radio and electrical
frequency interference (it should not be
too close to electric motors, fluorescent
lights, etc.). If you must place cable in
environments with lots of potential
interference, or if you must place cable in
extremely sensitive environments that
may be susceptible to the electrical
current , the Shielded twisted pair may be
the solution.

55. • Shielded twisted pair cable is available in
three different configurations:
1. Each pair of wires is individually shielded
with foil.
2. There is a foil or braid shield inside the
jacket covering all wires (as a group).
3. There is a shield around each individual
pair, as well as around the entire group of
wires (referred to as double shield twisted
pair).

56. Coaxial Cable
The Coaxial cable has a single copper
conductor
at its center. A plastic layer provides
insulation
between the center conductor and a
braided
metal shield . The metal shield helps to
block
any outside magnetic interference from
fluorescent lights, motors, and other

57. Coaxial Cable

58. Coaxial Cable
• Although coaxial cabling is difficult to
install, it is highly resistant to signal
interference. In addition, it can support
greater cable lengths between network
devices than twisted pair cable. The two
types of coaxial cabling are thick coaxial
and thin coaxial.

59. • Coaxial Cable Connectors
The most common type of connector used
with
coaxial cables is the Bayone-Neill-
Concelman
(BNC) connector.

60. Coaxial Cable Connector.

61. Fiber Optic Cable
• The fiber optic cable consists of a center glass
core surrounded by several layers of
protective materials . It transmits light rather
than electronic signals eliminating the
problem of electrical interference.
• This makes it ideal for certain environments
that contain a large amount of electrical
interference.
• It has also made it the standard for
connecting networks between buildings, due
to its immunity to the effects of moisture and
lighting.

62. Fiber Optic Cable
• The fiber optic cable has the ability to
transmit signals over much longer
distances than coaxial and twisted pair.
• It also has the capability to carry
information at vastly greater speeds. This
capacity broadens communication
possibilities to include services such as
video conferencing and interactive
services.

63. Fiber Optic Cable diagram.

64. Wireless LANs
• More and more networks are operating
without cables, in the wireless mode.
Wireless LANs use high frequency radio
signals, infrared light beams, or lasers to
communicate between the workstations,
servers, or hubs. Each workstation and file
server on a wireless network has some
sort of transceiver/antenna to send and
receive the data.

65. • Information is relayed between
transceivers as if they were physically
connected. For longer distance, wireless
communications can also take place
through cellular telephone technology,
microwave transmission, or by satellite.

66. Advantages of wireless networks:
• Mobility - With a laptop computer or mobile device, access
can be available throughout a school, at the mall, on an
airplane, etc.
• Fast setup - If your computer has a wireless adapter,
locating a wireless network can be as simple as clicking
"Connect to a Network" -in some cases, you will connect
automatically to networks within range.
• Cost - Setting up a wireless network can be much more cost
effective than buying and installing cables.
• Expandability - Adding new computers to a wireless
network is as easy as turning the computer on (as long as
you do not exceed the maximum number of devices).

67. Disadvantages of wireless
networks:
• Security - Be careful. Be vigilant. Protect your
sensitive data with backups, isolate private
networks, provide strong encryption and
passwords, and monitor network access traffic to
and from your wireless network.
• Interference - Because wireless networks use
radio signals and similar techniques for
transmission, they are susceptible to interference
from lights and electronic devices.
• Inconsistent connections - Wireless connections
are not nearly as stable as those through a
dedicated cable.

68. • Speed - The transmission speed of
wireless networks is improving; however,
faster options (such as gigabit Ethernet)
are available via cables. If you are also
moving large amounts of data around a
private network, a cabled connection will
enable that work to proceed much faster.

69. Installing Cable - Some Guidelines
• When running cables, it is best to follow a
few simple rules:
• Always use more cable than you need.
Leave plenty of slack.
• Test every part of a network as you install
it. Even if it is brand new, it may have
problems that will be difficult to isolate
later.

70. • Stay at least 3 feet away from fluorescent
light boxes and other sources of electrical
interference.
• If it is necessary to run cable across the
floor, cover the cable with cable
protectors.
• Label both ends of each cable for easy
identification.
• Use cable ties (not tape) to keep cables in
the same location together.

71. THE INTERNET
• The Internet is a global system of
interconnected computer networks that use
the standard Internet Protocol suit (TCP/IP) ,
although not all applications use TCP to serve
billions of users worldwide.
• It is a network of networks that consists of
millions of private, public, academic,
business, and government networks, of local
to global scope, that are linked by a broad
array of electronic, wireless and optical
networking technologies.

72. INTRANET & EXTRANET
• INTRANET - This is a Local Area Network
used internally in an organization to
facilitate communication and access to
information that is sometimes restricted
by use of passwords.
NB: Two or more intranets can be termed
as an extranet.
• .

73. • EXTRANET- This is a private much wider
network compared to an intranet in terms
of area that is covered. Extranets
normally cover regions or continents but
with limited accessibility to only those
authorized to do so. For example the
Government of Uganda may connect all
its Embassies abroad on a single network
which can constitute an extranet.

74. Brief history of the Internet
• The Internet was conceived during the
early 1960’s as a solution to the pending
cold war problems. The USA government
came to a conclusion of finding a network
that could operate without any
centralized control, since communication
lines that existed had been damaged.

75. Components of the Internet
• Hosts: These are computers directly
connected to an Internet.
• Browser: This is a software program used
to access information from a website via
the Internet.
• Client: This is some one surfing the
Internet using a browser.
• Server: This is the central computer that
communicates with computer clients.

76. CONNECTING A COMPUTER TO THE
INTERNET
• There are so many ways of connecting a
computer to the Internet, but the most
common ones are: -
(i) Through the use of satellites. It is also
called Internet Protocol
(ii) Through telephone lines also called dial-
up or virtual dial network.

77. REQUIREMENTS FOR INTERNET
CONNECTION
To connect a computer to the Internet,
one needs the following:
(i) A computer with browser software,
e.g. Internet explorer, Mozilla firefox
, Netscape Navigator,Opera, Google
chrome … that allows you to
communicate with a company (ISP)
that provides you access to the
Internet.

78. (ii) A computer must have a Network
Interface Card (NIC)
(iii) A modem - This is a device that helps a
computer to communicate through a
telephone line.

79. REQUIREMENTS FOR INTERNET
CONNECTION…
(iv) ISP- Internet service provider is a company
that provides Internet connection to its
customers. Examples of ISPs include; MTN
Uganda, Warid Telecom, Info COM Uganda,
AIR telecom, Orange telecom,i-Way Africa
among others.
(iv) Technical support i.e. setting up connection
to the Internet can sometimes be confusing.
And therefore, you need to hire technical
personnel from the service provider to
connect you to the Internet.

80. INTERNET PROTOCOLS:
• A protocol refers to an agreed set of rules and
procedures concerning how devices
(computers and peripherals) will transmit and
receive data from one to another.
(i) TCP/IP- (Transmission Control Protocol
/Internet Protocol). It is the basic
communication language of the internet, it
can also be used as a communication
protocol in the private networks called
intranets and extranets.

81. TCP/ IP is a suite of protocols and includes:
• HTTP (Hypertext Transfer Protocol)- Is a
set of rules for transferring files (text,
graphic images, sound, video, and other
multimedia files) on the World Wide Web.
As soon as a web user opens his /her
Web browser, the user is indirectly
making use of HTTP.

82. • FTP (File Transfer Protocol) is network
protocol used to transfer files from one
computer to another computer over a
TCP based network, such as the Internet.
FTP is often used to upload web pages
and other documents from host
computers to web-hosting servers.

83. • SMTP: Simple Mail Transfer Protocol. It is
a protocol for sending E-mail messages
between servers. Most e-mail systems
that send mail over the Internet use SMTP
to send messages from one server to
another; the messages can then be
retrieved by the e-mail client using either
POP or IMAP

84. • POP3(Post Office Protocol version 3). Is
the protocol or "language" that's used to
download your email from your ISP to
your mail program.
• IMAP: Internet Message Access Protocol.
It is the latest protocol that is more robust
(strong) than POP3 . It is a method for
accessing E-mail messages that are kept
on E-mail server.

85. • Telnet: The main protocol for creating a
connection with a remote system(server).
It gives the user the opportunity to be on
one
computer system and do the work on
another
computer.
• IRC (Internet Relay Chat) - a protocol
used for Internet chat and other
communications

86. • DNS (Domain Name System) - translates
network address (such as IP addresses)
into terms understood by humans (such
as Domain Names) and vice-versa
• DHCP (Dynamic Host Configuration
Protocol) This protocol automatically
assigns Internet addresses to computers
and users

87. ELECTRONIC MAIL (E-MAIL)
• Is the transmission of messages at high speeds
between computers over communication
channels.
• E-mail allows computer users locally and
worldwide to exchange messages. Each user
of an e-mail has a mailbox address to which
messages are sent, Messages sent through e-
mail can arrive within a matter of seconds.

88. • A powerful aspect of E-mail is the option to send
electronic files to a person’s e-mail address.
• These files are referred to as MIME attachments
(Multimedia Internet Mail Extension) and this
was developed to help e-mail software handle a
variety of file types e.g.
A document created in Microsoft word be
attached to an E-mail message and retrieved by
the recipient with the appropriate e-mail
program

89. Examples of e-mail software of programs:
• Eudora, Netscape, Messenger, Pegasus
and Outlook express. Offer the ability to
read files written in HTML.

90. Examples internet mail service
providers:
• Hotmail
• Yahoo
• Gmail
• zoho mail
• yandex.mail
• outlook
• AIM mail
• icloud mail
• mail.com amd GMX mail
• inbox.com
• my way mail

91. Features of e-mail
• To: (recipient’s e-mail address)-requires the E.mail
address of the person you are sending mail to.
• CC: Refers to Carbon copy of the message to the
selected person (second recipient)
• BCC: Blind carbon copy, a blind carbon copy is a
copy of the message that is sent to someone in
secret, other recipients of the message will not
know that the selected person has received the
message.
• Subject: A short overview of the message into the
text.

92. ADVANTAGES OF E-MAIL
• It is a fast means of Communication
• Very cheap to manage and it takes the same
amount of money to E.mail across the globe
• highly private and confidential compared to
other means of communications
• E.mails are efficient as the mails reach the
rightful person.
• In addition to text you can send graphics and
sound using e.mail
• It is not affected by geographical location or
weather.

93. DISADVANTAGES
• When someone comes across a password
s/he may have access to all your mails.
• E-mail only sent to people with these
services
• It only caters for computer literate people

94. RETRIEVING DOCUMENTS ON THE WEB (WORLD WIDE
WEB)
The World Wide Web (WWW or W3) commonly known as
the
Web, or the "Information Superhighway"), Is a system of
interlinked hypertext documents accessed via the internet
system.
• The URL and Domain name
• URL stands for Uniform Resource Locator or Universal
Resource Locator
The URL specifies the internet address of a file stored
on a host computer connected to the internet.
every file on the internet, no matter what its access
protocol, has a unique URL.

95. • Web software program use the URL to
retrieve the file from the host computer
and the specific directory in which it
resides. This file is then displayed on the
monitor connected to the user’s local
machine.

96. • URLs are translated into numeric
addresses using the Domain Name
System (DNS)
• The DNS is a world wide system of servers
that stores location pointers to web sites.

97. Anatomy of a URL.
• URLs have the following format:
Protocol://www. hostname.subdomain.top-level-
domain.
• My school's URL, for example, is
http://www.igangass.sc.ug . This naming
structure will give you clues about the
address. igangass is the name of the host; sc.
signifies that this is an educational institution
and ug. is the top-level- domain to signify
Uganda.

98. • Here are some the existing top-level
domains of URLs on the Internet:
.com - commercial
.edu - educational
.net - network
.org - organization
.gov - government
.mil - military

99. Terms in relation to internet.
• A Web Browser: Is a software application
for retrieving, presenting, and traversing
information resources on the World Wide
Web.
• A Web Page: It is a document written in
HTML code that contains text, pictures,
sound, and video and links to other
pages, files, or parts of the document

100. • A Website: s the location of data stored on a
www server which can be freely accessed by
people through surfing the net using a domain
name ie www.transworld.educ.ug.
• Home page: This is the first page you see at a
website, it acts like a title page of a book, the hope
page or welcome page identifies the web site and
contains links to other pages at the site

101. • Web server : A www server is just a
computer not different but just bigger
and faster, also a www server is
permanently connected to the internet so
that other people can surf 24 hours a day.
• Web publishing : This when designed
pages (documents of html nature) acquire
space on the www server to be shared by
other people on the net.

102. • Hyperlink:
It is part of the text or graphic on a web page, that
when clicked at will automatically do the following:
– take you to a different part of the same page
– take you to a different page within the website
– take you to a page in a different web site
– enable you to down load a file
– launch an application, video, or sound

103. • Browsing : Searching for particular
/specific items.
• Surfing : Means moving from one website
to another for topics of interest, the term
surf is generally used to describe a rather
undirected type of web browsing.

104. Other Terms
• Account: An Internet account allows you to
access the Internet. If you have an Internet
Service Provider (ISP), you will have one of
these.
• ADSL (Asymmetric Digital Subscriber
Line) A high-speed technology that allows
large volumes of data to be sent over a
telephone line. ADSL allows data rates of 1.5
to 9 Mbps when receiving data and from 16
to 640 Kbps when sending data.

105. • Bandwidth: The amount of data that can
be transmitted in a fixed amount of time.
For digital devices, the bandwidth is
expressed in bits per second (bps).
• Backup: Is to make a duplicate of the
contents of a computer, usually onto a
floppy disk or tape, in case of computer
breakdown or viruses.

106. • Baud: The number of signaling elements that
can be transmitted per second on a circuit.
Used in referring to the speed at which a
modem transmits data. This is an older term
being replaced by bps - bits per second. We
still speak of the baud rate of modems.
• Bit (Binary Digit). Either 1 or 0 in the binary
system. In processing and storage, a bit is the
smallest unit of information handled by a
computer.

107. • Bookmark: Is a term used in Netscape to
describe a Web site that is marked for
later reference. Called a 'favourite' in
Internet Explorer. Bookmarks offer a
convenient means to retrieve pages
whose locations (URLs) you have saved.
You store your bookmarks in a list that is
saved on your hard disk.

108. • Broadband: Broadband provides high speed
Internet access by delivering multiple
channels of data (such as data/voice/video)
over a single communication medium.
• Buffer : An amount of memory that
temporarily stores data to help compensate
for differences in the rate of transfer of data
from one device to another.
• Bug: An error or fault in computer software
or hardware, which causes a program to
malfunction.

109. • Bus: A collection of wires through which data
is transmitted from one part of a computer to
another. In networking, a bus is a central
cable that connects all devices on a local-area
network.
• Byte : (Binary term) A unit of storage capable
of holding a single character. A byte is equal
to 8 bits. Large amounts of memory are
indicated in terms of kilobytes, megabytes
and gigabytes.

110. • Driver: A program/software that controls
a device. Every device, whether it be a
printer, disk drive, or keyboard, must have
a driver program.
• Plug and play:Refers to the ability of a
computer system to automatically
configure peripherals and devices such as
video adaptors, sound cards and graphic
accelerators.

111. • Spam: The verb and noun referring to
sending a commercial email message to a
large number of people. Also used to
cover a multitude of other disruptive,
nasty things that happen via email from
time-to-time.

112. ADVANTAGES OF THE INTERNET
• E-mail - Is now an essential
communication tool in business (free),
communicating to professionals and
subject matter experts.
• Source of Information- There is a lot of
information available on the internet
about every subject, ranging from
government, academic issues, trade etc.

113. • Employement - Carring out office work
from any where away from the office and
communicating with the employer
through the use of internet is possible.
• Services- Online banking, Job seeking and
application and hotel airline
reservation…etc can all be possible on the
internet.

114. • E- Commerce (advertising)- Buying or selling
goods. The internet is a very effective way to
buy and sell products all over the world.
• Communities- Communities of all types have
sprung up on the internet it’s a great way to
meet up with people of similar interest.
• Conferencing- Conducting a conference
between two or more people in
geographically distant places e.g chat rooms
is possible.

115. • Multimedia displays- Entertainment e.g
music, video and many others
• Real time broadcasting
• Down loading and file

116. DISADVANTAGES
• Immorality (pornography)
• Addiction (internet games)
• Virus spread
• Cultural value elusion

117. • Through telephone wires and satellite
links, Internet users can share information
in a variety of forms. The size, scope and
design of the Internet allows users to:
• connect easily through ordinary personal
computers and local phone numbers;
• exchange electronic mail (E-mail) with
friends and colleagues with accounts on
the Internet;

118. • post information for others to access, and
update it frequently;
• access multimedia information that
includes sound, photographic images and
even video; and
• access diverse perspectives from around
the world.

119. Network Protocols.
• What is a Protocol?
• A protocol is a set of rules that governs the
communications between computers on a
network.
• In order for two computers to talk to each other,
they must be speaking the same language. Many
different types of network protocols and
standards are required to ensure that your
computer (no matter which operating system,
network card, or application you are using) can
communicate with another computer located on
the next desk or half-way around the world.

120. • FTP - File Transfer Protocol - a protocol
that is used to transfer and manipulate
files on the Internet
• HTTP - HyperText Transfer Protocol - An
Internet-based protocol for sending and
receiving webpages

121. • IMAP - Internet Message Access Protocol
- A protocol for e-mail messages on the
Internet
• POP3 - Post Office protocol Version 3 - a
protocol used by e-mail clients to retrieve
messages from remote servers
• SMTP - Simple Mail Transfer Protocol - A
protocol for e-mail messages on the
Internet