A computer network connects two or more computers to share resources and communicate, requiring a network interface card and software. Different types of networks include LAN (local area network) for smaller areas and WAN (wide area network) for broader geographic connections, with Wi-Fi enabling wireless communication. The document also discusses network topologies (ring, star, and bus) which determine how devices are interconnected, along with the advantages and disadvantages of each type.

2. WHAT IS COMPUTER NETWORK?
 A network is when two or more computers are connected together to
exchange data.
 Each Computer must have:
 A network interface card (NIC)
 A network communication software.
 Once the computers are linked together they can share resources and
communicate between each other.
 A computer that is not linked to a network is called stand-alone
computer.

3. LAN AND WAN
Local Area Network
 A network of computer in the same building or
on the same site is called LAN i.e., in homes,
offices or schools.
 The links connect the computers using cabling
or wireless.
Wide Area Network
 A network of computers connected over wide
geographic are is called WAN i.e., a business
that have offices in different countries around
the world.
 The connections are made using telephone
networks or satellite.

4. WI-FI
 Wi-Fi refers to any system where it is possible to connect to a
network or to a single computer through wireless
communications, for example:
 Wireless LAN (WLAN) are similar to LANs but there are no wires or
Cables.
 Laptops computers which are Wi-Fi enables.
 Peripheral devices such as Printers, Keyboards and Mouse which are
wireless.

5. WHAT IS NETWORK TOPOLOGY?
 The art of connecting different computers in a network is known as
Topology.
 The term network topology refers to the way in which the nodes (Computer
or other devices that need to communicate) of a network are linked
together.
 It determines the data paths, which may be used between any pair of nodes
in the network.

6. RING TOPOLOGY
 The workstations in a ring topology
are connected in the shape of a
closed ring.
 Data is simply passed around from
one workstation to another.
 The data travels only in one
direction in a ring and cannot be
reversed back.
 Each workstation passes the data
onto the next one in the line
automatically.
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7. ADVANTAGES AND DISADVANTAGES OF RING TOPOLOGY
Disadvantages
 Adding a device in
network is difficult.
 Data flows only in one
direction.
 If one node or
computer fails, the
entire network gets
affected.
Advantages
 The ring works well
where there is not
central-site computer
system.
 It is possible to create
very large networks
using this topology.

8. STAR TOPOLOGY
 In a star topology, all the
workstations are connected to a
central device called a
HUB/SWITCH.
 The hub controls traffic on the
network.
 If the hub breaks down, the
network will not function.
HUB

9. ADVANTAGES AND DISADVANTAGES OF STAR TOPOLOGY
Disadvantages
 The system crucially
depends on the
Central Hub. If hub
fails, the entire network
fails.
 The system use large
amount of cabling.
Advantages
 If any of the local
computer fails, the
remaining portion of
the network is
unaffected.
 Its easy to identify an
error if the network is
not working.
 New computers can be
easily added.

10. BUS TOPOLOGY
 All the devices in a network are connected
to a single continuous cable called the Bus.
 Data travel along the central line until it
reaches the device that requires it.
 If the signal reaches the end of the cable, it
bounces back and returns in the direction
it came from.
Backbone

11. ADVANTAGES AND DISADVANTAGES OF BUS TOPOLOGY
Disadvantages
 It is difficult to isolate any
fault in network.
 If central line or bus fails
then entire network fails.
 Performance decreases
when more devices are
added.
Advantages
 Its quite easy to set up.
 Failure of one station
does not affect the rest of
the network.
 Uses the least amount of
cable and does not
require hub or switch.

12. DIFFERENCE BETWEEN INTERNET AND WORLD WIDE WEB (WWW)
Internet
 It is a network of networks (i.e.,
all the computers connected
together)
 This does not contain information
but provides transport links for
information to pass between
computers.
WWW
 It is an application that runs on
the Internet.
 It is the largest and most used
services on the internet.

13. NETWORKS VS STAND-ALONE COMPUTERS
Stand-alone
 It is less vulnerable to virus attack
and hacking.
 It has no communication with
other computers.
 It has its own printer, scanner and
storage devices.
 Data is only available to the user
of that computer.
Network Computer
 It needs extra protection, such as
a firewall.
 It has communication with all the
computers on the network.
 Computers on a network can
share the hardware devices.
 Data can be shared on the
network with all computers.