Introduction to Computers
Communications and
Networks
Communications
communications
What are computer___________________?

Process in which two or more computers or devices transfer data,
instructions, and information
What is needed for successful
communications?






A sending device that initiates an instruction to
transmit data, instructions, or information.
A communications device that connects the sending
device to a communications channel.
A communications channel, or transmission media on
which the data, instructions, or
information travel.
A communications device that connects the
communications channel to a receiving device.
A receiving device that accepts the transmission of
data, instructions, or information.
3
Uses of Computer Communications
What are some uses of communications technology?
Internet
Web
E-Mail
Instant
Messaging
Chat Rooms
Newsgroups
Blogs
Wikis
RSS
VoIP
FTP
Web Folders
Video
Conferencing
Fax Machine
or Computer
Fax/Modem
Uses of Computer Communications
•
Users can send and receive wireless messages using
wireless messaging services
5
Uses of Computer Communications
Text messaging (SMS) allows users to send and receive short
text messages on a phone or other mobile device or computer
Picture messaging allows users to send pictures and sound files
Video messaging allows users to send short video clips
Wireless instant messaging allows wireless users to exchange
real-time messages with one or more other users
6
Uses of Computer Communications
•
Wireless Internet access points allow people to
connect wirelessly to the Internet from home, work,
school, and in many public locations
7
Uses of Computer Communications
•
A cybercafé is a coffeehouse, restaurant, or other
location that provides personal computers with
Internet access to its customers
8
Uses of Computer Communications
•
•
A global positioning system (GPS) is a navigation
system that consists of one or more earth-based
receivers that accept and analyze signals sent by
satellites in order to determine the GPS receiver’s
geographic location
GPS receivers are:
Built into
Available as a
Available
many mobile
handheld
with new
devices
device
vehicles
Page 466
9
Uses of Computer Communications
Groupware
Voice mail
• Helps groups of people work
together on projects and
share information over a
network
• Component of workgroup
computing
• Major feature is group
scheduling
• Allows someone to leave a
voice message for one or
more people
• Computer in voice mail
system converts an analog
voice message into digital
form
• A voice mailbox is a storage
location on a hard disk in the
voice mail system
Page 467
10
Uses of Computer Communications
•
•
Many programs provide a means to collaborate, or
work online, with other users connected to a server
Collaboration software includes tools that enable
users to share documents via online meetings and
communicate with other connected users
Online
meetings
Page 468
Web
conferences
Document
management
systems
11
Networks
•
•
A network is a collection of computers and devices
connected together via communications devices and
transmission media
Advantages of a network include:
Facilitating
communications
Sharing
software
Pages 470 - 471
Sharing
hardware
Sharing data and
information
Transferring
funds
12
Networks
Network classifications
LAN
 ____________is
a network in limited geographical area
such as home or office building

LAN (WLAN)
Wireless ____________
LAN
 _____________________________
Metropolitan area network (MAN) connects _____s
in city or town
Wide area network (WAN)
is a network that
 _____________________________
covers large geographic area using many types of media
Internet
WAN
 ____________is
world’s largest_________
Networks
Network Architectures
•
The design of computers, devices, and media on a
network is sometimes called the network architecture
Client/server network
Pages 473 – 474
Figures 9-13 – 9-14
Peer-to-peer network
14
Network
Network Architectures
Client/Server
 _____________:
architecture of a computer network in
which many clients (remote processors) request and
receive service from a centralized server (host computer)
 Client computers provide an interface to allow a
computer user to request services of the server and to
display the results the server returns. Servers wait for
requests to arrive from clients and then respond to them.
Peer-to-peer
 _______________:
Simple network that connects fewer
than 10 computers. Each computer has equal
capabilities
 Enables users to connect to each other’s hard disks and
exchange files directly. Sometimes called a file sharing
network.
Networks
•
A network topology refers to the layout of the
computers and devices in a communications network
Star network
Pages 475 – 477
Figures 9-16 – 9-18
Bus network
Ring network
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Network
Bus network All computers and devices connect to
1. _____________:
central cable or bus
Network
Network Topology
Ring network Cable
2. _____________:
forms closed loop (ring),
with all computers and
devices arranged along ring.
Data travels from device to
device around entire ring, in
one direction
Network
Network Topology
Star network
3. _____________:
All
devices connect to a central
device (hub or switch)
All data transferred from
one computer to another
passes through hub or
switch.
Networks
An intranet is an
internal network
that uses Internet
technologies
Page 477
An extranet allows
customers or
suppliers to access
part of its intranet
21
Network Communications Standards
Ethernet is a network standard that specifies no computer
controls when data can be transmitted
The token ring standard specifies that computers and devices
on the network share or pass a special signal (token)
TCP/IP is a network standard that defines how messages are
routed from one end of a network to another
Page 478
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Network Communications Standards
•
•
Page 479
Figure 9-20
Wi-Fi identifies any
network based on the
802.11 standard that
facilitates wireless
communication
Sometimes referred
to as wireless
Ethernet
23
Network Communications Standards
•
•
•
•
Bluetooth defines how two Bluetooth devices use shortrange radio waves to transmit data
UWB (ultra-wideband) specifies how two UWB devices
use short-range radio waves to communicate at high
speeds
IrDA transmits data wirelessly via infrared (IR) light
waves
RFID uses radio signals to communicate with a tag
placed in or attached to an object, animal, or person
Pages 480 - 481
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Communications Software
•
Communications software consists of programs that:
Help users establish
a connection to
another computer
or network
Manage the
transmission of
data, instructions,
and information
Provide an interface
for users to
communicate with
one another
Page 482
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Communications Devices
•
•
A communications device is any type of hardware
capable of transmitting data, instructions, and
information between a sending device and a receiving
device
A dial-up modem converts signals between analog
and digital
Page 485
26
Communications Devices
•
A digital modem sends and receives data and
information to and from a digital line
DSL
modem
Page 486
Cable
modem
27
Communications Devices
•
A wireless modem uses the cell phone network to
connect to the Internet wirelessly from a notebook
computer, a smart phone, or other mobile device
Page 487
Figure 9-28
28
Communications Devices
•
•
•
Page 487
Figure 9-29
A network card
enables a computer
or device to access a
network
Available in a variety
of styles
Wireless network
cards often have an
antenna
29
Communications Devices
•
•
Page 488
Figure 9-31
A router connects
multiple computers
or other routers
together and
transmits data to its
correct destination on
a network
Many are protected
by a hardware
firewall
30
Communications Devices
•
A hub or switch connects several devices in a
network together
Pages 488 – 489
Figure 9-32
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Communications Channel
•
•
•
•
Page 491
Figure 9-34
The amount of data that
can travel over a
communications channel
sometimes is called the
bandwidth
Latency is the time it takes
a signal to travel from one
location to another on a
network
Transmission media carries
one or more signals
Broadband media transmit
multiple signals
simultaneously
32
Physical Transmission Media
What is physical transmission media?

Wire, cable, and other tangible materials used
to send communications signals
Physical Transmission Media


Twisted-pair
______________cable
consists of one or more twisted-pair wires
bundled together. It is used for telephone systems and network cabling
Coaxial
_________cable consists of a single copper wire. It is often used for
cable television wiring
Physical Transmission Media
fiber-optic
What is __________cable?
 Consists of dozens or
hundreds of thin
strands of glass or
plastic
 Capable of carrying
significantly more
data at faster speeds
than wire cables
 Less susceptible
to interference
(noise) and, therefore,
more secure
Wireless Transmission Media
What is wireless transmission media?


Used when inconvenient, impractical, or impossible to
install cables
Includes Bluetooth and IrDA
Wireless Transmission Media
Broadcast radio
 ________________
distributes radio
signals over long
and short distances
Cellular radio
 ________________
is form of
broadcast radio
________________
used for mobile
communications