Peripheral Devices
Device Drivers
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A program to tell the system software how to
work with that piece of hardware
Some common device drivers are built in the
system software (Operating System) e.g.
keyboard and mouse drives
Plug-n-Play Devices
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Devices designed such that Windows can
detect them, install and configure the device
driver automatically
For non plug-n-play devices, we have to install
and configure the device driver manually.
Input Devices (1)
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Keyboard
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P/S2 keyboard
USB keyboard
Wireless keyboard
Input Devices (2)
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Pointing Devices
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Mouse, trackball, touch pad, light pen, digitizer
Touch screen
Input Devices (3)
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Scanning devices
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Image scanner
Fax machine – scan image to bitmap
Bar code scanner – scan Universal Product Code
(UPC)
Magnetic ink character scanner (MICR)
Optical character scanner (OCR)
Optical mark scanner (OMR)
Input Devices (4)
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Voice Input Device
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Microphone – to receive the sound signal
Sound card – to convert the sound signal to digital
form
Use speech recognition software to recognize
human speech
Input Devices (5)
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Handwriting Recognition Device
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Need handwriting recognition software
Called natural input
Slow inputting speed
Output Devices (1)
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Visual Display Unit (VDU)
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Commonly called monitor
2 common types of monitor
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CRT (Cathode Ray Tube) monitor
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High radiation and bulky
LCD (Liquid Crystal Display) monitor
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No radiation and slim
Output Devices (2)
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Printer – to produce hard copy
Laser printer
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to produce high quality output
resolution up to 2400 dpi (dot per inch)
use carbon toner, usually for black and white
printout, colour is very expensive
Output Devices (3)
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Inkjet printer
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produce good quality colour output
resolution up to 1440 dpi
use ink droplets to compose the image
The printer is much cheaper than laser printer but
the ink is very expensive
Output Devices (4)
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Dot matrix printer
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Use impact principle
Can print multiple (carbon) copies at a time, usually
use in printing invoices
The ink ribbon is cheap
Poor quality of printout
Output Devices (5)
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Plotter
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Drawing high quality image, use colour pens, can
draw smooth curves
Can print on large paper size, use roll of paper
To draw posters and maps
Use in CAD (Computer Aided Design)
Output Device (6)
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Voice output devices
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Sound card, to convert computer signals to sound
Speakers, to amplify the sound output
Storage Devices (1)
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Floppy Disk (Diskette)
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A flexible plastic circular disc
Packed in a plastic square jacket
Formatted to 1.44MB
Divided to many circular tracks
Each track is divided to many sectors
Use magnetic technology to store data ‘0’ or ‘1’
Random access
Slow accessing speed
Storage Devices (2)
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Hard Disk
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High storage capacity, over 100 GB
Hard metallic surface
Consists of several metallic disks
Data are stored in cylinder (a deck of tracks)
(see p.86)
Use magnetic technology
Very high access speed
Random access
Storage Device (3)
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Optical disk
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CDROM, DVDROM, CDRW, DVDRW
Use optical technology, laser reflection on pits
‘1’ will reflect the laser beam while ‘0’ does not
High storage capacity, 700 MB for a CDROM,
17GB for a DVDROM
Random access
High access speed
Storage Device (4)
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Tape
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Cheap
Sequential access
Use magnetic technology
Ideal for backup data, we need to backup and restore all
data
High storage capacity
Slow access speed
Group of records are stored in a block
Inter-block gaps are needed for stopping and starting the
read/write head.
Storage Device (5)
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Other Storage devices – can be read/write
Removable disks -Zip disk(100/250MB),
superdisk(120MB), Jazz disk(1GB)
MO disk
Flash memory cards – compact flash, smart
media and memory stick, commonly used in
digital camera
Network Devices (1)
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Network Interface Card (NIC) (LAN card)
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Connection between the network and the computer bus
Have built-in transceiver, for data transmitting and receiving
Usually 100 MB/s
Wireless LAN card
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Usually 11 MB/s
Work within the distance range, and no blocking in between.
Network Devices (2)
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Connectors
RJ-45 telephone jack connector
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For connecting twisted pairs LAN cable
BNC connector
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For connecting coaxial cables
Network Device (3)
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Terminators
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Use in bus network, to prevent signal rebounce and
echo at the ends of bus.
Network Device (4)
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Hub
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Switch
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To connect the workstations within a room on same
floor
To connect the workstations for different floors in a
building, it is faster and more efficient than a Hub.
Router
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To connect different LANs together to form a Wide
Area Network (WAN)
Network Device (5)
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Repeater
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When a network spans a long distance, the signal
weaken, repeater is used to reproduce the signal.
Exchange
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To boost the signals along the network path for a
Wide Area Network.
Network Device (6)
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Computer
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Server
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Different computers play different roles on a network
Provide services to other computers connected to
the network, usually have higher processing power
and larger storage capacity.
Workstation
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The computers connected to the network but not act
as a server.
Network Device (7) - Servers
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File server
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Print server
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To host a web site and publish web pages on the web,
support HTML, Java script, CGI, PHP and ASP web
languages
Email server
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Manage the print jobs from different computers to different
network printers, and manage the print queues.
Web server
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control the sharing and access of files over the network,
must have a huge storage capacity.
To store, send and receive emails over the Internet
Internet server
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To provide Internet access
Communication Device
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Modem - Modulator-demodulator
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It transforms digital signals of computer to analog
signals to be transmitted through telephone lines.
(Modulation)
It also transforms analog signals back to digital
signals for the computer that receives the signals.
(Demodulation)
Data/Signal Rate
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Data Rate
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Signaling Rate (Baud Rate)
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Refer to the no. of bits per second sent
Refer to the no. of signals per second sent
Each signal may consists of several bits e.g. 101
Bandwidth
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The frequency range of a particular media
is directly proportional to the data rate
Types of network
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Client-Server Network
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Some computers act as server to provide services to clients
on the network
Server programs are running on the server
Client programs are running on client computers
Peer-to-peer Network
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Every computer plays the same role in the network. They
form a workgroup, no server and no client
The security in a peer-to-peer network is low.
It is easy to set up, since no server programs or client
programs need to be run.