5-1
Chapter
5
Hardware: Input &
Output
5.1 Input & Output
5.2 Input Hardware
5.3 Output Hardware
5.4 I/O Quality of Life: Health & Ergonomics
5.5 Future of Input & Output
McGraw-Hill/Irwin
© 2007 The McGraw-Hill Companies, Inc. All rights reserved.
Input & Output
Input Hardware
 Devices
that translate data into a form the computer can
process
 Translates words, numbers, sounds, and pictures into
binary
Output Hardware
 Devices
that translate information processed by the
computer into a form humans can understand
 Translates binary into words, numbers, sounds, and
pictures
5-3
Input Hardware
 Keyboards: convert letters, numbers, and characters into electrical
signals
 English keyboards differ from foreign language keyboards
 Follow this link to see what a Russian Cyrillic keyboard layout
looks like

http://www.geocities.com/fontboard/cyrillic.html
 Even
languages that are close to ours like German have
different keyboard layouts, such as can be seen on Microsoft’s
web site

http://www.microsoft.com/globaldev/keyboards/kbdgr.htm
 Even
touch typists must watch their fingers when they travel to
Internet Cafes in foreign countries!
5-4
Input Hardware
 How keyboards work:
 You
press a key
 This interrupts the current flowing through the circuits
 Processor determines where the break occurs
 It compares the location of the break with the (x,y) character map
for the language on the keyboard’s ROM chip
 A character is stored in 16-byte keyboard memory buffer
 Then sent to PC as a data stream via wire or wireless connection
 OS interprets its own operating-system-specific commands and
sends the others to the application for interpretation
5-5
Input Hardware
Keyboard types
 104 – 108 keys desktop standard
 85 keys for laptops
 Wired
 Connect
 Wireless
to CPU via a serial or USB port
use either
 IR
(infrared) technology
 Radio Frequency (RF) technology
 Require line of sight to connect
 Virtual keyboard used with PDAs and smartphones
5-6
Input Hardware
Terminal Types
 Dumb Terminals
 a.k.a.
Video Display Terminal (VDT)
 Has display screen and keyboard
 Can do input and output only – no data processing
 Intelligent Terminals
 Has screen, keyboard, and memory
 Can perform some local functions
 Internet Terminals
 Powers directly up into a browser
Web terminal displays web pages on a TV set
 Network computer is a stripped-down PC to connect people to
networks
 Online game player connects to internet for online gaming
 PC/TV merges a full-blown PC with a TV
 PDA is a handheld computer with a tiny keyboard

5-7
Input Hardware
PDA Keyboards
 Problem:
Make them too small and they are unusable
 Problem: Make them too big and the PDA is too big
 Solutions:
 Some
PDAs use a stylus
 Some PDAs use a foldable keyboard
 Some PDAs use a 20-key mini-keyboard
5-8
Input Hardware
Pointing Devices
 Control the position of the cursor or pointer in the screen and
allow the user to select options displayed on the screen
 Mouse is the principal pointing tool
 Rolls around on a mouse pad or desktop and directs a pointer
on the computer’s display screen
Ball inside the mouse touches the desktop and rolls around
 Two internal rollers touch the ball
 One roller picks up motion in x (up), the other in y (down)
 The rollers turn a shaft that spins a disk that breaks an LED signal
into light pulses that are seen by an infrared sensor
 Processor chip in mouse reads the pulses and turns it into binary

Discussion Question: What is the difference between “cursor” and “curser”?
5-9
Input Hardware
Pointing Devices
Trackball
 A movable
ball mounted on top of a stationary device
 Good for locations where a mouse couldn’t move enough
 Requires more frequent cleaning to remove finger oils
Touchpad
 To
use: slide your finger over this small flat surface
 Click by tapping you finger on the surface
 May require more practice to use than a mouse
Pointing Stick
 Looks
like a pencil eraser in the lower center of a laptop
keyboard
5-10
Input Hardware
Pointing Devices
Touch Screens
 A video
display screen sensitized to receive input from a
finger
 Cruder than a mouse, because fingers are big
 Problems: touch screens that show a display that is not
precisely aligned with the input
Pen input
 Use
a pen-like stylus for input rather than typing on a
keyboard
 Use handwriting recognition to translate cursive writing
into data
5-11
Input Hardware
Light Pen
 A light-sensitive
pen-like device that uses a wired
connection to a computer terminal
 Bring the pen to the desired point on the display screen
and press a button to identify the screen location
 Used in situations that require gloves
 Less crude than a touch screen
Digitizer
 Uses
an electronic pen or puck to convert drawings and
photos to digital data
 Digitizing tablets are used in architecture
5-12
Input Hardware
Scanning & Reading Devices
Source Data Entry devices create machine-readable
data and feed it directly into the computer
 Scanners
 Use
light-sensing equipment to translate images of text,
drawings, and photos into digital form
 Image scanners are used in electronic imaging
 Resolution refers to the image sharpness, measured in dots
per inch (dpi)
 Flatbed scanners work like photocopiers – the image is
placed on the glass surface, then scanned
 Other types are sheet-fed, hand-held, drum, and pen
scanners
5-13
Input Hardware
Bar-Code Readers
 Photoelectric (optical) scanners that translate bar code symbols
into digital code
The digital code is then sent to a computer
 The computer looks up the item and displays its name and pricing
info

 Bar
code types
1D holds up to 16 ASCII characters
 2D can hold 1,000 to 2,000 ASCII characters
 3D is “bumpy” code that differentiates by symbol height


Can be used on metal, hard rubber, other tough surfaces
5-14
Input Hardware
Mark Recognition Readers
Bar code readers
 MICR
– Magnetic-ink character recognition
 Uses
special magnetized inks
 Must be read by a special scanner that reads this ink
 OMR
– Optical mark recognition
 Uses
a special scanner that reads bubble marks
 Used in standardized tests like the ACT and SAT
 OCR
– Optical character recognition
 Converts
scanned text from images (pictures of the text) to
an editable text format
 You use this to read in non-computer documents where you
don’t have the source files
5-15
Input Hardware
Fax Machines
Facsimile Transmission Machines – scan an image
and send it as electronic signals over telephone lines
to a receiving fax, which prints out the image on paper
 Dedicated
fax machine
 Is
a stand-alone unit that only sends and receives faxed
documents
 Fax
modem
 Is
a circuit board installed in the PC
 Is a modem that can send and receive faxes
Can send documents directly from your word processor to a fax
machine
 Saves you printing out the document, then faxing it

5-16
Input Hardware
Audio Input Devices
Records analog sound and translates it into digital files
for storage and processing
Two ways to digitize audio
 Sound
Board
 An
add-on board in a PC that converts analog sound to
digital sound, stores it, and plays it back to speakers or amp
 MIDI
Board
 Stands
for Musical Instrument Digital Exchange
 Uses a standard for the interchange between musical
instruments, synthesizers, and PCs
5-17
Input Hardware
Webcams and Video-input Cards
Webcams
 Video cameras attached to a computer to record live moving
images then post them to a website in real time
 Require special software, usually included with the camera
Frame-grabber video card
 Can capture and digitize 1 frame at a time
Full-motion video card
 Can convert analog to digital signals at rates up to 30
frames per second
 Looks like a motion picture
Discussion Question: Why might it be unwise to install a webcam on your
PC?
5-18
Input Hardware
Digital Cameras
Use a light-sensitive processor chip to capture
photographic images in digital form and store them on
a small diskette in the camera or on flash memory
cards
 Most
can be connected to a PC by USB or FireWire
 Can allow you to take more pictures and decide which
ones to print and save
 But pictures are subject to loss by diskette or flash
memory failure or computer virus if you store them on the
PC
5-19
Input Hardware
Camera Phones
Digital cameras are now on cellphones
 Convenience
of being able to take photos, then instantly
email or message them to someone else
 Can provide instant record of traffic accidents, etc
Discussion Question: Why do you suppose cellphones are now banned
on secure U.S. military bases? Where else besides military bases might
they pose a security problem?
5-20
Input Hardware
Speech-Recognition Systems
Uses a microphone or telephone as an input device.
Converts a person’s speech into digital signals by
comparing against 200,000 or so stored patterns.
in places where people need their hands free –
warehouses, car radios, stock exchange trades
 Helpful for people with visual or physical disabilities that
prevent them from using other input devices
 Still not easy enough to use to substitute for the
mouse/keyboard for fast document processing
 Used
 ScanSoft’s
Open Speech Dialog
 Apple Speech Recognition
 ScanSoft’s Navigon MobileNavigator 5
5-21
Input Hardware
RFID Tags
Radio-frequency ID tags are based on an identifying
tag with a microchip containing specific code numbers
 Scanners
use radio waves to read them and match the
codes to a database
 Enables items to be tracked without physical contact
 Drivers
put RFID tags in cars to automatically pay tolls
 FDA is tagging certain drugs with RFID to avoid counterfeits
 Carmakers are using it for car electronic keyless entry
 RFID tags are implanted under skin of pets to aid in
recovery and identification when they get lost
5-22
Input Hardware
Biometrics
The science of measuring individual body
characteristics, then using them to identify a person
through a fingerprint, hand, eye, or facial characteristic
 Becoming
a big business as more companies become
concerned about security
 Makes identity theft much more difficult when records are
identified by biometrics as well as passwords
 For more information see
 http://www.xtec.com/home.html
 http://www.identix.com/
 http://www.precisebiometrics.com/
5-23
Output Hardware
Softcopy
 Data
that is shown on a display screen or is in audio or
voice form; exists electronically
 Output that is ephemeral in nature
Hardcopy
 Printed
and film output
 Output that is more permanent in nature
5-24
Output Hardware
Display Screens
 Making a good choice when choosing a display
 Dot
pitch (dp) is the amount of space between adjacent pixels
(picture elements) on screen
The closer the pixels, the crisper the image
 Get .25 dp or better

 Resolution
refers to the image sharpness
The more pixels the better the resolution
 Expressed in dots per inch (dpi)

 Color
depth or bit depth is the number of bits stored in a dot
The higher the number the more true the colors
 24-bit color depth is better than 8-bit color depth

 Refresh
rate is the number of times per second the pixels are
recharged – a higher rate gives less flicker
5-25
Output Hardware
Monitors
Cathode Ray Tube (CRT) is a vacuum tube used in a
computer or terminal display screen
 Watch
the PC ads to make sure your monitor is included
Flat panel displays are made of 2 plates of glass
separated by a layer of liquid crystals that line up to
transmit or block light
 Preferable
to CRTs because they take up less room on
the desktop
 Latency problems make them less desirable for online
games players
5-26
Output Hardware
Monitors
 Video Standard
 Principal resolution (pixels)
 SVGA
 800
x 600
 1024 x 768
 1280 x 1024
 1600 x 1200
 2048 x 1536
 XGA
 SXGA
 UXGA
 QXGA
5-27
Output Hardware
Printers
 Impact Printers
 Form characters or images by striking a
print hammer or wheel against an ink ribbon

 Laser Printers
Dot matrix printers
 Use drums and toner like in photocopiers
Page Description Language (PDL)
 PostScript and PCL are PDL types
 Produce crisp, professional pages

 Inkjet Printers
 Spray ink from 4 nozzles at high speed
Quiet, inexpensive color printers
 Often less precise than laser printers

 Thermal Printers
 Low to medium resolution printers that use
thermal paper that darkens in time
5-28
Output Hardware
Plotters
A specialized output device designed to produce large
high-quality graphics in a variety of colors
 The
earliest output device that could produce graphics
 Pen plotters use one or more colored pens
 Electrostatic plotters lie partially flat on a table and use
toner like photocopiers
 Large-format plotters are large-scale inkjet printers used
by graphic artists
5-29
Output Hardware
Mixed Output
Sound output
 You
need a sound card and sound software
 Good equipment can produce very high-quality 3-D
sound
Voice Output
 TTS
systems (text to speech) are becoming popular
 Requires a sound card and speakers with TTS software
Video Output
 Requires
a powerful processor and a video card
 Video files are large, so a lot of storage is needed too.
5-30
I/O Quality of Life: Health &
Ergonomics
PCs impact health
 Overuse
injuries and repetitive stress injuries
 Result
when muscle groups are forced through fast,
repetitive motions
 May effect data-entry operators who average 15,000
keystrokes an hour
 May effect PC users whose monitor, keyboard, and
workstation are not arranged for comfort
 Carpal tunnel syndrome is caused by pressure on the
median nerve in the wrist, caused by short repetitive
movement
 Computer vision syndrome is eyestrain, headaches, and
double vision caused by improper use of computer display
screens
5-31
I/O Quality of Life: Health &
Ergonomics
Ergonomics is the methodology of designing a
workplace to make working conditions and equipment
safer and more efficient
 Keyboards
must be placed at the correct height
depending on each worker’s size
 Monitor refresh rates must be fast enough to avoid
eyestrain
 Monitor heights must be correct for comfortable viewing
 Sound-muffling should be used for loud printers to reduce
workplace noise
 Wrist rests may help avoid carpal tunnel syndrome
5-32
Future of Input and Output
This is a fruitful area for research, including
 Intelligent
sensors
 More data input from remote locations
 More source data automation
 Input help for the disabled
 More sophisticated touch devices
 Better speech recognition
 Improved digital cameras
 Gesture recognition
5-33
Future of Input and Output
This is a fruitful area for research, including
 Pattern-recognition
and biometric devices
 Brainwave
devices
 Better and cheaper display screens
 Improved video on PCs
 3-Dimensional output
 Miniaturization for improved data transfer speeds to I/O
devices
5-34
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William Sawyer - McGraw