GIT 335
Computer Systems Technology
Lecture 5
Hardware – Input and Output
Dr. Thomas Schildgen, Professor
Arizona State University
Department of
Technology Management
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Lecture 5
Introduction to Information Technology
Content taken from the McGraw Hill Textbook Chapter 5
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Hardware: Input & Output
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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
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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!
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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
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Input Hardware
 Keyboard types
 104 – 108 keys desktop standard
 80 – 85 keys for laptops
 Wired
 Connect to CPU via a serial or USB port
 Wireless use either
 IR (infrared) technology
 Radio Frequency (RF) technology
 Require line of sight to connect
 Virtual keyboard used with PDAs and
smartphones
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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
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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 one-hand mini-keyboard
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Input Hardware
Pointing Devices
 Control the position of the cursor or pointer on 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
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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
 Pointing Stick
 Looks like a pencil eraser in the lower center of a laptop
keyboard
 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
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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
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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
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Input Hardware
 Digital Pen
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Writing instrument
Writers can write on paper
A tiny camera in the pen tip captures the writing
A microchip in the pen converts the pen to digital ink
The writing is sent as an image file to the computer
Original versions: Logitech’s IO pen and Leapfrog’s FLY
Fusion pen required special paper
 Later versions, like Mobile Digital Scribe do not require
special paper
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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 and drum
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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
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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 SAT and GRE
 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
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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
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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
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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
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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
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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
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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.
 Used 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
 ScanSoft and Nuance
 Fonix Speech
 Aculab
 Verbio
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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
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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/
 http://www.identix.com/
 http://www.precisebiometrics.com/
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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
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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
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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
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Output Hardware
Monitors
 Video Standard
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XGA
SXGA
UXGA
QXGA
WXGA
WUXGA
 Principal resolution
(pixels)
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1024 x 768
1280 x 1024
1600 x 1200
2048 x 1536
1,386 x 768
1,920 x 1,200
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Output Hardware
Printers
 Impact Printers
 Laser Printers
 Inkjet Printers
 Thermal Printers
 Form characters or images by striking a print
hammer or wheel against an ink ribbon
 Dot matrix printers
 Use drums and toner like in photocopiers
 Page Description Language (PDL)
 PostScript and PCL are PDL types
 Produce crisp, professional pages
 Spray ink from 4 nozzles at high speed
 Quiet, inexpensive color printers
 Often less precise than laser printers
 Low to medium resolution printers that use
thermal paper that darkens in time
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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
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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.
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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
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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
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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
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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
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