Copyright © 2005, Pearson Education, Inc. Chapter 9 Interaction Devices.
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Transcript of Copyright © 2005, Pearson Education, Inc. Chapter 9 Interaction Devices.
Copyright © 2005, Pearson Education, Inc.
Chapter 9
Interaction Devices
Copyright © 2005, Pearson Education, Inc.
Keyboard Layouts
• QWERTY layout– 1870 Christopher Latham Sholes – design slowed down the users to avoid key jamming– frequently used letter pairs far apart to increase finger travel
distances
• Dvorak layout– 1920 – reduces finger travel distances by at least one order of
magnitude – 1 week of regular typing to make the switch– Acceptance has been low
• ABCDE style– 26 letters of the alphabet laid out in alphabetical order nontypists
will find it easier to locate the keys
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Keyboards for Small Devices
• Wireless or foldable keyboards• Virtual keyboards• Cloth keyboards• Soft keys
• Pens and touchscreens
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Copyright © 2005, Pearson Education, Inc.
Pointing Devices
Six Types of Interaction Tasks
1. Select
2. Position
3. Orient
4. Path
5. Quantify
6. Text
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Direct-control Pointing Devices
1. Lightpen– users point to a spot on a screen and to perform a
select, position, or other task
– allows direct control by pointing to a spot on the display
– incorporates a button for the user to press when the cursor is resting on the desired spot on the screen
– three disadvantages• users' hands obscured part of the screen• users had to remove their hands from the keyboard to pick
up the lightpen• Too fragile for public-access environments
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Direct-control pointing devices (cont.)
2. Touchscreen– allows direct control touches on the screen using a finger
– early designs caused fatigue, hand-obscuring-the-screen, hand-off-keyboard, imprecise pointing, and the eventual smudging of the display
– lift-off strategy enables users to point at a single pixel
– can produce varied displays to suit the task
– are fabricated integrally with display surfaces
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Direct-control pointing devices (cont.)
3. Tablet PCs and Mobile Devices: – Natural to point on the LCD surface
– Stylus
– Keep context in vie
– Inconvenient to pick up and put down stylus
– Accommodates gestures and handwriting recognition
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Indirect pointing devices• mouse *
– the hand rests in a comfortable position– buttons on the mouse are easily pressed– long motions can be rapid– positioning can be precise
• trackball– usually implemented as a rotating ball 1 to 6 inches in
diameter that moves a cursor • joystick
– are appealing for tracking purposes
• graphics tablet– a touch-sensitive surface separate from the screen
• touchpad– offers the convenience and precision of a touchscreen while
keeping the user's hand off the display surface
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Comparison of pointing devices
• Human-factors variables– speed of motion for short and long distances – accuracy of positioning – error rates – learning time – user satisfaction
• Other variables– cost – durability – space requirements – weight – left- versus right-hand use – likelihood to cause repetitive-strain injury – compatibility with other systems
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Comparison of pointing devices (cont.)
• Some results– direct pointing devices faster, but less accurate – graphics tablets favored when on device for long
periods – mouse is faster than isometric joystick – for tasks that mix typing and pointing, cursor keys are
faster and preferred over a mouse– muscular strain is low for cursor keys
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Model of human hand movement
Fitts' LawConsider three components:1. Index of difficulty = log2 (D / W + 1)
where D is distance to move and W is target size
2. Time to point = C1 + C2 (index of difficulty)where C1 and C2 are device specific
3. Fine tuning = C3 log2 (d / W)
Time for precision pointing = C1 + C2 (index of difficulty) + C3 log2 (d / W)
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Novel devices
1. Foot controls2. Eye-tracking3. Multiple-degrees-of-freedom devices4. DataGlove5. Haptic feedback6. Bimanual input7. Ubiquitous computing and tangible user
interfaces8. Handheld devices
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Speech and auditory interfaces
• Speech recognition still does not match the fantasy of science fiction:
– demands of user's working memory – background noise problematic – variations in user speech performance impacts
effectiveness – most useful in specific applications, such as to
benefit handicapped users
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Speech and auditory interfaces (cont.)
• Audio tones, audiolization, and music– Sound feedback can be important:
• to confirm actions • offer warning • for visually-impaired users • music used to provide mood context, e.g. in games
• can provide unique opportunities for user, e.g. with
simulating various musical instruments
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Displays – Small and Large
• Primary source of feedback to the user from the computer
– Features:• Physical dimensions (usually the diagonal
dimension and depth)• Resolution (the number of pixels available)• Number of available colors, color correctness• Luminance, contrast, and glare• Power consumption• Refresh rates (sufficient to allow animation and
video)• Cost• Reliability
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Displays – Small and Large (cont.)
Usage characteristics distinguish displays:• Portability• Privacy• Saliency• Ubiquity• Simultaneity
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Display technology
• Monochrome displays RGB shadow-mask displays
• Raster-scan cathode-ray tube (CRT)
• Liquid-crystal displays (LCDs)
• Plasma panel
• Light-emitting diodes (LEDs)
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Display technology (cont.)
• Electronic ink– Paper like resolution– Tiny capsules with negatively and positively charged
particles
• Braille displays– Pins provide output for the blind
• Large displays– Informational wall displays– Interactive wall displays– Multiple desktop displays
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Displays – Large and Small (cont.)
• Heads-up and helmet mounted displays– A heads-up display projects information on a
partially silvered widescreen of an airplane or car
– A helmet/head mounted display (HMD) moves the image with the user
– 3D images
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Mobile device displays
• Currently mobile devices used for brief tasks, except for game playing
• Optimize for repetitive tasks
• Custom designs to take advantage of every pixel
• DataLens allows compact overviews
• Web browsing difficult
• Okay for linear reading, but making comparisons can be difficult
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Animation, image, and video
• Accelerated graphics hardware• More information shared and downloaded on
the web• Scanning of images and OCR• Digital video• CDROMS and DVDs • Compression and decompression through
MPEG• Computer-based video conferencing
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Printers
Important criteria for printers: – Speed – Print quality – Cost – Compactness – Quiet operation – Use of ordinary paper (fanfolded or single sheet) – Character set – Variety of typefaces, fonts, and sizes – Highlighting techniques (boldface, underscore, and
so on) – Support for special forms (printed forms, different
lengths, and so on) – Reliability
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Summary
1. Choosing hardware involves making a compromise between the ideal and the practical
2. Devices should be tested in the application domain
3. Keyboard entry is established but consider other devices where appropriate
4. Speech systems not feasible presently – next obstacle
5. Consistency, functionality and versatility must be maintained