Transcript I/O Devices: Input
Input and Output Devices
I/O Devices: Input An input device one that, together with appropriate software, transforms
information
from the user into
data
that the computer application can process.
Choice and method of use of an input device should contribute positively to
usability
of the system The usability of an input device depends greatly on the provision of appropriate
feedback
Types of Keyboard
Qwerty
keyboard Uses most common alphabetic character arrangement Required for highly variable data entry. Many trained typists. Slow for non-typists
Dvorak
keyboard Similar to Qwerty. More efficient layout
Chord
Various arrangements. Words are formed by combinations of key presses
Keyboards (lesser known)
Klockenberg
(1926) /
Malton
(1977) “ Ergonomic keyboard”. Varying key heights. Lessens physiological strain
Palantype
stenographic use
Numeric keypad
may eliminate need for use of alphanumeric keyboard in some applications
Pointing devices A variety of devices are available, but many are experimental
pointing
and
tracking
Various characterstics and features may suit different
users
or different
tasks Eyes
,
heads
and
feet
can be used to control computers as well as
hands
Pointing devices: cursor control
3D tracker
Relays position and orientation to a receiver. Replaces mouse where desk space is limited (e.g., laptops)
Joystick
Small stick, movable in any direction in a fixed socket.
Mouse
continuous input device. Buttons for discrete input. Relative device.
Trackball
(a.k.a. “dead mouse”) Rotatable ball in fixed socket
Tablet
used with stylus or puck. Absolute device
Mole
(a.k.a. “foot mouse”)
Pointing devices: Other
Dataglove
Communicates hand and finger position to an application. Used for manipulating virtual objects
Touch-sensitive screen
Special screen that detects the position of a finger touching it.
Light pen
Location found by beam passing through screen during refresh cycle
Comparison of major devices
Device
Touch-screen Light pen Mouse Trackball Joystick
Advantages Disadvantages
No moving parts, durable, low price, attractive to novices useful with flat screen, no training needed tiring for prolonged use, smudging of screen not activated by dark areas fast, inexpensive, training accurate, minimal inexpensive, fine control, little desk space neede inexpensive, little desk space needed requires flat, dedicated surface area trailing lead. Awkward in combination with keyboard less easy to use than awkward Can be inconvenient to use if built-in. Otherwise, trailing lead
Developments in input
Speech recognition
advantages: minimal user training, freedom of hands etc., opportunities for physically disabled
disadvantages
: recognition system often needs training, liable to error; subject to interference from background noise; difficult for application to interpret human speech
Handwritten input
advantages: easier to separate words, may need some training for users disdavantages: cursive script difficult to read, wide variety of handwriting styles, system may need training
Output devices Output devices provide information or
feedback
in a form which is understandable by humans Visual output, in 2-D, using a awareness of the human eye
Visual Display Unit
(VDU) is by far the most common form. Progress has been in the direction of matching the colour New trends and possibilities include Graphical User Interfaces (GUIs) Output devices suitable for laptop or notebook-size hardware Multimedia
Visualisation
Dynamic visualisation
is becoming increasingly important in information-rich applications visualisation of data, processes, scientific phenomena The key issue is finding visual forms that support the users’
mental model
“
Perceptualisation
” is the multimedia equivalent of visualisation 3-D animation and
Virtual Reality
are likely to increase in importance for “perceptual” interfaces
Sound
Sounds
users’ attention is likely to turn away from a VDU screen can complement a visual interface when the An important use is to deliver information on
“background” events
that need continual monitoring The “seven plus or minus two” rule for
information overload
applies to sounds, too Sound can be critically important in interfaces for the
visually disabled
Digital speech techniques
Concatenation
involves digitally recording human speech in large chunks (words, short sentences) and reassembling it and playing back e.g., “talking clock”
Synthesis-by-rule
rhythm involves synthesizing speech according to prescribes rules of sound formation to generate more “natural-sounding” tone, pitch,
Issues Involving Vision
Range Total blindness Impaired vision Technologies: Screen readers Color blindness Photosensitive epilepsy Braille Descriptive audio Don’t use tables in HTML to control layout; use tags to identify table cells and headers
Screen reader Narrates (reads aloud) the text on the screen Important considerations: HTML must note change in language, e.g., English to Spanish, using the “lang” attribute HTML tables must not be used to control layout: doing so makes the narration difficult to understand HTML tables used to display tabular material need additional markup to make the meaning clear
One form of Braille, with contractions
Refreshable Braille display
A screen magnifier: the right portion here
Color blindness 8% of the male population There are three kinds, one of which is extremely rare The most common type is deuteranopia commonly called red/green confusion , The following slides show how some colored materials would look to a color blind person, simulated by software from Vischeck, Inc.
Do you prefer red peppers or green peppers? How would you pick?
What is a green salad?
A color wheel, to the color blind
How do traffic lights look to a color blind driver?
So: learn that red is always on top Always?
Are you sure?
Is red on the right or left?
Did you get it right? Are you sure we got it right, or is the red sometimes on the other side?
The worst
Issues Involving Mobility Impairment
As applies here: any conditions that affects a person’s ability to use keyboard and mouse Can be caused by: Diseases: arthritis, muscular dystrophy, multiple sclerosis Stroke Injury Loss of limb Repetitive strain injury Natural aging processes
Assistive technologies available in Windows StickyKeys permits one-finger typing Press Shift, Ctrl, or Alt followed by another key, rather than pressing two keys at same time FilterKeys helpful for people with hand tremors or problems with fine-motor control Ignores brief or repeated keystrokes MouseKeys permits moving pointer with the numeric keypad SerialKey permits access, via serial port or USB port, to alternatives for mouse and keyboard functions Foot mouse
Predictive typing
The Eyegaze TM system
Eyegaze ® A video camera tracks eye movement as the user looks at an on-screen keyboard Customizable as to how long a key must be looked at to be recorded When system has identified the key looked at, the symbol appears and the user looks at next key
Issues Involving Hearing Impairment
Deafness Hard of hearing; can be helped by hearing aids Can be caused by prolonged exposure to noisy environments Hearing often degrades with age
Closed captioning
An avatar signs from English text See asl.cs.depaul.edu for more information and a demo. The project is led by Dr. Rosalee Wolfe.
The Web Accessibility Initiative
The World Wide Web Consortium (W3C) is committed to promoting usability for people with disabilities The goal: Universal access. Everyone.
Must take into account magnifiers, etc.
user agents other than browsers: mobile phones, PDAs, screen readers and Not easy; not free It’s simply the right thing to do
Multimedia The potential for multimedia includes the fact that it is estimated that only 7% of business-critical information is “record-based” Multimedia databases including photos, video clips, sounds, animation etc., may permit digitalisation of much of the other 93% Object Technology is a critical technical enabler for such advances
Animation
Definition: synthetic apparent motion created through artificial means Can sometimes be stored more compactly than video, speeding downloads Offers a richer set of interactions than video An attention-getter Good for demonstrating transitions and for explaining complex systems
Using animation to focus attention, 1
Using animation to focus attention, 2
Tour of the Munich Airport Center, in interactive 3D, 4
An avatar
Level of detail, 1
Level of detail, 2
Level of detail, 3
Choosing appropriate devices Matching devices with
work
The particular manipulations needed to accomplish a piece of work need to be analyzed Natural mappings between use, feedback, meaning of result and user’s mental model are needed Matching devices with
users
e.g., eye and head input for the physically disabled Matching devices with
environment of use
space relation to other concurrent tasks etc.,