Input and Output Devices

I/O Devices: Input

An input device one that, together with appropriate software, transforms informationinformation from the user into datadata that the computer application can process.

Choice and method of use of an input device should contribute positively to usabilityusability of the system

The usability of an input device depends greatly on the provision of appropriate feedbackfeedback

Types of Keyboard

QwertyQwerty keyboard Uses most common alphabetic character

arrangement Required for highly variable data entry. Many trained typists. Slow for non-typists

DvorakDvorak keyboard Similar to Qwerty. More efficient layout

ChordChord Various arrangements. Words are formed by

combinations of key presses

Keyboards (lesser known)

KlockenbergKlockenberg (1926) / MaltonMalton (1977) “Ergonomic keyboard”. Varying key heights. Lessens

physiological strain PalantypePalantype

stenographic use Numeric keypadNumeric keypad

may eliminate need for use of alphanumeric keyboard in some applications

Pointing devices

A variety of pointingpointing and tracking tracking devices are available, but many are experimental

Various characterstics and features may suit different usersusers or different taskstasks

EyesEyes, headsheads and feetfeet can be used to control computers as well as handshands

Pointing devices: cursor control

3D tracker3D tracker Relays position and orientation to a receiver. Replaces

mouse where desk space is limited (e.g., laptops)

JoystickJoystick Small stick, movable in any direction in a fixed socket.

MouseMouse continuous input device. Buttons for discrete input.

Relative device.

Trackball Trackball (a.k.a. “dead mouse”) Rotatable ball in fixed socket

TabletTablet used with stylus or puck. Absolute device

MoleMole (a.k.a. “foot mouse”)

Pointing devices: Other

DatagloveDataglove Communicates hand and finger position to an

application. Used for manipulating virtual objects Touch-sensitive screenTouch-sensitive screen

Special screen that detects the position of a finger touching it.

Light penLight pen Location found by beam passing through screen

during refresh cycle

Comparison of major devices

Device Advantages Disadvantages

Touch-screen No moving parts, durable,low price, attractive tonovices

tiring for prolonged use,smudging of screen

Light pen useful with flat screen, notraining needed

not activated by darkareas

Mouse fast, accurate,inexpensive, minimaltraining

requires flat, dedicatedsurface areatrailing lead. Awkward incombination withkeyboard

Trackball inexpensive, fine control,little desk space neede

less easy to use thanmouse, “dragging” isawkward

Joystick inexpensive, little deskspace needed

Can be inconvenient touse if built-in. Otherwise,trailing lead

Developments in input

Speech recognitionSpeech 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 inputHandwritten 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 feedback in a form which is understandable by humans

Visual output, in 2-D, using a Visual Display Visual Display Unit Unit (VDU) is by far the most common form. Progress has been in the direction of matching the colour-awareness of the human eye

New trends and possibilities include Graphical User Interfaces (GUIs) Output devices suitable for laptop or notebook-size

hardware Multimedia

Visualisation

Dynamic 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 modelmental model “PerceptualisationPerceptualisation” is the multimedia equivalent

of visualisation 3-D animation and Virtual Reality Virtual Reality are likely to

increase in importance for “perceptual” interfaces

Sound

SoundsSounds can complement a visual interface when the users’ attention is likely to turn away from a VDU screen

An important use is to deliver information on “background” events “background” events that need continual monitoring

The “seven plus or minus two” rule for information overload information overload applies to sounds, too

Sound can be critically important in interfaces for the visually disabledvisually disabled

Digital speech techniques

ConcatenationConcatenation involves digitally recording human speech in large chunks (words, short sentences) and reassembling it and playing back e.g., “talking clock”

Synthesis-by-rule Synthesis-by-rule involves synthesizing speech according to prescribes rules of sound formation to generate more “natural-sounding” tone, pitch, rhythm

Issues Involving Vision Range

Total blindness Impaired vision Color blindness Photosensitive epilepsy

Technologies: Screen readers 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 blindness8% of the male populationThere 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 EyegazeTM 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 ImpairmentDeafnessHard 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 user agents other than

browsers: mobile phones, PDAs, screen readers and magnifiers, etc.

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 workwork

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 usersusers e.g., eye and head input for the physically disabled

Matching devices with environment of useenvironment of use space relation to other concurrent tasks etc.,