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8/7/2019 IO Devices [EDocFind.com]

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Input and Output Devices


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I/O Devices: Input

An input device one that, together with appropriatesoftware, 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 onthe provision of appropriate feedbackfeedback


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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 combinationsofkey presses


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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 alphanumerickeyboard insome applications


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Pointing devices

A variety ofpointingpointing and trackingtrackingdevices are available, but many areexperimental

Various characterstics and features maysuit differentusersusers or differenttaskstasks

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


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Pointing devices: Other

DatagloveDataglove

Communicates hand and finger position to an application.Used for manipulating virtual objects

TouchTouch--sensitive screensensitive screen

Special screen that detects the position of a finger touchingit.

Light penLight pen

Location found by beam passing through screen duringrefresh cycle


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Comparison of major devices

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Choosing appropriate input

devices Matching devices with workwork

The particular manipulations needed to accomplish a piece of workneed to be analyzed

Natural mappings between use, feedback, meaning of result andusers 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.,


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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 toerror; subject to interference from background noise; difficult forapplication 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


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Output devices

Output devices provide information or feedbackfeedback in aform which is understandable by humans

Visual output, in 2-D, using a Visual Display UnitVisual Display Unit(VDU) is by far the most common form. Progress hasbeen 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-sizehardware

Multimedia


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Visualisation

Dynamic visualisationDynamic visualisation is becoming increasinglyimportant in information-rich applications

visualisation of data, processes, scientificphenomena

The key issue is finding visual forms that support theusersmental modelmental model

Percept

u

alis

ationPerceptu

alis

ation is the multimedia equivalent ofvisualisation

3-D animation and Virtual RealityVirtual Reality are likely toincrease in importance for perceptual interfaces


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Sound

SoundsSounds can complement a visual interface when theusers attention is likely to turn away from a VDU

screen An important use is to deliver information onbackground eventsbackground eventsthat need continualmonitoring

The seven plus or minus two rule for informationinformationoverloadoverload applies to sounds, too

Sound can be critically important in interfaces for thevisually disabledvisually disabled


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Multimedia

The potential for multimedia includes the fact that itis estimated that only 7% of business-critical

information isrecord-based

Multimedia databases including photos, video clips,sounds, animation etc., may permit digitalisation ofmuch of the other 93%

ObjectTechnology is a critical technical enabler forsuch advances

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