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Human Computer Interaction

Week 5Interaction Devices and Input-

Output

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Introduction

Current Input/Output Devices: Keyboard, Mouse, CRT or LCD

displays, Printers. Future Input/Output Devices:

Gestural Input, 3-D pointing, more voice input/output, wearable devices, whole body involvement for some input/output tasks.

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Text Input Devices

Text Input, implemented by: Keyboard Speech Recognition Handwriting Gloves

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Pointing Input Devices

Pointing, implemented by: Mouse Touch Screen Track-Ball Eye-Tracking

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The Choice of Input Device

The choice of input device should contribute as positively as possible to the usability of the system. It should be the one that:

Matches the physiological and psychological characteristics of users, their training and their expertise.

Is appropriate for the tasks that are to be performed. Is suitable for the intended work and environment.

There must also be adequate and appropriate system feedback to guide, reassure, inform and, if necessary, correct users’ errors.

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Keyboard Keyboard is a discrete entry device. Keyboard types:

Qwerty keyboard:- the most common keyboard.- derived from typewriters (1874).- designed to avoid keys jamming in manual typewriters.

Dvorak keyboard: - first patented in 1932.- more efficient input than Qwerty.- not commercially successful.

Chord keyboard:- press several keys at once to enter one character. - training is required.

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Pointing devices

Pointing devices are continuous entry devices.

Examples: Mouse Trackball Joystick

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Touch Screen Touch Screen allows the user to input

information into the computer simply by touching an appropriate part of the screen or a touch-sensitive pad near to the screen.

Advantages: easy to learn, require no extra work space, have no moving part.

Disadvantages: lack of precision, high error rates, arm fatigue, finger obscuring detail on the screen and screen smudging.

Best for large targets and untrained users.

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Speech Input Advantages:

Easier to learn (natural communication). Does not require the use of hands. Offers disabled people to use computers.

Disadvantages: Applied only in very specialized and highly

constrained tasks. Speech recognizers have severe limitations. Speech recognizers are subject to

interference. Natural language used by people is very

difficult for a computer to interpret.

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Two Main Aspects of Input Devices

Direct vs. IndirectDevice’s physical movement directly correspond to the reaction on the screen.

Absolute vs. RelativeDevice’s location directly control the object’s location and reaction on the screen.

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Taxonomy of user-centered pointing devices

Absolute Relative

Direct Touch Screen Light Pen

Mouse

Indirect ?? Track Ball Joystick Cursor Keys

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Task - Device Numeric Data Entry: Numeric Keypad Text Data Entry: Alphanumeric

Keyboard Object Selection (e.g. icon selection):

Mouse, TrackBall Object Manipulation (e.g. drag & drop):

Mouse, TrackBall Tracking (e.g. drawing): Mouse,

LightPen

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Output Devices (1)

Printed Output Laser Printer, Ink Jet, Impact and

Thermal Printer Graphical Output

CRT or LCD displays, projectors

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Output Devices (2)

Audio Output Stereo/Surround Speakers,

Headphones

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Sound Output

Current uses: alerting and feedback.

Different kinds of sound: Speech Musical Sounds Natural Sounds

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Sound output has already proved valuable

Complements visual interface When the users are visually

occupied Monitoring background processes Addressing the needs of blind users Data Sonification Algorithm Animation

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Types of Sound Output Natural Sound: Gaver, uses everyday

sounds to convey computer objects / events, called auditory icons. Example: Sonic Finder (1989).

Musical Sound: Blattner, uses musical tones to convey computer objects / events, called earcons.

Speech Output: The most obvious means of using sound.

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Further Reading

Preece, chapter 11,12