1 Human Computer Interaction Week 5 Interaction Devices and Input-Output

2 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.

3 Text Input Devices Text Input, implemented by: Keyboard Speech Recognition Handwriting Gloves

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

5 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.

6 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 more efficient input than Qwerty. - not commercially successful. Chord keyboard: - press several keys at once to enter one character. - training is required.

7 Pointing devices Pointing devices are continuous entry devices. Examples: Mouse Trackball Joystick

8 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.

9 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.

10 Two Main Aspects of Input Devices Direct vs. Indirect Device’s physical movement directly correspond to the reaction on the screen. Absolute vs. Relative Device’s location directly control the object’s location and reaction on the screen.

11 Taxonomy of user-centered pointing devices

12 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

13 Output Devices (1) Printed Output Laser Printer, Ink Jet, Impact and Thermal Printer Graphical Output CRT or LCD displays, projectors

14 Output Devices (2) Audio Output Stereo/Surround Speakers, Headphones

15 Sound Output Current uses: alerting and feedback. Different kinds of sound: Speech Musical Sounds Natural Sounds

16 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

17 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.

18 Further Reading Preece, chapter 11,12