Input and Output Devices

I/O Devices: Input information data An input device together with appropriate software, transforms information from the user into data that the computer application can process. usability Choice and method of use of an input device should contribute positively to the usability of the system feedback by the system The usability of an input device depends greatly on the provision of appropriate feedback by the system

Types of Keyboard Qwerty Qwerty keyboard Uses most common alphabetic character arrangement Good for variable data entry and flexible. Fast for trained touch typists. Slow for non-typists Keyboards for other languages use different layouts Chord – Can be used for texting on mobiles Chord – Can be used for texting on mobiles Various arrangements. Words are formed by combinations of key presses – fewer keys – smaller What size do the keys need to be? What shape should it be? How robust should it be

Pointing devices Two types of pointing devices Indirect – user uses a secondary device Direct – Allow users to point directly users tasks Various characteristics and features may suit different users or for different tasks Eyesheadsfeet hands Eyes, heads and feet can be used to control computers as well as hands

Pointing devices: Indirect 3D tracker 3D tracker Relays position and orientation to a receiver. Replaces mouse where desk space is limited (e.g., laptops) Joystick Joystick Small stick, movable in any direction in a fixed socket. Mouse Mouse continuous input device. Buttons for discrete input. Relative device. Trackball Trackball (a.k.a. “dead mouse”) Rotatable ball in fixed socket Tablet Tablet used with stylus or puck. Absolute device Mole Mole (a.k.a. “foot mouse”)

Pointing devices: Direct Touch-sensitive screen Touch-sensitive screen Special screen that detects the position of a finger touching it. – i.e Interactive White Board Pen Systems Uses a touch screen but users select using a pen/stylus rather than using their finger – i.e Dsi Note: Dsi can be touch screen or pen.

Developments in input Speech recognition 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 Handwritten input advantages: easier to separate words, may need some training for users disadvantages: cursive script difficult to read, wide variety of handwriting styles, system may need training Dataglove Dataglove Communicates hand and finger position to an application. Used for manipulating virtual objects

Output devices feedback from the computer Output devices provide information or feedback from the computer in a form which is understandable by humans Visual Display Unit Visual output, in 2-D, using a Visual Display Unit (VDU) is by far the most common form.

Issues Involving Vision Range Total blindness Impaired vision Color blindness Photosensitive epilepsy Technologies: Screen readers – reads out the text aloud Screen magnifier Braille Descriptive audio – adds description to the audio

Refreshable Braille display

A screen magnifier: the right portion here

Colour Blindness – Red peppers or Green peppers? This is how they are seen by a colour blind person

Avoid Red Text on Green Background

Issues Involving Mobility/Motor Impairment Conditions that affect a person’s ability to use keyboard and mouse effectively 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

The Eyegaze TM system

Eyegaze ® A video camera tracks eye movement as the user looks at an on-screen keyboard Customisable 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 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.

Choosing appropriate devices work/purpose Match the devices with work/purpose The device chosen needs to be able to accomplish the piece of work or purpose it is intended for users Matching devices with users e.g., eye and head input for the physically disabled Child, adult environment of use Matching devices with environment of use space relation to other concurrent tasks etc.,