Lecture 6: Usage environment : Computer input and output

ERGONOMICS
Ergonomics
The study of human abilities and characteristics affecting the design of equipment or systems to improve efficiency and safety.
Its role is to define and design tools that are used for different work, leisure and domestic environments to suit the needs and capacities if the user

Repetitive Strain Injury (RSI)
The amount of time spent at the keyboard appears to increase the risk of RSI
with rates above 10,000 keystrokes per hour putting the operator at the highest risk of RSI

Eyes disorders
Loss of visual focus, sore eyes, double vision, seeing different colors, dry eyes, sore, red and watering eyes
The eyes need to be focused at a fixed distance on a vertical image on a bright screen.
This causes the eye muscles to be continually under tension

COMPUTER INPUT-KEYBOARD

QWERTY Keyboard
Designed in 1870s, by Charles Sholes
It is called QWERTY because of the top – left hand keys
Designed to minimize typing speed, in order to prevent frequent jams of the typebars


DVORAK Keyboard
It is arranged on the basis of the frequency usage of letters (in English)
Vowels and frequently – used consonants on the 2nd row
Advantages:
Reduction in finger travel
Consequent improvement in accuracy


Mini Keyboard
Same layout as laptop computer keyboard
Lightweight
Useful for people with restricted arm, hand or finger movement


Big keys LX Keyboard
High contrast black lettering on white large keys
Useful for users with visual impairment


Ergonomics Keyboard
Ergonomic design allows hands and wrists to be held in more comfortable position
Useful for people suffering from RSI (Repetitive Strain Injury)/ carpal tunnel syndrome


Cable Free Keyboard
Keyboard can be used away from desk (range 5 meters)
Useful for wheel chair users


Vertical Split Keyboard
Compatibility:  PC, both QWERTY and Dvorak
What is the orthopedic neutral position for the human body?

OTHER TEXT ENTRY DEVICES


HANDWRITING RECOGNITION

Handwritten text can be input into the computer using a pen and a digitizing tablet.
Problems are in capturing useful information, segmenting join up writing into individual letters, interpreting individual letters and copying with different styles of handwriting.

SPEECH RECOGNITION

Promising but only successful in limited situation - single user, limited vocabulary systems.
Problems with:
External noise interfering
Imprecision of pronunciation
Accents

POSITIONING AND POINTING DEVICES

Ergonomics Mouse
Thumb operated mouse
Ergonomic design
Useful for people suffering from RSI as hand remains vertical and strain on wrist and lower arm is reduced


Cable Free Mouse
Light weight
Portable
Useful for wheel chair users


The NoHands Mouse virtually eliminates stress on the delicate hand-wrist area by moving mouse control to the feet!


Trackball
Only a small amount of movement is required to operate a tracker ball
useful for people with restricted movement who find moving the mouse difficult.


Joystick
Can be operated by other parts of the body e.g mouth, foot etc.
Can be used alongside standard mouse
Useful for people with limited motor control


Mouse Tray
Allows the mouse to be put into a comfortable position e.g on leg and there allowing arm to rest in its natural position
Flat working area with cushion on back
Useful for wheel chair users and people with upper limb discomfort





SUMMARY

Interface designer needs to be aware of the properties of the devices with which a system is built