Interaction Devices (Human Computer Interaction)

Keyboard Layouts

QWERTY layout (1870 Christopher Latham Sholes)

• Good mechanical design and a clever placement of the letters that slowed down the users enough that key jamming was infrequent.
• Put frequently used letter pairs far apart, thereby increasing finger travel distances

Dvorak layout (1920)

• Reduces finger travel distances by at least one order of magnitude
• Acceptance has been slow despite the dedicated efforts of some devotees 
• It takes about 1 week of regular typing to make the switch, but most users have been unwilling to invest the effort

ABCDE style

26 letters of the alphabet laid out in alphabetical order nontypists will find it easier to locate the keys


Additional keyboard issues

IBM PC keyboard was widely criticized because of the placement of a few keys

• backslash key where most typists expect SHIFT key
• placement of several special characters near the ENTER key
• Number pad layout
• wrist and hand placement 

Keyboard and keypads for small devices

• Wireless or foldable keyboards
• Virtual keyboards
• Cloth keyboards
• Soft keys
• Pens and touchscreens

 Pointing Devices

Pointing devices are applicable in six types of interaction tasks:

• Select
• Position
• Path
• Orient
• Quantify
• Text

Direct Control Devices

• Lightpen
• Touchscreen
• Stylus

Indirect Control Devices

• Mouse
• Trackball
• Joystick
• Trackpoint
• Touchpad
• Graphics tablet 

Human-factors variables

• Speed of motion for short and long distances
• Accuracy of positioning
• Error rates
• Learning time
• User satisfaction 

Other variables

• Cost
• Durability
• Space requirements
• Weight
• Left- versus Right-hand use
• Likelihood to cause repetitive-strain injury
• Compatibility with other systems

Speech and Auditory Interfaces

Voice information systems
Stored speech commonly used to provide information about tourist sites, government services, after-hours messages for organizations

Audio tones, audiolization, and music
Sound feedback can be important:

• to confirm actions
• offer warning
• for visually-impaired users
• music used to provide mood context, e.g. in games
• can provide unique opportunities for user, e.g. with simulating various musical instruments

Displays – Small and Large

The display has become the primary source of feedback to the user from the computer. The display has many important features, including:

• Physical dimensions (usually the diagonal dimension and depth)
• Resolution (the number of pixels available)
• Number of available colors, color correctness
• Luminance, contrast, and glare
• Power consumption
• Refresh rates (sufficient to allow animation and video)
• Cost
• Reliability

Usage characteristics distinguish displays:

• Portability
• Privacy
• Saliency
• Ubiquity
• Simultaneity 

 Display technology

• Monochrome displays

Are adequate, and are attractive because of their lower cost

• RGB shadow-mask displays

Small dots of red, green, and blue phosphors packed closely

• Raster-scan cathode-ray tube (CRT)

Electron beam sweeping out lines of dots to form letters
Refresh rates 30 to 70 per second

• Liquid-crystal displays (LCDs)

Voltage changes influence the polarization of tiny capsules of liquid crystals Flicker-free
size of the capsules limits the resolution
Plasma panel
rows of horizontal wires are slightly separated from vertical wires by small glass-enclosed capsules of neon-based gases

• Light-emitting diodes (LEDs)

certain diodes emit light when a voltage is applied
arrays of these small diodes can be assembled to display characters