Chapter 2 - The Computer
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| is made up of various elements each of these elements affects the interaction input devices | Computer/Computer System
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| basic parts of computer system | screen, or monitor, keyboard, &
mouse/trackpad
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| Most common text input device | Keyboards
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| Allows rapid entry of text by experienced users, & Usually connected by cable, but can be wireless | Keyboards
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| non-alphanumeric keys are placed differently, & accented symbols needed for different scripts, & minor differences between UK and USA keyboards | QWERTY
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| arrangement not optimal for typing, & layout to prevent typewriters jamming! | QWERTY
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| keys arranged in alphabetic order, & not faster for trained typists, & not faster for beginners either! | Alphabetic
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| common letters under dominant fingers, & biased towards right hand, & common combinations of letters alternate between hands | Dvorak
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| designs to reduce fatigue for RSI, & for one handed use | special keyboards
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| only a few keys - four or 5 letters typed as combination of keypresses | Chord keyboards
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| use numeric keys with multiple presses 2 – a b c 6 - m n o 3 - d e f 7 - p q r s 4 - g h i 8 - t u v 5 - j k l 9 - w x y z hello = 4433555[pause]555666 surprisingly fast! | phone pad and T9 entry
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| type as if single key for each letter, & use dictionary to ‘guess’ the right word, & hello = 43556 … | T9 predictive entry
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| Text can be input into the computer, using a pen and a digesting tablet, & natural interaction | Handwriting recognition
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| Improving rapidly, & Most successful when: | Speech recognition
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| for entering numbers | Numeric keypads
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| Handheld pointing device: very common, & easy to use | Mouse
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| Two characteristics of the mouse | planar movement, & buttons
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| Ball on underside of mouse turns as mouse is moved, & Rotates orthogonal potentiometers, & Can be used on almost any flat surface | Mechanical
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| light emitting diode on underside of mouse, & may use special grid-like pad or just on desk | Optical
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| small touch sensitive tablets | Touchpad
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| ‘stroke’ to move mouse pointer used mainly in laptop computers | Touchpad
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| ball is rotated inside static housing. & like an upsdie down mouse! | Trackball
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| two dials for X-Y cursor position | Thumbwheels …– for accurate CAD
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| single dial on mouse | Thumbwheels …– for fast scrolling
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| indirect, pressure of stick = velocity of movement | Joystick
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| often used for computer games, & aircraft controls and 3D navigation | Joystick
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| for laptop computers, & miniature joystick in the middle of the keyboard | Keyboard nipple
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| Detect the presence of finger or stylus on the screen., & works by interrupting matrix of light beams, capacitance changes or ultrasonic reflections | Touch-sensitive screen
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| direct pointing device | Touch-sensitive screen
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| small pen-like pointer to draw directly on screen | Stylus
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| may use touch sensitive surface or magnetic detection | Stylus
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| used in PDA, tablets PCs and drawing tables | Stylus
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| now rarely used, & uses light from screen to detect location | Light Pen
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| Mouse like-device with cross hairs, & used on special surface and rather like stylus | Digitizing tablet
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| very accurate & used for digitizing maps | Digitizing tablet
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| control interface by eye gaze direction. & uses laser beam reflected off retina | Eyegaze
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| Four keys (up, down, left, right) on keyboard. & Very, very cheap, but slow. | Cursor keys
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| screen is vast number of coloured dots | bitmap displays
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| diagonal lines that have discontinuities in due to horizontal raster scan process. | Jaggies
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| softens edges by using shades of line colour & also used for text | Anti-aliasing
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| Stream of electrons emitted from electron gun, focused and directed by magnetic fields, hit phosphor-coated screen which glows | Cathode ray tube
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| used in TVs and computer monitors | Cathode ray tube
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| Smaller, lighter, and … no radiation problems. | Liquid crystal displays
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| draw the lines to be displayed directly, & no jaggies, & lines need to be constantly redrawn , & rarely used except in special instruments | Random Scan (Directed-beam refresh, vector display)
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| Similar to random scan but persistent => no flicker. & Can be incrementally updated but not selectively erased. & Used in analogue storage oscilloscopes | Direct view storage tube (DVST)
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| used for meetings, lectures, etc. | large displays
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| usually wide screen | plasma
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| lots of small screens together | video walls
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| RGB lights or LCD projector. & hand/body obscures screen | projected
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| frosted glass + projector behind | back-projected
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| displays in ‘public’ places. Large or small & very public or for small group | situated displays
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| thin flexible sheets, & updated electronically | Digital paper
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| steering wheels, knobs and dials … just like real! | cockpit and virtual controls
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| six-degrees of movement: x, y, z + roll, pitch, yaw | the 3D mouse
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| fibre optics used to detect finger position | data glove
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| detect head motion and possibly eye gaze | VR helmets
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| accelerometers strapped to limbs or reflective dots and video processing | whole body tracking
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| ordinary screen, mouse or keyboard control, & perspective and motion give 3D effect | desktop VR
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| use stereoscopic vision, & VR helmets, & screen plus shuttered specs, etc. | seeing in 3D
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| mve head … lag … display moves | time delay
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| headset gives different stereo distance, & but all focused in same plane | depth perception
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