Chapter 2: The Computer - Human-Computer Interaction PDF

Chapter 2 the computer Interacting with computers to understand human–computer interaction … need to understand computers! what goes in and out devices, paper, sensors, etc. what can it do? memory, processing,...

Chapter 2 the computer Interacting with computers to understand human–computer interaction … need to understand computers! what goes in and out devices, paper, sensors, etc. what can it do? memory, processing, networks  A ‘typical’ computer system ? a computer system is made up of various elements each of these elements affects the interaction – input devices – text entry and pointing – output devices – screen (small&large), digital paper – virtual reality – special interaction and display devices – physical interaction – e.g. sound, haptic, bio-sensing – paper – as output (print) and input (scan) – memory – RAM & permanent media, capacity & access – processing – speed of processing, networks If we use different devices, then the interface will support a different style of interaction Interactivity? Long ago in a galaxy far away … batch processing – punched card stacks or large data files prepared – long wait …. – line printer output … and if it is not right … Now most computing is interactive – rapid feedback – the user in control (most of the time) – doing rather than thinking … Is faster always better? Richer interaction sensors and devices everywhere  text entry devices keyboards (QWERTY et al.) chord keyboards, phone pads handwriting, speech Keyboards Most common text input device Allows rapid entry of text by experienced users Keypress closes connection, causing a character code to be sent Usually connected by cable, but can be wireless  layout – QWERTY Standardised layout but … – non-alphanumeric keys are placed differently – minor differences between UK and USA keyboards QWERTY arrangement not optimal for typing – layout to prevent typewriters jamming! Alternative designs allow faster typing but large social base of QWERTY typists resist to change.  alternative keyboard layouts Alphabetic – keys arranged in alphabetic order – not faster for trained typists – not faster for beginners either! designs to reduce fatigue for RSI: Repetitive strain injury for one handed use e.g. the Maltron left-handed keyboard Chord keyboards only a few keys - four or 5 letters typed as combination of keypresses compact size ideal for portable applications short learning time keypresses reflect letter shape fast BUT - social resistance, plus fatigue after extended use NEW – niche market for some wearables phone pad and T9 entry use numeric keys with multiple presses 2 –abc 6 - mno 3 -def 7 - pqrs 4 -ghi 8 - tuv 5 -jkl 9 - wxyz hello = 4433555[pause]555666 surprisingly fast! T9 predictive entry – type as if single key for each letter – use dictionary to ‘guess’ the right word – hello = 43556 … – but 26 -> menu ‘am’ or ‘an’ Handwriting recognition Text can be input into the computer, using a pen and a digesting tablet – natural interaction Technical problems: – capturing all useful information in a natural manner – segmenting joined up writing into individual letters – interpreting individual letters – coping with different styles of handwriting Used in PDAs, and tablet computers … … leave the keyboard on the desk! Speech recognition Improving rapidly Most successful when: – single user – initial training and learning – limited vocabulary systems Problems with – external noise interfering – imprecision of pronunciation – large vocabularies – different speakers positioning, pointing and drawing mouse, touchpad trackballs, joysticks etc. touch screens, tablets eyegaze, cursors  the mouse (ctd) Mouse located on desktop – requires physical space – no arm fatigue – Easy to use & very common Screen cursor oriented and mouse movement in (x, y) plane, … an indirect manipulation device. – device itself doesn’t obscure screen, is accurate and fast. – hand-eye coordination problems for novice users. Two methods for detecting motion Mechanical – Ball on underside of mouse turns as mouse is moved Optical – light emitting diode on underside of mouse. – less susceptible to dust and dirt  Even by foot … some experiments with the footmouse – controlling mouse movement with feet … – not very common :-) but foot controls are common elsewhere: – car pedals – sewing machine speed control – organ and piano pedals Touchpad & Trackball Touchpad: – small touch sensitive tablets – used mainly in laptop computers – good ‘acceleration’ settings important fast stroke – lots of pixels per inch moved – initial movement to the target slow stroke – less pixels per inch – for accurate positioning Trackball: – like an upside down mouse! – very fast for gaming, hard to draw with. Why? – used in some portable and notebook computers. – Alternative mouse for RSI sufferers. Thumbwheels: (Adv & Dis) ? Joystick & Cursor keys Joystick – Indirect pointing device pressure of stick = velocity of movement – buttons for selection on top or on front like a trigger – often used for computer games aircraft controls and 3D navigation Cursor keys Four keys (up, down, left, right) on keyboard. Very, very cheap, but slow. Useful for not much more than basic motion for text- editing tasks. Examples: in phones, TV controls etc. Cursor pads or mini-joysticks discrete left-right, up- down  Touch-sensitive screen Detect the presence of finger or stylus on the screen. – direct pointing device Advantages: – fast, and requires no specialised pointer – good for menu selection – suitable for use in hostile environment: clean and safe from damage. Disadvantages: – finger can mark screen – imprecise (finger is a fairly blunt instrument!) difficult to select small regions or perform accurate drawing – lifting arm can be tiring  Stylus and light pen Stylus – small pen-like pointer to draw directly on screen – may use touch sensitive surface or magnetic detection – used in PDA, tablets PCs and drawing tables Light Pen Digitizing tablet – now rarely used – uses light from screen to detect location BOTH … – very direct and obvious to use – but can obscure screen  Eyegaze control interface by eye gaze direction – e.g. look at a menu item to select it but not for drawing. uses laser beam reflected off retina – … a very low power laser! potential for hands-free control high accuracy requires headset Rarity for it expense & novelty. Eyegaze used in VR and AR.