The Computer a com puter system is m ade up of various elem ents - PDF document

The Computer a com puter system is m ade up of various elem ents chapter 2 each of these elem ents affects the interaction – input devices – t ext entry and pointing the computer – 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) – m em ory – RAM & permanent media, capacity & access – processing – speed of processing, networks Interacting with computers A ‘typical’ computer system ? • screen, or monitor, on which there are windows to understand human– computer interaction • keyboard … need to understand computers! window 1 • mouse/ trackpad window 2 • variations what goes in and out – desktop devices, paper, – laptop sensors, etc. – PDA 12-37pm the devices dictate the styles of interaction that the system supports what can it do? If we use different devices, then the interface will support a memory, processing, different style of interaction networks How many … How many computers … • computers in your house? in your house? in your pockets? – hands up, … – PC – PDA … none, 1, 2 , 3, more!! – TV, VCR, DVD, HiFi, – phone, cam era cable/ satellite TV – sm art card, card with – m icrowave, cooker, m agnetic strip? • computers in your pockets? washing m achine – electronic car key – central heating – USB m em ory – security system are you thinking … try your pockets and … PC, laptop, PDA ?? can you think of m ore? bags 1

Interactivity? Richer interaction 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 m ost com puting is interactive – rapid feedback – the user in control (most of the time) sensors – doing rather than thinking … and devices I s faster always better? everywhere Keyboards • Most common text input device text entry devices • Allows rapid entry of text by experienced users • Keypress closes connection, causing a character code to be sent keyboards (QWERTY et al.) • Usually connected by cable, but can be chord keyboards, phone pads wireless handwriting, speech layout – QWERTY QWERTY (ctd) • Standardised layout but … – non-alphanumeric keys are placed differently 2 3 4 5 6 8 9 1 7 0 – accented symbols needed for different scripts Q W E R T Y U I O P – minor differences between UK and USA keyboards S D F G H J K L A • QWERTY arrangem ent not optim al for typing X C V B N M , . Z – layout to prevent typewriters jam m ing! SPACE • Alternative designs allow faster typing but large social base of QWERTY typists produces reluctance to change. 2

alternative keyboard layouts special keyboards Alphabetic • designs to reduce fatigue for RSI – keys arranged in alphabetic order • for one handed use – not faster for trained typists – not faster for beginners either! e.g. the Maltron left-handed keyboard Dvorak – common letters under dominant fingers – biased towards right hand – common combinations of letters alternate between hands – 10-15% improvement in speed and reduction in fatigue – But - large social base of QWERTY typists produce market pressures not to change Chord keyboards phone pad and T9 entry only a few keys - four or 5 • use num eric keys with m ultiple presses letters typed as combination of keypresses 2 – a b c 6 - m n o compact size 3 - d e f 7 - p q r s – ideal for portable applications 4 - g h i 8 - t u v short learning time 5 - j k l 9 - w x y z – keypresses reflect letter shape hello = 4433555[ pause ] 555666 fast surprisingly fast! – once you have trained • T9 predictive entry – type as if single key for each letter – use dictionary to ‘guess’ the right word BUT - social resistance, plus fatigue after extended use – hello = 43556 … NEW – niche market for some wearables – but 26 -> menu ‘am’ or ‘an’ Handwriting recognition Speech recognition • Text can be input into the computer, using a • Im proving rapidly pen and a digesting tablet • Most successful when: – natural interaction – single user – initial training and learns peculiarities • Technical problem s: – lim ited vocabulary system s – capturing all useful inform ation - stroke path, pressure, etc. in a natural m anner • Problem s with – segm enting joined up writing into individual letters – external noise interfering – interpreting individual letters – im precision of pronunciation – coping with different styles of handwriting – large vocabularies • Used in PDAs, and tablet computers … – different speakers … leave the keyboard on the desk! 3

Numeric keypads • for entering numbers quickly: positioning, pointing and drawing – calculator, PC keyboard • for telephones 1 2 3 7 8 9 not the same!! 4 5 6 4 5 6 mouse, touchpad trackballs, joysticks etc. 7 8 9 1 2 3 ATM like phone touch screens, tablets . * 0 # 0 = eyegaze, cursors telephone calculator the Mouse the mouse (ctd) • Handheld pointing device Mouse located on desktop – requires physical space – very common – no arm fatigue – easy to use Relative movement only is detectable. • Two characteristics Movement of mouse moves screen cursor – planar movement Screen cursor oriented in (x, y) plane, mouse movement in (x, z) plane … – buttons … an indirect manipulation device. (usually from 1 to 3 buttons on top, used for – device itself doesn’t obscure screen, is accurate and fast. m aking a selection, indicating an option, or to initiate drawing etc.) – hand-eye coordination problems for novice users How does it work? Even by foot … Two m ethods for detecting m otion • some experiments with the footmouse – controlling m ouse m ovem ent with feet … • Mechanical – not very com m on : -) – Ball on underside of mouse turns as mouse is moved – Rotates orthogonal potentiometers – Can be used on almost any flat surface • but foot controls are common elsewhere: • Optical – car pedals – light emitting diode on underside of mouse – sewing m achine speed control – may use special grid-like pad or just on desk – organ and piano pedals – less susceptible to dust and dirt – detects fluctuating alterations in reflected light intensity to calculate relative motion in (x, z) plane 4

Touchpad Trackball and thumbwheels • small touch sensitive tablets Trackball – ball is rotated inside static housing • ‘stroke’ to move mouse pointer • like an upsdie down mouse! • used m ainly in laptop com puters – relative m otion m oves cursor – indirect device, fairly accurate • good ‘acceleration’ settings im portant – separate buttons for picking – fast stroke – very fast for gam ing • lots of pixels per inch moved – used in som e portable and notebook com puters. • initial movement to the target – slow stroke Thumbwheels … • less pixels per inch – for accurate CAD – two dials for X-Y cursor position • for accurate positioning – for fast scrolling – single dial on m ouse Joystick and keyboard nipple Touch-sensitive screen • Detect the presence of finger or stylus on the screen. Joystick – works by interrupting matrix of light beams, capacitance changes – indirect or ultrasonic reflections pressure of stick = velocity of m ovem ent – direct pointing device – buttons for selection • Advantages: on top or on front like a trigger – fast, and requires no specialised pointer – often used for com puter gam es – good for menu selection – suitable for use in hostile environment: clean and safe from aircraft controls and 3D navigation damage. • Disadvantages: Keyboard nipple – finger can mark screen – for laptop com puters – imprecise (finger is a fairly blunt instrument!) • difficult to select small regions or perform accurate drawing – m iniature joystick in the m iddle of the keyboard – lifting arm can be tiring Stylus and light pen Digitizing tablet Stylus • Mouse like-device with cross hairs – small pen-like pointer to draw directly on screen – may use touch sensitive surface or magnetic detection • used on special surface – used in PDA, tablets PCs and drawing tables - rather like stylus Light Pen – now rarely used • very accurate – uses light from screen to detect location - used for digitizing maps BOTH … – very direct and obvious to use – but can obscure screen 5