Human-Computer Interaction Chapter 2 - The Computer PDF

chapter 2 the computer  display devices bitmap screens (CRT & LCD) large & situated displays digital paper bitmap displays screen is vast number of coloured dots virtual reality and 3D interaction positioning in 3D space moving and grasping seeing 3D (helmets and...

chapter 2 the computer  display devices bitmap screens (CRT & LCD) large & situated displays digital paper bitmap displays screen is vast number of coloured dots virtual reality and 3D interaction positioning in 3D space moving and grasping seeing 3D (helmets and caves)  positioning in 3D space cockpit and virtual controls – steering wheels, knobs and dials … just like real! the 3D mouse – six-degrees of movement: x, y, z + roll, pitch, yaw data glove – fibre optics used to detect finger position and thumb VR helmets/googles – detect head motion and possibly eye gaze whole body tracking pitch, yaw and roll yaw roll pitch 3D displays desktop VR – ordinary screen, mouse or keyboard control – perspective and motion give 3D effect seeing in 3D – use stereoscopic vision – VR helmet VR headsets small TV screen for each eye slightly different angles 3D effect also see extra slides on 3D vision  simulators and VR caves Stereo Vision: Generation of image from different perspectives. scenes projected on walls realistic environment real controls and other people Caves: general purpose rooms have large displays around the user The user look around and see the virtual world surrounding them. Example: large flight simulators.  Touch, feel, smell touch and feeling important – in games … vibration, force feedback – in simulation … feel of surgical instruments – called haptic devices texture, smell, taste – current technology very limited Sounds beeps, bongs, clonks, and whistles used for error indications confirmation of actions e.g. keyclick  physical controls specialist controls needed … – industrial controls, consumer products, etc. easy-clean smooth buttons multi-function control large buttons clear dials tiny buttons paper: printing and scanning print technology fonts, page description, WYSIWYG scanning, OCR Printing image made from small dots – allows any character set or graphic to be printed, critical features: – resolution size and spacing of the dots measured in dots per inch (dpi) – speed usually measured in pages per minute – cost!! Types of dot-based printers dot-matrix printers – use inked ribbon (like a typewriter – line of pins that can strike the ribbon, dotting the paper. – typical resolution 80-120 dpi ink-jet and bubble-jet printers – tiny blobs of ink sent from print head to paper – typically 300 dpi or better. laser printer – like photocopier: dots of electrostatic charge deposited on drum, which picks up toner (black powder form of ink) rolled onto paper which is then fixed with heat – typically 600 dpi or better.  Printing in the workplace shop tills – dot matrix – same print head used for several paper rolls – may also print cheques thermal printers – special heat-sensitive paper – paper heated by pins makes a dot – poor quality, but simple & low maintenance – used in some fax machines Fonts Font – the particular style of text Courier font Helvetica font Palatino font Times Roman font §´µº¿Â Ä¿~ (special symbol) Size of a font measured in points (1 pt about 1/72”) (vaguely) related to its height This is ten point Helvetica This is twelve point This is fourteen point This is eighteen point and this is twenty-four point Fonts (ctd) Pitch – fixed-pitch – every character has the same width e.g. Courier – variable-pitched – some characters wider e.g. Times Roman – compare the ‘i’ and the “m” Serif or Sans-serif – sans-serif – square-ended strokes e.g. Helvetica – serif – with splayed ends (such as) e.g. Times Roman or Palatino Readability of text lowercase – easy to read shape of words UPPERCASE – better for individual letters and non-words e.g. flight numbers: BA793 vs. ba793 serif fonts – helps your eye on long lines of printed text – but sans serif often better on screen Scanners Take paper and convert it into a bitmap Two sorts of scanner – flat-bed: paper placed on a glass plate, whole page converted into bitmap – hand-held: scanner passed over paper, digitising strip typically 3-4” wide Shines light at paper and record intensity of reflection – colour or greyscale Scanners (ctd) Used in – desktop publishing for incorporating photographs and other images – document storage and retrieval systems, doing away with paper storage + special scanners for slides and photographic negatives Paper-based interaction paper usually regarded as output only can be input too – OCR, scanning, etc. Xerox PaperWorks – glyphs – small patterns of /\\//\\\ used to identify forms etc. used with scanner and fax to control applications  memory short term and long term speed, capacity, compression formats, access Short-term Memory - RAM Random access memory (RAM) – on silicon chips – 100 nano-second access time – usually volatile (lose information if power turned off) – data transferred at around 100 Mbytes/sec Some non-volatile RAM used to store basic set-up information Typical desktop computers: 64 to 256 Mbytes RAM Long-term Memory - disks magnetic disks – floppy disks store around 1.4 Mbytes – hard disks typically 40 Gbytes to 100s of Gbytes access time ~10ms, transfer rate 100kbytes/s optical disks – use lasers to read and sometimes write – more robust that magnetic media – CD-ROM - same technology as home audio, ~ 600 Gbytes – DVD - for AV applications, or very large files Blurring boundaries PDAs – often use RAM for their main memory Flash-Memory – used in PDAs, cameras etc. – silicon based but persistent – plug-in USB devices for data transfer virtual memory Problem: – running lots of programs + each program large – not enough RAM Solution - Virtual memory : – store some programs temporarily on disk – makes RAM appear bigger But … swopping – program on disk needs to run again – copied from disk to RAM – slows t h i n g s d o w n