HCI-Ch2.pdf

HUMAN-COMPUTER INTERACTION CHAPTER 2 – THE COMPUTER 2.1 INTRODUCTION 2.1.1 A typical computer system 2.2 TEXT ENTRY DEVICES - computer ‘box’ - keyboar...

HUMAN-COMPUTER INTERACTION CHAPTER 2 – THE COMPUTER 2.1 INTRODUCTION 2.1.1 A typical computer system 2.2 TEXT ENTRY DEVICES - computer ‘box’ - keyboard Entering a text - mouse - one of our main activities when using the - color screen computer Some variants on basic devices are driven by different… Keyboard Hardware configurations - most obvious means of text entry 1. Desktop use 2. Laptop computers 2.2.1 The alphanumeric keyboard 3. PDAs (personal digital assistants) *diversity of devices reflects that there are many diff Keyboard types of data that may have to be entered into and - used for entering textual data and commands obtained from a system, and there are many diff types of users, each with their own unique reqs Alternatives of QWERTY: 1. 26 key layouts 2.1.2 Levels of interaction – batch processing - rearranges the order of the alphabetic keys - putting the most commonly used letters In the early days… under the strongest fingers, or - Information: entered into the computer in a - adopting simpler practices large mass – batch data entry Examples: - there was minimal interaction with the 1. alphabetic machine: 2. DEVORAK user would simply dump a pile of punched 2. Chord keyboards cards onto a reader, press start button, and return few hrs later (1) The QWERTY keyboard *still continues today although now w/ pre- - layout of the digits and letters is fixed prepared electronic files or possibly - non-alphanumeric keys vary between machine-read forms keyboards: - clearly the most appropriate mode for certain - British (UK) kinds of app, for example: - American (US) - printing pay checks, or… - a standard keyboard layout still used today - entering the results from a questionnaire - derived from typewriters - with common letters spaced to prevent key Batch processing jams - with this, the interactions take place over hrs - in addition, diff national keyboards include or days accented letters and the traditional French *in contrast: typical desktop computer system layout places the main letter in diff locations has interactions taking secs or fractions of a sec – the top line starts AZERTY 2.1.3 Richer interaction – everywhere, everywhen (2) Ease of learning – alphabetic keyboard - letters are arranged alphabetically across the Information appliances are putting internet access or keyboard dedicated systems onto the: - not proven to improve typing speed - fridge - used in some pocket electronic personal - microwave organizers - washing machine *perhaps because the layout looks simpler To: to use than the QWERTY one - automate shopping - give email in your kitchen, or - simply call for maintenance when needed (3) Ergonomics of use – DVORAK keyboard and - numeric keypads are used for text input with split designs a dictionary to predict words, e.g. T9 - this layout enhances typing speed and simplifies typing on mobile phones ergonomics by placing commonly used letters in optimal positions T9 algorithm *split designs reduce strain - uses a large dictionary to disambiguate - uses similar layout of keys to QWERTY words by simply typing the relevant letters system but assigns letters to diff keys once - designed to help people reach faster typing example: speeds ‘3926753’ becomes ‘example’ - biased towards right-handed people (56% as there is only one word with letters that keystrokes are made with the right hand) match 2.2.2 Chord keyboards 2.2.4 Handwriting recognition - uses few keys (4 or 5) - letters are produced by pressing one or more Handwriting of the keys at once - a common and familiar activity, therefore example, in the… attractive as a method of text entry Microwriter - the pattern of multiple keypresses is chosen disadvantages with handwriting recognition in to reflect the actual letter shape computer: 1. current technology is still inaccurate Advantages: - makes significant number of mistakes in - extremely compact: simply reducing the recognizing letters, though it has improved size of a conventional keyboard makes the rapidly keys too small and close together, with 2. individual differences in handwriting are correspondingly large increase in difficulty enormous of using it - make the recognition process even more - fairly short learning time (order of a few difficult horus) but social resistance is still high - capable of fast typing speeds in the hands The most significant information in handwriting is (or right hand) of a competent user not in the letter shape itself but in the stroke information – the way in which the letter is drawn Chord Keyboards - can be used where only one-handed *the diff nature of handwriting means that we may operation is possible, in cramped and find it more useful in situations where a keyboard- confined conditions based approach would have its own problems - lack of familiarity = unlikely ever to be Pen-based systems mainstream - use handwriting recognition - have applications in niche areas: - actively marketed in the mobile computing - courtroom stenographers market, especially for smaller pocket - use special form of 2-handed organizers chord keyboard and associated shorthand to - typically used for: enter text at full spoken speed - taking notes - jotting down and sketching ideas 2.2.3 Phone pad and T9 entry - acting as a diary Phone keypad - address book - has become an important form of text input - organizer - only has 0-9 digits, not a full alphanumeric - can be small and yet still accurate and easy keyboard to use, whereas small keys become very - keys are pressed several times tiring, or even impossible, to use accurately most phones: - (pen-based approach) does not have to be - have at least 2 modes for numeric buttons: altered when we move from jotting down 1. where the keys mean the digits text to sketching diagrams; pen-based input 2. where they mean letters is highly appropriate for this also  Mouse – still most common for desktop computer, but is facing challenges as laptop and hand-held Gesture recognition computing increase their market share - To tell the system what to do, example: - drawing a line through a word in 2.3.1 The mouse order to delete it - developed around 1964 by - converts handwriting into text Douglas C. Engelbart - challenges include: - device that detects hand movements via a ball, accuracy and variations in translating them into cursor movements handwriting styles - has become major component of majority of desktop computer systems sold today 2.2.5. Speech recognition - the little box with the tail connecting it to the - promising area of text entry, BUT has been machine in our basic computer system picture promising for a number of years and is still - a small, pal-sized box housing a weighted only used in very limited situations ball - converts spoken words into text but faces *as the box is moved over the tabletop, the limitations like: ball is rolled by the table and so rotates inside 1. vocabulary size the housing 2. training for speakers **this rotation is detected by small rollers 3. background noise that are in contact with the ball, and these - has found niche markets: adjust the values of… - telephone information systems Potentiometers - access for the disabled - are aligned in diff directions so that they can - in hands-occupied situations detect both horizontal and vertical motion (especially military) *the relative motion information is passed to - for those suffering RSI the computer via a wire attached to the box, 3 possibilities: or in some cases using wireless or infrared, 1. an alternative text entry device to replace the and moves a pointer on the screen, called the keyboard within an environment and using cursor software originally designed for keyboard - (mouse) has typically one, two or three use buttons on top 2. to redesign a system, taking full advantage of *are used to indicate selection or to initiate the benefits of the technique whilst action minimizing the potential problems - Operates in a planar fashion: 3. it can be used in areas where keyboard-based - moving around the desktop, and is input is impractical or impossible an indirect input device, since a transformation is required to map from the horizontal nature of the 2.3 POSITIONING, POINTING AND DRAWING desktop to the vertical alignment of the screen Central to most modern computing systems is the Left-right motion ability to point at something on the screen and thereby - directly mapped manipulate it, or perform some function. Up-down motion - achieved by moving the mouse CAD (computer-aided design) away-towards the user - where positioning and drawing are the major activities Footmouse - a foot-operated device, although more akin to Pointing devices an isometric joystick than a mouse - allow the user to point, position and select - cursor is moved by foot pressure on one side items, either directly or by manipulating a or the other of a pad pointer on the screen - this allows one to dedicate hands to the - many can also be used for free-hand drawing keyboard although the skill of drawing with a mouse is very diff from using a pencil 2.3.2 Touchpad *the appropriateness of the device depends - touch-sensitive tablets usually around 2-3 on the task to be performed inches (50-75 mm) square - first used extensively in Apply Powerbook 2.3.4 Joystick and keyboard nipple portable computers but are now used in many other notebook computers Joystick - can be obtained separately to replace the - indirect input device, taking up very little mouse on the desktop space - operated by stroking a finger over their - consist of small palm-sized box with a stick surface, rather like using a simulated or shaped grip sticking up from it trackball - a simple device with w/c movements of the - stick cause a corresponding movement of the screen cursor 2.3.3 Trackball and thumbwheel - inexpensive and fairly robust, often found in computer games Trackball - relatively familiar to users - just an upside-down mouse Keymouse - a weighted ball faces upwards and is rotated - older variant inside a static housing, the motion being - a single key detected in the same way as for a mechanical 2 types of joystick: mouse, and the relative motion of the ball 1. Absolute moves the cursor. - movement is the important characteristic, Because of this… since the position of the joystick in the base - requires no additional space in which to corresponds to the position of the cursor on operate, and is therefore a very compact the screen device 2. Isometric - is an indirect device - the pressure on the stick corresponds to the - requires separate buttons for selection velocity of the cursor, and when released, the - fairly accurate, but hard to draw with, as stick returns to its usual upright centered long movements are difficult position - heavily used in video games where their - a.k.a. velocity-controlled joystick highly responsive behavior, including being able to spin the ball, is ideally suited to the - a stick or small device controlling cursor movement demands of play - used in laptops and gaming Thumbwheels 2.3.5 Touch-sensitive screens (touchscreens) - have two orthogonal dials to control the - Another method allowing user to point and cursor position select objects on screen - very cheap, but slow - Much more direct than the mouse - difficult to manipulate the cursor in any way - Detect presence of user’s fingers, or a stylus, other than horizontally or vertically on the screen itself *this limitation can sometimes be a useful constraint in the right application Work in diff ways: For instance… 1. by the finger interrupting a matrix of light beams in CAD: 2. by capacitance changes on a grid overlaying - designer: almost always concerned with the screen exact verticals and horizontals 3. by ultrasonic reflections in Etch-a-Sketch: - no mapping required cus user indicates - a drawing game exactly w/c item is required by pointing to it - straight lines can be created on a simple - a direct device screen, since the predominance of straight lines in simple drawings means that the motion restrictions are an advantage rather than a handicap  Disadvantages of touchscreens: Problems of digitizing tablets: 1. finger can leave greasy marks on screen - Require large amount of desk space 2. a blunt instrument, quite inaccurate - May be awkward to use if displaced to one - selection of small regions is very difficult, side by the keyboard as is accurate drawing 3. lifting arm to point to vertical screen = very Resistive tablet tiring - Detects point contact between two separated conducting sheets *research shown: optimal angle for touchscreen - Advantage: can be operated without a is about 15 degrees of from the horizontal specialized stylus (pen or user’s finger is enough) - allows direct interaction with the screen by touching Magnetic tablet it - Detects current pulses in magnetic field using small loop coil housed in special pen 2.3.6 Stylus and light pen Sonic tablet Stylus - Similar to magnetic but requires no special - popular in PDAs but also used in some laptop surface computers - Ultrasonic pulse is emitted by a special pen which is detected by two or more Light pen microphones which then triangulate the pen - older tech used in same way position - connected to screen by cable - Can be adapted to provide 3D input, if - held to screen and detects burst of light from required screen phosphor during the display scan - can address individual pixels and, - detects pen movements to create digital drawings or - much more accurate than the touchscreen for precise cursor positioning both stylus and light pen 2.3.8 Eyegaze - can be used for fine selection and drawing - BUT both can be tiring to use on upright Eyegaze systems displays and, - Allow you to control the computer by simply - harder to take up and put down when used looking at it together with a keyboard - Some require wearing special glasses or small head-mounted box - devices for drawing or selecting on the screen, often - Other: built into screen or sit as a small box used for precision tasks below the screen - *Low-power laser is shone into the eye and is 2.3.7 Digitizing tablet reflected off the retina - more specialized device typically used for - *reflection changes as angle of eye alters, and freehand drawing by tracking the reflected beam the system can - BUT may be used as mouse substitute determine the direction in which the eye is - Some usually using a puck (mouse-like looking device) are used in special apps such as - Very fast and accurate device, but more digitizing info for maps accurate versions can be expensive - Provides positional info by measuring - WITHIN HCI: particularly useful as part of position of some device on a special pad, or evaluation as one is able to trace exactly tablet, and where the user is looking - Can work in number of ways - Capable of high resolution - tracks eye movements to control the screen cursor, - Available in a range of sizes requiring calibration - Can be used to detect relative motion or absolute motion but is an indirect device 2.3.9 Cursor keys and discrete positioning since there is mapping from plane of operation of tablet to screen - keys used for moving the cursor in a controlled way - often part of a keyboard  2.5 DEVICES FOR VIRTUAL REALITY AND 2.4 DISPLAY DEVICES 3D INTERACTON 2.4.1 Bitmap displays – resolution and color 2.5.1 Positioning in 3D space Bitmap - Display is made of vast numbers of colored (1) Cockpit and virtual controls dots or pixels in rectangular grid - interfaces mimicking real-world control panels *pixels can be limited to black and white, in grayscale, or full color (2) The 3D mouse - the color/intensity at each pixel is held by the - a mouse used for navigating three-dimensional computer’s video card spaces - 1 bit per pixel can store on/off info, hence only black and white (term ‘bitmap’ come (3) Dataglove from such displays) - a glove tracking hand movements for 3D control - More bits per pixel = more color/intensity possibilities (4) Virtual reality helmets - Set of colors make up what is called the - headgear providing immersive visual experiences by Colormap showing virtual environments - can be altered at any time to produce a diff set of colors (5) Whole-body tracking 2 numbers to consider: - a system that tracks all body movements to interact 1. total number of pixels with a virtual space - in standard computer displays : always in 4:3 ratio, perhaps 1024 pixels across by 768 2.5.2 3D displays down - for PDAs : will be more in the order of a few (1) Seeing in 3D hundred pixels in each direction - visual systems designed to present 3D images 2. density of pixels - measured in pixels per inch (2) VR motion sickness - a discomfort caused by a mismatch between visual CRT (cathode ray tube) stimuli and physical movement in virtual reality - - use pixels to form images (3) Simulators and VR caves - with resolution defining the pixel count - virtual environments designed for immersive interaction 2.4.2 Technologies - often used for training (1) Cathode ray tube - an older display technology using electron beams to light phosphor screens 2.6 PHYSICAL CONTROLS, SENSORS AND SPECIAL DEVICES (2) Liquid crystal display - a flat-panel display using liquid crystals to control 2.6.1 Special displays light - displays created for niche apps, such as heads-up - popular in laptops displays (3) Special displays 2.6.2 Sound output - includes devices like digital paper - audio output devices like speakers - designed for specific uses 2.4.3 Large displays and situated displays 2.6.3 Touch, feel and smell - larger screens for public or specialized use - haptic feedback and other sensory interactions with computers 2.4.4 Digital paper - a display technology that mimics the appearance of 2.6.4 Physical controls paper, often used in e-readers - devices like foot pedals for controlling computer functions  - systems where computers share resources over a 2.6.5 Environment and bio-sensing network - sensors that detect environmental factors or biological signals like temperature 2.10 SUMMARY - the combination of input and output systems defines 2.7 PAPER: PRINTING AND SCANNING how users interact with computers 2.7.1 Printing - processes that transfer electronic data to paper 2.7.2 Fonts and page description languages - technologies that render text and graphics on screens and paper 2.7.3 Screen and page - the relationship between what appears on a screen and how it is printed 2.7.4 Scanners and optical character recognition - devices converting physical documents into digital data 2.8 MEMORY 2.8.1 RAM and short-term memory (STM) - volatile memory used for active processes - lost when power is off 2.8.2 Disks and long-term memory (LTM) - non-volatile storage for long-term data, such as hard drives 2.8.3 Understanding speed and capacity - factors determining how fast and how much data can be stored and retrieved 2.8.4 Compression - the process of reducing the size of data files 2.8.5 Storage format and standards - different formats for storing and accessing data 2.8.6 Methods of access - the ways in which data can be retrieved from memory 2.9 PROCESSING AND NETWORKS 2.9.1 Effects of finite processor speed - how limited processing power affects performance 2.9.2 Limitations on interactive performance - restrictions on how quicky a computer can respond to user input 2.9.3 Networked computing