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• Interaction efficiency relies on understanding both human and computer elements.

Computer Systems

• Computer systems consist of various elements that influence user interaction.
• Key elements include input devices, output devices, virtual reality, physical interaction, memory, paper, and processing capabilities.

Input Devices

• Input devices involve text entry and pointing:
• Keyboards
• Microphones

Output devices

• Include screens (small & large)
• Digital paper

Interacting with Computers

• Understanding human-computer interaction requires understanding computers, specifically what goes in and out (devices, paper, sensors) and what it can do (memory, processing, networks).

Typical Computer System Components

• Typical computer systems include a screen and a keyboard and mouse.
• Computer systems come in various forms like desktops, laptops and PDAs

User Interactivity

• Modern computing is characterized by interactivity.
• Interactive computing involves quick feedback, user control, and action-oriented tasks.

Richer interaction

• Richer interaction comes from a range of sensors and devices, including items like the Internet fridge, mobile phones, video cameras, and pressure mats

How many computers are there?

• Computers include PCs, TVs, VCRs, DVDs, cable/satellite boxes, microwaves, cookers, washing machines, central heating systems and security systems.
• Computers can be PDAs, phones, cameras, smart cards, cards with magnetic strips, electronic car keys, and USB memory.

Text Entry Devices

• Popular text entry devices consist of keyboards and chord keyboards.
• Handwriting and speech recognition can also be used.

Keyboards

• Keyboards are the most common text input device.

• Experienced users use keyboards for rapid text entry.

• Wireless and cable-based keyboards exist.

• Keypresses close a connection, which sends a character code. Standardized Layout – QWERTY

• Non-alphanumeric keys, highlighted symbols, and minor UK/USA differences exist.

• The QWERTY layout prevents typewriters from jamming.

• Faster typing is possible with alternative designs.

Alternative Keyboard Layouts

• Alphabetic layouts have keys in alphabetic order.
• DVORAK keyboards have common letters under dominant fingers.
• The DVORAK layout has common letter combinations alternating between hands.
• The DVORAK layout offers a has a 10-15% improvement in speed and fatigue reduction.

Chord Keyboards

• Chord keyboards use 4-5 keys typed as a combination of key presses.
• Portable applications benefit from their compact size.
• Key presses reflect letter shapes.
• Chord keyboards are fast once trained.

Numeric Keypads

• Calculator style keypads are used to enter numbers,
• Telephone-style keypads are also used
• Keypad layout is not consistent for telephones and ATMs.

Phone Pad and T9 Entry

• Multiple presses per key are used with numeric keys.
• T9 predictive entry involves typing a single key for each letter and using a dictionary to guess the right word.

Handwriting Recognition

• Handwriting recognition involves using a pen and digitizing tablet to input text.
• Stroke paths and pressure and segmented into individual letters
• Handwriting recognition is used in PDAs and tablet computers.

Speech Recognition

• Single-user systems with limited vocabularies are most successful with speech recognition.
• External noise, imprecise pronunciation, large vocabularies, and different speakers are problems.

Positioning, Pointing, and Drawing Devices

• Common input devices:
  • Mouse
  • Touchpad
  • Trackballs
  • Joysticks
  • Touchscreens
  • Tablets
  • Eyegaze systems
  • Cursors

The Mouse

• The mouse is a handheld pointing device.
• The mouse is very common and easy to use.
• It has two characteristics: planar movement and buttons.
• The planar movement and buttons usually initiates drawing or indicates an option.
• A mouse is an indirect manipulation device.
• The pointer does not obscure the screen and is fast and accurate.

How Mice Work

• Mechanical mice include a ball that turns on the underside.
• The ball rotates orthogonal potentiometers and can be used on any flat surface.
• Optical mice include a light-emitting diode on the underside.
• Optical mice reflect alterations in light intensity in the (x, z) plane.

Alternative Mice

• Some experiments have been undertaken with foot mice.
• Foot controls are common for car pedals, sewing machines, and pianos/organs.

Touchpad

• Touchpads consist of small touch-sensitive tablets.
• 'Stroke' is used to move mouse pointer.
• Used mainly in laptop computers with acceleration settings.
• Fast strokes move lots of pixels per inch.
• Slow strokes move less pixels per inch for accurate positioning.

Trackball and Thumbwheels

• In a trackball, a ball rotates inside a static housing.
• Trackballs cause relative motion, making the cursor an indirect accurate device.
• Trackballs have separate buttons for picking.
• Trackballs are fast for gaming and used in portable and notebook computers.
• Thumbwheels have two dials for X-Y cursor position in CAD.
• A single dial on a mouse is used for fast scrolling

Joystick and Keyboard Nipple

• Joystick pressure is equal to velocity of movement
• Joysticks have buttons for selection.
• Joysticks are often used for computer games, aircraft controls, and 3D navigation.
• Keyboard nipples are for laptop computers
• Keyboard nipples are miniature joysticks in the middle of the keyboard.

Touch-Sensitive Screen

• A touch-sensitive screen detects the presence of a finger or stylus.
• Capacitance changes, interrupting light beams or ultrasonic reflections.
• This is a direct pointing device.
• Touch-sensitive screens are fast and require no specialized pointer.
• The screens are good for menu selection and safe to use in hostile environments.
• One disadvantage is fingers mark the screen.
• Touch-sensitive screens are imprecise if you need perform accurate drawing.
• Lifting the arm for long periods used can be tiring.

Stylus and Light Pen

• A stylus is a small pen-like pointer to draw directly on a screen.
• They may use touch sensitive surface or magnetic detection.
• They are found in PDAs, tablet PCs, and drawing tables.
• Light pens use used light from screen to detect location.
• Both styluses and light pens are obvious to use.

Digitizing Tablet

• Digitizing Tablets have mouse-like devices with crosshairs.
• Digitizing Tablets are used on surfaces and like to styluses.
• They are very accurate and used for digitizing maps.

Eyegaze

• The interface is controlled by eye gaze direction.
• It involves looking at a menu item to select it.
• A low power laser is used in the process.
• Primarily used for evaluation and potential for hands-free control.
• High accuracy requires a headset.
• Cheaper lower accuracy devices sit under the screen.

Cursor Keys

• Four keys (up, down, left, right) on keyboard move the cursor.
• Cursor keys are slow, simple, and cheap.
• This is useful for basic motion.
• The most common layout is the inverted "T" layout.

Discrete Positioning Controls

• Cursor pads or mini-joysticks control phones and TVs.
• The controls provide discrete left-right and up-down,

Display devices

• Display devices include bitmap screens (CRT & LCD).
• Further display devices are large & situated displays and digital paper.

Bitmap Displays

• Screens have a vast number of colored dots called pixels.
• Pixel counts can measure screen resolution as width x height
• Density of pixels can be measured with dpi

Aspect ratio

• Aspect ratio can be measured between width and height
• 4:3 for most screens, 16:9 for wide-screen TV

Colour depth

• Black/white or greys only
• 256 from a palette
• 8 bits each for red/green/blue = millions of colours
• Number of different colours for each pixel ?

Health Hints

• Sit at a reasonable distance from the screen.
• Do not use very small fonts.
• Look away from the screen periodically to avoid eye strain.
• Do not place the screen directly in front of a bright window.
• Work in well-lit surroundings.

Liquid Crystal Displays

• Smaller and lighter than traditional monitors with no radiation emissions.
• LCDs are commonly found on PDAs, portables, notebooks, desktops and TVs.
• LCDs are also used in dedicated displays like digital watches and mobile phones.

Large Displays

• Used for meetings and lectures.
• Plasma – usually wide screen
• Video walls - lots of small screens together
• Projection - Can face issue where hand obscures image and projectors may be needed to remedy issue
• Back-projected uses frosted glass + projector behind

Virtual Reality and 3D Interaction

• 3D interaction involves positioning in 3D space, moving and grasping, and seeing 3D through helmets and caves.

Positioning in 3D Space

• Cockpits have steering wheels, knobs, and dials.
• Six degrees of movement: x, y, z + roll, pitch, yaw.
• Data gloves have fibre optics to detect finger position.
• VR helmets detect head motion and possibly eye gaze.
• Whole body tracking includes accelerometers strapped to limbs or reflective dots and video processing.
• The 3D mouse provides six degrees of movement, including roll, pitch, and yaw.

Pitch, Yaw and Roll

• Rotation around the pitch axis is movement up and down.
• Rotation around the yaw axis is movement left and right.
• Rotation around the roll axis is barrel-roll turning.

3D Displays

• Desktop VR has ordinary screens and mouse/keyboard for control.
• Perspective and motion give 3D effect.
• Stereoscopic vision is used to give 3D effects
• This can involve VR helmets and screen plus shuttered specs.

VR Headsets

• VR headsets consists of small TV screen for each eye at slightly different angles producing a 3D effect.

VR Motion Sickness

• Time delays cause a conflict between head movement and eyes.
• Depth perception issues include headset giving different stereo distance that are all focused in the same plane, which is an eye conflict.
• Conflicting depth perception cues lead to sickness, but this motivates technology improvements.

Physical Controls and Sensors

• Sound, touch, feel, and smell can be physical controls.
• Environmental and bio-sensing is another form of physical control and sensors.

Dedicated Displays Features

• Analogue representations use dials, gauges, and lights.
• Digital displays feature small LCD screens and LED lights.
• Head-up displays are found in aircraft cockpits and show key controls.

Sounds

• Beeps, bongs, clonks, whistles, and whirrs are types of sounds used in computing.
• Sounds are used for confirmation of actions (e.g. keyclick) and error indications.

Haptics

• Haptics deals with touch and feeling.
• Vibration and force feedback are in games.
• Simulation delivers the feel of surgical instruments.

Haptic Devices

• Refers to haptic technology and its use in physical interfaces
• BMW uses haptic iDrive technologies to allow use of menus by feel through small pumps

Physical Controls

• Industrial controls and consumer products exist.
• This includes easy clean smooth buttons, large buttons, clear dials, and multi function controls

Environmental and Bio-Sensing

• Sensors exist all around, including car courtesy lights, ultrasound detectors, and RFID security tags.
• Temperature, weight, and location determine the sensor.
• Iris scanners, body temperature, heart rate, galvanic skin response, and blink rate use can be sensed.

Paper: Printing and Scanning

• Includes information on print technology such as fonts, page description, scanning, OCR.

Printing

• Printing is the process of outputting dots to a physical surface

Critical Printing features include:

• Resolution
• Size & spacing of the dots
• Measured in dots per inch (dpi)
• Speed, usually measured in pages per minute
• Cost

Types of Dot Matrix Printers

• Dot matrix printers use inked ribbon and a line of pins to strike the ribbon.
• The typical resolution is 80-120 dpi.
• Ink-jet and bubble-jet printers send tiny blobs of ink from the print head to the paper.
• The typical resolution of inkjet printers is 300 dpi or better.
• Laser printers function like photocopiers that deposit electrostatic charge on a drum.
• Toner (black powder) is rolled onto paper and fixed with heat, at 600 dpi or better.

Workplace Printing

• Dot matrix printers are used in shop tills.
• Thermal printers use special heat-sensitive paper heated by pins to make a dot.
• Thermal printers have poor quality, but are low maintenance.

Fonts

• A font is the particular style of text.
• Font size is measured in points, which are vaguely related to height.

Font Attributes

• Pitch
• Serif
• Sans-serif

Pitch

• Fixed-pitch fonts have a constant width for every character, eg. Courier.
• Variable-pitched fonts vary in width from character to character, eg. Times New Roman.
• Serif fonts have splayed ends, such as Times Roman or Palatino.
• Sans-serif fonts have square-ended strokes such as Helvetica.

Text Readability

• Lowercase is easy to read the shape of words.
• UPPERCASE letters are better for individual letters and BA793 vs. ba793.
• Serif fonts help the eye on long lines of printed text.

Page Description Languages

• Pages are complex and have digitized photos, different fonts, bitmaps, and lines.
• A page can be converted into a bitmap but this is huge in size.
• Alternatively Use a page description language sends a description of the curves,lines, text, etc to the printer. -PostScript is the most common page description language

Screen and Page Similarities

• The goal of WYSIWYG is to have "what you see is what you get".
• Screen: 72 dpi and landscape image.
• Print: 600+ dpi & portrait.

Scanners

• Scanners take paper and convert it to a bitmap.
• Flat-bed scanners place paper on a glass plate.
• Hand-held scanners pass over paper and digitize a strip.
• Scanners shine light at paper and note intensity of reflected light as grayscale or colour.

Scanning Resolution

• Typical scanner resolutions range from 600-2400 dpi.
• Scanners are used in desktop publishing and document storage.
• Special scanners are used to scan slides and photographic negatives.

Optical Character Recognition (OCR)

• OCR converts bitmap images back into text.
• Different fonts create problems for template-matching algorithms.
• Complex systems segment text and decompose it into lines and arcs.
• OCR translates page formats, columns, pictures, headers, and footers.

Paper-Based interaction

• Paper is usually thought of as only an output system but also an input system.
• Xerox PaperWorks
• glyphs - small patterns of /\//\\ used to identify forms etc.

Memory

• memory can either be short or long term
• speed capacity compression and formats all impact accessibility

Short-Term Memory - RAM

• RAM, or random access memory, uses silicon chips.
• RAM access time is 100 nano-seconds.
• RAM is usually volatile (loses information if the power is turned off).
• Data is transferred at around 100 Mbytes/sec.

Long-Term Memory - Disks

• Floppy disks store around 1.4 Mbytes.
• Optical disks use lasers to read and write data.
• Optical disks feature CD-ROMs and DVDs that can be used for AV applications or large files.
• Optical disks are robust that magnetic media

Blurring of Memory Boundaries

• PDAs use RAM.
• Flash Memory is used in cameras and PDAs.
• Flash memory is silicon-based & persistent.

Virtual Memory

• When we're running lots of programs that are very large and we don't have enough RAM we need virtual memory store some programs temporarily on disk, makes RAM appear bigger

Compression

• Compressing data is done to reduce amount of storage required
• Lossless compression can be done of text/images look for commonalties
• Lossy compression allows you to recover something like the original – e.g. JPEG, MP3, uses perception

Storage Formats Options

• Includes ASCII, UTF-8, RTF, SGML, and XML formats

images formats

Includes the following technologies :

• Postscript
• GIFF
• JPEG
• TIFF PICT

Audio/Video formats

Includes the following technologies:

• QuickTime :
• MPEG
• WAV and more
• Compression is important for optimization for use in networks

Processing and Networks

• Finite speed (but also Moore's law).
• Limits of interaction.
• Networked computing.

Finite Processing Speed

• Designers tend to assume fast processors, and make interfaces more and more complicated.
• Problems occur because processing cannot keep up with all the tasks.
• Problems include cursor overshooting because system has buffered key presses.
• Fast systems can have help screens scroll too quickly.

Moore's Law

• Computers get faster and faster!

Networked Computing

• Networks provide access to large memory, processing, groupware, email and shared Web resources.
• Issues include network delays, conflicts when multiple people update data, and unpredictability.

The Internet

• DARPANET first occurred in 1969
• 1971: had 23 sites, by , 1984:1’000 by 1989: 10’000
• TCP –Transmission Control protocol
• IP - Internet Protocol
• Email, and HTTP all use these.