Human-Computer Interaction: The Computer

Human-Computer Interaction: The Computer A comprehensive exploration of computer systems, components, and technologies that enable human-computer interaction. Learning Outcome: Ability to explain comp...

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Human-Computer Interaction: The Computer

A comprehensive exploration of computer systems, components, and technologies that enable human-computer interaction.

Learning Outcome: Ability to explain computer factors in Human-Computer Interaction (HCI).

1. Definition

What is a Computer?

A computer is an electronic system that helps humans carry out tasks in HCI. It can manipulate data quickly and accurately, automatically receive and store input, process it, and produce output under a set of program instructions stored in its memory.

What can a computer do?

  • Input/Output: Devices (keyboard, mouse, touchscreen), paper, sensors, etc.
  • Functions: Memory, processing, networking, etc.

A computer is an electronic device capable of:

  1. Accepting input
  2. Processing input according to commands
  3. Storing commands and results
  4. Providing output as information
  5. Operating automatically

2. Computer Components

  • Input Devices: Keyboard, mouse, touchscreen, light pen
  • Output Devices: Monitor, scanner, printer
  • Memory
    • Short-term: RAM (Random Access Memory)
    • Long-term: CD, DVD, hard disk, etc.
  • Processing: Speed can vary (too fast or too slow)

Characteristics

  • Standard setup: screen (monitor), keyboard, mouse/trackpad
  • Variations: desktop, laptop, PDA
  • Device form factor affects supported interaction styles

3. Input and Output

Input Types

  • Direct Input: Mouse, keyboard
  • Indirect Input: Scanner, network (e.g., document downloads)

System Input Methods

  • Batch Input: Indirect I/O with minimal human intervention
  • Interactive Input: Entered directly by the user

4. Text Input Devices

  • Keyboards

    • QWERTY: Standard layout
    • Alphabetic: Local-language layouts (Arabic, Russian)
    • DVORAK: Optimized for finger efficiency
    • Chord: Combinations of keys
    • Special: Left-handed, projection, wearable ("kitty"), finger keyboards

  • Cursor Keys

    • Four-direction keys (up, down, left, right), inverted "T" layout

  • Positioning Controls

    • Mobile keypad pads, mini-joysticks for menu selection

  • Phone Pad & T9

    • Multi-press numeric entry; T9 predictive text

  • Numeric Keypads

    • Telephones, calculators

  • Function Keys

    • +: Reduce keystrokes, errors
    • –: No standard, depends on user familiarity

  • Handwriting Recognition

    • Pen + tablet; challenges in stroke segmentation

  • Speech Recognition

    • Microphone + ADC; best for single user, limited vocabulary; noise & pronunciation issues

5. Pointing Devices

  • Mouse (mechanical or optical)
  • Trackball
  • Joystick
  • Touchpad
  • Touchscreen
  • Light Pen
  • Digitizing Tablet

Mouse

  • Detects relative motion; 1–3 buttons

Trackball

  • Stationary; roll the ball

Joystick

  • Lever for fine control (games, 3D navigation)

Touchpad

  • Finger-movement pointer (laptops)

Touchscreen

  • Fast; no separate pointer; smudges & imprecision

Light Pen

  • Detects light from CRT screens; tiring & fragile

Digital Tablet

  • Resistive: Two-layer contact
  • Magnetic: Field pulses
  • Sonic: Acoustic sensing

6. Biometric Devices

  • Fingerprint Scanner
  • Hand Geometry Reader
  • Eye Biometric (iris/retina scanning)

7. Output Devices

Visual Output

  • CRT (raster, random scan, DVST)
  • LCD
  • LED
  • Plasma
  • Large Displays: smart boards, projectors, wall displays
  • Located Displays: interactive public info screens

Other Output

  • Wearables
  • Simulators
  • Sound: alerts, multimedia
  • Haptics: tactile feedback (e.g., BMW iDrive)
  • Physical Controls: industrial/consumer

Environment & Bio-sensing

  • External sensors (light, ultrasound, RFID), body-mounted sensors (iris, heart rate)

8. Printing

  • Principle: Images from pixel dots
  • Key Features
    • Resolution (dpi)
    • Speed (ppm)
    • Cost

Printer Types

  • Dot-matrix (80–120 dpi)
  • Ink-jet (≤ 600 dpi)
  • Thermal (heat paper)
  • Laser (≤ 1200 dpi)

Fonts

  • Pitch: fixed vs. variable
  • Serif vs. Sans-serif
  • Size: points (pt)
  • Readability: lowercase for text, uppercase for headings

9. Memory and Storage

Memory Types

  • RAM (volatile, ~100 ns access)
  • Disks (magnetic & optical)
  • Flash (non-volatile, PDAs, USB drives)

Speed & Capacity Examples

  • Scanned page: ~128 MB
  • Photo: ~10 MB
  • Video: ~10 MB/s

Compression

  • Lossless: GIF, ZIP
  • Lossy: JPEG, MP3

Storage Formats

  • Text: ASCII, UTF-8, RTF, SGML, XML
  • Image: PostScript, GIF, JPEG, TIFF
  • Audio/Video: QuickTime, MPEG, WAV

10. Performance Limitations

Interactive Limits

  • Computation Bound: slow calculations
  • Storage Bound: disk→memory bottleneck
  • Graphics Bound: display update lag
  • Network Bound: slow speeds

Processing Speed Effects

  • Too slow → interface lag, cursor overshoot
  • Too fast → content scrolls before read

Networked Computing

  • Pros: shared memory, processing, groupware
  • Cons: delays, data conflicts, unpredictability

Summary

Computer systems in HCI represent the technological foundation that enables human-computer interaction through diverse input/output devices, processing capabilities, and performance characteristics. Understanding computer limitations and capabilities is essential for designing effective interactive systems.

Key Takeaways:

  • System Architecture: Modern computers integrate input devices, processing units, memory systems, and output devices to create complete interactive environments.

  • Input Diversity: Multiple input modalities (text, pointing, voice, biometric, touch) provide different interaction styles suited to various user needs and contexts.

  • Output Capabilities: Visual, auditory, and haptic output channels enable rich feedback and information presentation to users.

  • Technology Evolution: From mechanical devices to touch interfaces, biometric sensors, and haptic feedback, computer technology continues expanding interaction possibilities.

  • Performance Constraints: System limitations in computation, storage, graphics, and networking directly impact user experience and interface design decisions.

  • Design Implications: Key considerations include:

    • Choose appropriate input methods for user tasks and capabilities
    • Balance output modalities for effective information delivery
    • Consider performance limitations in interface design
    • Account for device form factors and their interaction constraints
    • Design for accessibility across diverse hardware configurations

  • Future Directions: Emerging technologies like wearable devices, ambient computing, and advanced biometric systems are expanding the boundaries of human-computer interaction.

  • User Considerations: Different user groups have varying needs for input precision, output clarity, and interaction speed that must be accommodated in system design.

Understanding computer capabilities and constraints enables designers to create interfaces that leverage technological strengths while compensating for limitations. This knowledge is crucial for developing systems that feel responsive, intuitive, and capable while remaining accessible to users with diverse needs and technical environments.