HCI

1
HCI

• Meeting 3
• Thursday, September 2

2
Class Poll

• What does the word interface mean in the context
  of HCI and user-system interface design?
• What verb should be used to describe the action a
  user takes with a physical key or button (and by
  extension, a virtual key or button)?

3
User Interface (1)

• Consider interfaces
• What is an interface?
• Can a system not have an interface?
• What have been the paradigm shifts for
  interfaces?
• What will come next?
• When should the interface be designed? (trick
  question)

4
User Interface (2)

• The user interface
• Properties
• GUI vs DMI vs WIMP
• Note Raskin calls it windows, icons, pull-down
  menus, mice
• Non-GID
• Mental model
• The players
• User with choices
• System with program
• Interface enhances communication
• Designer anticipates choices

5
Raskin Says

• Discover the difference between how something
  should work and how it does work.
• Design so that the simple parts remain simple.
• Examples of success and failure?
• Design the interface first.

6
Design Principles

• Design for productivity, even if retraining is
  required.
• The system should treat all user input as sacred.
• A (computer) system should not harm the users
  work, nor allow (by inaction) it to be harmed.
• A system should not waste the users time, nor
  cause the user to do more work than necessary.
• Users should set the pace of the interaction.

7
Light Switches

• A model for turning things on and off
• Exercise (Light switch styles) Discover
  fifteen (15) different ways of turning a light on
  and offthat is, fifteen different switch
  designs.
• Reference The physics teacher said, Class,
  here is a barometer. How would you use it to
  find the height of the bell tower on campus?

8
Input Devices (1)

• Class survey Give the verb that best describes
  the action a user takes with a key
• Assume a physical momentary contact switch

9
Input Devices (2)

• Summary of available input devices
• Keyboard
• GID
• Mouse
• Trackball
• Light pen
• Tablet pen
• Joystick
• Touchpad
• All with buttons Lmb, Cmb, Rmb

10
Input Devices (3)

• Fundamental operations (the syntax)
• Point
• Depress a key (down arrow)
• Release a key (previously depressed) (up arrow)
• Notations Card Moran, Raskin
• Cognitive models GOMS, Keystroke Level

11
Next time

• Read Raskin, Chapter 2.
• Find two examples where the phenomenon of locus
  of attention affects the use of Windows XP,
  preferably one positive effect and one negative
  effect.
• Find two examples of habit formation that affect
  the use of Windows XP, preferably one positive
  effect and one negative effect.