HCI Meeting 3 Thursday, September 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)?

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)

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

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.

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 user’s work, nor allow (by inaction) it to be harmed. A system should not waste the user’s time, nor cause the user to do more work than necessary. Users should set the pace of the interaction.

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 off—that 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?”

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

Input Devices (2) Summary of available input devices –Keyboard –GID Mouse Trackball Light pen Tablet pen Joystick Touchpad All with buttons: Lmb, Cmb, Rmb

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

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.