User Interface Design Make Your Program Easy to Use and Look Good

Interface Design Three types of interfaces System to external context Subsystem to subsystem (internal) System to user

User Interface Models User Model: What the user is like Design Model: What the designer intended Implementer’s Model: What the programmer built Mental Model (or System Perception): What the user thinks the application is like Goal: harmony between the mental model, the implementer’s model and the design model

Know Your User Age, gender, physical capability, education, vocation, culture, nationality, motivation, preferences, experience level Do your requirements document reflect the characteristics of your typical user? If not, you risk missing the correct abstraction for the UI or miss an opportunity to use a helpful metaphor to enhance user understanding and acceptance.

“Golden Rules” for UI Design Place User in Control Use modes w/o forcing unnecessary action Be flexible: keyboard, mouse, voice, etc. Allow interruptions and undoing Streamline: allow macros and shortcuts Hide details use the correct abstraction Implement direct manipulation Reduce the User’s Memory Load Don’t require memory of past actions Establish meaningful defaults Make mnemonics mnemonic (Alt-S for “Save”) Use a real-world metaphor Disclose information or functions progressively Make the Interface Consistent Provide indicators about system context Be consistent across families of applications Adhere to “defacto” practices (e.g., cut, copy, and paste)

UI Design Cycle Analyze user, task, behavioral, and environmental requirements Create user scenarios Design UI look and feel Prototype Evaluate Modify Implement

Additional Points of Emphasis Info on usability (pg 317 7/e, pg 329 6/e) Prescriptive advice on UI design steps, (section 11.4, pgs /e, section 12.4 pgs /e) When UI screen layout should occur (pg 329 7/e, pg 342 6/e) Balance between UI sketches and prototyping (see “advice” pg 330 7/e, pg 343 6/e) Four major design issues (response, help, error handling, menuing), plus two (pgs /e, pgs /e) UIs are evaluated both quantitatively and qualitatively (pg 343 7/e, pg 350 6/e)