1. Usability and user Interfaces
CS 560
Lecture 13

2. Human computer interaction
Human Computer Interaction (HCI) is the discipline that studies how people interact with computers.
Study of how we interface with information.
Not just “how large should I make buttons” or “menu layout”
Motivations:
User Effectiveness/Productivity
Morale
Safety
HCI fields of study:
Computer Science
Psychology
Communication
Education
Anthropology
Design (Graphic and Industrial)

3. The importance of user interface design
A software system is only as good as the interface it provides to its users.
System effectiveness depends on:
Functionality
Easy navigation
Fast response times
If a system is hard to use:
Users may fail to find results
Users may become frustrated and give up
Developing good user interfaces takes time.

4. Interface Usability: The analyze/design/build/evaluate loop

5. Tools for usability requirements: mock-up/Wire Frame (documentation)

6. Tools for usability requirements: Prototype screenshots (documentation)

7. Usability Requirements: accessibility (Documentation)
Software designers must be prepared for users with
Poor eyesight
Lack of hearing
Poor manual dexterity
Limited knowledge of English, etc.
Requirements about accessibility
Support for users with disabilities are likely to arise in the user interface.
You may have a legal requirement to support people with disabilities.
Example:
The system must comply with Section 508 of the US Rehabilitation Act.
See

8. Usability Requirements: equipment (Documentation)
Your project may also have requirements to support:
Computers/systems with poor performance
Limited screen sizes
Bad network connections
Etc.
Be explicit about the equipment assumptions that you make.
Perform user testing with both good and bad equipment (if possible).
Example
OS X Mail has a requirement that operations terminate cleanly if the network connection is lost, but its behavior is erratic if the network connection becomes extremely slow. It would not terminate in that case.

9. Design from a system viewpoint
Usability is more than user interface design.

10. Examples of Mental Models (Documentation)
The mental model is the development team’s internal model of what the system provides.
The desktop metaphor:
files and folders
The web search model:
one vast collection of pages, which are searched on request

11. Examples of Mental Models (Documentation)
Mental models can evolve
No files, only pictures
Arguably, the key reason why people
who have never used a computer
become active iPad users is that Apple
provides great mental models of how to use
their software.

12. Principles of User interface design
General principles of user interface design:
Consistency:
Appearance, controls, and function.
Style sheets
Feedback:
What is the computer system doing?
Why does the user see certain results?
Users should be able to interrupt or reverse actions.
When applicable
Error handling should be simple and easy to comprehend.
The user should feel in control.

13. Interface functions
The interface functions determine the actions that are available to the user:
Search a list or sort the results
View help information
Manipulate objects on a screen
Pan or zoom
Alternative user interface
designs for the same interface
functions may exist

14. Computer systems and networks: Requirements
As computer systems improve, users have got more demanding.
A response time that is good enough today, may not be good enough five years from now.
Example: Response times
0.1 sec:
The user feels that the system is reacting instantaneously
1 sec:
The user will notice the delay, but his/her flow of thought stays uninterrupted
10 sec:
The limit for keeping the user's attention focused on the interface

15. Computer systems and networks: Device-aware interfaces
Interfaces must take into account physical constraints of computers and networks:
How does a desktop computer differ from a laptop?
What is special about a smart phone?
How do you make use of a touch-sensitive screen?
What works well with a digital camera?
Constraints that the interfaces must allow for:
performance of device (e.g., fast or slow graphics/CPUs)
limited form factor (e.g., small display, on-screen keyboard)
connectivity (e.g., intermittent, wireless only)

16. Interface design: menus
Easy for users to learn and use
Certain categories of error are avoided
Enables context-sensitive help
Major difficulty is structure of large choices:
Scrolling menus (Ex: states of USA)
Hierarchical
Associated control panels
Menus plus command line

17. Interface design: command line
User interacts with computer by typing commands
Ex: Linux shell script
Allows complex instructions to be given to the computer
Skilled users can input commands quickly
Unless very simple, requires learning or training
Can use multiple programming languages
Suitable for scripting

18. Help system design Help system design is difficult
Must prototype with mixed users
Must have many routes to same information
Categories of help:
Overview and general information
Specific or context information
Tutorials (general)
Wizards
Emergency ("I am in trouble ...")

19. Usability and cost
User interface development is a major part of your software project.
Web-based projects
Good usability may be expensive in hardware or require special software development.
Usability and performance are related
Costs are multiplied if a user interface has to be used on different computers or migrate to different versions of systems.
Client devices: laptops, desktops, smart phones, etc.

20. Changes in user interface design
Examples of change: to today

21. Yahoo 1995

22. Yahoo 2000

23. Yahoo 2005

24. Yahoo 2010

25. Yahoo 2015

26. Yahoo Today

27. Google November 11, 1998

28. Google December 2, 1998

29. Google 2000

30. Google 2005

31. Google 2010

32. Google Today

33. wku 1998

34. wku 2000

35. wku 2005

36. wku 2010

37. wku 2015

38. wku Today

39. Microsoft windows

40. Microsoft windows

41. Microsoft windows

42. Microsoft windows xp 2001

43. Microsoft windows Vista 2007

44. Microsoft windows

45. Microsoft windows

46. Microsoft windows