1. Proper functionality Good human computer interface Easy to maintain
Good Software?
Proper functionality
Good human computer interface
Easy to maintain

2. Human Computer Interface (HCI)
Computer Systems are designed with technical persons with little behavioral Training. System are complex in the eyes
of Users.

3. Measuring factor of HCI
Error rates of users
Efficiency
Time to learn
Retention period of knowledge

4. Error rate of users Perform a task with fewest errors
Recover from error with fastest method

5. Error handling Preventive measure Error recovery
e.g. Input mask, radio button, etc.
Error recovery
Report errors to users as soon as possible
Give a meaningful error message
Indicate exactly what’s wrong
Tell the user how to correct the error

6. Efficiency
Time required to complete the task

7. Time to learn
Time required to train users to a certain skill level

8. Retention period of Knowledge
How well users maintain their knowledge after a certain period (e.g. one month).

9. Problems in HCI
Application Requirement
Human diversity

10. Syntactic knowledge Crtl-C Keyboard layout Command
E.g. Copy a:abc.doc c:

11. Semantic Knowledge Objects Actions e.g. file, directory
e.g. create a file, delete a file

12. User Profiles
Novice users
Intermittent users
Frequent / Expert users

13. Novice users No syntactic knowledge Little semantic computer knowledge
little knowledge of the task

14. Intermittent Users Good semantic knowledge
Have problems to remember syntactic knowledge
Good knowledge of the task
Perform the task periodically

15. Frequent users Good semantic and syntactic knowledge
Very good knowledge of the task
Perform the task frequently
Want to complete the task quickly

16. Interaction style
Menu selection
Form fill-in
Command
Natural language

17. Types of memory
Short term memory
Long term memory

18. Guideline for HCI Design
Maintain consistency
Provide shortcut to frequent users
Offer meaningful feedback
Provide simple error handling
Allow easy reversal of actions (undo)
Reduce short term memory
Provide dialogs to guide users