1. Software Usability and Design
Users and Principles
Jeff Offutt
SWE 205
Software Usability and Design

2. It is important to know who the user is
Understand the Users
It is important to know who the user is
Work experience
Computer experience
Age
Education
Reading skills
Language skills
Work environment
Task frequency
… many more possibilities
18-Apr-19
© Jeff Offutt

3. Nine Golden Usability Principles
Build a UI that is consistent
Design in, then evaluate
Changes break consistency …
Design usable and discoverable shortcuts
Users must be able to find them
Users must be able to remember them
Provide appropriate feedback
Not just error messages
Yield closure
Have a clearly defined end-point in the interaction
Provide appropriate error handling
Clearly tell users what was wrong
Only make users redo the part that was wrong
18-Apr-19
© Jeff Offutt

4. Nine Golden Usability Principles
Allow users to undo all actions
If the operation cannot be “undone,” use hesitation
Put the user in charge
Inexperienced users may be intimidated when the software makes decisions
Experienced users want to control the flow
Reduce the STM load
Design for the USER
First
Last
Then test it
18-Apr-19
© Jeff Offutt

5. Preventing Errors People often make mistakes
Faster computers can increase errors
Prevention strategies :
Flow : Users make fewer mistakes when the flow through the UI makes sense
Education : Better error messages can reduce errors
18-Apr-19
© Jeff Offutt

6. Software Seatbelts
The software can prevent the user from making dangerous choices
If the dangerous choice must be available, allow it with a hesitation (“are you sure?”)
Exiting editors with changed, unsaved text
Should not hesitate if unchanged!
Unix: rm *.o … rm * .o
rm –i *.o forces hesitation (alias rm “rm –i”)
Omit menu choices that should not be used
18-Apr-19
© Jeff Offutt

7. Highlighting Highlighting can appear in many ways :
bold
marking
size
font
CAPITALIZE
inverse video
blinking
color
audio
BE GENTLE!! HIGHLIGHTING ALWAYS LOOKS STRONGER TO THE USER THAN TO THE DESIGNER !!!
18-Apr-19
© Jeff Offutt

8. All an interface designer has to do is
Summary
Understand the users
Nine general usability principles
Prevent errors
Highlight gently
All an interface designer has to do is
Be polite
Be considerate
Be clear
18-Apr-19
© Jeff Offutt