1. User-Centered Design Good design The user says “Yes, I see” or “Of course”. A simple explanation is sufficient. Bad design The user says “How am I going to remember that?” after the explanation.

2. 7 principles of good design OR 7 principles for transforming difficult tasks into simple ones 1. Use both knowledge in the world and knowledge in the head. 2.Simplify the structure of the tasks. 3. Make things visible: bridge the gulfs of Execution and Evaluation. 4. Get the mappings right. 5. Exploit the power of constraints, both natural and artificial. 6. Design for error. 7. When all else fails, standardize.

3. Use knowledge in the world and knowledge in the head Users are more comfortable and learn better when the knowledge they need to perform a task is readily available in the world or through constraints. Users perform faster and more efficiently when they can synthesize the knowledge needed for their task. So it should be easy to go back and forth – to combine knowledge in the head with knowledge in the world. The designer must develop a conceptual model for the user that captures the important parts of the device and that is understandable by the user.

4. Simplify the structures of tasks The amount of planning and problem solving for a task should be minimized.

5. Make things visible On the execution side of an action: So that users know what actions are possible and how the actions can be done. On the evaluation side of an action: So that users know what the results of the actions are and the current state of the system.

6. Get the mappings right Make sure the user can understand the relationship between intentions and possible actions, actions and their effects on the system, the actual system state and what is reflected in the interface, and the perceived system state and the needs, intentions and expectations of the users.

7. Exploit the power of constraints, both natural and artificial Use natural and artificial constraints to make users feel that there is only one possible action.

8. Design for error Assume that any error is possible and plan for it. Allow users to recognize errors and recover from them. Make it easy to reverse operations and hard to do irreversible actions.

9. When all else fails, standardize When the above principles cannot be put into place, standardize the actions, layout, display, and results. With standardization, users only have to learn it once but they must be trained to the new standard.