Functionality Isn’t Enough
For an interface to be a success, it must provide the right functionality, at the right time, in the right place, and in the right form from the user’s point of view.
Such interfaces are called usable.
Example: if we are designing an ATM, we should be able to justify each user action:
- Insert card?
- Enter PIN?
- Press Quick Cash key?
- Press Okay?
- Remove card?
- Remove money?
- Remove receipt?