Usability for Nerds/The user should be in control
Imagine this situation:
A man sits in front of a computer screen. A message on the screen says: Enter name. The user writes his name.
Nothing happens. The user finds out that he has to press the Enter key.
Computer says: Enter address.
The user enters his address.
After a few more questions the computer says: Enter fax number.
The user has no fax, so he just presses the Enter key.
The computer repeats: Enter fax number.
The user writes 0 and presses the Enter key.
The computer says: Illegal entry. Enter fax number.
The user looks up the fax number of his wife's workplace and enters the number.
The computer accepts the fax number and says: Enter account number.
The user has no account number, so he writes 123456789.
The computer says: Illegal entry. Enter account number.
By now the user has realized that he has got into something wrong. He writes: Stop.
The computer says: Illegal entry. Enter account number.
The user writes: Help.
The computer says: Illegal entry. Enter account number.
The user presses the Escape key several times, but nothing happens.
The user turns off the computer and loses his data.
What is wrong here? The problem is that the computer issues commands and expects the user to obey. The user would certainly prefer that he can make commands and the computer obey. The computer should be a helpful servant, not a cruel master. How is this possible? The picture below shows the answer:
The user clicks a menu that says new user. Then he gets a dialog box where he can write his name etc. He can see at once which information is needed, so there is no need to write a name and address if he doesn't have an account number. He can enter the details in any order he wants. He can press the Cancel button if he regrets. He can press the Help button or the question mark button if he wants to know what Account number means.
In the former situation the user gets stressed and frustrated because the computer is controlling him and taking away his freedom to do what he wants. In the latter situation the user is happy and relaxed because he is controlling the computer and can make it do what he wants.