Mapping

Why
Mapping as a design principle is important because it allows the user to more easily use the system since the user will understand how the physical aspects of the design are set up so that they can accomplish what they want with less confusiong and ambiguity.

What
Mapping is the way that a design is set up physically (buttons, levers, switches, etc.) and what action each of these physical elements are responsible for performing.

How
Good Mapping

Good mapping is achieved when it is clear how to accomplish a task through just looking at the physical layout of the design. Things are where they are supposed to be and they act according to how they should. For example, pressing the plus button on the side of an iphone increases the volume. There is no abiguity about this and even a user who was not trained in the usage of the iphone would understand this.

Bad Mapping
A slide projector system with only one button is an example of bad mapping because there is ambiguity about how to go forwards and back in the slides without being formally trained. There is neither reason nor rhyme to the operation.