The manner in which control layout andaction match those of the controlled elements is called a mapping. Theclassic example is the control layout for the burners of a stove. In myexperience, stove controls rarely map well, often requiring a second attemptto get the correct burner lit. Consistency When multiple occurrences of similarinterface features are handled uniformly, the interface exhibits consistency. For example, a music system with separate button pairs for CD track selection,tape search, and FM tuning should have the right hand buttons all increaseor advance the media.
Consistency is generally highly desirable, althoughthere are exceptions.
A product should encourage the developmentof a mental model of its operation. Errors Good design will result in a product thatis so clear that there will be few errors. Those errors that do occur shouldbe handled by the product with grace, forgiveness, and a way of backingout. Certain Hewlett Packard calculators have several features that reducethe pain of errors. If you enter a digit of a long number incorrectly,you can backspace and correct it.