Humane Interface, The: New Directions for Designing Interactive Systems

3-4. Visibility and Affordances

On a clear disk you can seek forever.

—Source unknown

Whether a product is a handheld two-way radio or a computer's desktop, it is not always clear what functions are available, what they do, or how they are accessed. You should be able to use your senses to easily discover both what abilities are available and how they are to be operated.

An interface feature is visible if it either is currently accessible to a human sense organ—usually the eyes, although this discussion applies also to other sensory modalities—or was so recently perceived that it has not yet faded from short-term memory. If a feature is not visible, we say that it is invisible. For an interface to work well, “[j]ust the right things have to be ...