Control Panel

Examples:

Stove and oven controls
Airplane cockpit
Power plant control room
Physical or electronic CD player

Bad Examples:

Most remote controls for TVs, stereos, and VCRs
Cellular phones

Context: The artifact must provide a way for the user to either change its state, or command it to do something.

Problem: How can the artifact best present the actions that the user may take?

Forces:

The user wants one place where they know they can find the necessary controls, without having to hunt for them.
The controls on it should be organized well enough so that the user can find what's needed, with minimal effort and with no confusion.
There might be a lot of controls involved, some of which may be complex.

Solution: For each function or state variable that is part of the user's mental model, choose one well-designed control that performs the function or displays the variable's value; put them all together such that the most commonly-used controls are the most prominent. Similar functions may have similar-looking controls, but make sure that they aren't so similar that the user gets confused about which is which, even if their labels are different. (Hence the remote controls and cellular phones that are bad examples. They usually have rows of buttons that all feel alike to one's fingers -- and these are the kinds of things that people like to use without being able to look at them!)

When someone uses the controls, give immediate feedback that something is happening; this could be visual feedback, verbal, aural, tactile, etc. The best controls are often those that also display the current state (thus combining Control Panel with Status Display), since it makes sense to people to affect something in the same place they see it.

If the thing(s) being controlled has an obvious and familiar spatial layout, use it in the control panel. In The Design of Everyday Things, Don Norman makes an example out of stoves -- their burners are arranged in a 2x2 grid, but the controls for them are usually not, and users have to stop and think about which goes with which. If analogous spatial arrangement doesn't make sense in a given situation, then try instead to group the controls semantically. Ideally, the controls relevant to a given high-level task will end up clustered together (Small Groups of Related Things), so the user doesn't have to hunt all over the control panel for the next needed control.

Resulting Context: Appropriate controls now have to be chosen. Some patterns you can use are Choice from a Small Set, Choice from a Large Set, Sliding Scale, or even an interactive Chart or Graph. Make it clear which controls represent artifact-wide actions (see Convenient Environment Actions), and which represent actions upon one object (see Localized Object Actions) -- and indicate which object is being acted upon, of course!. When a given control is not meant to be used at a given time, disable it (Disabled Irrelevant Things).

To help naive users figure out what's what on a counterintuitive display, or on one that's meant for experts, you could employ Short Description or Optional Detail On Demand. To alert the user to side effects and to unexpected situations, use Reality Check and Important Message, respectively.

Comments to: jtidwell@alum.mit.edu
Last modified May 17, 1999