Choose the Proper Screen-Based Controls 479

Step 7: Choose the Proper Screen-Based Controls 479

Windows. Others names include toggle buttons, switches, and two state nonexclusive settings. Not only their names differ; differences also exist in the way these fields are presented on screens. One very common display method is a check box, which, resembling its namesake, consists of a square placed adjacent to each alternative. When the choice is selected, some systems place an X in the square to provide a visual indication that it is active. Others, including Microsoft Windows, place a check mark in the square, or fill in the selected square or make it look depressed when selected.

Interestingly, in the past decade, Microsoft Windows and others have switched from Xs to checks as the “on” mark in a check box. This has occurred because of possible confusion concerning Xs that have existed in some using communities. In an engineering environment, for example, an X marked in a box means not applicable or not set, while a check mark customarily means active or set. Internationally, also, an X is not universally recognized. (This control is called

a check box, isn’t it?)

Another style for this type of field is a button or box with the choice descrip- tion inscribed inside. When selected, the alternative is highlighted in some way. To distinguish these fields visually from similarly constructed fields presenting mutually exclusive choices, the buttons are not adjacent to, or butted up against, one another. Check boxes are illustrated in Figures 7.39 and 7.40. Again, deciding on which style to use seems to be more a matter of preference than performance (other than for the possible confusion of Xs and checks). No published compari- son studies are available for guidance.

Purpose. The purpose of a check box, then, is to set one or more options either on or off.

Figure 7.39: Check boxes.

Figure 7.40: Check boxes.

480 Part 2: The User Interface Design Process

Advantages/disadvantages. With check boxes, all alternatives are always visible. Therefore, it is easy to access and compare choices. Like radio buttons, check boxes were the preferred, and fastest to use, controls in the Johnsgard et al. (1995) study. One disadvantage is the large amount of screen real estate they consume, limiting the number of alternatives that can be efficiently displayed. Another potential disadvantage is that it can be difficult to align a single check box with other arrayed screen controls because they often possess long descriptions for clarity purposes.

Proper usage. Check boxes are useful for setting attributes, properties, or values where adequate screen space is available. The alternatives should be discrete, small in number, and in need of a textual description to identify meaningfully. Check boxes are helpful in situations where the alternatives cannot always be easily remembered and the displaying of the alternatives together aids in under- standing and selecting the proper choice. The choices displayed should be stable, never changing in content.

Check boxes can be used to affect other controls. The contents of a list can, for example, be filtered by setting check boxes. Use a check box only when both states of a choice are clearly opposite and unambiguous. If opposite states are not clear, use two radio buttons, clearly stating the opposite states.