Principles of Good Interface and Screen Design 187

Step 3: Principles of Good Interface and Screen Design 187

Use a mixed-case font.

Capitalize the first letter of each significant word.

End each caption with a colon (:).

Choose distinct captions that can be easily distinguished from other captions. — Minimal differences (one letter or word) cause confusion.

Provide consistency. Identify controls with captions. All screen controls should have captions or labels

that identify the content of the control. Create labels using words that users use to refer to items and avoid jargon. Captions should be included for most controls. The context in which information is found in the world at large provides cues to the information’s meaning. A number on a telephone dial is readily identifiable as a telephone number; the number on a metal plate affixed to the back of an automobile is readily identified as a license number. The same information dis- played on a screen, having lost context, may not be readily identifiable.

There are, however, some exceptions to this rule on read-only or inquiry screens. The structure of the data itself in some cases may be enough to identify its meaning. The most obvious example is name, street, city, state, and zip code. Date may be another possibility. Elimination of these common captions will serve further to clean up read-only screens. Before eliminating captions, however, it should be determined that all screen users will be able to identify these fields all the time.

Structure and size. Captions on screens must clearly, concisely, and unambiguously describe the information displayed. Captions are very important for inexperi- enced screen users. As one becomes more experienced, their importance dimin- ishes. Therefore, captions should be fully spelled out in the natural language of the user. In general, abbreviations and contractions should not be used. To achieve the alignment recommendations to be discussed shortly, an occasional abbreviation or contraction may be necessary, but choose those that are common in the everyday language of the application or those that are meaningful and eas- ily learned. Also, display captions in a moderate brightness or intensity. Visual emphasis will be directed to the screen data or information.

Significant word capitalization. With mixed-case field captions, capitalize the first letter of each significant word using the headline style previously described. A caption is not a sentence but the name for an area into which information will be keyed. This makes it a proper noun. In situations in which a caption is phrased as

a question, it is a sentence, and then only its initial letter should be capitalized. Never begin a caption or sentence with a lowercase letter. A capital letter makes it easier for the eye to identify the start of each caption. Unfortunately some style guides do not follow the headline style of using a capital letter for the initial let- ter of each significant word of the caption. They prefer and recommend the sen- tence style, capitalization of the initial letter of the first word only (except for acronyms, abbreviations, proper nouns, and so on).

188 Part 2: The User Interface Design Process Designate with a colon.

A caption should be ended with a colon (:) to clearly iden- tify it as a caption, and also to clearly distinguishing it from a data field. The colon is unobtrusive, does not physically resemble a letter or number, and is grammatically meaningful, since it is used chiefly to direct attention to matter that follows. Unfortunately, many graphical systems do not follow this conven- tion, and captions visually blend with other screen elements.

Because the recommended entry area for an entry control will be a box, ade- quately distinguishing the caption from the entry field itself, the inclusion of a colon may seem redundant. However, read-only, display, and inquiry screens are most effective if the data displayed is not presented in a box, making a colon to distinguish caption from data absolutely necessary. Including a colon after all captions, therefore, will provide consistency across all screens.

Distinctiveness. Captions that are similar often repeat the same word or words over and over again. This directs a viewer’s attention to the pattern created by the repetitive word, increases the potential for confusion, adds to density, and adds to screen clutter. A better solution is to incorporate the common words into headings, subheadings, or group identifiers, as illustrated in Figure 3.21.

Consistency. Provide the same caption wording for all identical data fields on all screens.

Figure 3.21: Providing better control caption discrimination. (The redundant word “amount” is incorporated into a heading.)