A user interface is visible when a user is able to figure out how to accomplish tasks just by looking at it. With a typical visible user interface, a user is able to perform tasks by making selections in the menu bar and dialog boxes and by manipulating objects on the screen with the mouse. Visible features don't require knowledge of special keyboard sequences or mouse interactions or any other mechanism that isn't visible on the screen.
So what specifically does it mean for a user interface to be visible? When a user interface feature is visible, its existence and functionality are obvious by simple inspection. A feature's existence is obvious by simple inspection when one of the following phenomena is true:
A feature's functionality is obvious by simple inspection when it meets one or more of the following requirements:
While a modern graphical user interface such as the one provided by Microsoft Windows is highly visual, not all the user interface elements of a typical program can be figured out by inspection alone. You must have some basic knowledge about how graphical user interfaces work to perform even the simplest tasks. Consider a program's menu bar. While the menu bar is visible on the screen, to use it you have to understand why you need to use a menu, how to recognize a menu bar, how to pull down a menu, and how to make a selection. Without this basic knowledge, you can't do anything with a menu bar. In fact, menu bars would not be appropriate in environments where the user cannot be assumed to be a computer user, such as in a walk-up kiosk. But for normal Windows programs, using the menu bar is so basic that even the most beginning user (with, say, more than an hour's experience) can be assumed to know how to use a menu. This basic knowledge makes the menu bar a highly visible, hierarchically organized catalog of a program's features.
Clearly, there is more to making a feature visible than simply displaying it visually on the screen. The user not only has to be able to see it but also has to be able to understand it. No matter how artistic a feature's visual appearance is, if the user doesn't understand it, it really isn't visible. The understanding can come from the user's knowledge of the real world, the user's common sense, the user's basic knowledge of graphical user interfaces, or completely from the feature's visual properties. One way or another, a feature is visible if a user with basic graphical user interface skills can easily figure out how to use it just by looking at it.
TIP
There is more to making a feature visible than displaying it visually on the screen. The user has to be able to understand it.
Visible user interfaces often result in what is called a noun-then-verb form of interaction. You see something (the "noun" in the construction above) that you want to manipulate on the screen, you select it, and then you perform some action (the "verb"). Visible user interfaces can also be viewed as being object-oriented in that you select an object and then change its properties or perform commands.
A visible user interface is similar to an intuitive user interface (which, by the way, should really be called an "intuitable" user interface to reflect that fact that the user, not the interface itself, is doing the intuiting). A user interface feature is intuitive when it meets all the criteria below:
In other words, a feature is intuitive if its existence and functionality are obvious by simple inspection, if it is consistent with the user's real-world experience and other software experience so that the user can infer its meaning, and if it doesn't require the user to have any knowledge of the standards.
TIP
Intuitive = Visible + Consistent - Standards
When describing a user interface, I prefer the terms "visible" and "consistent" over "intuitive" for two reasons. First, the "intuitive user interface" has become such a cliché that it hardly means anything anymore. Too many horrible, difficult-to-use user interfaces have been described as intuitive. Second, the terms "visible" and "consistent" are more specific and are both significant user interface attributes in their own right. Burying these two important design concepts in a single design cliché is a far less effective way of characterizing user interfaces.