Metaphor

The desktop is the primary metaphor for the Macintosh interface. It appears to be a surface on which people can keep tools and documents. Several other metaphors are integrated into the desktop metaphor. It makes sense in the context of a desktop environment to include folders and a trash can (even though most trash cans don’t sit on the desktop). Menus are an extension of the desktop metaphor. People can connect the idea of making choices from a computer menu with making choices from a restaurant menu. Although people don’t keep restaurant menus on the edge of their desks, using the term menu in the computer environment reinforces the idea that people can use computer menus to make choices.Metaphors in the computer interface suggest a use for something, but that use doesn’t define or limit the implementation of the metaphor. For example, a paper file folder has a limited storage capacity, but a folder on the Macintosh doesn’t have to be constrained by the same limitations. Computer folders can hold a limitless number of files (up to the storage capacity of the hardware), and this is an advantage that the computer can offer. Try to strike a balance between the metaphor’s suggested use and the ability of the computer to support and extend the metaphor.

See-and-point

In one paradigm, the user selects an object of interest (the noun) and then chooses the actions to be performed on the object (the verb). All actions available for the selected object are listed in the menus, so users who are unsure of what to do next can refresh their memory by scanning through the menus. At any time, users can choose any available action without having to remember any particular command or name. For example, a user clicks a document icon (the noun) and then prints (the verb) the document by choosing Print from the File menu.In the second paradigm, the user drags an object (the noun) onto some other object that has an action (the verb) associated with it. On the desktop, for example, the user can drag icons to the Trash, to folders, or to disks. The user doesn’t choose an action from the menus, but it’s clear what happens to one object when it’s placed on another object. For example, dragging a document icon to the Trash means that the user wants to discard that document. For this metaphor to work, the user must recognize what an object such as the Trash is for, so it is especially important that objects look like what they do in the real world. If the document icon didn’t look like a piece of paper with text and the Trash didn’t look like the place to discard something, the interface would be more difficult to use.

Perceived stability

Computers often introduce a new level of complexity for people. If people are to cope with this complexity, they need some stable reference points. The Macintosh interface is designed to provide a computer environment that is understandable, familiar, and predictable.To give users a visual sense of stability, the Macintosh interface provides the desktop, a two-dimensional space on which objects are placed. It also defines a number of consistent graphics elements (menu bar, window border, and so on) to maintain the illusion of stability. Note that it is the perception of stability that you want to preserve, not stability in any strict physical sense.To give users a conceptual sense of stability, the interface provides a clear, finite set of objects and a clear, finite set of actions to perform on those objects. Even when particular actions are unavailable, they are not eliminated from a display but are merely dimmed.