Consistency

Consistency allows users to transfer existing knowledge to new tasks, learn new things more quickly, and focus more on tasks because they need not spend time trying to remember the differences in interaction. By providing a sense of stability, consistency makes the interface familiar and predictable.

Consistency is important through all aspects of the interface, including names of commands, visual presentation of information, and operational behavior. To design consistency into software, you must consider several aspects:

• Consistency within a product. Present common functions using a consistent set of commands and interfaces. For example, avoid implementing a Copy command that immediately carries out an operation in one situation but in another presents a dialog box that requires a user to type in a destination. As a corollary to this example, use the same command to carry out functions that seem similar to the user.
• Consistency within the operating environment. By maintaining a high level of consistency between the interaction and interface conventions provided by Windows, your software benefits from users' ability to apply interaction skills they have already learned.
• Consistency with metaphors. If a particular behavior is more characteristic of a different object than its metaphor implies, the user may have difficulty learning to associate that behavior with an object. For example, an incinerator communicates a different model than a wastebasket for the recoverability of objects placed in it.

Although applying the principle of consistency is the primary goal of this guide, the following chapters focus on the elements common to all Windows-based software: Chapter 6, "Windows," Chapter 7, "Menus, Controls, and Toolbars," and Chapter 8, "Secondary Windows." For information about closely integrating your software with the Windows environment, see Chapter 10, "Integrating with the System," and
Chapter 11, "Working with OLE Embedded and OLE Linked Objects."