Mac® Security Bible

4.8. Assistive Device Access

Mac OS X was designed to be operated with a keyboard and mouse. However, some users are unable to use one or both devices, so as part of Apple's mandate to make their operating system as accessible as possible, they've built in hooks that enable controls to be manipulated by other means. For example, instead of manually clicking a button with your mouse, you might use software that simulates a click on the button in response to a verbal command or a customized input device of some kind. Almost every control in Mac OS X, including menus, radio buttons, check boxes, sliders, and other widgets, can be operated with software that mimics the effect of keyboard or mouse action, without having to refer to specific coordinates on-screen (which, of course, are highly variable).

The capability to use other software to operate on-screen controls isn't restricted to accessibility products. Speech recognition programs, mouse drivers, automation utilities, and even Apple's own AppleScript may need to be able to click a button or choose a menu command when no API (application programming interface) is available to trigger an action directly. In all these cases, software access to the user interface is possible only when the user has explicitly enabled it. Follow these steps to do so:

1. Choose System Preferences to open System Preferences and then click Universal Access ...