While sound user interfaces have a secondary role in common desktop computing, usually limited to system sounds as feedback, software producers take into account people who can't hear, either for personal disability, noisy environments, silence requirements or lack of sound hardware. Such system sounds like beeps can be substituted or supplemented with visual notifications and captioned text (akin to closed captions).
Software API exist to allow assistive technology products (like screen readers, Text-to-speech, etc.) to work with software. The current or past APIs are:
· Microsoft Active Accessibility (MSAA) on Microsoft Windows
· Microsoft UI Automation on Microsoft Windows, replacing MSAA
· IAccessible2 on Microsoft Windows, a competitor of Microsoft UI Automation also replacing MSAA
· AT-SPI on UNIX and Linux
· Mac OS X Accessibility
· Java Accessibility and the Java Access Bridge for Java software.
Accessibility Features in Mainstream Software
Accessibility software can also make input devices easier to use at the user level:
· Keyboard shortcuts and MouseKeys allow the user to substitute keyboarding for mouse actions. Macro recorders can greatly extend the range and sophistication of keyboard shortcuts.
· Sticky keys allows characters or commands to be typed without having to hold down a modifier key (Shift, Ctrl, Alt) while pressing a second key. Similarly, ClickLock is a Microsoft Windows feature that remembers a mouse button is down so that items can be highlighted or dragged without holding the mouse button down throughout.
· Customization of mouse or mouse alternatives' responsiveness to movement, double-clicking, and so forth.
· ToggleKeys is a feature of Microsoft Windows 95 onwards. A high sound is heard when the CAPS LOCK, SCROLL LOCK, or NUM LOCK key is switched on and a low sound is heard when any of those keys are switched off.
· Customization of pointer appearance, such as size, color and shape.
· Predictive text
· Spell checkers and grammar checkers
Support for Learning Disabilities
Other approaches that may be particularly relevant to users with a learning disability include: