In human-computer interaction, computer accessibility (also known as Accessible computing) refers to the accessibility a computer system to all people, regardless of disability or age-related limitations. It is largely a software concern; when hardware, or a combination of hardware and software, is used to customize a computer for a disabled person this is known as Assistive Technology.

There are several types of disabilities that impact computer use. These include:

In Free software contexts, accessibility is often abbreviated to a11y, where the number 11 refers to the number of letters omitted. This parallels the abbreviations of internationalization and localization as i18n and l10n respectively.

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Considerations for specific disabilities[edit]

Cognitive disabilities and illiteracy[edit]

The biggest challenge in computer accessibility is to make resources accessible to people with cognitive disabilities - particularly those with poor communication skills - and those without reading skills.

Visual disabilities[edit]

Another significant challenge in computer accessibility is to make software usable for people with visual impairment since computers are largely visual devices. For people with poor vision, it is helpful to use large fonts, high-contrast icons etc. supplemented with auditory feedback and screen magnifying software. In the case of blindness, text to speech (screen reader) software is essential.

About 8% of people, mostly males, suffer from some form of colour-blindness. In a well-designed user interface, colour should not be the only way of distinguishing between different pieces of information. However, the only colours that matter are colours that people with a deficiency might confuse, which generally means red and green and blue and green.

An example in Web accessibility is a set of guidelines [1] and two accessible[2] web portals designed for people developing reading skills are peepo.com [3] — try typing a letter with your keyboard for more — and peepo.co.uk [4] with enhanced graphics, unique style controls and improved interactivity (requires SVG supported browser).

Motor disabilities[edit]

Some people may not be able to use a conventional input device, such as the mouse or the keyboard. Therefore it is important for software functions to be accessible using both or either device; ideally, software uses a generic API that permits the use even of highly specialized devices unheard of at the time of software development. Keyboard shortcuts and mouse gestures are ways to achieve this. More specialized solutions like on-screen keyboards and alternate input devices like switches, joysticks and trackballs are also available.

The astrophysicist Stephen Hawking is a famous example of a person suffering from motor disability. He uses a switch, combined with special software, that allows him to control his wheelchair-mounted computer using his remaining small movement ability. This performs as a normal computer, allowing him to research and produce his written work, and as a Voice Output Communication Aid (VOCA) and environmental control unit.

Aural disability[edit]

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. The system sounds like beeps can be substituted or supplemented with flashing parts of the screen or text (akin to closed captions).

Web accessibility[edit]

Enabling access to Web content for all users is the concern of the Web accessibility movement. Websites can be designed to be more accessible by their conformance to certain design principles.

Screen readers are of only limited use when reading text from websites; this can be due to the differences between spoken and written language and the complexity of text, but it is mainly due to poor page design practices. The tendency to indicate semantic meaning using methods that are purely presentational (e.g. larger or smaller font sizes, using different font colors, or images or multimedia to provide information) restricts meaningful access to some users. Therefore designing sites in accordance with Web accessibility principles helps enable meaningful access for all users.

For example, web designers can ensure that navigation and content is as plain and simple as appropriate and long texts should provide summaries. Texts can be supplemented by symbols, illustrations, comics and photographs[citation needed].

See also[edit]

Live Forums[edit]

External links[edit]

Accessibility features of Operating Systems[edit]

Web browser accessibility features[edit]