Cognitive impairments and illiteracy The biggest challenge in computer accessibility is to make resources accessible to people with cognitive disabilities—particularly those with poor communication and reading skills. For example, people with learning disabilities may rely on proprietary symbols and identify particular products via the product's symbols or icons. Unfortunately, copyright laws can limit icon or symbol release to web-based programs and websites by owners who are unwilling to release them to the public. In these situations, an alternative approach for users who want to access public computer-based terminals in
libraries,
ATMs, and information kiosks is for the user to present a token to the computer terminal - such as a
smart card - that has configuration information to adjust the computer speed, text size, etc. to their particular needs. This concept is encompassed by the
CEN standard "Identification card systems – Human-machine interface". This development of this standard has been supported in Europe by
SNAPI and has been successfully incorporated into the Local Authority Smartcards Standards e-Organisation (LASSeO) specifications.
Visual impairment Since computer interfaces often require visual input and provide visual feedback, another significant challenge in computer accessibility involves making software usable by people with visual impairments. For people with mild to medium vision impairment, things like large
fonts, high DPI displays, high-contrast themes and
icons combined with auditory feedback and screen magnifying software are very useful. In the case of severe vision impairment such as blindness,
screen reader software that provides feedback via
text to speech or a
refreshable braille display is a necessary accommodation for interaction with a computer. About 8% of men and about 0.4% of women have some form of
color-blindness. The main color combinations that might be confused by people with visual deficiency include red/green and blue/yellow. However, in a well-designed user interface, color isn't the primary way to distinguish between different pieces of information.
Motor and dexterity impairments that enables the user to access an
on-screen keyboard 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 devices. Ideally, the software will use a generic input
API that permits the use even of highly specialized devices unheard of at the time of software's initial development.
Keyboard shortcuts and
mouse gestures are ways to achieve this access, as are more specialized solutions, including on-screen software keyboards and alternate input devices (
switches,
joysticks and
trackballs). Users may enable a
bounce key feature, allowing the keyboard to ignore repeated presses of the same key.
Speech recognition technology is also a compelling and suitable alternative to conventional keyboard and mouse input as it simply requires a commonly available audio headset.
UI design can also improve accessibility for users with motor impairments. For example,
barrier pointing design allows commonly used functions to require less accuracy to select. The
astrophysicist Stephen Hawking is an example of someone with severe motor and physical limitations who used assistive technology to support
activities of daily living. He used a switch, combined with special software, that allowed him to control his
wheelchair-mounted computer using his limited and small movement ability. This personalized system allowed him to remain mobile, do research, and produce his written work. Prof. Hawking also used
augmentative and alternative communication technology to speak and an
environmental control device to access equipment independently. A small amount of modern research indicates that utilizing a standard computer mouse device improves fine-motor skills.
Hearing impairment While
sound user interfaces have a secondary role in common desktop computing, these interfaces are usually limited to using
sound effects as feedback. Some software producers take into account people who cannot hear due to hearing impairments,
silence requirements, or lack of sound-producing software. The system sounds like beeps can be substituted or supplemented with visual notifications and captioned text (akin to
closed captioning). Closed captions are a very popular means of relaying information for the Deaf and hearing-impaired communities. Modern
computer animation also allows for translation of content into sign language by means of sign language avatars, such as SiMAX. == Types of software accessibility ==