Computer accessibility
In human-computer interaction, computer accessibility refers to the usability of a computer system by people with disabilities. It is largely a software feature. However, when hardware or software is used to customize a computer for a disabled person, that equipment is known as adaptive technology.There are several types of disabilities that impact computer use:
- Complete or partial blindness, including colorblindness.
- Hearing impairment.
- Motor or dexterity disability such as paralysis, cerebral palsy, or carpal tunnel syndrome.
- Impairments due to old age.
- Cognitive disabilities, such as dyslexia, ADHD or autism.
Accessibility is strongly related to Universal Design in that it is about making things as accessible as possible to as wide a group of people as possible. However, products marketed as having benefited from a Universal Design process are often actually the same devices customized specifically for use by people with disabilities. It is rare to find a Universally Designed product at the mass-market level that is used mostly by nondisabled people; Oxo Good Grips housewares are continually held up as an example.
The biggest 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 colorblindness. In a well-designed user interface, color 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.
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 joysticks and trackballs are also available.
The astrophysicist Stephen Hawking is a famous example of a person suffering from motor disability. He uses special software that allows him to control his computer using his remaining small movement ability. His computer also talks for him.
On the World Wide Web, the W3C has produced specific guidelines for accessibility via the Web Accessibility Initiative (WAI).
The Cascading Style Sheets system has been devised with this in mind, since it gives the reader full control over the appearance of the page.
As an example, most web browsers have an option to ignore the font size specified in a webpage, so that the user can circumvent a small font forced upon him or her by a webpage author. However, sometimes a webpage author fails to take into account that users may want to apply such an option and designs a webpage such that applying this option gives poor results, such as too small a distance between lines, disabled scrolling even though texts do not fit in assigned spaces, overlapping texts, etc.
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