Computer accessibility
Encyclopedia
In human-computer interaction, computer accessibility (also known as Accessible computing) refers to the accessibility
of a computer system to all people, regardless of disability
or severity of impairment. It is largely a software concern; when software, hardware, or a combination of hardware and software, is used to enable use of a computer by a person with a disability or impairment, this is known as Assistive Technology
.
There are numerous types of impairment that impact computer use. These include:
These impairments can present themselves with variable severity; they may be acquired from disease
, trauma
or may be congenital or degenerative in nature.
Accessibility is often abbreviated to the numeronym
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.
consultant (such as an occupational therapist
or clinical scientist) to help them identify and configure appropriate assistive hardware and software.
Where a disabled person is unable to leave their own home, it may be possible to assess them remotely using remote desktop software
and a webcam
. The assessor logs on to the client's computer via a broadband
Internet
connection. The assessor then remotely makes accessibility adjustments to the client's computer where necessary and is also able to observe how they use their computer.
Their further development relies on public domain icons being available. Many people with a learning disability learn and rely on proprietary symbols. They thus become tied to particular products. The copyright owners are generally unwilling to release them on the web.
Other examples include Web accessibility
a set of guidelines and two accessible web portals designed for people developing reading skills are peepo.com http://www.peepo.com — try typing a letter with your keyboard for more — and peepo.co.uk http://www.peepo.co.uk with enhanced graphics, unique style controls and improved interactivity (requires an SVG supported browser).
s, high DPI displays, high-contrast themes and icon
s supplemented with auditory feedback and screen magnifying software.
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 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 colour combinations that matter are those that people with a deficiency might confuse, which generally means red and green and blue and green.
, such as the mouse or the keyboard
. Therefore it is important for software functions to be accessible using both devices; ideally, software uses a generic input API that permits the use even of highly specialized devices unheard of at the time of software development. Keyboard shortcuts and mouse gesture
s are ways to achieve this. More specialized solutions like on-screen software keyboards and alternate input devices like switches
, joystick
s and trackball
s are also available. 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.
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 an Augmentative and Alternative Communication
and environmental control device
.
requirements or lack of sound hardware.
Such system sounds like beep
s can be substituted or supplemented with visual notifications and captioned text (akin to closed captions).
s, Text-to-speech, etc.) to work with software. The current or past APIs are:
Aaccessibility Software can also make input devices easier to use at the user level:
Other approaches that may be particularly relevant to users with a learning disability include:
movement. Websites can be designed to be more accessible by their conformance to certain design principles.
Screen readers are of limited use when reading text from websites designed without consideration to accessibility; 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.
Accessibility
Accessibility is a general term used to describe the degree to which a product, device, service, or environment is available to as many people as possible. Accessibility can be viewed as the "ability to access" and benefit from some system or entity...
of a computer system to all people, regardless of disability
Disability
A disability may be physical, cognitive, mental, sensory, emotional, developmental or some combination of these.Many people would rather be referred to as a person with a disability instead of handicapped...
or severity of impairment. It is largely a software concern; when software, hardware, or a combination of hardware and software, is used to enable use of a computer by a person with a disability or impairment, this is known as Assistive Technology
Assistive technology
Assistive technology or adaptive technology is an umbrella term that includes assistive, adaptive, and rehabilitative devices for people with disabilities and also includes the process used in selecting, locating, and using them...
.
There are numerous types of impairment that impact computer use. These include:
- Cognitive impairments and learning disabilities, such as dyslexiaDyslexiaDyslexia is a very broad term defining a learning disability that impairs a person's fluency or comprehension accuracy in being able to read, and which can manifest itself as a difficulty with phonological awareness, phonological decoding, orthographic coding, auditory short-term memory, or rapid...
, ADHD or autismAutismAutism is a disorder of neural development characterized by impaired social interaction and communication, and by restricted and repetitive behavior. These signs all begin before a child is three years old. Autism affects information processing in the brain by altering how nerve cells and their...
. - Visual impairmentVisual impairmentVisual impairment is vision loss to such a degree as to qualify as an additional support need through a significant limitation of visual capability resulting from either disease, trauma, or congenital or degenerative conditions that cannot be corrected by conventional means, such as refractive...
such as low-vision, complete or partial blindnessBlindnessBlindness is the condition of lacking visual perception due to physiological or neurological factors.Various scales have been developed to describe the extent of vision loss and define blindness...
, and color blindnessColor blindnessColor blindness or color vision deficiency is the inability or decreased ability to see color, or perceive color differences, under lighting conditions when color vision is not normally impaired...
. - Hearing impairmentHearing impairment-Definition:Deafness is the inability for the ear to interpret certain or all frequencies of sound.-Environmental Situations:Deafness can be caused by environmental situations such as noise, trauma, or other ear defections...
including deafnessHearing impairment-Definition:Deafness is the inability for the ear to interpret certain or all frequencies of sound.-Environmental Situations:Deafness can be caused by environmental situations such as noise, trauma, or other ear defections...
or hard of hearing. - Motor or dexterity impairment such as paralysisParalysisParalysis is loss of muscle function for one or more muscles. Paralysis can be accompanied by a loss of feeling in the affected area if there is sensory damage as well as motor. A study conducted by the Christopher & Dana Reeve Foundation, suggests that about 1 in 50 people have been diagnosed...
, cerebral palsyCerebral palsyCerebral palsy is an umbrella term encompassing a group of non-progressive, non-contagious motor conditions that cause physical disability in human development, chiefly in the various areas of body movement....
, or carpal tunnel syndromeCarpal tunnel syndromeCarpal Tunnel Syndrome is an entrapment idiopathic median neuropathy, causing paresthesia, pain, and other symptoms in the distribution of the median nerve due to its compression at the wrist in the carpal tunnel. The pathophysiology is not completely understood but can be considered compression...
and repetitive strain injuryRepetitive strain injuryRepetitive strain injury is an injury of the musculoskeletal and nervous systems that may be caused by...
.
These impairments can present themselves with variable severity; they may be acquired from disease
Disease
A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...
, trauma
Physical trauma
Trauma refers to "a body wound or shock produced by sudden physical injury, as from violence or accident." It can also be described as "a physical wound or injury, such as a fracture or blow." Major trauma can result in secondary complications such as circulatory shock, respiratory failure and death...
or may be congenital or degenerative in nature.
Accessibility is often abbreviated to the numeronym
Numeronym
A numeronym is a number-based word.Most commonly, a numeronym is a word where a number is used to form an abbreviation . Pronouncing the letters and numbers may sound similar to the full word: "K9" for "canine"...
a11y, where the number 11 refers to the number of letters omitted. This parallels the abbreviations of internationalization and localization as i18n and l10n
L10n
For L10n or L10N , see:* Language localisation* Internationalization and localization...
respectively.
Special needs assessment
People wishing to overcome an impairment in order to be able to use a computer comfortably and productively may need a "special needs assessment" by an assistive technologyAssistive technology
Assistive technology or adaptive technology is an umbrella term that includes assistive, adaptive, and rehabilitative devices for people with disabilities and also includes the process used in selecting, locating, and using them...
consultant (such as an occupational therapist
Occupational therapist
An occupational therapist is trained in the practice of occupational therapy. The role of an occupational therapist is to work with a client to help them achieve a fulfilled and satisfied state in life through the use of "purposeful activity or interventions designed to achieve functional...
or clinical scientist) to help them identify and configure appropriate assistive hardware and software.
Where a disabled person is unable to leave their own home, it may be possible to assess them remotely using remote desktop software
Remote desktop software
In computing, the term remote desktop refers to a software or an OS feature allowing applications, either command line programs or graphical applications, to be run remotely on a server, while being displayed locally. Remote desktop applications have varying features...
and a webcam
Webcam
A webcam is a video camera that feeds its images in real time to a computer or computer network, often via USB, ethernet, or Wi-Fi.Their most popular use is the establishment of video links, permitting computers to act as videophones or videoconference stations. This common use as a video camera...
. The assessor logs on to the client's computer via a broadband
Broadband
The term broadband refers to a telecommunications signal or device of greater bandwidth, in some sense, than another standard or usual signal or device . Different criteria for "broad" have been applied in different contexts and at different times...
Internet
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...
connection. The assessor then remotely makes accessibility adjustments to the client's computer where necessary and is also able to observe how they use their computer.
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 skills - and those without reading skills.Their further development relies on public domain icons being available. Many people with a learning disability learn and rely on proprietary symbols. They thus become tied to particular products. The copyright owners are generally unwilling to release them on the web.
Other examples include Web accessibility
Web accessibility
Web accessibility refers to the inclusive practice of making websites usable by people of all abilities and disabilities. When sites are correctly designed, developed and edited, all users can have equal access to information and functionality...
a set of guidelines and two accessible web portals designed for people developing reading skills are peepo.com http://www.peepo.com — try typing a letter with your keyboard for more — and peepo.co.uk http://www.peepo.co.uk with enhanced graphics, unique style controls and improved interactivity (requires an SVG supported browser).
Visual impairment
Another significant challenge in computer accessibility is to make software usable by people with visual impairment, since computer interfaces often solicit input visually and provide visual feedback in response. For individuals with mild to medium vision impairment, it is helpful to use large fontTypeface
In typography, a typeface is the artistic representation or interpretation of characters; it is the way the type looks. Each type is designed and there are thousands of different typefaces in existence, with new ones being developed constantly....
s, high DPI displays, high-contrast themes and icon
Icon
An icon is a religious work of art, most commonly a painting, from Eastern Christianity and in certain Eastern Catholic churches...
s supplemented with auditory feedback and screen magnifying software.
In the case of severe vision impairment such as blindness, screen reader
Screen reader
A screen reader is a software application that attempts to identify and interpret what is being displayed on the screen . This interpretation is then re-presented to the user with text-to-speech, sound icons, or a Braille output device...
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 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 colour combinations that matter are those that people with a deficiency might confuse, which generally means red and green and blue and green.
Motor and dexterity impairments
Some people may not be able to use a conventional input deviceInput device
In computing, an input device is any peripheral used to provide data and control signals to an information processing system such as a computer or other information appliance...
, such as the mouse or the keyboard
Computer keyboard
In computing, a keyboard is a typewriter-style keyboard, which uses an arrangement of buttons or keys, to act as mechanical levers or electronic switches...
. Therefore it is important for software functions to be accessible using both devices; ideally, software uses a generic input API that permits the use even of highly specialized devices unheard of at the time of software development. Keyboard shortcuts and mouse gesture
Mouse gesture
In computing, a pointing device gesture or mouse gesture is a way of combining pointing device movements and clicks which the software recognizes as a specific command. Pointing device gestures can provide quick access to common functions of a program. They can also be useful for people who have...
s are ways to achieve this. More specialized solutions like on-screen software keyboards and alternate input devices like switches
Switch Access
Many people with severe physical or cognitive impairment use one or more switches to access computers. A switch is an assistive technology device that replaces the need to use a computer keyboard or a mouse.-Types of switch:...
, joystick
Joystick
A joystick is an input device consisting of a stick that pivots on a base and reports its angle or direction to the device it is controlling. Joysticks, also known as 'control columns', are the principal control in the cockpit of many civilian and military aircraft, either as a center stick or...
s and trackball
Trackball
A trackball is a pointing device consisting of a ball held by a socket containing sensors to detect a rotation of the ball about two axes—like an upside-down mouse with an exposed protruding ball. The user rolls the ball with the thumb, fingers, or the palm of the hand to move a cursor...
s are also available. 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.
The astrophysicist
Astrophysics
Astrophysics is the branch of astronomy that deals with the physics of the universe, including the physical properties of celestial objects, as well as their interactions and behavior...
Stephen Hawking
Stephen Hawking
Stephen William Hawking, CH, CBE, FRS, FRSA is an English theoretical physicist and cosmologist, whose scientific books and public appearances have made him an academic celebrity...
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
Wheelchair
A wheelchair is a chair with wheels, designed to be a replacement for walking. The device comes in variations where it is propelled by motors or by the seated occupant turning the rear wheels by hand. Often there are handles behind the seat for someone else to do the pushing...
-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 an Augmentative and Alternative Communication
Augmentative and alternative communication
Augmentative and alternative communication is an umbrella term that encompasses the communication methods used to supplement or replace speech or writing for those with impairments in the production or comprehension of spoken or written language...
and environmental control device
Environmental control device
An environmental control system is a form of electronic assistive technology which enables people with significant disabilities to independently access equipment in their environment e.g. home or hospital....
.
Hearing impairment
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, silenceSilence
Silence is the relative or total lack of audible sound. By analogy, the word silence may also refer to any absence of communication, even in media other than speech....
requirements or lack of sound hardware.
Such system sounds like beep
Beep (sound)
A beep is a single tone onomatopoeia, generally made by a computer or a machine.-Use in computers:In some computer terminals, the ASCII character code 7, bell character, outputs an audible beep. The beep is also sometimes used to notify the user when the BIOS is not working or there is some other...
s can be substituted or supplemented with visual notifications and captioned text (akin to closed captions).
Software accessibility
Software API exist to allow assistive technology products (like screen readerScreen reader
A screen reader is a software application that attempts to identify and interpret what is being displayed on the screen . This interpretation is then re-presented to the user with text-to-speech, sound icons, or a Braille output device...
s, Text-to-speech, etc.) to work with software. The current or past APIs are:
- Microsoft Active AccessibilityMicrosoft Active AccessibilityMicrosoft Active Accessibility is an Application Programming Interface for user interface accessibility. MSAA was introduced as a platform add-on to Microsoft Windows 95 in 1997...
(MSAA) on Microsoft WindowsMicrosoft WindowsMicrosoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal... - Microsoft UI AutomationMicrosoft UI AutomationMicrosoft UI Automation is an Application Programming Interface for User Interface accessibility that is designed to help Assistive Technology products interact with standard and custom UI elements of an application as well as to access, identify, and manipulate an application's UI elements...
on Microsoft WindowsMicrosoft WindowsMicrosoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
, replacing MSAA - IAccessible2IAccessible2IAccessible2 is a new accessibility API for Microsoft Windows applications. Initially developed by IBM under the codename Project Missouri, IAccessible2 has been placed under the aegis of the Free Standards Group, now part of the Linux Foundation...
on Microsoft WindowsMicrosoft WindowsMicrosoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
, a competitor of Microsoft UI Automation also replacing MSAA - AT-SPI on UNIXUnixUnix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
and LinuxLinuxLinux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds... - Mac OS X Accessibility
- Java Accessibility and the Java Access Bridge for JavaJava (programming language)Java is a programming language originally developed by James Gosling at Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities...
software.
Aaccessibility 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 recorderMacro recorderA macro recorder is a piece of software that "records" user actions for "playback at a later time".The main advantage of using a macro recorder is that it allows a user to easily perform complex operations much faster and with less effort without requiring custom computer programming / scripting.-...
s can greatly extend the range and sophistication of keyboard shortcuts. - Sticky keysSticky keysStickyKeys is an accessibility feature to help computer users who have physical disabilities, but it is also used by others as a means to reduce RSI...
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 WindowsMicrosoft WindowsMicrosoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
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 WindowsMicrosoft WindowsMicrosoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
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 textPredictive textPredictive text is an input technology used where one key or button represents many letters, such as on mobile phones and in accessibility technologies. Each key press results in a prediction rather than repeatedly sequencing through the same group of "letters" it represents, in the same,...
- Spell checkerSpell checkerIn computing, a spell checker is an application program that flags words in a document that may not be spelled correctly. Spell checkers may be stand-alone capable of operating on a block of text, or as part of a larger application, such as a word processor, email client, electronic dictionary,...
s and grammar checkerGrammar checkerA grammar checker in computing terms, is a program, or part of a program, that attempts to verify written text for grammatical correctness. Grammar checkers are most often implemented as a feature of a larger program, such as a word processor, but are also available as stand-alone application that...
s
Other approaches that may be particularly relevant to users with a learning disability include:
- Cause and effect software
- Switch accessible software
- Hand-eye co-ordination skills software
- Diagnostic assessment software
- Mind mapMind mapA mind map is a diagram used to represent words, ideas, tasks, or other items linked to and arranged around a central key word or idea. Especially in British English, the terms spidergram and spidergraph are more common, but they can cause confusion with the term spider diagram used in mathematics...
ping software - Study skills software
- Symbol-based software
- Text-to-speech
- Touch typingTouch typingTouch typing is typing without using the sense of sight to find the keys. Specifically, a touch typist will know their location on the keyboard through muscle memory. Touch typing typically involves placing the eight fingers in a horizontal row along the middle of the keyboard and having them...
software
Web accessibility
Enabling access to Web content for all users is the concern of the Web accessibilityWeb accessibility
Web accessibility refers to the inclusive practice of making websites usable by people of all abilities and disabilities. When sites are correctly designed, developed and edited, all users can have equal access to information and functionality...
movement. Websites can be designed to be more accessible by their conformance to certain design principles.
Screen readers are of limited use when reading text from websites designed without consideration to accessibility; 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.
See also
- ModdingModdingModding is a slang expression that is derived from the verb "modify". Modding refers to the act of modifying a piece of hardware or software or anything else for that matter, to perform a function not originally conceived or intended by the designer...
- Assistive TechnologyAssistive technologyAssistive technology or adaptive technology is an umbrella term that includes assistive, adaptive, and rehabilitative devices for people with disabilities and also includes the process used in selecting, locating, and using them...
- Web accessibilityWeb accessibilityWeb accessibility refers to the inclusive practice of making websites usable by people of all abilities and disabilities. When sites are correctly designed, developed and edited, all users can have equal access to information and functionality...
- Game accessibilityGame accessibilityWithin the field of human-computer interaction, game accessibility refers to the accessibility of video games. Game accessibility is considered a subfield of computer accessibility, which studies how software and computers can be made accessibility to users with various types of impairments.With an...
- Section 508 Amendment to the Rehabilitation Act of 1973Section 508 Amendment to the Rehabilitation Act of 1973In 1998 the US Congress amended the Rehabilitation Act to require Federal agencies to make their electronic and information technology accessible to people with disabilities...
- Fire VoxFire VoxFire Vox is a free and open source extension for the Mozilla Firefox web browser that transforms it into a self-voicing application. Easy to install and operate, it works on Windows, Mac, and Linux. It can work independently, or together with screen readers such as Orca. Since its debut in 2005,...
- AccessAppsAccessAppsAccessApps is an initiative supported by the JISC Regional Support Centres and JISC TechDis. It consists of over 50 open source and freeware Microsoft Windows applications, running from a USB stick...
- a collection of accessibility software which fits on a USB drive - KnowbilityKnowbilityKnowbility is an American non-governmental organization based in Austin, Texas, working to support the independence and empowerment of people with disabilities by promoting the use and improving the availability of accessible information technology...
External links
- The annual ERCIM Workshop on 'User Interfaces for All' emphasising accessibility
- Better Living Through Technology - contains guides on accessibility options and information about specialist assistive hardware and software
- HP Accessibility
- Illinois Accessible Web Publishing Wizard for Microsoft Office
- AbilityNet - provides information on Accessibility, Assistive Technology and Remote Assessment
- C4EA Consortium For E-learning Accessibility
- W3C Web Accessibility Initiative (WAI)
- Accessibility in the Opera web browser
- Mozilla Accessibility Project
- Internet Explorer 6 Accessibility Resources
- Design resources and Javascript libraries for Accessible websites from the Fluid Project
- Mono Accessibility Implementation
- Open Office Accessibility Project
- EU Project GUIDE: Multimodal user interfaces for elderly people with mild impairments
- The Computer Accessibility Wiki