About Application Software Accessibility


The goal of accessibility is to ensure that application software is available to and usable by the widest possible audience. This requires that all users can perceive and understand what is on the screen and operate the controls.

To achieve this, the design must take into account the fact that the ability to see, hear, make inputs, read text or process information varies from user to user, across time and across situations of use. Some users require special assistive input and output technologies or specific display characteristics to help them carry out these activities. Application software design should also take this into account.

Mobility considerations

"I use the keyboard with one hand. I can't use a mouse. - computer user


Allow keyboard only access
Many people use a keyboard but cannot use a pointing device.

Some users have restricted movement or control of their arms, hands and fingers. This might be due to a medical condition, injury or even old age. Many older people, for example, have reduced dexterity or even a slight hand tremor. These users may have difficulty in controlling a mouse accurately enough to point to small buttons. If they are unable to use a mouse at all, they will rely on keyboard control. The two main methods of keyboard control are tabbing and using shortcut keys.


Alternative pointers
Not all users operate their computer with a mouse.

Tabbing is moving the focus between menus, controls and application objects by repeatedly pressing the Tab key, or sometimes other special keys. Pressing the Enter key or spacebar activates or selects the object that has the focus. By tabbing, users who cannot use a mouse can still reach and activate every element on the screen. The order in which the elements are visited when tabbing is called the tab order and is determined by the way the interface is coded. If the tab order does not follow the logical ordering of the elements, it will be frustrating and inefficient to use. This may result in user errors, such as missing out fields when the tab skips over them.

Shortcut keys are key combinations that are permanently assigned to a specific command, enabling keyboard users to access the command instantly. For example, In Windows, holding down the Control (Ctrl) key and pressing P is usually used to print the current document. This makes keyboard use much more efficient for users who are very slow, because it takes only a single key press to do something that might require 10 or more key presses to do by tabbing to the menu command.

To enable users with reduced mobility to use an application, it must be possible to activate all objects and functions using the keyboard and the tab order should follow the logical order of the elements.

Visibility considerations

"I have to lean very close to see the screen. My eyes get very tired after using the screen for a couple of hours. Strictly speaking, I'm not supposed to work with a screen for more than 2-3 hours a day but sometimes you have to." - partially sighted user


Trouble with small text 
People with partial sight may find small text very difficult to read.

Visual impairment includes blindness, partial sight and colour blindness. This includes people who have temporarily lost or forgotten their glasses or anyone who is operating a computer in an environment where there is either insufficient light or too much glare from windows or lighting.

"The biggest problems are small type, poor contrast between the colour of type and background and I can't focus on moving text.
" - partially sighted user

Users whose sight is impaired may have problems perceiving the various elements of a user interface. They may have difficulty distinguishing buttons and menus, reading text or identifying the content of pictures. This is made worse if text is very small and cannot be resized by the user, or if the colour combinations used do not have good contrast.

"Some programs seem to use their own cursor and you can't get at the fields." - partially sighted user

Users who are blind access computers using a screen reader. This is a piece of software that reads out the contents of the screen. This includes the written text, the names of buttons and commands and even images and icons if they have some text associated with them. Some applications achieve a customized look and feel by using their own cursors and controls, rather than the standard operating system tools. This can cause problems for screen readers which may be unable to detect these cursors and controls or their current state. Then they will not know what is on the screen or where the current input focus is. If this happens, a user who is blind may be unable to interact with the application at all.

The key to serving these users' needs is to make sure text is large or resizable, colours contrast well, images (and other multimedia items) have text descriptions associated with them and the application is compatible with assistive technologies.

guidelines_dia_resizeable_text (1)

Resizable onscreen text 
Many partially sighted users enlarge system fonts to aid legibility.

Cognitive and learning considerations

Some users may have difficulty dealing with letters, words and numbers, understanding concepts and instructions, or learning procedures. Often these users are in all other respects highly intelligent.

This can be a particular problem if the user interface or task flow varies from one function to the next or if it is significantly different from other applications. People with cognitive or learning impairments rely more on rote learning and less on interpretation and reasoning, so consistency and predictability are very important for them. If the required procedure for a task changes or if they cannot rely on what they have previously learned, they find it far more difficult to use the application.

The key is to maintain consistency across functions and screens and to follow the user interface standards used by other applications. This will also be of tremendous benefit to the average user who, whilst not being permanently impaired, may well at times be tired, stressed or in a hurry, all of which affect cognition and learning. In addition, there are many, particularly older, users who use computers rarely and may find them intimidating, simply because they are not familiar with them.

Language considerations

Most people find large blocks of text difficult to read on screen, especially if it contains complex language or industry jargon. People who do not speak English as their first language or who do not read very well may find it particularly difficult.

25% of the Irish population are "functionally illiterate", meaning that while they can read to some degree, they would have difficulty reading a newspaper, filling in a form or following the instructions on a medicine bottle. The trick is to keep it simple.

Hearing considerations

Users who are deaf or hard of hearing may have problems perceiving information that is presented as sound. Even users with good hearing may be working in a quiet environment such as a library or office, where the sound may be turned down or the loudspeakers could be disconnected. Conversely, the users' hearing may be impaired by a noisy environment, such as an industrial plant.

These users' needs can be met by simply ensuring that all audible information is supplemented by a visual form such as screen flashes, captions and subtitles.

Other sources of information

IBM application software accessibility guidelines Provides general guidelines covering application software and specific guidelines for Java applications.