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There are three primary issues regarding the feasibility of a particular operating system for individuals with a variety of disabilities. First, operating systems that use text interfaces (for example, early DOS) are generally easier to navigate for handicapped users. For example, screen readers are much more easily used when they do not have to handle Flash, JavaScript, links, graphics, etc. Second, the features built into each platform are extremely important in determining its accessibility, not only in the features’ availability, but also in their ease of use. Third, the accessibility of third party software for a particular platform may also be relevant depending on the type of disability and the number of features built into the OS; for example, if screen readers built into Windows XP and Mac OS X are less than optimal but there are no third party solutions for a Windows computer, the Mac OS would be a better choice.
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Microsoft products tend to have more options than those of Apple, but in a less user friendly format. Finding accessibility options requires some searching, as opposed to being configured at setup. There are some additional keyboard modifications, however, that give it a “leg up” on Apple products.
Visual options are plentiful but relatively basic in Windows XP. These changes include font size and color on the desktop, size of icons, screen resolution and contrast, the size and blinking state of the cursor, and the ability to magnify particular parts of the screen.
Audio options include visual cues instead of sound for those are hard of hearing, either for system sounds (SoundSentry) or special events. ShowSounds creates captions for speech and sounds, while Microsoft Narrator converts options and other text into voice. This program, however, informs the user that it is not sufficient for day to day use, only for setting up your computer. ToggleKeys allows sound cues for when certain keys are pressed, for example, to indicate that Caps Lock is on.
The input options for Windows XP are relatively easy to change and contain multiple options depending on the user’s disabilit(y/ies). FilterKeys ignores brief keystrokes to avoid accidentally hitting other keys or repeatedly hitting the same key. The repeat rate can also be changed or eliminated for people who move their fingers more slowly and cannot lift them fast enough to only type one letter at a time. StickyKeys functions in the same way Mac OS X’s version works, by allowing users to type keys in sequence instead of having to hold them down to get a certain shortcut. MouseKeys allows mouse navigation via the numerical keypad. Other keyboard options include different layouts, such as Dvorak, or an on screen keyboard that can allow typing by a joystick or a mouse.
There are also numerous options to modify the mouse or screen pointer. For example, ClickLock allows users to drag or highlight without holding down the mouse button, and another options lets the functions of the right and left mouse buttons be reversed. SnapTo can move the pointer to the default button in a dialog box, allowing the user to click without having to move the mouse to a particular location. The appearance of the pointer can also be changed, for example, how fast it moves, its size and color, whether it leaves a trail, and whether it is hidden while typing. (7)
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 The Mac OS X is one of the most comprehensive operating systems in terms of accessibility. Many options are available easily upon setup, including VoiceOver, the spoken text interface for OS X. The webpage detailing these features is set up by category of disability, making it easier for users to determine the system’s usefulness for them.
Screen and visual modifications are some of the most easily changed accessibility features on a Macintosh. These range from basics such as a scalable cursor, changes in contrast and color schemes, and visual alerts (as opposed to sounds) when an item needs attention all the way to closed captioning in QuickTime videos and enough clarity via iChat and iSight that sign language can be read from either end. There is also a zoom function that works on graphics, text, and videos.
Auditory outputs can also be modified, for example, by having text be read aloud or have alerts be associated with sounds instead of visual cues. For those with learning or cognitive disabilities, the combination of voice and text or voice and numbers (in the case of the calculator) can aid in comprehension.
There is also a significant amount of modification that can be done in terms of computer inputs. OS X comes with a speech recognition program that allows for general navigation throughout the computer and a few specific applications. The keyboard can be modified to allow the numeric keypad to act as a mouse; a user can also change the rate at which the keyboard accepts keystrokes so as to avoid accidentally typing the same character twice (SlowKeys). In the same vein, the delay rate on keys can be changed. Finally, StickyKeys allows combinations of keys (for example, Option + Apple + Q) to be typed in sequence instead of at the same time for users who, for example, can only type with one finger or a mouth stick. (6)
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DOS’s text based interface makes it much easier for screen readers and other programs for the disabled, for example, those that work with Braille readouts or refreshable displays. Other accessibility features, however, have to be installed through AccessDos and do not come with the OS itself.
AccessDOS includes a significant number of keyboard options, starting with the more traditional StickyKeys, RepeatKeys, MouseKeys, and ToggleKeys (see Apple, Microsoft descriptions). It also includes SerialKeys, which allows you to control the computer using an alternative input device, although Windows XP has a similar feature to allow for various keyboard setups. BounceKeys can ignore quick double strokes of a particular key from its “bounce,” while SlowKeys ignores keys that aren’t held down for a specified period of time.
AccessDos doesn’t support many alternative visual or auditory signals except for SoundSentry, which provides visual cues instead of audio ones. For users with vision impairments, third party screen readers would be necessary.
AccessDos also has a unique feature called TimeOut, which will automatically turn off its features if the computer is idle for a certain period of time. This is particularly useful for a computer that may be used by multiple people, for example, in a library. (8)
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 Linux is a unique OS in that it is open source, meaning that options are constantly changing and becoming more accessible. This can, however, make it more difficult to pick and choose between competing programs, and it also means that the operating system doesn’t come with many options “built in” for easy first time use. For this reason, many people with disabilities need assistance in setting up a Linux based computer. A sampling of Linux based accessibility tools are provided below.
- GNOME Accessibility Project – specifically for the GNOME desktop environment for Linux
- Gnopernicus – screen reader and magnifier
- Gnome Onscreen Keyboard – allows control of the keyboard through other input devices, such as joysticks.
- KDE Accessibility Project – for the K desktop environment
- KmouseTool – works with alternative mice to click the mouse via other movements.
- Kmag – a magnifying tool
- Kmouth – a text-to-speech tool
- AccessX – provides things like StickyKeys, MouseKeys, RepeatKeys, SlowKeys, ToggleKeys, and BounceKeys (see Apple, DOS, and Microsoft descriptions)
- SmartNav – allows hands free control of a mouse.
- Festival – a popular speech synthesizer
- CVoiceControl – speech recognition software to specifically affiliate words with Linux commands
- SuSe Linux – a version of Linux that supports Braille
- BLINUX – “Blind Linux” – runs in the background to enable Braille displays.
- Socrates – text based OCR scanning (9)
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