Brent
>
>...
> At it most simplest level, any computer
> operating system, to be accessible for blind people must be designed in such
> a way that it can be possible for the OS's developers, or for third-party
> developers to add software and/or hardware that can do three basic things.
> The access interface, sometimes referred to, somewhat incorrectly, as a
> "screen reader," must be able to intercept any and all input going to the
> system from such devices as keyboards, and programs, and intercept all
> output going from those programs to the screen, and possibly to other output
> devices, such as printers. Once intercepted, this material gets converted
> from, usually text, to something that an interactive speech synthesizer can
> convert to phonemes which can be strung together to give spoken output. Or,
> that output must be able to be sent to an interactive "refreshable" braille
> display or to a very-high-contrast much enlarged image on a good quality
> monitor. The output devices must be able to communicate back with the
> interface software such that the user can control stopping and starting of
> the information stream, the rate at which it is accessed, and the size of
> blocks of the data that will be accessed at one time, such as one character,
> word, line, sentence, or paragraph, or screen, or whole document. The
> simplest OS to make accessible to totally blind people is one which is
> completely character-based, no pictures, and no graphical representations of
> text, as in pictures of printed pages. The classic example of such an
> interface is, surprise! DOS with its outputs being sent to the screen
> through the computer's BIOS routines.
OH. There have been many other OS doing that! CPM, Apple II,
SCO-UNIX ...
It's not only the step to GUIs, making the computer more "invisuable"
for the blind. The problem often starts with the two dimensional
placement of information on the screen. Sometimes the arrengement
of texts on the screen contains informations.
This socalled "information by placement" must be found out by
the screenreader, because it's not directly accessible by
a sequencial media like TTS or Brailledisplay.
You have to tell god screen readers how to handle pulldowns,
color attributes, messages only appearing for half a second on the
screen etc. There are a lot of textbased applications know,
which work in a pseudo grafic mode. A nice example is the YAST
setup tool for linux.
> When the interface gets graphical and visual in nature, then much more work
> must be done to try to interpret the presented data in a form that the
> access software can then sent to the character-oriented, line-oriented
> output devices that blind people use to access the information that is going
> to their programs, and to their screens.
You are right. What's missing is a clear cut between
the real operating system and the userinterfaces.
Such an "of screen model" can make the UI interchangable:
GUI, text UI, speech UI etc. Perhaps linux goes a little bit
in this direction.
Regards
Klaus
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