Mail Archives: opendos/1997/02/02/21:57:55
I think an environmental variable that could be set in config.sys or
autoexec.bat for either BIOS calls or direct screen writing would be a
suitable solution. Incidentally, programmes that write text data directly
into the video memory are only a problem for speech synthesizer users, who
would lose the benefit of having the output read to them automatically.
It is normally quite possible to issue explicit keyboard commands to the
screen reading programme in order to read text that has been written
directly to video memory. Indeed, the more advanced of these programmes
use sophisticated monitoring techniques in an attempt to detect changes on
the screen that are not due to BIOS calls. I think they intercept the
computer's timer and examine the video memory on a regular basis, but I am
not a technical expert and hence do not know the details. Braille display
devices are not affected, so far as I know, by how text is sent to the
screen. My braille display functions equally well regardless of whether or
not the system is using the BIOS for output. However, for speech
synthesizer users, it is obviously not convenient to have to give specific
commands (normally by pressing keys on the keyboard that are under the
control of the access software) whenever they want to read a prompt or
message displayed by the operating system. Therefore, allowing the writing
technique to be selected by the user as a global configuration option
would be the best solution for all, including those who are using
computers that are not compatible with pc's as far as their video services
are concerned.
Regards,
Jason White.
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