cramer@optilink.UUCP (Clayton Cramer) (03/24/90)
In trying to disable the ^C echo (but not the ^C interrupt), I have
run into something rather interesting and irritating: putting hooks
into INT 16 (the software interrupt for requesting characters from
the keyboard) doesn't allow me to suppress the ^C echo, because
INT 9 (the keyboard hardware interrupt) is redirected by DOS from
the BIOS to an ISR in DOS. This ISR treats ^C, ^S, ^Q, and ScrollLock
"special", which means that ^C doesn't even make it into the keyboard
input queue that INT 16 gets characters from. It appears from
trying to read the code in the DOS INT 9 ISR that control goes
somewhere else in DOS, which apparently does the ^C\r\n echo to
the screen at the current cursor position.
I know that it is possible to shut off this echo without disabling
^C interrupt -- Turbo C uses ^C as a command character. Does anyone
know a way to do this that doesn't involve trying to trace forward
from the INT 9 ISR vector address, and stomping on the compare to
the scan code?
--
Clayton E. Cramer {pyramid,pixar,tekbspa}!optilink!cramer
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