infovox@infovax.UUCP (Talsvar Gruppens Gemensamma) (07/27/89)
Hello!
I have been trying to write a TSR program that would do the following:
1) Use the timer interrupt (1C hex) to update a counter
2) When the counter reaches a given value, the TSR should
wait for a password to be entered, without echoing the
characters to the screen.
3) Use the keyboard interrupt (09 hex) and the BIOS interrupt
(10 hex) to reset the counter if it hasn't reached the value.
In other words, the TSR would work as a security program.
If a key hasn't been pressed, or BIOS hasn't done any work for a
while the TSR would act like a lock, and wait for a password to
be entered...
When the TSR is in locked mode, I would like it not to echo any
character, just be dead, so that a person who doesn't know about
the TSR and the password would think that the computer has crashed.
A variation could be to blank the screen, and print a message like
"Busy" or something.
Well, let's get to the point.
I have succeded in making the TSR work for an AT with a one character
password, but not more.
The problem is, how do I read characters from the keyboard, and
prevent DOS or any other program to take care of them when I'm in
the middle of an interrupt (09).
I would appreciate any help you can give me!
Maybe, if there has been a tool like this on UseNet for the IBM PC/AT
you could mail it to me.
Many thanks,
Anders Ohlsson
infovox@infovox.se