ALT Key 1

[xGrob]

How do you detect keystrokes from a keyboard in DOS
-WITHOUT- using getch(). I am specifically trying to detect when the ALT Key is depressed, NOT an ALT+* event.

 

[greatkingrat]

You can read ROM bios data address :

#include <stdio.h>
#include <conio.h>

#define KEY_ADDRESS 0x417 /* ROM BIOS data address */
#define KEY_RSHIFT 0x01
#define KEY_LSHIFT 0x02
#define KEY_CTRL 0x04
#define KEY_ALT 0x08
#define KEY_SCROLL 0x10
#define KEY_NUMLOCK 0x20
#define KEY_CAPSLOCK 0x40
#define KEY_INS 0x80


int main( void )
{
getch();

if( *((char*)KEY_ADDRESS) & KEY_ALT ) {
puts( &quot;Alt key was pressed&quot; );
}
return 0;
}

Compile and execute this program. And then it waits
a key input and you can press alt key at that time.
Hold the alt key and now press any key ( if you
use a dos console on Windows, esc, enter, space, ...
keys can give the special meaning to Windows so use
an alphabet or a digit key for this case. )
to return the 'getch' function. If this program
works fine for you, you can see the message
&quot;Alt key was pressed&quot;.
Hee S. Chung
heesc@netian.com

http://www.netian.com/~heesc

 

[xGrob]

thanks anyway but that's no good, i want to capture the ALT without having to press another key.. eg: press ALT and a pop-up menu opens

 

[greatkingrat]

You can detect whether ALT key is pressed or not
by using my source code. Surely you can capture
ALT without having to press another key. The
reason why I commented to use some other keys
is that, you need to confirm my source can
detect that ALT key is pressed.

As I mentioned it is very simple and fast
to detect ALT key is pressed.

if( *((char*)KEY_ADDRESS) & KEY_ALT ) {
/* alt key is pressed now */
}

KET_ADDRESS and KEY_ALT are defined in the
source which I previously supplied.

Above code is not related to other keys -
it just detect ALT key status.

Thanks.
Hee S. Chung
heesc@netian.com

http://www.netian.com/~heesc

 

[xGrob]

dammit, you're right.. i just didn't try to implememt it it any other way

by doing:

while(1) {
sleep(1);
if( *((char*)KEY_ADDRESS) & KEY_ALT ) {
//bla
}
}

it clearly does work, thanks alot ;-)

 

[greatkingrat]

Is it really helpful? Can you give me a vote ?

Thank you! Enjoy your programming!
Hee S. Chung
heesc@netian.com

http://www.netian.com/~heesc