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Keyboard Handler

Posted on 1997-07-25
Last Modified: 2012-06-21
I need to write a set of keyboard handler functions.  It should allow me to check for multiple keypresses.  It should take over the port from the BIOS.
Question by:IsaacW

Expert Comment

ID: 1252599
Why don't you want to use the BIOS. Would make it a lot easier.


Expert Comment

ID: 1252600
What operation system you using ? DOS ? Windows ? WIN32 ?
What king of handlers you need ? You need to have callbacks caling when key pressed ? You need to check key state ?


Author Comment

ID: 1252601
The BIOS functions don't allow me to know when a key is released, so if I want to detect say, Ctrl-S for save or something, I need to overwrite it.  I'm programming for DOS in protected mode.  I have a function to handle the keypresses, I just need to know how to get it called whenever an int 9 occurs.  Thanks for all your help.
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Accepted Solution

mosfet earned 300 total points
ID: 1252602
Just run SetNewKbdInt() to install, and SetOldKbdInt() to deinstall. The kbdtable array has values for all the scancodes for the keys. For examples: the scan code for "Enter" is 28.
if(kbdtable[28]==1) cout << "Enter pressed";
if(kbdtable[28]==0) cout << "Enter released";

This can moniter the status of all the keys at the same time.

volatile unsigned char far kbdtable[128];

#ifdef __cplusplus
            #define __CPPARGS ...
            #define __CPPARGS

void interrupt ( *OldKbdInt)(__CPPARGS);
void interrupt NewKbdInt( __CPPARGS )
      unsigned char keyp;
      keyp = inp( 0x60 );

      if( keyp < 128 )
    kbdtable[keyp] = 1;
            kbdtable[keyp-128] = 0;

  outp( 0x20, 0x20 );

void SetNewKbdInt()
  OldKbdInt = getvect( 0x9 );
  setvect( 0x9, NewKbdInt );
  int q;
  for(q=0;q<128;q++) kbdtable[q]=0;

void SetOldKbdInt()
      setvect( 0x9, OldKbdInt );

Author Comment

ID: 1252603
I need to know what include files to use, getvect and setvect aren't recognized by my compiler as library functions.  I am using DJGPP v2.01.  Thanks for your help.


Expert Comment

ID: 1252604
I think all you need is dos.h. I programmed this code to work in Turbo C++ 3.0, so you might need to change something if it doesn't work.

Author Comment

ID: 1252605
Thanks, but since I'm using DJGPP, I have to use real mode calls.  All your other code looks like I can use it, so I'll give you a B.  Thanks once again.

Author Comment

ID: 1252606
Thanks, but since I'm using DJGPP, I have to use protected mode calls.  All your other code looks like I can use it, so I'll give you a B.  Thanks once again.

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