PRODUCT  :  Borland C++                           NUMBER  :  1155
  VERSION  :  3.1
       OS  :  DOS
     DATE  :  October 19, 1993                         PAGE  :  1/2

    TITLE  :  Detecting unusual keystrokes and key combinations.





            Detecting unusual keystrokes and key combinations.
            -------------------------------------------------

       Some keystrokes, such as CTRL-1, cannot be caught with
  bioskey() or an INT 15,4H interrupt handler because the BIOS does
  not pass the scan code along to INT 15.  If you need to catch
  these keystrokes, you will need to intercept the keystroke
  directly at the INT 9 level.  This example of code demonstrates
  exactly how to catch keystrokes such as CTRL-1.  When the program
  is run, keystrokes will echo the screen as normal, but whenever a
  CTRL-1 is pressed, the machine will beep.

  #include <dos.h>
  #include <bios.h>
  #include <stdio.h>

  /* 0x02 is the value for 1 */
  #define KEY_TO_CATCH 0x02

  /* Old INT 9 handler routine */
  void interrupt ( *Old09Handler )(...);

  void interrupt New09Handler(...)
  {
      _AL = inportb( 0x60 );              // Read the Scan Code
      if ( _AL == KEY_TO_CATCH )          // Is it that key?
      {
          _AH = 0x02;                     // Check the Shift
          geninterrupt( 0x16 );           // Status using BIOS
          if ( _AX & 0x04 )               // Is Control Held Down?
          {
              _AL  = inportb( 0x61 );     // Reset the Keyboard
              _AH  = _AL;
              _AL |= 0x80;
              outportb( 0x61, _AL );
              _AL  = _AH;
              outportb( 0x61, _AL );
              outportb( 0x20, 0x20 );     // EOI to 8259

















  PRODUCT  :  Borland C++                           NUMBER  :  1155
  VERSION  :  3.1
       OS  :  DOS
     DATE  :  October 19, 1993                         PAGE  :  2/2

    TITLE  :  Detecting unusual keystrokes and key combinations.




              _AX = 0x0E07;               // Beep to indicate that
              geninterrupt( 0x10 );       // we caught the desired
                                          // key
              return;                     // Do not chain!
          }
      }
      Old09Handler();                     // Chain to Old Handler
  }

  int main( void )
  {
      Old09Handler = getvect( 0x09 );     // Save the original
      setvect( 0x09, New09Handler );      // Install new

      puts( "Please hit the ESC key to terminate..." );

      LABEL:
      asm {
                  mov     ah, 8h
                  int     21h
                  or      al, al
                  jz      LABEL
                  mov     dl, al
                  mov     ah, 2
                  int     21h
                  cmp     dl, 27
                  jne     LABEL
          }

      setvect( 0x09, Old09Handler );      // Restore Original
      return( 0 );
  }

  /*
  Keywords:  bioskey, CTRL-3, CTRL-4, CTRL-5, CTRL-7, CTRL-8,
  CTRL-9, CTRL-0, keyboard, keypress
  */



  DISCLAIMER: You have the right to use this technical information
  subject to the terms of the No-Nonsense License Statement that














  PRODUCT  :  Borland C++                           NUMBER  :  1155
  VERSION  :  3.1
       OS  :  DOS
     DATE  :  October 19, 1993                         PAGE  :  3/3

    TITLE  :  Detecting unusual keystrokes and key combinations.




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