Disabling the keyboard

[Mark William Hopkins]

In article <1991Mar11.193729.3291 at ssd.kodak.com> wieser at bissun.kodak.com (Jim Wieser) writes:
>How do you temporarily disable the keyboard on a PC under
>DOS using MSC short of installing a new interrupt handler?

Installing a new interrupt handler is the easiest way by far.  This should
work on IBM-compatibles (possibly except for the PcJr):

------------------------------------------------------------
KbdInt.h:
extern void DisableKbd(void);
extern void EnableKbd(void);

------------------------------------------------------------
KbdInt.c:
#include <dos.h>

#pragma check_stack(off)
#pragma check_pointer(off)

static unsigned /* Keyboard buffer */
   far *HeadP = (unsigned far *)0x0040001a,
   far *TailP = (unsigned far *)0x0040001c;

static void (interrupt far *OldKbd)(void);

static void interrupt far Ignore(void) {
/* Get the key but ignore it. */
   (*OldKbd)();
   if (*HeadP == *TailP) return;
   *HeadP += 2;
   if (*HeadP > 0x003d) *HeadP = 0x001e;
}

void DisableKbd(void) {
   OldKbd = _dos_getvect(0x09);
   _dos_setvect(0x09, Ignore);
}
void EnableKbd(void) { _dos_setvect(0x09, OldKbd); }

------------------------------------------------------------
The only question I have is: how do you plan to re-enable the keyboard?