MS-DOS Interrupt Service Routine Example

ISR.CPP

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

void interrupt far (*oldhandler)(...);

void interrupt myhandler(...) {
  printf("Timer Tick!\n");
  oldhandler();
}

int main() {
  printf("Hooking timer interrupt 0x1C...\n");
  oldhandler = getvect(0x1c);
  setvect(0x1c, myhandler);
  return 0;
}