PRODUCT  :  TURBO C                                NUMBER  :  396
  VERSION  :  1.0
       OS  :  PC-DOS
     DATE  :  November 18, 1987                        PAGE  :  1/1

    TITLE  :  CAPTURING INTERRUPTS




  The following program demonstrates the use of getvect and setvect
  to safely capture and restore interrupt vectors.  This code could
  be easily modified to disable  the  print  screen  utility during
  program execution.

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

  void interrupt (*oldfunc)();
  int __LOOPING__ = 1;

  /*--------------------------------------------------------------------
   * get_out - this is our new interrupt routine
   *------------------------------------------------------------------*/
  void interrupt get_out() {
         setvect(5,oldfunc); /* restore to original interrupt routine */

       __LOOPING__ = 0;

  }

  /*--------------------------------------------------------------------
   * capture_prtscr - installs a new interrupt for <Shift><PrtSc>
   *  arguments :  func  -- new interrupt function pointer
   *------------------------------------------------------------------*/
  void capture_prtscr(void interrupt (*func)()) {
       oldfunc  = getvect(5);        /* save the old interrupt */
       setvect(5,func);              /* install our interrupt handler */
  }

  void main () {

       puts("Press <Shift><PrtSc> to terminate");
       capture_prtscr(get_out);  /* capture the print screen interrupt */

       while (__LOOPING__)
         ;   /* do nothing */

       puts("Success");
  }