Listing 1

KILLIT.C

 /*
 *KILLIT.COM - A small utility to kill or re-enable the PrtScr function
 *      Usage: Call with no argument to disable PrtScr function
             Call with any argument to enable PrtScr function
                Written by M.L. Lesser, 10/27/89
             Compiled with Turbo C (TCC) v 2.00, switches -mt -lt -o
              to link as COM file
 */
 
 #include <MIO><N>.h
 
 char far *PrtScr = (void far *)((unsigned long)0x50 << 16);
 
 void main(argc)
   {
   if (argc == 1)       /* No arguments on the command line */
      {
      *PrtScr = 1;    /* Set PrtScr "busy" signal */
      cprintf("Print screen function has been disabled");
      }
   else
      {
      *PrtScr = 0; /* Set PrtScr <169>available<170> signal */
      cprintf("Print screen function has been enabled");
      }
   }