// This program uses INT 33H to see if mouse driver is installed and if so it displays 
// the number of buttons on the mouse 
#include <stdio.h>
#include <dos.h>
#include <conio.h>
main()
 {
 union REGS ri,ro;
 clrscr();
 ri.x.ax=0x0; 	//check to see if there is mouse
 int86(0x33,&ri,&ro);
 if(ro.x.ax>0)
 printf("\n\nYou have %d button(s) on the mouse on this PC",ro.x.bx);
 else
 printf("This PC has no mouse\n");
 }