Hardware program to implement the filling of a rectangle with a click

This is a hardware program to implement the filling of a rectangle on a click. If you have any doubts, please let me know. 

#include<graphics.h>

#include<stdlib.h>

#include<stdio.h>

#include<conio.h>

#include<dos.h>

int main(void)

{

    clrscr();

   int gdriver = DETECT, gmode;

   int left, top, right, bottom,c,poly[8],x,y;

   union REGS in,out;

   initgraph(&gdriver, &gmode, "c:\\turboc3\\bgi ");

   left = getmaxx() / 2 - 50;

   top = getmaxy() / 2 - 50;

   right = getmaxx() / 2 + 50;

   bottom = getmaxy() / 2 + 50;

   rectangle(left,top,right,bottom);

   in.x.ax=7;

   in.x.cx=left;

   in.x.dx=right;

   int86(0x33,&in,&out);

   in.x.ax=8;

   in.x.cx=top;

   in.x.dx=bottom;

   int86(0x33,&in,&out);

   in.x.ax=1;

   int86(0x33,&in,&out);

    poly[0]=left;

    poly[1]=top;

    poly[2]=left+100;

    poly[3]=top;

    poly[4]=right;

    poly[5]=bottom;

    poly[6]=right-100;

    poly[7]=bottom;

    printf("BUTTON STATUS");

    while(!kbhit())

    {

      in.x.ax=3;

      int86(0x33,&in,&out);

      c=out.x.bx;

      gotoxy(2,2);

      switch(c)

      {

      case 0:

                 break;

      case 1:

                 in.x.ax=2;

                 int86(0x33,&in,&out);

                 setfillstyle(SOLID_FILL,15);

                 fillpoly(4,poly);

                 in.x.ax=1;

                 int86(0x33,&in,&out);

                 printf("\nLEFT  PRESS");

                 break;

      case 2:

                 in.x.ax=2;

                 int86(0x33,&in,&out);

                 setfillstyle(SOLID_FILL,0);

                 fillpoly(4,poly);

                 in.x.ax=1;

                 int86(0x33,&in,&out);

                 printf("\nRIGHT PRESS");

                 break;

      }

      gotoxy(2,4);

      printf("\nPress any key to exit");

    }

    in.x.ax=0;

    int86(0x33,&in,&out);

    getch();

    closegraph();

    return 0;

}