/* ==============  Program Description  ============= */
/*   ball moving application.                         */
/* ================================================== */
#include  <graphics.h>
#include  <dos.h>

void main()
{
    int     driver = DETECT,mode;
    int     i,x = 100, y = 160, radius = 20, xdir=4;

    initgraph(&driver,&mode,"a:\\bgi");
    rectangle(79,139,521,181);
    for(i=100; i<=500;i=i+4)
    {
       setcolor(BLACK);
       circle(x,y,radius);

      // if ( x == 500 )           /* touch the rightmost */
      //	  xdir = -4;
      // else if ( x == 100 )      /* touch the leftmost  */
	//  xdir = 4;
       x += xdir;
       setcolor(WHITE);
       circle(x,y,radius);
       delay(50);
    }
    getch();
    closegraph();
}