uses graph, crt;
var d, m: integer;
    x: real;
begin
 d:=Vga; m:=VgaMed;
 initgraph(d, m, '');
 x:=0;
 repeat
  cleardevice;
  circle(round(100*x), 200-round(80*sin(x)), 20);
  delay(20);
  x:=x+0.01;
  if x>2*Pi then x:=0;
 until keypressed;
 readkey;
 closegraph;
end.