radar:
  enter graphics mode;
  print heading;
  determine parameters;
  draw radar;
  wait for confirmation (2 * graphics x limit DIV 3, 1);
  leave graphics mode.

print heading:
  put ("Radar");
  line;
  put ("=====").

determine parameters:
  REAL CONST radius ::
	real (min (graphics x limit, graphics y limit)) / 2.1;
  INT CONST centre x :: graphics x limit DIV 2,
			centre y :: graphics y limit DIV 2.

draw radar:
  INT VAR i;
  FOR i FROM 0 UPTO 359
  REP
    move (centre x, centre y);
    draw (centre x + round (aspect * sin (i) * radius),
          centre y + round (cos (i) * radius))
  ENDREP.