rem bj gleason
  rem sample circles
  rem cx,cy are the center x,y coordinates
  rem r is the radius
  screen 6  ' graphics mode
  for cx = 20 to 70 step 10
    r = cx/2   ' draw a series of circles
    cy = 32
    gosub 1000
  next cx
  alarm
  screen 7  ' text mode
  end

1000 ' circle subroutine
  locate cx+r, cy
  stv = 360/r/7  ' step is based on radius
  for theta = 0 to 360 step stv
    angle=theta*3.1415/180
    sx = r*cos(angle)
    sy = r*sin(angle)
    sx = cx+sx : sy = cy+sy
    pset (sx,sy),1
  next theta
  return