proc drawfillcircle (x, y, radius, clr : int)
    var row : real := -radius %start at bottom of the circle
    var col : real := 0.0
    var dir := 1    %1 is right, -1 is left
    var dist : real
    loop
        dist := (row ** 2 + col ** 2) ** 0.5
        if dist <= radius then
            drawdot (round (x + col), round (y + row), clr)
        elsif dist >= radius then
            dir *= -1
            row += 1
            loop    %jump back into the circle
                col += dir
                dist := (row ** 2 + col ** 2) ** 0.5
                exit when dist <= radius or row >= radius
            end loop
        end if
        col += dir
        exit when row >= radius
    end loop
end drawfillcircle
drawfillcircle (maxx div 2, maxy div 2, maxy div 2, green)