Circle Drawing Algorithm

We only need to calculate the values on the border of the circle in the first octant. The other values may be determined by symmetry. Assume a circle of radius r with center at (0,0).

    Procedure Circle_Points(x,y: Integer);
    Begin
    Plot(x,y);
    Plot(y,x);
    Plot(y,-x);
    Plot(x,-y);
    Plot(-x,-y);
    Plot(-y,-x);
    Plot(-y,x);
    Plot(-x,y)
    End;