include c:\cxpl\codes;          \include 'code' declarations

proc Circle(X0, Y0, Radius, Color);     \Display a circle
int  X0, Y0,    \coordinates of center
     Radius,    \radius in (pixels)
     Color;     \line color
int  X, Y, E, U, V;

        proc PlotOctants;               \Segment
        [Point(X0+Y, Y0+X, Color);      \ 0
        Point(X0+X, Y0+Y, Color);       \ 1
        Point(X0-X, Y0+Y, Color);       \ 2
        Point(X0-Y, Y0+X, Color);       \ 3
        Point(X0-Y, Y0-X, Color);       \ 4
        Point(X0-X, Y0-Y, Color);       \ 5
        Point(X0+X, Y0-Y, Color);       \ 6
        Point(X0+Y, Y0-X, Color);       \ 7
        ]; \PlotOctants

[X:= 0;  Y:= Radius;
U:= 1;
V:= 1 -Radius -Radius;
E:= 1 -Radius;
while X < Y do
        [PlotOctants;
        if E < 0 then
                [U:= U+2;  V:= V+2;  E:= E+U]
        else    [U:= U+2;  V:= V+4;  E:= E+V;  Y:= Y-1];
        X:= X+1;
        ];
if X = Y then PlotOctants;
]; \Circle

[SetVid($112);          \640x480 in 24-bit RGB color
Circle(110, 110, 50, $FFFF00);
if ChIn(1) then [];     \wait for keystroke
SetVid(3);              \restore normal text mode
]