pascal chess board drawing

chessboard.pas

USES CRT, GRAPH;
VAR
gd, gm: integer;
x, y: integer;

{chess_board}
c_offset, c_side, c_step,
c_cursor_x, c_cursor_y,
c_cl_black, c_cl_white,
c_pixels_offset: integer;
c_black: boolean;
{/chess_board}

BEGIN
clrscr;
gd:=detect;
initgraph(gd, gm, '');

{chess_board_draw}
c_side:=400;
c_offset:=10;
c_cl_black:=8;
c_cl_white:=15;
c_pixels_offset:=3;

if (c_side mod 8) <> 0 then
begin
    closegraph;
    writeln('c_side error');
    readkey;
    exit;
end;

c_step:=c_side div 8;
c_black:=false;
setcolor(c_cl_black);
setlinestyle(0, 0, 3);

for y:=8 downto 1 do
begin
     c_cursor_x:=0;
     for x:=1 to 8 do
     begin
          if c_black then
          begin
               setfillstyle(1, c_cl_black);
               c_black:=false;
          end
          else
          begin
               setfillstyle(1, c_cl_white);
               c_black:=true;
          end;
          bar(c_cursor_x+c_offset, c_cursor_y+c_offset,
          c_cursor_x+c_offset+c_step, c_cursor_y+c_offset+c_step);
          c_cursor_x:=c_cursor_x+c_step;
     end;
     if c_black then c_black:=false else c_black:=true;
     c_cursor_y:=c_cursor_y+c_step;
end;

rectangle(c_offset-c_pixels_offset, c_offset-c_pixels_offset,
c_offset+c_side+c_pixels_offset, c_offset+c_side+c_pixels_offset);
{/chess_board_draw}

readkey;
closegraph;
END.