СПиОС LR_5 VAR_10

program LR_5;
{ Melnik Victor  ISPR A1  10 var  }

uses crt;
var color : byte;

procedure plot(x, y : word);
   var video_offset : word;
       pix_col, value, shift: byte;
begin
    { вычисляем смещение в видеобуфере }
    video_offset := 80 * (y div 2) + (x div 4);
    if (y mod 2 = 1) then video_offset := video_offset + $2000;
    shift := 6 - 2 * (x mod 4);

  asm
    mov ax, 0b800h
    mov es, ax
    mov di, [video_offset]
    lodsb

    xor ah, ah
    mov bl, 0
    and al, bl
    mov [value], al
  end;
    pix_col := color shl shift;
    value := value or pix_col;

  asm
    mov ax, 0b800h
    mov es, ax
    mov al, [value]
    mov di, [video_offset]
    stosb
  end;
end;

function sign(value: integer) : integer;
begin
    if (value > 0) then sign := 1
    else sign := -1;
end;

procedure drawLine(x1, y1, x2, y2 : integer);
    var dx, dy, i, sx, sy, check, e, x, y : integer;
begin
    dx := abs(x1 - x2);
    dy := abs(y1 - y2);
    sx := sign(x2 - x1);
    sy := sign(y2 - y1);
    x := x1;
    y := y1;
    check := 0;
    if (dy > dx) then begin
        dx := dx + dy;
        dy := dx - dy;
        dx := dx - dy;
        check := 1;
    end;
    e:= 2 * dy - dx;
    for i := 1 to dx do begin
        plot(x, y);
        if (e >= 0) then begin
            if (check = 1) then x := x + sx
            else y := y + sy;
            e := e - 2 * dx;
        end;
        if (check = 1) then y := y + sy
        else x := x + sx;
        e := e + 2 * dy;
    end;
end;

begin
{ граф. режим 320x200x4 }
   asm
       mov ax, 4
       int 10h
   end;

   color := 1;
   drawLine(60, 25, 20, 155);
   drawLine(60, 25, 100, 155);
   drawLine(35, 110, 85, 110);

   color := 2;
   drawLine(180, 25, 125, 25);
   drawLine(125, 25, 125, 90);
   drawLine(125, 90, 180, 90);
   drawLine(180, 90, 180, 155);
   drawLine(180, 155, 125, 155);

   color := 3;
   drawLine(215, 155, 215, 25);
   drawLine(215, 25, 250, 90);
   drawLine(250, 90, 285, 25);
   drawLine(285, 25, 285, 155);

   readln;
   { текст режим }
   asm
       mov ax, 3
       int 10h
   end;
end.