{
For all of you who are interested on fractals, here is a little program,
taken from a source code in Modula-2, that will draw a Mandelbrot fractal.

Just one problem: If your computer doesn't have a math coprocessor, the
program will run "a bit" slow :).

Try modifying all the constants, you'll get strange results :).}

{$U+} { Supposed to be used for Breaking During Programs }


Program Mandelbrot;     {Using real numbers. For TP 6.0 and above }

Type Filestr = String[14];

Const Colours=15;       {Number of colors to be on the image.     }
      Width=640;        {Width of the image.                      }
      Height=400;       {Height of the image.                     }
      Limit=8.0;        {Until when we calculate.                 }
      XRMin=-2.0;       {Left limit of the fractal.               }
      XRMax=1.0;        {Right limit of the fractal.              }
      YRMin=-1.3;       {Lower limit of the fractal.              }
      YRMax=1.3;        {Upper limit of the fractal.              }
      Bufsize = 128;

Var XPos,YPos:Integer;
    Coldata : array[0..16000] of byte absolute $4000;
    recsread : integer;
    source : file;

Procedure Save(filename:Filestr);
 begin
  recsread:=125;
  assign(source,filename);
  rewrite(source);
  blockwrite(source,Coldata,recsread);
  close(source);
 end;

Procedure mode(mo:byte);
 begin
   Inline($3A/mo/
          $CD/$9B/$BE/
          $0E/$BC);
 end;

Procedure grapen(col:byte);
 begin
   Inline($3A/col/
          $CD/$9B/$BE/
          $DE/$BB);
 end;

Procedure Plot(Xpos, Ypos : integer);
 begin
   Inline($2A/ypos/
          $ED/$5B/xpos/
          $CD/$9B/$BE/
          $EA/$BB);
 end;





{ Calculates the color for each point. }
Function ComputeColour(XPos,YPos:Integer):Byte;
Var RealP,ImagP:Real;
    CurrX,CurrY:Real;
    a2,b2:Real;
    Counter:Byte;

Begin
CurrX:=XPos/Width*(XRMax-XRMin)+XRMin;
  CurrY:=YPos/Height*(YRMax-YRMin)+YRMin;
  RealP:=0;
  ImagP:=0;
  Counter:=0;
  Repeat
    a2:=Sqr(RealP);
    b2:=Sqr(ImagP);
    ImagP:=2*RealP*ImagP+CurrY;
    RealP:=a2-b2+CurrX;
    counter:=succ(counter);
  Until (Counter>=Colours) or (a2+b2>=Limit);
  ComputeColour:=Counter-1;
End;

Procedure Setup(xpos2, ypos2, count, stop : integer);
begin
 repeat
  begin
   xpos2:=0;
   repeat
    begin
     Coldata[count]:=ComputeColour(xpos2,ypos2);
     xpos2:=xpos2+2;
     count:=succ(count);
    end;
   until (xpos2=width);
  ypos2:=ypos2-2;
  end;
 until (ypos2=stop);
end;

Begin
  mode(1);
   setup(0,400,0,298);
    save('mandel1.dat');
    gotoxy(1,1); write('Mandel 1/4 Completed');
   setup(0,298,0,198);
    save('mandel2.dat');
    gotoxy(1,2); write('Mandel 2/4 Completed');
   setup(0,198,0,098);
    save('mandel3.dat');
    gotoxy(1,3); write('Mandel 3/4 Completed');
   setup(0,098,0,0);
    save('mandel4.dat');
    gotoxy(1,4); write('Mandel 4/4 Completed');
  repeat until keypressed;
  mode(2);
End.