Program Sine;
{This program creates a sample file for the plotting programs.}

Var
  File_var:    Text;
  I:           Integer;
  J:           Integer;
  Scale:       Real;
  Sine_point:  Real;

Begin
  Assign(File_var, 'Sinc.dat');
  Rewrite(File_var);
  Scale := 2.0 * pi / 20.0;
  Writeln(File_var, 41); {number of lines in the data}
  Writeln(File_var, 41); {number of points in each line}
  For I:=-20 to 20 do
  For J:=-20 to 20 do
  Begin
    Sine_point := Sqrt(Sqr(1.0*I) + Sqr(1.0*J))*Scale;
    If Abs(Sine_point) < 0.0000001 then
      Writeln(File_var, 1.0)
    Else
      Writeln(File_var, Sqr(Sin(Sine_point)/Sine_point));
  End;
  Close(File_var);
End.