Creating Excel (XLS) from Delphi

const
  CXlsBof: array[0..5] of Word = ($809, 8, 00, $10, 0, 0);
  CXlsEof: array[0..1] of Word = ($0A, 00);
  CXlsLabel: array[0..5] of Word = ($204, 0, 0, 0, 0, 0);
  CXlsNumber: array[0..4] of Word = ($203, 14, 0, 0, 0);
  CXlsRk: array[0..4] of Word = ($27E, 10, 0, 0, 0);

procedure XlsBeginStream(XlsStream: TStream; const BuildNumber: Word);
begin
  CXlsBof[4] := BuildNumber;
  XlsStream.WriteBuffer(CXlsBof, SizeOf(CXlsBof));
end;

procedure XlsEndStream(XlsStream: TStream);
begin
  XlsStream.WriteBuffer(CXlsEof, SizeOf(CXlsEof));
end;

procedure XlsWriteCellRk(XlsStream: TStream; const ACol, ARow: Word; const AValue: Integer);
var
  V: Integer;
begin
  CXlsRk[2] := ARow;
  CXlsRk[3] := ACol;
  XlsStream.WriteBuffer(CXlsRk, SizeOf(CXlsRk));
  V := (AValue shl 2) or 2;
  XlsStream.WriteBuffer(V, 4);
end;

procedure XlsWriteCellNumber(XlsStream: TStream; const ACol, ARow: Word; const AValue: Double);
begin
  CXlsNumber[2] := ARow;
  CXlsNumber[3] := ACol;
  XlsStream.WriteBuffer(CXlsNumber, SizeOf(CXlsNumber));
  XlsStream.WriteBuffer(AValue, 8);
end;

procedure XlsWriteCellLabel(XlsStream: TStream; const ACol, ARow: Word; const AValue: string);
var
  L: Word;    
begin
  L := Length(AValue);
  CXlsLabel[1] := 8 + L;
  CXlsLabel[2] := ARow;
  CXlsLabel[3] := ACol;
  CXlsLabel[5] := L;
  XlsStream.WriteBuffer(CXlsLabel, SizeOf(CXlsLabel));
  XlsStream.WriteBuffer(Pointer(AValue)^, L);
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  FStream: TFileStream;
  I, J: Integer;
begin
  FStream := TFileStream.Create('J:\e.xls', fmCreate);
  try
    XlsBeginStream(FStream, 0);
    for I := 0 to 99 do
      for J := 0 to 99 do
      begin
        XlsWriteCellNumber(FStream, I, J, 34.34);
       // XlsWriteCellRk(FStream, I, J, 3434);
       // XlsWriteCellLabel(FStream, I, J, Format('Cell: %d,%d', [I, J]));
      end;
    XlsEndStream(FStream);
  finally
    FStream.Free;
  end;
end;