Function DecToBin(DecNum: integer): String;
var
  BinStr: String;
begin
  BinStr := '';
  While DecNum <> 0 do
  begin
    If ((DecNum Mod 2) = 1) Then
      BinStr := '1' + BinStr
    Else
      BinStr := '0' + BinStr;
    DecNum := DecNum div 2;
  end;
  If BinStr = '' Then BinStr := '0000';
  setlength(result, length(BinStr));
  result := BinStr;
end;