[angvelem]

Открываем исходники Дельфи (ValEdit.pas) и видим:

Код:

function TNumberEdit.DecToBin(aValue: LongInt): String;
var
  w: Array[1..2] of Word absolute aValue;
  St: String;

  function BinByte(b: Byte): String;
  const
    Bin: Array[False..True] of Char = '01';
  begin
    Result := Bin[b and 128 = 128] + Bin[b and 64 = 64] + Bin[b and 32 = 32] + Bin[b and 16 = 16] +
              Bin[b and 8 = 8] + Bin[b and 4 = 4] + Bin[b and 2 = 2] + Bin[b and 1 = 1];
  end;

  function BinWord(w: Word): String;
  begin
    BinWord := BinByte(Hi(w)) + BinByte(Lo(w));
  end;

begin
  St := BinWord(w[2]) + BinWord(w[1]);
  while (St[1] = '0') and (Length(St) > 1) do
   Delete(St, 1, 1);
  Result := St;
end;