How to convert a string or a character to its binary representation

are you going to be using unicode in the future ?
every character may consist of 1, 2 or 4 bytes ... :)

just so you know what your possible next challenge is ...

your fillnibles function doesn't work ... it's not formatting correctly

anynumber mod 4 only gives 0,1,2 or 3 as result, never 25 or 50

ow forget, add

uses StrUtils;

Hi Geert. Thanks for your reply.

First, thank for your note about FillNibbles function. I tested in my program and it add the correct num,ber of zeros, but I see you're right about the result of anynumber mod 4. So I could change my function replacing 75, 50 and 25 with 3, 2 and 1... but your function is more elegant, I see this :-)

About your first comment, are you saying that binary representation is different depending on character set (ASCII vs Unicode)? But what I wish is to know which is the logic of the conversion: to convert an integer number to its binary code you can use the divide by two algorithm. I wish to know if there is something equivalent to convert string...

Well, I would like to understand the logic behind this: http://easycalculation.com/ascii-hex.php. I wish only the logic so I can develop a convertion function by my self - and then ask to Geert where is the error ;-)

Thanks

Ok, I found the solution and I post it here if some other is crazy enough to make this type of question.

Effectively using the program hosted in the site I linked above, we can see this:  char 'k' (lowercase) result in this binary string: 0110 1011 - that is the result of a division-by-two iterated on the ASCII value for the 'k' char, 107.

107     odd       -> 1  L.O.
  53,... odd       -> 1
  26,... even     -> 0      
  13,... odd       -> 1
    6,... even     -> 0
    3,... odd       -> 1
    1,... odd       -> 1
    0,...  is zero -> 0  H.O

that is 0110 1011


Dear Geert, this is the second time you try to help me and I would like to award points to you since your comment, not being the solution to my problem, has solved another problem I ignored! I think to have to accept my answer as solution without points and I could post another question about formatting conversion result in order to award you well deserved points. Do you agree with this?

Ah, I forgot... In the ASCII table here http://easycalculation.com/ascii-hex.php what are the first two rows? What are NUL, SOH, STX, ETX, EOT,      ENQ,      ACK... and so on? Can you tell me a resource about this? Thanks a lot :-)

I post here the full code. Simply add to the form 2 Tedit, a TMemo and 2 TButton: the program is simple so I think no other explanation is needed.

procedure TForm1.btnMyInt2BinClick(Sender: TObject);
var
  s: string;
begin
  {se ci sono caratteri numerici e alfabetici raise an error
   se ci sono solo numeri vanno trattati come un Intero
   altrimenti usare la tabella ASCII}
  mmo2.Lines.Clear;
  s := MyIntToBin(StrToInt(edtInt.Text));
//  s := MakeReadable(s);
  mmo2.Lines.Add(s);
end;

function TForm1.FillNibbles(s: string): string;
var
  n: Integer;
begin
  n := Length(s) mod 4;
  if n <> 0 then
    Result := DupeString('0', 4-n) + s
  else
    Result := s;
end;

function TForm1.MakeReadable(s: string): string;
var
  i, counter: Integer;
begin
  Result := '';
  counter := 1;
  for i := Length(s) downto 1 do
  begin
    if counter < 4 then
    begin
      Result := s[i] + Result;
      Inc(counter);
    end
    else
    begin
      Result := s[i] + Result;
      if i > 1 then
        Result := ' '+ Result;
      counter := 1;
    end;
  end;
end;

function TForm1.MyIntToBin(n: LongInt; Fill: Boolean = True): string;
var
  t, r: Integer;
  s: string;
begin
  s := '';
  t := n;
  repeat
    if (t mod 2) = 0 then
      s := '0' + s
    else
      s := '1' + s;
    t := t div 2;
  until t = 0;
  if Fill then
    s := FillNibbles(s);
  Result := s;
end;

procedure TForm1.btnString2BinClick(Sender: TObject);
var
  c: Char;
  i, val: Integer;
  s: string;
begin
  for i := Length(edtInt.Text) downto 1 do
  begin
    c := edtInt.Text[i];
    val := Ord(c);
    s := MyIntToBin(val) + s;
    if i > 1 then
      s := ' ' + s;
  end;
//  s := MakeReadable(s);
  mmo2.Lines.Add(s);
end;


function TForm1.MyBinToInt(v: string): LongInt;
var
  i, r, p: Integer;
begin
  Result := 0;
  p := 0;
  for i := Length(Trim(v)) downto 1 do
  begin
    r := Round(StrToInt(v[i]) * Power(2, p));
    Inc(p);
    Result := Result + r ;
  end;
end;

procedure TForm1.btnMyBin2IntClick(Sender: TObject);
var
  i: LongInt;
begin
  i := MyBinToInt(mmo2.Text);
  edtMyBin2Int.Text := IntToStr(i);
end;

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The question now is: hot to convert the binary string to the original text string? Any idea?

I think I can try to convert binary strings to their Integer value and get the correspondent char using Chr function, I don't?

Done: binary to string is accomlished this way:

 

procedure TForm1.btnBin2StringClick(Sender: TObject);
var
  i: Integer;
  s: string;
  c: Char;
  sl: TStringList;
begin
  mmo2.Clear;
  sl := TStringList.Create;
  try
    Split(' ', mmo2.Text, sl);
    for i := 0 to Pred(sl.Count) do
    begin
      c := Chr(MyBinToInt(sl[i]));
      s := s + c;
    end;
  finally
    sl.Free;
  end;
  edtMyBin2Int.Text := s;
end;

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Obviously, you have to change components names accordingly to yours.

Cheers

A note about FillNibbles function: you was totally right, of course. I tested nothing: simply, my code always added a zero! :-(

Hi Geert. Thank you very mutch for your help. I decided to award you points because your comment has been very useful. Even if it is not the solution, I think wee have not to be too slavess to burocracy logic and close this question to open another one only to give point.
Hope what I mean be clear enough, since my english is not so good.
Thank you.