A: It is fairly simple. 
Study this example source code, with the
manual, if need be.
  uses Crt;
  var password : string;
  {}
  (* Read without echoing *)
  procedure GETPASS (var s : string);
  var key : integer;
      ch : char;
  begin
    s := '';
    repeat
      ch := ReadKey; key := ord (ch);
      case key of
         0 : ch := ReadKey;  (* Discard two-character keys, like F1 *)
        13 : exit;           (* Enter has been pressed *)
        1..12,13..31,255 :;  (* Discard the special characters *)
        else s := s + ch;
      end;
   until false;
  end;  (* getpass *)
  {}
  (* The main program *)
  begin
    write ('Password: ');
    GETPASS (password);
    writeln;
    writeln (password);
  end.
  {}
If you wish to be able to edit the input stream, like having the
BackSpace functional, that is more complicated, and is left as an
exercise after these basics. A hint: 8 : Delete (s, Length(s), 1);
   There is another approach to this problem pointed out by Colin
Lamond colin@sound.demon.co.uk. Quite innovative in its 
simplicity
once one comes to think of it. "Set the textcolor, and the
textbackground to the same color, and so the typed text can not be
seen on the screen."