uses crt;
type
  ta = object
    error: ^string;

    constructor init(st: string);
    procedure print; virtual;
  end;
constructor ta.init;
begin new(error); error^ := st; end;
procedure ta.print;
begin writeln('TA object') end;

procedure proc(var obj: ta);
begin
  writeln('error = ', obj.error^);
  obj.print;
end;

type
  ta2 = object(ta)
    constructor init(st: string);
    procedure print; virtual;
  end;
constructor ta2.init;
begin inherited init(st) end;
procedure ta2.print;
begin writeln('TA2 object') end;

type
  tb = object(ta2)
    constructor init(st: string);
    procedure print; virtual;
  end;
constructor tb.init;
begin {inherited init(st);} end;
procedure tb.print;
begin writeln('TB object') end;

var
  A: ta;
  B: ta2;
  c: tb;
begin
  clrscr;
  a.init('no error'); proc(a);
  b.init('no error'); proc(b);
  c.init('no error'); proc(c);
end.