TMemo

Code:

procedure TForm1.Memo1Change(Sender: TObject);

const

  MaxLineCount = 5;

begin

  if Memo1.Lines.Count > MaxLineCount then

    // undo the last change

   // letze Дnderung rьckgдngig machen

   Memo1.Perform(EM_UNDO, 0, 0);

  // The EM_EMPTYUNDOBUFFER message clears the undo flag,

// which means that you can no longer undo your last change

// to the edit control.

// Die Message EM_EMPTYUNDOBUFFER lцscht das UnDo Flag,

// damit kann die letzte Дnderung nicht Rьckgдngig gemacht werden.

Memo1.Perform(EM_EMPTYUNDOBUFFER, 0, 0);

end;