To allow users to Select All text in a memo or edit component by pressing
[Ctrl]A, set the form's KeyPreview property to True and add the following
handler to the form's OnKeyPress event:

     procedure TMyForm.FormKeyPress(Sender: TObject; var Key: Char); begin
     if (ActiveControl is TCustomEdit) and (Key=#1) then
     begin (ActiveControl as TCustomEdit).SelectAll; Key:=#0; end
     end;

The Key:=#0 statement suppresses the annoying beep that occurs when
non-text characters are entered.