In older versions of Delphi, like D7, you could do like
ord(s[i]) where s was a string, but trying this with an AnsiString results in an exception (access violation).
P.S. I was w/delphi 7 for a long time.
Here are the steps to reproduce the error:
Create a new project and through a memo on the form (let it be memo1) than add the following code to the form create event handler:
procedure TForm1.FormCreate(Sender: TObject);
var u: ansistring;
u := 'stringtest';
For me this code produces an AV.