Автор: PILOTIK
WEB-сайт: http://forum.vingrad.ru

procedure TForm1.Button1Click(Sender: TObject);
type
  AnyType = byte;
var
  F: file of AnyType;
const
  FName = 'D:/Exp.exe';
begin
  begin
    AssignFile(F, FName); { File selected in dialog }
    FileMode := fmOpenRead;
    Reset(F);
    // ...
    // ...
    CloseFile(F);
    FileMode := fmOpenReadWrite;
  end;
end;