internal char ScanControl()
{
char ch;
if (CharsRight() <= 0)
throw MakeException(SR.MissingControl);
ch = MoveRightGetChar();
// \ca interpreted as \cA
if (ch >= 'a' && ch <= 'z')
ch = (char)(ch - ('a' - 'A'));
if ((ch = (char)(ch - '@')) < ' ')
return ch;
throw MakeException(SR.UnrecognizedControl);
}