def sendcontrol(self, char):
        '''Helper method that wraps send() with mnemonic access for sending control
        character to the child (such as Ctrl-C or Ctrl-D).  For example, to send
        Ctrl-G (ASCII 7, bell, '\a')::

            child.sendcontrol('g')

        See also, sendintr() and sendeof().
        '''
        char = char.lower()
        a = ord(char)
        if 97 <= a <= 122:
            a = a - ord('a') + 1
            byte = _byte(a)
            return self._writeb(byte), byte
        d = {'@': 0, '`': 0,
            '[': 27, '{': 27,
            '\\': 28, '|': 28,
            ']': 29, '}': 29,
            '^': 30, '~': 30,
            '_': 31,
            '?': 127}
        if char not in d:
            return 0, b''

        byte = _byte(d[char])
        return self._writeb(byte), byte