<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def getch(self):
 """ Get a single character and advance the scan pointer. 'a' 'b' 'c' 3 """

        self.pos += 1
        return self.string[self.pos - 1:self.pos]