streambuf            Low Level I/O Stream


            The streambuf class makes up the lowest base class in the I/O
    class library. This class is an unformatted I/O stream, and the next
    level up, ios class, has a pointer to this class. The streambuf class
    provides the methods for using the actual memory buffers that C++ uses.
    The other I/O classes are derived from this one.