<bitset>

namespace std {
template<size_t N>
    class bitset;
//    TEMPLATE FUNCTIONS
template<class E, class T, size_t N>
    basic_istream<E, T>& operator>>(basic_istream<E, T>& is,
        bitset<N>& x);
template<class E, class T, size_t N>
    basic_ostream<E, T>& operator<<(basic_ostream<E, T>& os,
        const bitset<N>& x);
    };

Include the standard header <bitset> to define the template class bitset and two supporting templates.