i have an assignment to write a string class in which the following are public methods:

iostream & hex (iostream & os);
istream & read(istream & os);
ostream & write(ostream & os);

I can easily write the second two, and know how to call them, but i'm not quite sure what i would do with the first one, or how i would call it. the read takes a istream argument (such as cin) and write takes an ostream (cout) but what would i use to access hex? This is the only info i was given. we just have the class prototype and have to implement it from that. thanks!