Input/Output with files:

C++ provides the following classes to perform output and input of characters to/from files:

ofstream: Stream class to write on files
ifstream: Stream class to read from files
fstream: Stream class to both read and write from/to files.
These classes are derived directly or indirectly from the classes istream, and ostream. We have already used objects whose types were these classes: cin is an object of class istream and cout is an object of class ostream. Therfore, we have already been using classes that are related to our file streams. And in fact, we can use our file streams the same way we are already used to use cin and cout, with the only difference that we have to associate these streams with physical files. Let's see an example:

I agree with you...
you have given the header file
#include <iostream>
#include <fstream>
using namespace std;

here we can give the header file like that also:
#include<iostram>
#include<ifstream>
#include<ofstream>
using namespace std;