title: Why 'ifstream' and 'ofstream' are added to "std", while 'fstream' can serve both the purposes?
body: <p>Using  <code>std::fstream</code> one can declare objects of both the types <code>ifstream</code> and <code>ofstream</code>. The only difference is that, with <code>fstream</code> we need to provide <code>in</code>, <code>out</code>, <code>app</code> as a parameter which may not always require for other two.</p>
  
  <p>Is there anything special about <code>ifstream,ofstream</code> which cannot be accomplished with <code>fstream</code> or just a coding convenience ?</p>