title: In simple terms, what is the purpose of flush() in ostream
body: <p>By definition taken from: <a href="http://www.cplusplus.com/reference/iostream/ostream/flush/" rel="noreferrer">http://www.cplusplus.com/reference/iostream/ostream/flush/</a> , it is not clear why the function exists, and for what purpose you would use it for. Why not call flush(), every time your write to the stream?  </p>