Hi:

I have a very primitive question on C++.
If I want include a library I use #include

say, #include <iostream> , iostream header file all I/O functions are declared.

But Including a Standard C++ header does not introduce any library names into the current namespace. For that we have to use

using namespace std;

What does this mean? Does it mean in namespace std all the functions in standard library files are defined and that's why we need that?