What are qualified-id/name and unqualified-id/name?

Question

I was wondering if someone could explain there terms since I encounter them in many places. I know some basic theory about them but not sure what I know is right or wrong.

Answer 1

A qualified name is one that specifies a scope.
Consider the following sample program, the references to cout and endl are qualified names:

#include 

int main()  
{
   std::cout<<"Hello world!"<

Notice that the use of cout and endl began with std::. These make them Qualified names.

If we brought cout and endl into scope by a using declaration or directive*(such as using namespace std;), and used just cout and endl just by themselves , they would have been unqualified names, because they would lack the std::.