Step 4 Brief Discussion:
C++ introduced the concept of
namespace, to avoid name conflicts that could surface in an
application created as a group effort or importing source codes from
another file. With the help of namespace, the name of the variable
could reused without loosing it's properties.
As C++ won't allow to duplicate variable names, and that can
become as issue when using external or remote applications. The same
name in the above scenario, would generate runtime errors. The
namespace with resolution operator can resolve such issues and reuse
same vocabularies over and again.
As shown in the above example, int n1 was common in two modules,
but namespace with resolution operator you can handles those two
variables without causing any conflicts.