• How to declare

namespace myspace {
    int var = 10; 
}

int main(){
   int var = 4;
   cout << var << endl;
   cout << myspace::var << endl;
}

• We can create classes in namespace
• We can use same namespace more than once. It is like extending the namespace
• We can create unnamed namespace => it replaces static declaration of variables. Compilers generates the unique name for it.
• we can access it using “using” directives e.g – using namespace myspace;
• We can create nested namespace
• We can provide alias – namespace new_name = myspace::inner;

namespace {
    int var_in_unnamed_ns = 10;
}
namespace myspace {
    int var = 10; 
    int value() { return 5 + var;}
    class cls_in_ns {
       public:
          void display(){
              cout << "class is in namespace" << endl;
          } 
    }
    nmespace innner {
        int in_inner = 20;
    }
}

int main(){
   int var = 4;
   cout << var << endl;
   cout << myspace::var << endl;
   cout << myspace::value() << endl;
   
   cout << var_in_unnamed_ns << endl; 
   myspace::cls_in_ns obj;
   obj.display();
   return 0;
}