using namespace in C++ Sample code

Here I am going to present a short example of using namespaces in C++.
There are three files named

1. a.h
2. b.h
3. namespace.cpp

copy all the three files using your editor and compile the code as shown in example below.
--------------

/*

 * a.h

 */

 #include <iostream>

 namespace A {

    using namespace std;

    void f() {

       cout << "f from A\n";

    }

    void g() {

       cout << "g from A\n";

    }

 }

--------------

/*

 * b.h

 */

 #include <iostream>

 namespace B {

    using namespace std;

    void f() {

       cout << "f from B\n";

    }

    void g() {

       cout << "g from B\n";

    }

 }

--------------

/*

 * namespace.cpp

 */

 #include "a.h"

 #include "b.h"

 #include <iostream>

 int main() {

    A::f();

    B::g();

    return 0;

 }

/*

 [sgupta@rhel55x86 namespaces]$ c++ -o namespace namespace.cpp

 [sgupta@rhel55x86 namespaces]$ ./namespace

 f from A

 g from B

 [sgupta@rhel55x86 namespaces]$

*/