C++ Namespaces

Namespaces in C++ are used to organize too many classes so that it can be easy to handle the application.

For accessing the class of a namespace, we need to use namespacename::classname. We can use using keyword so that we don't have to use complete name all the time.

In C++, global namespace is the root namespace. The global::std will always refer to the namespace "std" of C++ Framework.

C++ namespace Example

Let's see the simple example of namespace which include variable and functions.

#include <iostream>
using namespace std;
namespace First {  
    void sayHello() { 
        cout<<"Hello First Namespace"<<endl;        
    }  
}  
namespace Second  {  
       void sayHello() { 
           cout<<"Hello Second Namespace"<<endl; 
       }  
} 
int main()
{
 First::sayHello();
 Second::sayHello();
return 0;
}

Output:

Hello First Namespace
Hello Second Namespace

C++ namespace example: by using keyword

Let's see another example of namespace where we are using "using" keyword so that we don't have to use complete name for accessing a namespace program.

#include <iostream>
using namespace std;
namespace First{
   void sayHello(){
      cout << "Hello First Namespace" << endl;
   }
}
namespace Second{
   void sayHello(){
      cout << "Hello Second Namespace" << endl;
   }
}
using namespace First;
int main () {
   sayHello();
   return 0;
}

Output: