C++ Namespace

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.

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C++ namespace Example

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

1. #include <iostream>  
2. using namespace std;  
3. namespace First {    
4.     void sayHello() {   
5.         cout<<"Hello First Namespace"<<endl;          
6.     }    
7. }    
8. namespace Second  {    
9.        void sayHello() {   
10.            cout<<"Hello Second Namespace"<<endl;   
11.        }    
12. }   
13. int main()  
14. {  
15.  First::sayHello();  
16.  Second::sayHello();  
17. return 0;  
18. }  

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.

1. #include <iostream>  
2. using namespace std;  
3. namespace First{  
4.    void sayHello(){  
5.       cout << "Hello First Namespace" << endl;  
6.    }  
7. }  
8. namespace Second{  
9.    void sayHello(){  
10.       cout << "Hello Second Namespace" << endl;  
11.    }  
12. }  
13. using namespace First;  
14. int main () {  
15.    sayHello();  
16.    return 0;  
17. }  

Output:

Hello First Namespace	

Anurag Rana