C++ Namespaces

by Online Tutorials Library July 14, 2022

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:

Hello First Namespace

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