Detailed Explanation of Namespaces in C++

Namespaces in C++ are used to organize an excessive number of classes for easier handling of applications.

To access classes within a namespace, we need to use namespacename::classname. We can also use the using keyword, so we don’t have to keep using the full name.

In C++, the global namespace is the root namespace. global::std always refers to the std namespace of the C++ framework.

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C++ Namespace Example

Let’s look at a simple example of a namespace that contains variables 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: Using Keyword

Let’s look at another example of a namespace where we used the using keyword, so we don’t have to use the full name to access the program within the namespace.

#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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