• The namespace is a logical division of the code which is designed to stop the naming conflict.
• The namespace defines the scope where the identifiers such as variables, class, functions are declared.
• The main purpose of using namespace in C++ is to remove the ambiguity. Ambiquity occurs when the different task occurs with the same name.
• For example: if there are two functions exist with the same name such as add(). In order to prevent this ambiguity, the namespace is used. Functions are declared in different namespaces.
• C++ consists of a standard namespace, i.e., std which contains inbuilt classes and functions. So, by using the statement “using namespace std;” includes the namespace “std” in our program.
• Syntax of namespace:

1. namespace namespace_name  
2. {  
3.  //body of namespace;  
4. }  

Syntax of accessing the namespace variable:

1. namespace_name::member_name;  

Let’s understand this through an example:

1. #include <iostream>  
2. using namespace std;  
3. namespace addition  
4. {  
5.     int a=5;  
6.     int b=5;  
7.     int add()  
8.     {  
9.         return(a+b);  
10.     }  
11. }  
12.   
13. int main() {  
14. int result;  
15. result=addition::add();  
16. cout<<result;  
17. return 0;  
18. }  

Output:

10