Hey friends please explain me how namespace works in this below code?

Question

#include <iostream>
using namespace std;
namespace alpha{int var =1;}
namespace beta{
int var = alpha ::var +1;
}

int main() {
beta::var+=alpha::var;
{
using namespace beta;
cout<<var;

}
return 0;
}
//output is 3,

Answer 1

Namespaces are used to group entities together and to avoid naming conflicts, especially in larger code bases.

In your code, each "var" is grouped in a different namespace, thus they are different variables.
Since alpha::var is equal to 1, beta::var is 1 +1 = 2.
Now in main() you add alpha::var (1) to beta::var (2), resulting in beta::var becoming 3.
The brackets define a local scope in main(), and in this scope, you basically tell the compiler to search inside "namespace beta" whenever it is unable to identify something by "using namespace beta;".
The compiler can't find "var", so it looks inside "beta", finds "var" there, and therefore uses "beta::var" in the cout-statement.
That is why the result is 3.

Some helpful links:
https://en.cppreference.com/w/cpp/language/namespace

https://www.geeksforgeeks.org/namespace-in-c/

http://www.cplusplus.com/doc/oldtutorial/namespaces/

Answer 2

your beta namespace variable named var is equal to 2 because alpha::var equals to 1 and you sum it with 1 and assigned the value to beta::var and then in main() you sum beta::var value with alpha::var which means that beta::var==2+1==3