How is the usage of “using” in C++?

In C++, the keyword “using” has two different uses.

1. To use namespace aliases: using namespace ;
   This method imports the name of the namespace into the current scope, allowing direct access to the members of the namespace without needing to use qualifiers. For example:
2. Use the standard namespace:
   std::cout << "Hello, world!" << std::endl;
3. This allows for using cout and endl from the std namespace directly without having to write std::cout and std::endl.
4. Syntax for type alias: using = ;
   This usage specifies a type to be defined as an alias, so that in the program, this alias can be used instead of the original type. For example:
5. Declare a new variable ‘num’ of type ‘int’ with a value of 10.
6. This defines myInt as an alias for int, allowing it to be used in place of int in the program.

Note: using statements should be used outside of functions or within namespaces, not inside functions. Be careful when using using namespace aliases to avoid naming conflicts and unnecessary namespace imports. It is best practice to use qualifiers only where needed to improve code readability and maintainability.