Why do we use the using directive in C

What is the purpose of the using directive?

The using directive allows you to abbreviate a type name by omitting the namespace portion of the name—such that just the type name can be specified for any type within the stated namespace.

What is using directive in namespace?

A using directive provides access to all namespace qualifiers and the scope operator. This is accomplished by applying the using keyword to a namespace identifier. The name must be a previously defined namespace. The using directive may be applied at the global and local scope but not the class scope.

Do not use namespace using directives?

Namespace usings are for your convenience, not for you to inflict on others: Never write a using declaration or a using directive before an #include directive. Corollary: In header files, don't write namespace-level using directives or using declarations; instead, explicitly namespace-qualify all names.

Why using should be inside namespace?

Putting it inside the namespaces makes the declarations local to that namespace for the file (in case you have multiple namespaces in the file) but if you only have one namespace per file then it doesn't make much of a difference whether they go outside or inside the namespace.