C++ Name space creation

                                    Namespace creation

Using namespace we can have class global variables function under one name : We can change global scope to Sub-scope.

Namespace is a container for identifiers. it puts the names of its members in a distinct space so that they don't conflict with the names in other namespaces or global namespace.

• Namespace is a logical compartment used to avoid naming collisions.

• The naming conflict or collision always Occur-

• When same program is using more than one library with some variables or functions having same name.

• The name collision may occur for global variable, global functions, classes etc.

• Default namespace is global namespace and can access global data and functions by proceeding (::) operator.

• We can create our own namespace. And naything declred within namespace has scope limited to namespace.

Creating a namespace :

• Creation of namespace is similar to creation of class.

• Namespace declartions can be nested within another namespace.

• Namespace declarations don't have access specifiers. (public or private)

• Namespace declaration appear only at global scope.

• No need to give semicolon after the closing brace of definition of namespace.

• We can split the defination of namespace over several units.

Syntax : 

Live Example : 

What is Unnamed Namespace  :

• Unnamed namespaces are the replacement for the static declaration of variables.

• In unnamed namespaces usable in the samespace in not mentioned in the declaration of namespace.

• They are directly usable in the sme program and are used for declaring unique indentifiers.

• The name of the namespace is uniquely generated by the compiler.

• The unnamed namespaces you have created will only be accessible within the file you created it in.

Output :

How to Use Name space in C++ Programming Language :

Following are the ways to refer to namespace members:

Way 1 :  Using Scope Resolution :

In this method, we use the namespace name, scope resolution operator (::) and member of that namespace.

Way 2: Using Directive: 

We can use 'using' directive to specify the namespace.

Way 3: Using declaration :

It is a declaration within the current scope. this means it can override names from a using directive.

 Output :