Namespace mechanism Guide, Meaning , Facts, Information and Description

A namespace, in the context of computer programming, refers to the concept of the name of a construct, variable or constant, and within which scopes it is visible.

Example:

class Chicken () : public Bird {
 public:
   int   nWings = 2;
   int   nLegs = 2;
   int   bFlight = FALSE;
   void  Cluck () {}
}

class Hen () : public Chicken {
 public:
   void  LayEggs () {}
}

class Cock () : public Chicken {
 public:
   void  Cockadoodledoo () {}
}

void main () {
   Chicken* pClucker;   // Chicken pointers can be used with Chickens, Hens and Cocks
   pClucker = new Hen;  // create a Hen

// The functions Cockadoodledoo (), Cluck (), and LayEggs () are not available at this scope.  
// They are within a different namespace.

   Cluck ();    // This function call will fail, there is no Cluck () in this namespace.
   LayEggs ();  // This function call will fail, there is no LayEggs () in this namespace.

// These function calls will succeed, because they are being called within a different namespace.

   pClucker -> Cluck ();    // you can call a Chicken function through a Chicken pointer
   pClucker -> LayEggs ();  // you can call a Hen function through a Chicken pointer

// If we define Cluck () outside the context of a Chicken...

   void Cluck () {}

// ...this function call will now succeed.

   Cluck ();

// Note that these two function calls...

   pClucker -> Cluck ();    
   Cluck ();

// Now do two different things, because they are being called from different namespaces; 
// the Chicken namespace, and the main () namespace.

}

(This example may have confused the concept of "scope" with the concept of "namespace". Please adjust accordingly.)

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