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C++ Namespaces



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Namespace in C++, is designed to overcome that type of difficulty where there is similar functions, variables, or classes, etc available in a C++ program, then namespace is used as additional information to differentiate those similar functions, classes, variables etc.

C++ Namespace Definition

Here is the general form to define a namespace in C++:

namespace namespace_name
{
   // declaration codes
}

Here is the general form to call a namespace in C++:

name::code;

Here, code represents the variable/function

C++ Namespace Example

Here are some example program using namespace in C++

/* C++ Namespace - Example Program */

#include<iostream.h>
#include<conio.h>
using namespace std;
namespace first_namespace
{
   void fun1()
   {
      cout<<"Inside first_namespace\n";
   }
}
namespace second_namespace
{
   void fun2()
   {
      cout<<"Inside second_namespace\n";
   }
}
void main()
{
   clrscr();
   first_namespace::fun1();
   second_namespace::fun2();
   getch();
}

Here is the output of the above C++ program:

Inside first_space
Inside second_space

Here is another example program, also demonstrating namespace in C++

/* C++ Namespace - Example Program */

#include<iostream.h>
#include<conio.h>
using namespace std;
namespace first_namespace
{
   void fun()
   {
      cout<<"Inside first_namespace\n";
   }
}
namespace second_namespace
{
   void fun()
   {
      cout<<"Inside second_namespace\n";
   }
}
using namespace first_namespace;
void main()
{
   clrscr();
   fun();      // calls function from first namespace
   getch();
}

Here is the sample output of this C++ program:

Inside first_namespace

Below is one more example program, illustrating namespace in C++

/* C++ Namespace - Example Program */

#include<iostream.h>
#include<conio.h>
using std::cout;
void main()
{
   clrscr();
   cout<<"std::endl is used with std"<<std::endl;
   getch();
}

Following is the sample output of the above C++ program:

std::endl is used with std

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