C++ library

Question

in C++, what is the difference between #include and using namespace

Answer 1

Hey ,

#include : the name itself defines its includes preprocessor directive that causes the named file.

for example :

include <iostream>

all C++ programs Begin with a #include directive that includes the specified header file contents into main program

The #include<iostream> preprocessor to add the content of the iostream file to the program.

there are Hundreds of headed files in C++.
I would list some of them

1. <cctype>
2.<cmath>
3.<cstdio>
4.<cstdlib>
5.<cstring>

and lot more

coming to namespace
Namespace defines scope for the identifiers that are uses in a program.
The best example for namespace is

using namespace std;

This tell to compiler that the members defined std namespace will be used frequently throughout the program.

We can define our own namespace in our program

example :

namespace name
{

void fun(){};
//code ;

}

int main ()

{
name:: fun(); //calls the fun function
}

Answer 2

namespaces are generally used to avoid name duplication of method , class, variable, function etc. for example different namespaces may contain varibale same variable name. so simply it is just used for logical separation. now include is just keyword in c to show that we are including definitions from other file.. in c++ we have using keyword for the same purpose but it need namespaces name instead of file name..