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Some help about C++ why we use in program using nanamespace std;?

why we use in program using nanamespace std;
plz anybody explain in simple detail

Posted 40 days ago

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Answers (4)

SkyWalker 		The true form of cout, cin and various other standard commands in C++ is
std::cout
std::cin

By having the
using namespace std
you can use
cin
cout

Have fun.

40 days ago

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answergal 		When you use simple functions such as cout, cin and all those similar functions, they are all stored in iostream under the namespace std. By writing using namespace std;, you can import the contents of the namespace std into the current file, without having to call them. Example: without using namespace std: std::cout << "hello";
with using namespace std::cout << "hello";
it just makes it easier and is not needed.

40 days ago

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PartyintheUSA 		if we write #include<iostream>
it means, we must have declare its functions that are we going to use in our program.
as std::cout, std::cin, std::endl etc.

and if we don't want to declare function like this, we use "using namespace std". This line declares the functions are given above.
But Most easy way is , write your preprocessing header file like this.
#include<iostream.h>
in this way, you do not need to write using namespace std and std::cout, std::cin, std::endl . you will be able to use all the functions of <iostream.h>

Hope you understand !

Just try it.

40 days ago

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PartyintheUSA 		Hi,

The functions like cout and endl are inside namespace std. To understand what that means, have a look at this simple example:

#include <iostream>

namespace temp{
void func();
}

void temp::func(){}

int main(){
// func(); // compile error
temp::func();
return 0;
}

In the above program, the function func() is defined inside a namespace called temp, so in order to call it, you need to do temp::func(). There is one more way to do it and that is by including the namespace in the global namespace area like this:

int main(){
using namespace temp;
func();
return 0;
}

This will also work fine.

Varun

40 days ago

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