Thread: namespace std

Why do people use namespace std for iostream functions if it's included in the header?

That sentance made no sense what so ever.

The namespace std includes most of your standard C++ I/O functions, and there 'using namespace std;' is typed early on in a program. This is of course down to personal taste - some prefer to use std::cout etc to show cout is a member of the std namespace.

Here's an example of using the namespace:

Code:

//Division Program
//An example of using namespace
#include <iostream>

using namespace std; //if you include this, you DONT have to put std:: before cout,cin, and endl

int main()
{    
    int num1, num2, quotient;
    cout << "Enter your first whole number:";
    cin >> num1;
    cout << "Enter your second whole number:";
    cin >> num2;
    quotient=num1/num2;
    cout << "Your quotient is " << quotient << endl;
    cin.ignore();
    cin.get();
    return 0;
}

The same example without using the namespace:

Code:

//Division Program

#include <iostream>

//Since there is no namespace, you must put std:: before cout & cin, and endl

int main()
{    
    int num1, num2, quotient;
    std::cout << "Enter your first whole number:";
    std::cin >> num1;
    std::cout << "Enter your second whole number:";
    std::cin >> num2;
    quotient=num1/num2;
    std::cout << "Your quotient is " << quotient << std::endl;
    std::cin.ignore();
    std::cin.get();
    return 0;
}

#include <iostream.h> -> Wrong! iostream.h is a deprecated header and is no longer standard.

void main() -> Very wrong! void main has never ever been standard, main must always return an int!

You use it now but when you move to a newer compiler that is more standard compliant all your code is wrong and you need to rewrite it because you are too lazy to follow the current standard. And those websites that uses those are old, outdated and in general not good learning resources.

And no no no no no no no NO NOOOOO!!!!!!!!! main always alwayas ALWAYS returns an int!!!!!

But ffs!!! this is perfectly valid C++ code:

Code:

#include <iostream>

int main()
{
    std::cout << "Some people just dont get it...main always returns an int!" << std::endl;
}

and so is this:

Code:

#include <iostream>

int main()
{
    std::cout << "Again some people just dont get it...main must always return an int!" << std::endl;
    return 0;
}

Ok listen to me..if you are so stupid that you dont follow my corrections even after posting about it several times. especially since I have been here for almost 2 years now then I wont tell you any more! Just dont post any source here where you use void main because that will be the first thing people tell you until you change it! And why bother posting here if you cant take advices from those who knows better?

Well apart from your compiler being one of the worst when it comes to standard compliance nowadays it also has a crappy and buggy implementation of STL and C++ string class.

Actually you dont have to buy a compiler, a compiler that is considered to be one of the best out there is MingW, do a search for Bloodshed DevC++ on google and you will get a very good IDE together with a very good compiler.