Thread: cout vs std::cout

Hi everyone.

I'm new to C++ so excuse the question. I've seen some source file that uses std::cout insted of just using cout to output text. why is that and what is the difference?

example

cout << "C++";

or

std::cout << "C++";

So when should I use the second form insted of the first and what does the second mean actually.

Thanks in advance.

The std:: is the namespace that cout is in. So for example if you include iostream.h the cout function is not in the namespace std so just use cout<< but if you include iostream (recommended)...then you need to put the std::

#include <iostream.h>

cout<<

#include <iostream>

std::cout<<

however, if you include iostream and not iostream.h I would recomment putting:
using namespace std; right under it. That way you don't have to keep putting std:: before it.

for example,

#include <iostream>

using namespace std;

void main()
{
cout<<"hi";
}

Paul Marshall

Thanks for the explanation ... it was very nice and clear.

Now isn't the difference between #include <iostream.h> and #include <iostream> is only about the ANSI standards or am I wrong. I mean using iostream conforms to the standards while using iostream.h does not. If I'm right then is there a way to use #include <iostream> without using any namespaces?

just wanting to know how things work and not trying to act smart.

Thanks again.

The statement 'using namespace std;' for all intents and purposes, removes the namespace. What it does is put every included symbol in the std namespace into the global namespace, just as the example in the first post. I would recommend against doing that, however, for exactly that reason: you really pollute the global namespace.

[The statement 'using namespace std;' for all intents and purposes, removes the namespace]

I thought this statement indicates that you want to use the std namespace? but you're saying that it removes the namespace?!

anyway, I think i should read more about namespace in c++ and then things will be clear to me.

Thanks anyway.

It doesn't put everything into the std namespace. Instead, it puts everything in the std namespace into the global namespace (that is, the default namespace which is equivalent to no namespace).

Prog-bman's code is better because it won't pollute the global namespace, with things you don't want or know about. (That is, an identifier may be used only once per namespace, so, for example, if you defined a function with the same name as one in the std namespace and included the appropriate header for that function, you would have an error if you had simply used 'using namespace std;'. If you had not used the all-inclusive using statement and had not explicitly imported that function into the global namespace, there would be no error.)

Originally Posted by Sang-drax

That could've been a nice explanation, if it weren't for a little malplaced four-letter word.

to expand on this very good comment by Sang-drax that everyone ignored, DONT USE VOID MAIN, use int main

Thanks guys ... I can't say I understood everything fully but thats only cos I'm new to C++ ... anyway its very nice to see that people are willing to help when i get stuck on my learning curve ...

Thanks again for the effort.