Two line do the same but are different (cout). Why?

Could you help me out understand the correct way to write c++?

I have 2 hello world examples:

Example 1:

Code:

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#include <iostream>

int main (int argc, char * const argv[]) {
    // insert code here...
    cout << "Hello, World!\n";
    return 0;
}

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Example 2:

Code:

---

#include <iostream>
using namespace std;
 
int main ()
{
  cout << "Hello World!";
  return 0;
}

---

They both do the same obviously but should it be done one way or the other or it doesn't matter (please explain way).

Quote:

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Originally Posted by kotoko

They both do the same obviously but should it be done one way or the other or it doesn't matter (please explain way).

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It is not obvious that they do the same thing. The first program should not compile since the name cout is used, but has not been declared. The second program should compile, as cout refers to std::cout by virtue of the using directive using namespace std;.

Hmm, I said they do the same thing because I was able to run them both and got the same output :S

Considering that you should not even be able to compile the first program, I find that hard to believe.