using std::cout

[Roger]

Hello, I'm pretty new to C++ programming, and I'm teaching myself the
language using various sources.

This sounds stupid, but I am really confused on this... I was
wondering why we have to write a C++ program with this:

#include <iostream>
using std::cout;
using std::endl;

int main() {
cout << "hello, world" << endl;
return 0;
}

or like this:

#include <iostream>

int main() {
std::cout << "hello, world" << std::endl;
return 0;
}
Why can't we just write it like this? :

#include <iostream>

int main() {
cout << "Hello, World << endl;
return 0;
}

My compiler, VC++ 2005 Express does not seem to compile the last chunk
of code. Why do we need std? I just need someone to clear up some
confusion. Hehe.

[Robert Bauck Hamar]

Roger wrote:

Hello, I'm pretty new to C++ programming, and I'm teaching myself the
language using various sources.

This sounds stupid, but I am really confused on this... I was
wondering why we have to write a C++ program with this:

#include <iostream>
using std::cout;
using std::endl;

int main() {
cout << "hello, world" << endl;
return 0;
}

or like this:

#include <iostream>

int main() {
std::cout << "hello, world" << std::endl;
return 0;
}
Why can't we just write it like this? :

#include <iostream>

int main() {
cout << "Hello, World << endl;
return 0;
}

My compiler, VC++ 2005 Express does not seem to compile the last chunk
of code. Why do we need std? I just need someone to clear up some
confusion. Hehe.

std is a namespace. Namespaces exist to prevent names from accidentally
clash with each other. Imagine you work on a project with someone else, and
both you and your colleague define a function named 'doWhatIWant'. If now
you and your colleague define the name in different namespaces, this would
not be a problem. As the standard library contains a lot of names, it
defines most of them in the namespace std.

A note: I think

#include <iostream>
int main() {
std::cout << "Hello, World\n";
return 0;
}

is better. std::endl just sends a newline character to the stream, and then
flushes it.

--
rbh

[Roger]

On Aug 16, 3:34 pm, Robert Bauck Hamar <[e-mail]>
wrote:

Roger wrote:

Hello, I'm pretty new to C++ programming, and I'm teaching myself the
language using various sources.

This sounds stupid, but I am really confused on this... I was
wondering why we have to write a C++ program with this:

#include <iostream>
using std::cout;
using std::endl;

int main() {
cout << "hello, world" << endl;
return 0;
}

or like this:

#include <iostream>

int main() {
std::cout << "hello, world" << std::endl;
return 0;
}

Why can't we just write it like this? :

#include <iostream>

int main() {
cout << "Hello, World << endl;
return 0;
}

My compiler, VC++ 2005 Express does not seem to compile the last chunk
of code. Why do we need std? I just need someone to clear up some
confusion. Hehe.

std is a namespace. Namespaces exist to prevent names from accidentally
clash with each other. Imagine you work on a project with someone else, and
both you and your colleague define a function named 'doWhatIWant'. If now
you and your colleague define the name in different namespaces, this would
not be a problem. As the standard library contains a lot of names, it
defines most of them in the namespace std.

A note: I think

#include <iostream>
int main() {
std::cout << "Hello, World\n";
return 0;

}

is better. std::endl just sends a newline character to the stream, and then
flushes it.

--
rbh

So by defining it after the #include <iostream>, I won't have to use
std::cout?

[kamistrike]

So by defining it after the #include <iostream>, I won't have to use
std::cout?

Yes.
You could also, write "using namespace std", to register the complete
namespace.

#include <iostream>
using namespace std;

int main() {
cout << "hello, world" << endl;
return 0;
}

[Roger]

On Aug 16, 5:28 pm, [e-mail] wrote:

So by defining it after the #include <iostream>, I won't have to use
std::cout?

Yes.
You could also, write "using namespace std", to register the complete
namespace.

#include <iostream>
using namespace std;

int main() {
cout << "hello, world" << endl;
return 0;

}

Wow! Thanks for the tip. I didn't know that. :-)

[red floyd]

Roger wrote:

On Aug 16, 5:28 pm, [e-mail] wrote:

>>So by defining it after the #include <iostream>, I won't have to use
std::cout?

Yes.
You could also, write "using namespace std", to register the complete
namespace.

Wow! Thanks for the tip. I didn't know that. :-)

However, a good piece of advice, if you're going to do that is to never,
NEVER, *NEVER* place "using namespace std" in a header file. It can
mess up any other headers that follow yours.

If you feel like using "using namespace std;", place it in your .cpp
source file, after all includes.

[Frank Birbacher]

Hi!

red floyd schrieb:

However, a good piece of advice, if you're going to do that is to never,
NEVER, *NEVER* place "using namespace std" in a header file. It can
mess up any other headers that follow yours.

:D Yes! A friend of mine recently got bitten by it. It made
std::ifstream and boost::filesystem::ifstream mix up.

If you feel like using "using namespace std;", place it in your .cpp
source file, after all includes.

Yes! *AFTER ALL INCLUDES*

Frank