[red_4900]

ok. I've seen in many tutorial, many books suggesting the code to have something like this:

.....
using namespace std;
....

what is it for?

[gabehabe]

The std namespace has all of the typical things that you'd expect to use within a program. (like cout, cin, endl, etc)

If you wasn't using namespace std;, your program would look something like this:

.....
std::cout <<"Hello world!" <<std::endl;
.....

another way to do it would be to have something like:

using std::cout;
using std::cin;

This only uses the features which you wish to use in your program.

I hope this clears it up =]

[red_4900]

#include<iostream.h>
int main(){
cout<<"yo\n";
return 0;
} 

compiled nicely without error and still run smoothly. and I didnt even use the std namespace.

[Amadeus]

Very true, but the code you've written does not comply to accepted ANSI standards. It is non portable. the iostream.h library has been deprecated (as have many .h libraries) in the move towards namespaces. This article may explain the matter.

http://www.cplusplus...namespaces.html

http://www.cprogramm...namespaces.html

http://en.wikipedia....mputer_science)

Most newer compilers will not even compile code including the non standard headers.