what does `extern "C++" ` mean?

[Andy]

Hi,

This is just a simple hello world program.

#include <iostream>
using namespace std;
int main()
{
cout<<"Hello,world\n";
}


Today I happened to look into the intermediate code genernated by
preprocessor. I found there is code like the follows:

extern "C++"{
....
}
Why we need such code?  I am using gcc-3.4.2.

Thanks a lot!

Andy