What does '&' mean in C++?

Question

What does \'&\' mean in C++?

As within the function

void Read_wav::read_wav(const string &filename)
{

}

And what is its equiv

Answer 1

& means that variable is passed via reference. So, inside your function you will have not a local copy of variable, but the original variable itself. All the changes to the variable inside the function will influence the original passed variable.