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

In this case, string &filename means the function will receive a reference (a memory address) as a parameter, instead of receiving it as a copy.

The advantage of this method is that your function will not allocate more space on the stack to save the data contained in filename.