c++ - What does this function do?

Question

I am reading a program which contains the following function, which is

int f(int n) {
    int c;
    for (c=0;n!=0;++c) 
        n=n&(n-1);
    return c;
}

I don't quite understand what does this function intend to do?

Answer 1

It counts number of 1's in binary representation of n