Why doesn't my function output what's expected

Question

Hi I'm currently learning C++ and I'm trying to pass the value by reference, but I'm having issues with getting the correct output. What seems to be the problem??

void ref(int a)
{
cout << "a = " << a << endl;
a = 1;
cout << "a = " << a << endl;
} 

int main()
{
int b = 10;
cout << "b = " << b << endl;
ref(b);
cout << "b = " << b << endl;
return 0;
}

Answer 1

Unless you put void ref(int &a){} you are not actually changing the value of a.

Answer 2

For pass by reference you have to use:-

void ref(int& a) {}