Passing data between functions and main

If I have declared variables in another function such as main, how do I access them in another function? (Instructor does not allow global variables)

100 bottles of beer on the wall, 100 bottles of beer, take one down pass it around, 99 bottles of beer on the wall....

Code:

---

void f(int& x) {
        // ...
}

int main() {
        int x = 0;
        f(x);
}

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though here I'm taking your "access them in another function" rather literally by passing by reference.

What are different methods to pass parameters to functions?