Swap example--as an exercise, indicate what this program prints
when using the 5 parameter passing modes we discussed in class.

subprogram swap (int a, int b) {
    int temp;
    temp = a;
    a = b;
    b = temp;
}

main() {
    int p = 12;
    int q = -4;
    swap(p, q);
    // Create list, an array of 5, containing: 1,3,5,7,9
    p = 888;
    swap(p, list[0]);
    p = 3;
    swap(p, list[p]);
}