explanation of passing by value

main.c

#include <stdio.h>

void swap_values_1(int p, int q) {
    printf("where are the local variables in this function allocated? p: %p, q: %p\n", &p, &q);
    int tmp = q;
    q = p;
    p = tmp;
}

void swap_values_2(int *m, int *n) {
    printf("the values of m and n: m: %p, n: %p\n", m, n);
    // note! this is different from where m and n are themselves allocated! it's where they point to!
    printf("where m and n are allocated: m: %p, n: %p\n", &m, &n);
    // and this is the value at the address they point to:
    printf("values at those addresses: %p: %d, %p: %d\n", m, *m, n, *n);
    // ok let's swap
    int tmp = *n;
    *n = *m;
    *m = tmp;
}

void print_values(int x, int y) {
    printf("a: %d\n", x);
    printf("b: %d\n", y);
}

int main() {
    int a = 5;
    int b = 10;
    printf("where are a and b allocated? a: %p, b: %p\n", &a, &b);
    print_values(a, b);

    // try swapping
    swap_values_1(a, b);
    printf("After swap 1:\n");
    print_values(a, b);

    // try swapping again
    swap_values_2(&a, &b);
    printf("After swap 2:\n");
    print_values(a, b);
}