If you want to alter the content of a variable in a function in C, pointer is a kinda variable as well, you have to pass it by pointer or indirect reference by using always & address and * dereference operators. I mean * operator is always used and preceded when changing the value of a variable.

#include <stdio.h>
#include <stdlib.h>


void changeIntVal(int *x) {
    *x = 5;
}

void changePointerAddr(int **q) {
    int *newad;
    *q = newad;
}

void changePPAddr(int ***q) {
    int **dummy;
    *q = dummy;
}

int main() {
    int *p;
    int **pp;
    int *tempForPP;
    int a = 0;
    printf("\n The address pointing by p -> %p, pp -> %p, value of a -> %d ", p, pp, a);


    p = &a;
    pp = &tempForPP;
    printf("\n The address pointing by p -> %p, pp -> %p, value of a -> %d ", p, pp, a);

    changeIntVal(&a);        // ----
                             //    |---
    changePointerAddr(&p);   // ----  |---->  parts of what I mean
                             //    |---
    changePPAddr(&pp);       // ----

    printf("\n The address pointing by p -> %p, pp -> %p, value of a -> %d ", p, pp, a);

    return 0;

}