Double Pointers (pointer to a pointer)

double_pointers.c

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

int main()
{
    /* ====================================================================== */
    /*  Double Pointers (Pointer to a Pointer) */
    /* ====================================================================== */
    // 2 levels of indirection
    int **dblPtr;

    int a = 1;
    int b = 2;
    int c = 3;

    int *ptrOne = &a;
    int *ptrTwo = &b;

    // assign the double pointer
    dblPtr = &ptrOne; // if you try to use ptrOne it will only be pointing at the pointers address

    printf("dblPtr = %d\n", **dblPtr); // 1

    printf("ptrOne = %d\n", ptrOne); // the address of &a
    printf("&ptrOne = %u\n", &ptrOne); // the address of ptrOne
    printf("dblPtr = %d\n", dblPtr); // the address of ptrOne

    printf("ptrOne == &a %d\n", ptrOne == &a); // true (1)
    printf("dblPtr == &ptrOne %d\n", dblPtr == &ptrOne); // true (1)
    return 0;
}