Simple example of how pointers work when passing into a function.

ptr_example.cpp

#include <cstdio>


/**
 * This function has a local reference to a pointer
 * Thus the memory address of the pointer is different
 * But the value the pointer contains remains the same
 */
void function(double* ptrlocal) {
    printf("ptr = %p [function ptr address]\n", &ptrlocal);
    printf("ptr = %p [function ptr held]\n", ptrlocal);
    printf("ptr = %f [function val]\n", *ptrlocal);
}


/**
 * This creates a double array and make a pointer to the first row
 * We print out:
 * 1) the address of the pointer
 * 2) value the pointer holds
 * 3) data that the pointer points to
 */
int main() {

    // Make our data
    double arr[4][4];
    arr[1][0] = 10;


    // Make a pointer
    double* ptr = arr[1];

    // Print pointer out
    printf("ptr = %p [main ptr address]\n", &ptr);
    printf("ptr = %p [main ptr held]\n", ptr);
    printf("ptr = %f [main val]\n\n", *ptr);
  
    // Pass to the function
    function(ptr);

}