How to use double pointers in C
A pointer is a variable that stores the memory address of another variable as its value.
#include <stdio.h>
#include <malloc.h>
void change_nr(int ** nr) {
*nr = (int *) malloc(sizeof(int));
}
int main()
{
int * p_nr = NULL;
change_nr(&p_nr);
* p_nr = 4;
printf("%d", *p_nr);
free(p_nr);
return 0;
}