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

// an example of code using a quadruple pointer.
// This example is not very realistic, but it shows
// how pointers of pointers can be manipulated.
void foo(char **** b)
{
  ***b = (char *) malloc(sizeof(char) * 6);
  (***b)[0] = 'h';
  (***b)[1] = 'e';
  (***b)[2] = 'l';
  (***b)[3] = 'l';
  (***b)[4] = 'o';
  (***b)[5] = 0;
}


int main()
{
  char * a = "john";
  char ** b = &a;
  char *** c = &b;
  char **** d = &c;

  printf("before calling foo:\n");
  printf("a = %s\n\n", a);
  foo(d);

  // note that the value of a
  // is different after calling the foo function
  printf("after calling foo:\n");
  printf("a = %s\n", a);
}