/*
 * ISA 563, Spring 2011
 * Copyleft by Muhammad Abdulla
 */

#include <stdio.h>

/*
 * varptr.c -- demonstrates variable and pointer properties
 */

int main (int argc, char *argv[] )
{
   int score = 100;
   int *score_ptr;

   int total_score = 2345;
   int *total_score_ptr;

   score_ptr = &score;
   total_score_ptr = &total_score;

   struct node {
      double value;
      struct node *next; 
   };

   struct node head;

   head.value = 12.34;

   struct node *node_ptr = &head;

   // properties of a variable
   fprintf(stdout, "value of   score = %d\n", score);
   fprintf(stdout, "address of score = %p\n", &score);
   fprintf(stdout, "size  of   score = %d\n", sizeof(score));
   fprintf(stdout, "address of total_score = %p\n", &total_score);
   printf("\n");

   // properties of a pointer
   fprintf(stdout, "value of score_ptr = %p\n", score_ptr);
   fprintf(stdout, "value pointed by score_ptr= %d\n", *score_ptr);
   fprintf(stdout, "address of score_ptr= %p\n", &score_ptr);
   fprintf(stdout, "sizeof  of score_ptr= %d\n", sizeof(score_ptr));
   fprintf(stdout, "sizeof  of *score_ptr= %d\n", sizeof(*score_ptr));
   fprintf(stdout, "sizeof  of *node_ptr= %d\n", sizeof(*node_ptr));

   // we can update the value of a variable through a pointer pointing to it 
   *score_ptr = 200;
   fprintf(stdout, "\nafter '*score_ptr = 200;':\n");
   fprintf(stdout, "value of   score = %d\n", score);
   fprintf(stdout, "address of score = %p\n", &score);

   // we can update the value (address held by the pointer) too.
   score_ptr = total_score_ptr;
   fprintf(stdout, "\nafter 'score_ptr = total_score_ptr;':\n");
   fprintf(stdout, "value of   score = %d\n", score);
   fprintf(stdout, "address of score = %p\n", &score);
   fprintf(stdout, "value of score_ptr = %p\n", score_ptr);
   fprintf(stdout, "address of score_ptr = %p\n", &score_ptr);
   fprintf(stdout, "value pointed by score_ptr = %d\n", *score_ptr);

   // pointer access to struct fields 
   fprintf(stdout, "\nhead.value = %g\n", head.value);
   fprintf(stdout, "node_ptr->value = %g\n", node_ptr->value);

   return 0;
}