//file: oct1.c
//author: jhd
//This code adapts pointer code from Tanenbaum and Bos, Ch 1, section 1.8, p75.
//It tries to demo pointers as placed in memory, in the data blocks of certain addresses.

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

int main(){
  
  printf("Hello:        \n");
  
  //declarations of variables
  char c;
  void *p = &c; 
  int i1, i2; 
  void *p1, *p2;  
  int *p3;

  //variables have addresses in memory
  p = &c; 
  printf("Declare a variable with type and name char c. \nDeclare a void pointer variable named *p.\nSet pointer p equal to address of c, &c.\n");
  printf("Use percent p to print the pointer containing the addr of var c:  p = &c = %p\n", p); 
  

  //set i1 
  i1 = 1;
  printf("The var i1 has data, so i1 = %d\n", i1); 
 
  //store address of i1 in void pointer p1 and copy it to a pointer of type int
  p1 = &i1;  
  p3 = (int *)p1;

  printf("The pointer p1 has data, address of var i1, so p1 = %p\n", p1); 
  printf("The pointer p3 has data, address of var i1, so p3 = %p\n", p3);

  //dereference (get data from) p3 (you cannot deref a void ptr!) 

  i2 =  *p3; 
  printf("The var i2 now has data, the contents of variable pointed to by p3, i2 = *p3 = %d\n", i2);
   
  
  printf("Hello:       Item:         Address:          Data:     \n");
  exit(0);
}