c - memory allocation for structures -

can please explain me peculiar output:

#include <stdio.h>  typedef struct node {   int i;   struct node *next; }node;  main() {     node *p,*q;     printf(" %u ",sizeof(node));              // 16     p = (node *)malloc(sizeof ( node ) ) ;          printf(" %p ",p);                    // 0x1cea010     q = (node *)malloc(sizeof ( node ) ) ;      printf("\n %p ",q);                    // 0x1cea030 } 

i have 64 bit processor. when size shown 16 byes, why 32 byte allocated node?? checked out 32- bit machine. addresses had separation of 8 bytes. no padding , stuff. difference of 4 bytes solely cause of padding issue of 64 bit machine??

two malloc calls aren't going return consecutive memory areas. better way test be:

main() {     node *p;     printf(" %u ",sizeof(node));     p = (node*)malloc(2 * sizeof (node));          printf(" %p \n %p ", &p[0], &p[1]);     free(p); } 

by allocating array, can sure back-to-back in memory.

depending on implementation of malloc, system may using memory in between p , q store bookkeeping information used realloc, free, , friends.