Как я...понимаю это(заполнение invlolved)?

#include <stdio.h>
#include <string.h>

/*  Below structure1 and structure2 are same.
    They differ only in member's allignment */
//#pragma pack ( 1 )
struct structure1
{
        char  _1;
        short int _2;
        char _3;
};


int main()
{
    struct structure1 a;

    printf("size of structure1 in bytes : %d\n",sizeof(a));
    printf ( "\n   Address of id1        = %u", &a._1 );
    printf ( "\n   Address of id2        = %u", &a._2 );
    printf ( "\n   Address of name       = %u", &a._3 );


    getchar();
    return 0;
}

tried on 32 bit compiler!
why am i getting 6 bytes??shoulnt i get 8 bytes...as there i padding involved here!!
as it always reads 4 bytes at a time!!