Help me undersstand structs

[telmo_d]

Why do we use &Elem->ID and &Elem->name? With & we are storing in the address of the pointer that is on the heap. Then what is the -> all about? Why not use a dot like &Elem.id?

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


typedef struct
{
    int id;
    char name[80];
    int mark;
}STUDENT;

STUDENT *CreateElement()
{

STUDENT *Elem;
Elem=(STUDENT *)malloc(sizeof(STUDENT));
if(Elem==NULL)
   return NULL
printf("ID = ");
scanf("%d", &(Elem->id)); 
printf("Name = ");
printf("\n");
fgets(&(Elem->name), 80, stdin);    

}

[Salem]

> Then what is the -> all about?
Because you have a pointer to a struct - a pointer to the memory you got back from malloc.

> Why not use a dot like &Elem.id?
You would use the dot form if you have a variable of that type.

Consider.

STUDENT s;
STUDENT *ps = malloc(sizeof(*ps));

// read into s
scanf("%d", &s.id); 

// read into ps (both are the same)
scanf("%d", &ps->id); 
scanf("%d", &(*ps).id); // use the dot form, but only because of all the extra syntax around ps

// you can even use array notation
scanf("%d", &ps[0].id);

The arrow notation is just the least cumbersome of the possible ways of getting from a pointer-to-struct to the actual data element within the struct.