C Programming - Typedef - Discussion

typedef struct
{
int data;
NODEPTR link; //NODEPTR is invalid
}*NODEPTR;


we should use:
typedef struct node
{
int data;
struct node *link;
}NODEPTR;

You all wondering about correct explanation. Let us start.

1. We can make a structure like this but point to be noted is typedef struct

{
int data;
NODEPTR link; // ----point to be noted----
}*NODEPTR;

In C language, we can not make a structure variable inside the structure of the same type.

(NODEPTER link) NODEPTER is a name of structure and link is the name of the variable of structure and we can't make a variable of structure inside a structure . if we do this thing the compiler is getting confused about the size of the structure.

2. But we can make a pointer variable of struct type example.
typedef struct
{
int data;
NODEPTR *link; // this is correct this type of structure we called self referential strucutre.
} NODEPTR; // this is the name of structure.

This type of structure is called self-referential structure.

Can anyone explain clearly?

Need correct explanation.

How can we use typedef struct in the declaration itself? Can anyone explain clearly?

typedef can not be used until it is defined.

It is defined only when a name is given or it is said to be anonymous.

Actully NODEPTR is the name to which typedef indicates. So after declaration only we can use in the function.

So, it is used earlier.

Typedef is used in the place of a declaration or type specifiers such as int, float.

Can any one explain??