circular data strcture

Question

how can i make circular data structure using pointer. . .

Answer 1

Do you mean a ring-like structure? You can use a linked list.

struct smthing {
/* int x; const char *id; etc */
smthing *next;
} ;

now you manage the individual elements of the linked list. Have the last element point to head:

llist->next = &head;

Be aware that you have to manage your memory manually with new and free.