Drawing picture of singly linked list

typedef void               * Any_ptr;
typedef struct list_struct * List_ptr;
typedef struct node_struct * Node_ptr;

typedef struct list_struct
{
   Node_ptr   head_ptr;
   // other stuff could go here too, like the count of nodes in the list and so on.
} List;

typedef struct node_struct
{
   Node_ptr   next_ptr;
   Any_ptr    data_ptr;
} Node;

/* we are now able to simply declare items as "Node" or "List" as well as "Node_ptr" and so on */

List_ptr CreateList()
{
   List_ptr ptr = malloc(sizeof(List));
 
   ptr->head_ptr = NULL:
 
   return ptr;
}


void InsertAtTail (List_ptr list_ptr, Any_ptr data_ptr)
{

   // Craete a new node and set it up.
 
   Node_ptr node_ptr = malloc(sizeof(Node));
 
   node_ptr->data_ptr = data_ptr;
   node_ptr->next_ptr = NULL;
 
   // Case 1. the list is currently empty

   if (list_ptr->head_ptr == NULL)  // The list is currently empty
      {
      list_ptr->head_ptr = node_ptr;
      return;
      }
     
    // Case 2. There is at least one node present
   
    Node_ptr curr_ptr = list_ptr->head_ptr;
   
    while (curr_ptr->next_ptr != NULL)
    {
       curr_ptr = curr_ptr->next_ptr;
    }
   
    // We know that curr_ptr now points to an element with a NULL next_ptr, this is the
    // last element, the tail element.
   
    curr_ptr->next_ptr = node_ptr;
   
    return;
}