stack error occured in link list

hello all.
I don't know why it output twice in "Node-data[%d]",so irritancy!

header file

Code:

/* this a header file for list.c */
/* file name: head-list.h */
/* author:mycount */
/* time:12:03 */


#define LEN sizeof(link)
typedef struct list
{
	char data;
	struct list * next;
}link;

my code:

Code:

/* this is a c programm */
/* file name:list.c */

#include "head-list.h"
#include <stdio.h>
#include <stdlib.h>
/* above is include files which are concerned in use */

link *create(void)
{
	link * head;
	head=NULL;
	head=(link *)malloc(LEN);
	if(head!=NULL)
	{
		return head;
	}
	else
	{
		exit(0);
	}
}/* this function is create a list */

link *Init(link *head,int num)
{
	int flag=1;
	head->data=0;
	link *p,*q;

	while(num--)
	{
		if(flag==1)
		{
			p=(link *)malloc(LEN);
			head->next=p;
			printf("\nfollowing is initialize the link list\n\nplease input the node'data.\n");
			printf("Node-data[%d]",flag);
			p->data=getchar();
		}
		
		else
		{
			printf("\n");
			p=(link *)malloc(LEN);
			printf("Node-data[%d]",flag);
			p->data=getchar();
			
		}
		q=p;
		p=p->next;
		q->next=p;
		flag++;
	
	}
	q->next=NULL;
	return head;
}/* this function is initialize a list */

void disp(link *h)
{
	while(h!=NULL)
	{
		h=h->next;
		printf("%c",h->data);
	}
}/* this function is display the list */


/* following is main function */

int main(void)
{
	link * head;
	link * init_head;
	head=create();
	init_head=Init(head,5);
        disp(init_head);	

}//end

> head=create();
This dummy node has no data, yet you print it.

please forgave
i yet do not understand.is the node "head" must have data?
somebody could you tell me in details.thanks very much.

It does if you're trying to print it!

> init_head=Init(head,5);
Think about what actually happens if you have
init_head=Init(head,0);

Apart from the crashing.

thanks Salem.