新手求助：链表问题

#include "stdio.h"
#include "iostream.h"
#include "string.h"
struct node
{
    int inum;
    int iscore;
    struct node *nnext;
};
node *create()
{
    int no;
    node *head,*pn,*pt;
    head=0;                           //为什么if中的语句不能放在这里？？
    cout<<"产生无序链表："<<endl;
    cin>>no;
    while(no!=-1)
    {
        pn=new node;
        pn->inum=no;
        cin>>pn->iscore;
        if(head==0)
        {
            head=pn;
            pt=pn;
        }
        else
        {
            pt->nnext=pn;
            pt=pn;
        }
        cin>>no;
    }
    pt->nnext=0;
    return head;
}
void print(node *head)
{
    node *p=head;
    cout<<"输出："<<endl;
    while(p!=0)
    {
        cout<<p->inum<<'\t'<<p->iscore<<endl;
        p=p->nnext;
    }
}
main()
{
    node *head;
    int no;
    head=create();
    print(head);
}

问题：建立新链表中，循环前就已经将head=0了，那循环中的if(head==0)不是多余的吗，为什么if中的语句不能放在head=0;后面？？十分迷茫，
望前辈给予指教！！！