源程序：
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#define MAXLINE 60
struct birthday
{
    int year,month,day;
};
struct address
{
    char province[MAXLINE],city[MAXLINE],road[MAXLINE];
    int code;
    char zip[MAXLINE];
};
struct friends
{
    char name[MAXLINE];
    int age;
    char telephone[MAXLINE];
    struct birthday bir;
    struct address add;
    struct friends *next;
};
struct friends *Create(struct friends *head);
struct friends *Insert(struct friends *head,struct friends *fri);
struct friends *Delete(struct friends *head,char name[]);
void Print(struct friends *head);
int main(void)
{
    struct friends *head=NULL,*p;
    char name[MAXLINE];
    int choice;
    while(1)
    {
        printf("功能选项:1.新建\t2.插入\t3.删除\t4.显示所有信息\t0.退出\n");
        printf("选择功能:");
        scanf("%d",&choice);
        if(choice==1)
            head=Create(head);
        else if(choice==2)
        {
            p=(struct friends *)malloc(sizeof(struct friends));
            printf("请输入姓名:");
            scanf("%s",p->name);
            printf("请输入年龄:");
            scanf("%d",&p->age);
            printf("请输入电话号码:");
            scanf("%s",p->telephone);
            printf("请输入出生年份:");
            scanf("%d",&p->bir.year);
            printf("请输入出生月份:");
            scanf("%d",&p->bir.month);
            printf("请输入出生日期:");
            scanf("%d",&p->bir.day);
            printf("请输入联系地址(省、市、街道、门牌号):");
            scanf("%s%s%s%d",p->add.province,p->add.city,p->add.road,&p->add.code);
            getchar();
            printf("请输入邮政编码:");
            gets(p->add.zip);
            head=Insert(head,p);
        }
        else if(choice==3)
        {
            printf("请输入要删除的联系人姓名:");
            scanf("%s",name);
            head=Delete(head,name);
        }
        else if(choice==4)
            Print(head);
        else if(choice==0)
            break;
    }
    printf("\n");
    return 0;
}
struct friends *Create(struct friends *head)
{
    struct friends *p,*temp;
    p=(struct friends *)malloc(sizeof(struct friends));
    printf("请输入姓名:");
    scanf("%s",p->name);
    printf("请输入年龄:");
    scanf("%d",&p->age);
    printf("请输入电话号码:");
    scanf("%s",p->telephone);
    printf("请输入出生年份:");
    scanf("%d",&p->bir.year);
    printf("请输入出生月份:");
    scanf("%d",&p->bir.month);
    printf("请输入出生日期:");
    scanf("%d",&p->bir.day);
    printf("请输入联系地址(省、市、街道、门牌号):");
    scanf("%s%s%s%d",p->add.province,p->add.city,p->add.road,&p->add.code);
    getchar();
    printf("请输入邮政编码:");
    gets(p->add.zip);
    p->next=NULL;
    if(head==NULL)
        head=p;
    else
        temp->next=p;
    temp=p;
    return head;
}
struct friends *Insert(struct friends *head,struct friends *fri)
{
    if(head==NULL)
    {
        head=fri;
        fri->next=NULL;
    }
    else
    {
        struct friends *temp1,*temp2;
        char a[3],b[3];
        int count=0;
        temp1=head;
        temp2=temp1->next;
        a[0]=fri->name[0];
        a[1]=fri->name[1];
        a[2]='\0';
        b[0]=temp1->name[0];
        b[1]=temp1->name[1];
        b[2]='\0';
        while(1)
        {
            if(strcmp(a,b)==0)
            {
                temp1->next=fri;
                fri->next=temp2;
                count++;
                break;
            }
            temp1=temp2;
            temp2=temp1->next;
            if((temp1!=head)&&(temp2==NULL))
                break;
        }
        if(count==0)
        {
            temp2=fri;
            fri->next=NULL;
        }
    }
    return head;
}
struct friends *Delete(struct friends *head,char name[])
{
    int count=0;
    struct friends *temp,*temp1,*temp2;
    if(head==NULL)
    {
        printf("查无此人!\n");
        return NULL;
    }
    else if((head->next==NULL)&&(strcmp(name,head->name))!=0)
        printf("查无此人!\n");
    else if((head->next==NULL)&&(strcmp(name,head->name)==0))
        free(head);
    else if((head->next!=NULL)&&(strcmp(name,head->name)==0))
    {
        temp=head;
        head=temp->next;
        free(temp);
    }
    else
    {
        temp1=head;
        temp2=temp1->next;
        while(1)
        {
            if(strcmp(name,temp2->name)==0)
            {
                temp1->next=temp2->next;
                free(temp2);
                count++;
                break;
            }
            temp1=temp2;
            temp2=temp1->next;
            if(temp2==NULL)
                break;
        }
        if(count==0)
            printf("查无此人!\n");
    }
    return head;
}
void Print(struct friends *head)
{
    struct friends *i;
    printf("显示所有信息:");
    if(head==NULL)
    {
        printf("信息为空!\n");
    }
    printf(" 姓名  年龄   出生年月日    电话号码     邮编      通信地址\n");
    for(i=head;i!=NULL;i=i->next)
    {
        printf("%s%4d%3d年%d月%d日%6s%6s%6s%s%s%d号\n",i->name,i->age,i->bir.year,i->bir.month,i->bir.day,i->telephone,i->add.zip,i->add.province,i->add.city,i->add.road,i->add.code);
    }
}

麻烦各位大神看看我这个错在哪？运行程序时，只能用一次新建功能或者是插入功能，第二次新建时最后会出错。怎么回事？小弟是自学C语言的。不太懂。