帮我看下这个程序问题在哪
#include<stdio.h>
#include<string.h>
#include<conio.h>
#include<stdlib.h>
#include<time.h>
#include<math.h>
#define A 3
void wait ( int seconds )
{
clock_t endwait;
endwait = clock () + seconds * CLOCKS_PER_SEC ;
while (clock() < endwait) {}
}
void dummy(){}
typedef
struct person
{
int num;
char name[20];
char sex;
int age;
char tel[20];
char mobile[30];
struct person *next;
}p;
p *head;
void main()
{

int choice;
void create();void show();
for(;;)
{
printf("请选择下面的一个项目：\n 1.创建\n 2.添加\n 3.查询\n 4.修改\n 5.删除\n 6.显示\n 7.退出\n 8.搞笑\n");
scanf("%d",&choice);
switch(choice)
{
case 1:create();break;

default:break;
}
if(choice==7) break;
if(choice<1||choice>8) printf("输入错误，请重新输入！\n");
}
}
void create()
{
p *cre,*sav;
head=NULL;

cre=(p *)malloc(sizeof p);
printf("请输入，如有未知项输入0即可\n");
printf("请输入联系人编号(1-999)\n");
scanf("%d",cre->num);
printf("请输入联系人姓名\n");
scanf("%s",cre->name);
getchar();
printf("请输入联系人性别\n");
scanf("%c",cre->sex);
printf("请输入联系人年龄\n");
scanf("%d",cre->age);
printf("请输入联系人家庭电话号码\n");
scanf("%s",cre->tel);
printf("请输入联系人手机号码\n");
scanf("%s",cre->mobile);
sav->next=cre;
sav=cre;

printf("输入完成！\n3s后返回主界面\n");
wait(1);printf("3...");wait(1);printf("2...");wait(1);printf("1...\n");wait(1);



}
void show()
{
p *k;
k=head;
while((k->next)!=NULL)
{
printf("******************************\n");
printf("联系人编号:%d\n",k->num);
printf("联系人姓名:%s\n",k->name);
printf("联系人性别:%c\n",k->sex);
printf("联系人年龄:%d\n",k->age);
printf("联系人家庭电话号码:%s\n",k->tel);
printf("联系人手机号码:%s\n",k->mobile);
printf("******************************\n\n\n");
}
}
部分的程序，已经无法运行了，这个链表到底是怎么使用啊，各种迷茫啊，谢谢大家了

[解决办法]

C/C++ code

#include<stdio.h>#include<string.h>#include<conio.h>#include<stdlib.h>#include<time.h>#include<math.h>#define A 3void wait ( int seconds ){    clock_t endwait;    endwait = clock () + seconds * CLOCKS_PER_SEC ;    while (clock() < endwait) {}}void dummy(){}typedefstruct person{        int num;    char name[20];    char sex;        int age;    char tel[20];    char mobile[30];    struct person *next;}p;p *head;void main(){    int choice;    void create();void show();    for(;;)    {        printf("请选择下面的一个项目：\n 1.创建\n 2.添加\n 3.查询\n 4.修改\n 5.删除\n 6.显示\n 7.退出\n 8.搞笑\n");        scanf("%d",&choice);        switch(choice)        {        case 1:create();break;        default:break;        }        if(choice==7) break;        if(choice<1||choice>8) printf("输入错误，请重新输入！\n");    }}void create(){    p *cre,*sav;    head=NULL;    cre=(p *)malloc(sizeof p);    printf("请输入，如有未知项输入0即可\n");    printf("请输入联系人编号(1-999)\n");    scanf("%d",&(cre->num));    printf("请输入联系人姓名\n");    scanf("%s",cre->name);    getchar();    printf("请输入联系人性别\n");    scanf("%c",&(cre->sex));    printf("请输入联系人年龄\n");    scanf("%d",&(cre->age));    printf("请输入联系人家庭电话号码\n");    scanf("%s",(cre->tel));    printf("请输入联系人手机号码\n");    scanf("%s",cre->mobile);    sav->next=cre;    sav=cre;    printf("输入完成！\n3s后返回主界面\n");    wait(1);printf("3...");wait(1);printf("2...");wait(1);printf("1...\n");wait(1);}void show(){    p *k;    k=head;    while((k->next)!=NULL)    {        printf("******************************\n");        printf("联系人编号:%d\n",k->num);        printf("联系人姓名:%s\n",k->name);        printf("联系人性别:%c\n",k->sex);        printf("联系人年龄:%d\n",k->age);        printf("联系人家庭电话号码:%s\n",k->tel);        printf("联系人手机号码:%s\n",k->mobile);        printf("******************************\n\n\n");    }}