老师布置了一道作业题，用C语言编写学生管理系统，求各位大神帮帮忙！感激不尽！

#include
#include
#include
#include
#define NULL 0
#define LEN sizeof(struct student)

struct student
{
char name[20];
long int num;
char sex[4];
int age;
char address[30];
double tele_num;
char aihao[20];
struct student *next;
};//定义一个结构题

int TOTAL_NUM = 0;//学生总数
struct student *head = NULL;

void welcome (); //欢迎界面
void mainmenu (); //主界面
void record (); //记录数据
void insert(struct student *stu); //插入数据
void display(struct student *stu); //显示一个学生的信息
void displayAll (); //显示所有学生的信息
void query_by_num (); //按学号查询学生信息
void readData (); //读取文件里学生的信息
void writeData (); //向文件写入学生信息
void freeAll (); //清空链表内容
void del (); //删除学生信息
void change (); //更改学生信息
void devise (struct student *p); //选择更改内容

int main (void)
{
welcome ();
//显示主菜单
mainmenu ();
return 0;
}
//显示欢迎信息
void welcome ()
{
printf ("+----------------------------------------------------+\n");
printf ("| |\n");
printf ("| 欢迎使用网络工程学院信息安全092班学生信息管理系统 |\n");
printf ("| |\n");
printf ("+----------------------------------------------------+\n");
}

//系统主菜单
void mainmenu ()
{
int choice;
choice = -1;
readData ();
printf ("\n温馨提示：为保证您的操作得到保存，请按正常顺序退出系统^_^\n");
do
{
printf ("\n\n\n");
printf ("\t\t\t--------------------------------------------\n");
printf ("\t\t\t+ 信息安全092班学生信息管理系统 |\n");
printf ("\t\t\t--------------------------------------------\n");
printf ("\t\t\t+ [1]----录入学生信息 |\n");
printf ("\t\t\t+ [2]----浏览学生信息 |\n");
printf ("\t\t\t+ [3]----查询学生信息 |\n");
printf ("\t\t\t+ [4]----删除学生信息 |\n");
printf ("\t\t\t+ [5]----修改学生信息 |\n");
printf ("\t\t\t+ [0]----退出系统 |\n");
printf ("\t\t\t+*·*·*·*·*·*·*·*·*·*·*·*·*·*·*|\n");
printf ("\t\t\t--------------------------------------------\n");
printf ("请输入您的选择：");
scanf ("%d", &choice);
switch (choice)
{
case 0:
writeData ();
freeAll ();
exit (0);
case 1:
record ();
break;
case 2:
displayAll ();
break;
case 3:
query_by_num ();
break;
case 4:
del ();
break;
case 5:
change ();
break;
default:
printf ("\n无效选项!");
break;
}
}
while (choice != 0);
}
//录入学生信息
void record ()
{
struct student *p0;

p0 = (struct student *)malloc(LEN);
printf ("请输入学生的姓名:");
scanf ("%s",p0->name);
printf ("请输入学生的学号:");
scanf ("%ld",&p0->num);
printf ("请输入学生的性别:");
scanf ("%s",p0->sex);
printf ("请输入学生的年龄:");
scanf ("%d",&p0->age);
printf ("请输入学生的地址:");
scanf ("%s",p0->address);
printf ("请输入学生的电话:");
scanf ("%lf",&p0->tele_num);
printf ("请输入学生的爱好:");
scanf ("%s",p0->aihao);

insert (p0);
printf ("该学生的信息为:\n");
printf ("-------------------------------------------------------------------------------\n");
printf ("姓名\t学号\t\t年龄\t性别\t地址\t\t电话\t\t爱好\n");
display (p0);
}

void insert (struct student *stu)
{
struct student *p0, *p1, *p2;

p1 = head;
p0 = stu;

if (head == NULL)
{
head = p0;
p0->next = NULL;
}
else
{
while ((p0->num > p1->num)&&(p1->next != NULL))
{
p2 = p1;
p1 = p1->next;
}
if (p0->num <= p1->num)
{

if (head == p1)
head = p0;
else
p2->next = p0;
p0->next = p1;
}
else
{
p1->next = p0;
p0->next = NULL;
}
}
TOTAL_NUM++;
}

void display (struct student *p)
{
printf ("%s\t%ld\t%d\t%s\t%s\t\t%.0f\t%s\n", p->name, p->num, p->age, p->sex, p->address, p->tele_num, p->aihao);
}
//浏览学生信息
void displayAll()
{
struct student *p;

printf("学生总数:%d\n", TOTAL_NUM);
p = head;
if (head != NULL)
{
printf("\n姓名\t学号\t\t年龄\t性别\t地址\t\t电话\t\t爱好\n");
printf("-------------------------------------------------------------------------------\n");
do
{
display(p);
p = p->next;
}
while(p != NULL);
}
printf ("\n");
}
//按学号查询学生信息
void query_by_num ()
{
int num;
struct student *p1;

printf("请输入学生的学号：");
scanf("%ld", &num);
if(head==NULL)
{
printf("无学生记录！\n");
return;
}
p1 = head;
while (num!=p1->num && p1->next!=NULL)
p1 = p1->next;
if (num == p1->num)
{
printf ("姓名\t学号\t\t年龄\t性别\t地址\t\t电话\t\t爱好\n");
printf ("-------------------------------------------------------------------------------\n");
display (p1);
}
else
printf ("没有该学生记录，请核对！");
}

//写入文件
void writeData ()
{
FILE* fp;//文件指针
struct student *p;

fp = fopen("1.txt", "w");
if (!fp)
{
printf("文件打开错误！");
return;
}

fprintf(fp,"%d\n", TOTAL_NUM);
for(p = head; p!= NULL; p= p->next)
{
fprintf(fp,"%s\t%ld\t%s\t%d\t%s\t%.0f\t%s\n", p->name, p->num, p->sex, p->age, p->address, p->tele_num, p->aihao);
}
fclose (fp);
}

void freeAll ()
{
struct student *p1, *p2;

p1 = p2=head;
while(p1)
{
p2=p1->next;
free (p1);
p1 = p2;
}
}
//读取文件
void readData ()
{
FILE* fp;//文件指针
struct student *p1, *p2;
fp = fopen("1.txt", "r");
if (!fp)
{
printf("文件打开错误！");
return;
}

fscanf(fp,"%d\n", &TOTAL_NUM);
head = p1 = p2 = (struct student *)malloc(LEN);
fscanf(fp,"%s\t%ld\t%s\t%d\t%s\t%lf\t%s\n", p1->name, &p1->num, p1->sex, &p1->age, p1->address, &p1->tele_num, p1->aihao);
while(!feof(fp))
{
p1 = (struct student *)malloc(LEN);
fscanf(fp,"%s\t%ld\t%s\t%d\t%s\t%lf\t%s\n", p1->name, &p1->num, p1->sex, &p1->age, p1->address, &p1->tele_num, p1->aihao);
p2->next = p1;
p2 = p1;
}
p2->next = NULL;
fclose(fp);
}
//删除学生信息
void del ()
{
struct student *p1, *p2;
long int num;

if (head == NULL)
{
printf("无学生记录！\n");
return;
}

printf("请输入您要删除的学生的学号：");
scanf("%ld", &num);
p1 = head;

while (num != p1->num && p1->next != NULL)
{
p2 = p1;
p1 = p1->next;
}
if(num == p1->num)
{
if(p1 == head)
head = p1->next;
else p2->next = p1->next;
free(p1);
TOTAL_NUM--;
}
else
printf("没有该学生记录，请核对！\n");
}
//修改学生信息
void change ()
{
struct student *p1, *p2;
long int num;
if (head == NULL)
{
printf ("无学生记录！\n");
return;
}
printf ("请输入您要修改的学生的学号：");
scanf ("%ld", &num);
p1 = head;
while (num != p1->num && p1->next != NULL)
{
p2 = p1;
p1 = p1->next;
}
if(num == p1->num)
devise (p1);
else
printf("没有该学生记录，请核对！\n");
}

void devise (struct student *p)
{
int choice;
choice = -1;
do
{
printf("请选择您要修改的学生的信息内容：\n");
printf("+----------------------+\n");
printf("| 姓名 请按 1 |\n");
printf("| 学号 请按 2 |\n");
printf("| 性别 请按 3 |\n");
printf("| 年龄 请按 4 |\n");
printf("| 地址 请按 5 |\n");
printf("| 电话 请按 6 |\n");
printf("| 爱好 请按 7 |\n");
printf("| 取消 请按 0 |\n");
printf("+----------------------+\n");

printf("请输入您的选择：");
scanf("%d", &choice);

switch (choice)
{
case 0:
return;
case 1:
printf("请输入新姓名：");
scanf("%s", p->name);
break;
case 2:
printf("请输入新学号：");
scanf("%d", &p->num);
break;
case 3:
printf("请输入新性别：");
scanf("%s", p->sex);
break;
case 4:
printf("请输入新年龄：");
scanf("%s", &p->age);
break;
case 5:
printf("请输入新地址：");
scanf("%s", p->address);
break;
case 6:
printf("请输入新电话：");
scanf("%lf", &p->tele_num);
break;
case 7:
printf("请输入新爱好：");
scanf("%s", p->aihao);
break;
default:
printf("\n无效选项!");
break;
}
}
while(choice != 0);
}