学生成绩管理系统C语言不用链表而用结构体数组如何实现

这是我用的，我同学做的，我也没仔细看，如果可以的话就用这个吧。
#include /*引用库函数*/
#include
#include
#include
typedef struct /*定义结构体数组*/
{
char num[10]; /*学号*/
char name[20]; /*姓名*/
int score; /*成绩*/
}Student;
Student stu[80]; /*结构体数组变量*/
int menu_select() /*菜单函数*/
{
char c;
do{
system("cls"); /*运行前清屏*/
printf("\t\t****Students' Grade Management System****\n"); /*菜单选择*/
printf("\t\t | 1. Input Records |\n");
printf("\t\t | 2. Display All Records |\n");
printf("\t\t | 3. Sort |\n");
printf("\t\t | 4. Insert a Record |\n");
printf("\t\t | 5. Delete a Record |\n");
printf("\t\t | 6. Query |\n");
printf("\t\t | 7. Statistic |\n");
printf("\t\t | 8. Add Records from a Text File|\n");
printf("\t\t | 9. Write to a Text file |\n");
printf("\t\t | 0. Quit |\n");
printf("\t\t*****************************************\n");
printf("\t\t\tGive your Choice(0-9):");
c=getchar(); /*读入选择*/
}while(c<'0'||c>'9');
return(c-'0'); /*返回选择*/
}
int Input(Student stud[],int n) /*输入若干条记录*/
{int i=0;
char sign,x[10]; /*x[10]为清除多余的数据所用*/
while(sign!='n'&&sign!='N') /*判断*/
{ printf("\t\t\tstudent's num:"); /*交互输入*/
scanf("\t\t\t%s",stud[n+i].num);
printf("\t\t\tstudent's name:");
scanf("\t\t\t%s",stud[n+i].name);
printf("\t\t\tstudent's score:");
scanf("\t\t\t%d",&stud[n+i].score);
gets(x); /*清除多余的输入*/
printf("\t\t\tany more records?(Y/N)");
scanf("\t\t\t%c",&sign); /*输入判断*/
i++;
}
return(n+i);
}
void Display(Student stud[],int n) /*显示所有记录*/
{
int i;
printf("\t\t\t-----------------------------------\n"); /*格式头*/
printf("\t\t\tnumber name score\n");
printf("\t\t\t-----------------------------------\n");
for(i=1;i{
printf("\t\t\t%-16s%-15s%d\n",stud[i-1].num,stud[i-1].name,stud[i-1].score);
if(i>1&&i%10==0) /*每十个暂停*/
{printf("\t\t\t-----------------------------------\n"); /*格式*/
printf("\t\t\t");
system("pause");
printf("\t\t\t-----------------------------------\n");
}
}
printf("\t\t\t");
system("pause");
}
void Sort_by_num(Student stud[],int n) /*按学号排序*/
{ int i,j,*p,*q,s;
char t[10];
for(i=0;ifor(j=0;jif(strcmp(stud[j].num,stud[j+1].num)>0)
{strcpy(t,stud[j+1].num);
strcpy(stud[j+1].num,stud[j].num);
strcpy(stud[j].num,t);
strcpy(t,stud[j+1].name);
strcpy(stud[j+1].name,stud[j].name);
strcpy(stud[j].name,t);
p=&stud[j+1].score;
q=&stud[j].score;
s=*p;
*p=*q;
*q=s;
}
}
int Insert_a_record(Student stud[],int n) /*插入一条记录*/
{char x[10]; /*清除多余输入所用*/
printf("\t\t\tstudent's num:"); /*交互式输入*/
scanf("\t\t\t%s",stud[n].num);
printf("\t\t\tstudent's name:");
scanf("\t\t\t%s",stud[n].name);
printf("\t\t\tstudent's score:");
scanf("\t\t\t%d",&stud[n].score);
gets(x);
n++;
Sort_by_num(stud,n); /*调用排序函数*/
printf("\t\t\tInsert Successed!\n"); /*返回成功信息*/
return(n);
}
int Delete_a_record(Student stud[],int n) /*按姓名查找，删除一条记录*/
{ char s[20];
int i=0,j;
printf("\t\t\ttell me his(her) name:"); /*交互式问寻*/
scanf("%s",s);
while(strcmp(stud[i].name,s)!=0&&iif(i==n)
{ printf("\t\t\tnot find!\n"); /*返回失败信息*/
return(n);
}
for(j=i;j{
strcpy(stud[j].num,stud[j+1].num);
strcpy(stud[j].name,stud[j+1].name);
stud[j].score=stud[j+1].score;
}
printf("\t\t\tDelete Successed!\n"); /*返回成功信息*/
return(n-1);
}
void Query_a_record(Student stud[],int n) /*查找并显示一个记录*/
{ char s[20];
int i=0;
printf("\t\t\tinput his(her) name:"); /*交互式输入*/
scanf("\t\t\t%s",s);
while(strcmp(stud[i].name,s)!=0&&iif(i==n)
{ printf("\t\t\tnot find!\n"); /*输入失败信息*/
return;

}
printf("\t\t\this(her) number:%s\n",stud[i].num); /*输出该学生信息*/
printf("\t\t\this(her) score:%d\n",stud[i].score);
}
void Statistic(Student stud[],int n) /*新增功能，输出统计信息*/
{ int i,j=0,k=0,sum=0;
float aver; /*成绩平均值*/
for(i=0;i{
sum+=stud[i].score;
if(stud[j].score>stud[i].score) j=i;
if(stud[k].score}
aver=1.0*sum/n;
printf("\t\t\tthere are %d records.\n",n); /*总共记录数*/
printf("\t\t\tthe hignest score:\n"); /*最高分*/
printf("\t\t\tnumber:%s name:%s score:%d\n",stud[j].num,stud[j].name,stud[j].score);
printf("\t\t\tthe lowest score:\n"); /*最低分*/
printf("\t\t\tnumber:%s name:%s score:%d\n",stud[k].num,stud[k].name,stud[k].score);
printf("\t\t\tthe average score is %5.2f\n",aver); /*平均分*/
}
int AddfromText(Student stud[],int n) /*从文件中读入数据*/
{ int i=0,num;
FILE *fp; /*定义文件指针*/
char filename[20]; /*定义文件名*/
printf("\t\t\tInput the filename:");
scanf("\t\t\t%s",filename); /*输入文件名*/
if((fp=fopen(filename,"rb"))==NULL) /*打开文件*/
{ printf("\t\t\tcann't open the file\n"); /*打开失败信息*/
printf("\t\t\t");
system("pause");
return(n);
}
fscanf(fp,"%d",&num); /*读入总记录量*/
while(i{
fscanf(fp,"%s%s%d",stud[n+i].num,stud[n+i].name,&stud[n+i].score);
i++;
}
n+=num;
fclose(fp); /*关闭文件*/
printf("\t\t\tSuccessed!\n");
printf("\t\t\t");
system("pause");
return(n);
}
void WritetoText(Student stud[],int n) /*将所有记录写入文件*/
{
int i=0;
FILE *fp; /*定义文件指针*/
char filename[20]; /*定义文件名*/
printf("\t\t\tWrite Records to a Text File\n"); /*输入文件名*/
printf("\t\t\tInput the filename:");
scanf("\t\t\t%s",filename);
if((fp=fopen(filename,"w"))==NULL) /*打开文件*/
{
printf("\t\t\tcann't open the file\n");
system("pause");
return;
}
fprintf(fp,"%d\n",n); /*循环写入数据*/
while(i{
fprintf(fp,"%-16s%-15s%d\n",stud[i].num,stud[i].name,stud[i].score);
i++;
}
fclose(fp); /*关闭文件*/
printf("Successed!\n"); /*返回成功信息*/
}
void main() /*主函数*/
{
int n=0;
for(;;)
{
switch(menu_select()) /*选择判断*/
{
case 1:
printf("\t\t\tInput Records\n"); /*输入若干条记录*/
n=Input(stu,n);
break;
case 2:
printf("\t\t\tDisplay All Records\n"); /*显示所有记录*/
Display(stu,n);
break;
case 3:
printf("\t\t\tSort\n");
Sort_by_num(stu,n); /*按学号排序*/
printf("\t\t\tSort Suceessed!\n");
printf("\t\t\t");
system("pause");
break;
case 4:
printf("\t\t\tInsert a Record\n");
n=Insert_a_record(stu,n); /*插入一条记录*/
printf("\t\t\t");
system("pause");
break;
case 5:
printf("\t\t\tDelete a Record\n");
n=Delete_a_record(stu,n); /*按姓名查找，删除一条记录*/
printf("\t\t\t");
system("pause");
break;
case 6:
printf("\t\t\tQuery\n");
Query_a_record(stu,n); /*查找并显示一个记录*/
printf("\t\t\t");
system("pause");
break;
case 7:
printf("\t\t\tStatistic\n");
Statistic(stu,n); /*新增功能，输出统计信息*/
printf("\t\t\t");
system("pause");
break;
case 8:
printf("\t\t\tAdd Records from a Text File\n");
n=AddfromText(stu,n); /*新增功能，输出统计信息*/
break;
case 9:
printf("\t\t\tWrite to a Text file\n");
WritetoText(stu,n); /*循环写入数据*/
printf("\t\t\t");
system("pause");
break;
case 0:
printf("\t\t\tHave a Good Luck,Bye-bye!\n"); /*结束程序*/
printf("\t\t\t");
system("pause");
exit(0);
}
}
}

四、函数调用关系图
注：“→”代表调用
Input函数
打印链表记录
Display函数
输入若干条记录
menu_select()函数
选择菜单
Sort_by_num函数
显示所有记录
Delete_a_record函数
按姓名查找，删除一条记录
Query_a_record查找并显示一条记录
Statistic函数
输出统计信息 （新增）
AddfromText函数
从正文中添加数据到结构体数组中
Main函数
Insert_a_record插入一条记录
WritetoText函数 将所有数据写入文件中
退出程序
Reverse(head)函数
按学号排序
五、设计测试流程
1、进入界面
2、输入选项1，回车；
按提示输入数据：
3、回到主菜单；
输入选项7，回车；
输入文件名：data.txt，回车；
出现成功提示，则读入文件操作成功。
4、回到主菜单，输入2，回车
每10个暂停显示数据
5、回到主菜单，输入3，回车
出现排序成功信息。
6、回到主菜单，输入4，回车
按提示插入一组数据
7、回到主菜单，输入5，回车
按提示输入姓名，删除数据
出现删除成功的信息
8、回到主菜单，输入6，回车
输入姓名进行查询
9、回到主菜单，输入7，回车
出现统计信息
10、回到主菜单，输入9，回车
输入result.txt，回车
出现成功写入文件的信息
11、回到主菜单，输入0，回车退出系统
回答者：kingkey001 - 试用期 一级 7-14 22:38
修改答复： kingkey001，您要修改的答复如下: 积分规则 关闭
C语言课程设计报告-------学生成绩简单管理程序
一、系统菜单的主要功能
（1）输入若干条记录
（2）显示所有记录
（3）按学号排序
（4）插入一条记录
（5）按姓名查找，删除一条记录
（6）查找并显示一条记录
（7）输出统计信息 （新增）
（8）从正文中添加数据到结构体数组中
（9）将所有数据写入文件中
（0）退出程序
二、题目分析
该题主要考察学生对结构体，指针，文件的操作，以及C语言算法的掌握,所以完成此道题目要求较强的设计能力，尤其是要有一种大局观的意识。如何调程序也非常重要，通过这个程序可以学习到以前调试短程序没有的的经验。
菜单中的每一个选项都对应一个子程序，子程序的算法几乎囊获了所有C语言学过的技巧，下面就各个子程序中的功能进行说明：
功能1和4的算法相似，输入一条记录到结构体中去，其中有一部很关键，就是通过gets将所有的多余的字符，回车读去，否则就会出错。
功能2是显示所有的记录，通过循环输出，格式也比较重要。
功能3为按学号排序，因为学号定义成了字符数组的形式，因此在运用冒泡法进行排序的时候，要用到strcmp,strcpy等函数。
功能5为按姓名删除记录，先输入姓名，再一一比较，如果没有则返回失败信息，如果找到就将此记录都向前移一位，返回n-1。
功能6的算法在5中就已经体现了，输入姓名，一一比较。
功能7为新增的功能，因为考虑到原来给出的函数中竟然没有对学生成绩的统计功能，因此新增此功能，可以得出所有的记录个数，最高、最低、平均分，并输出相关的学生信息等。
功能8和9是对文件的操作，提前准备好数据。
三、程序正文部分
#include /*引用库函数*/
#include
#include
#include
typedef struct /*定义结构体数组*/
{
char num[10]; /*学号*/
char name[20]; /*姓名*/
int score; /*成绩*/
}Student;
Student stu[80]; /*结构体数组变量*/
int menu_select() /*菜单函数*/
{
char c;
do{
system("cls"); /*运行前清屏*/
printf("\t\t****Students' Grade Management System****\n"); /*菜单选择*/
printf("\t\t | 1. Input Records |\n");
printf("\t\t | 2. Display All Records |\n");
printf("\t\t | 3. Sort |\n");
printf("\t\t | 4. Insert a Record |\n");
printf("\t\t | 5. Delete a Record |\n");
printf("\t\t | 6. Query |\n");
printf("\t\t | 7. Statistic |\n");
printf("\t\t | 8. Add Records from a Text File|\n");
printf("\t\t | 9. Write to a Text file |\n");
printf("\t\t | 0. Quit |\n");
printf("\t\t*****************************************\n");
printf("\t\t\tGive your Choice(0-9):");
c=getchar(); /*读入选择*/
}while(c<'0'||c>'9');
return(c-'0'); /*返回选择*/
}
int Input(Student stud[],int n) /*输入若干条记录*/
{int i=0;
char sign,x[10]; /*x[10]为清除多余的数据所用*/
while(sign!='n'&&sign!='N') /*判断*/
{ printf("\t\t\tstudent's num:"); /*交互输入*/
scanf("\t\t\t%s",stud[n+i].num);
printf("\t\t\tstudent's name:");
scanf("\t\t\t%s",stud[n+i].name);
printf("\t\t\tstudent's score:");
scanf("\t\t\t%d",&stud[n+i].score);
gets(x); /*清除多余的输入*/
printf("\t\t\tany more records?(Y/N)");
scanf("\t\t\t%c",&sign); /*输入判断*/
i++;
}
return(n+i);
}
void Display(Student stud[],int n) /*显示所有记录*/
{
int i;
printf("\t\t\t-----------------------------------\n"); /*格式头*/
printf("\t\t\tnumber name score\n");
printf("\t\t\t-----------------------------------\n");
for(i=1;i{
printf("\t\t\t%-16s%-15s%d\n",stud[i-1].num,stud[i-1].name,stud[i-1].score);
if(i>1&&i%10==0) /*每十个暂停*/
{printf("\t\t\t-----------------------------------\n"); /*格式*/
printf("\t\t\t");
system("pause");
printf("\t\t\t-----------------------------------\n");
}
}
printf("\t\t\t");
system("pause");
}
void Sort_by_num(Student stud[],int n) /*按学号排序*/
{ int i,j,*p,*q,s;
char t[10];
for(i=0;i for(j=0;j if(strcmp(stud[j].num,stud[j+1].num)>0)
{strcpy(t,stud[j+1].num);
strcpy(stud[j+1].num,stud[j].num);
strcpy(stud[j].num,t);
strcpy(t,stud[j+1].name);
strcpy(stud[j+1].name,stud[j].name);
strcpy(stud[j].name,t);
p=&stud[j+1].score;
q=&stud[j].score;
s=*p;
*p=*q;
*q=s;
}
}
int Insert_a_record(Student stud[],int n) /*插入一条记录*/
{char x[10]; /*清除多余输入所用*/
printf("\t\t\tstudent's num:"); /*交互式输入*/
scanf("\t\t\t%s",stud[n].num);
printf("\t\t\tstudent's name:");
scanf("\t\t\t%s",stud[n].name);
printf("\t\t\tstudent's score:");
scanf("\t\t\t%d",&stud[n].score);
gets(x);
n++;
Sort_by_num(stud,n); /*调用排序函数*/
printf("\t\t\tInsert Successed!\n"); /*返回成功信息*/
return(n);
}
int Delete_a_record(Student stud[],int n) /*按姓名查找，删除一条记录*/
{ char s[20];
int i=0,j;
printf("\t\t\ttell me his(her) name:"); /*交互式问寻*/
scanf("%s",s);
while(strcmp(stud[i].name,s)!=0&&i if(i==n)
{ printf("\t\t\tnot find!\n"); /*返回失败信息*/
return(n);
}
for(j=i;j {
strcpy(stud[j].num,stud[j+1].num);
strcpy(stud[j].name,stud[j+1].name);
stud[j].score=stud[j+1].score;
}
printf("\t\t\tDelete Successed!\n"); /*返回成功信息*/
return(n-1);
}
void Query_a_record(Student stud[],int n) /*查找并显示一个记录*/
{ char s[20];
int i=0;
printf("\t\t\tinput his(her) name:"); /*交互式输入*/
scanf("\t\t\t%s",s);
while(strcmp(stud[i].name,s)!=0&&i if(i==n)
{ printf("\t\t\tnot find!\n"); /*输入失败信息*/
return;

}
printf("\t\t\this(her) number:%s\n",stud[i].num); /*输出该学生信息*/
printf("\t\t\this(her) score:%d\n",stud[i].score);
}
void Statistic(Student stud[],int n) /*新增功能，输出统计信息*/
{ int i,j=0,k=0,sum=0;
float aver; /*成绩平均值*/
for(i=0;i {
sum+=stud[i].score;
if(stud[j].score>stud[i].score) j=i;
if(stud[k].score }
aver=1.0*sum/n;
printf("\t\t\tthere are %d records.\n",n); /*总共记录数*/
printf("\t\t\tthe hignest score:\n"); /*最高分*/
printf("\t\t\tnumber:%s name:%s score:%d\n",stud[j].num,stud[j].name,stud[j].score);
printf("\t\t\tthe lowest score:\n"); /*最低分*/
printf("\t\t\tnumber:%s name:%s score:%d\n",stud[k].num,stud[k].name,stud[k].score);
printf("\t\t\tthe average score is %5.2f\n",aver); /*平均分*/
}
int AddfromText(Student stud[],int n) /*从文件中读入数据*/
{ int i=0,num;
FILE *fp; /*定义文件指针*/
char filename[20]; /*定义文件名*/
printf("\t\t\tInput the filename:");
scanf("\t\t\t%s",filename); /*输入文件名*/
if((fp=fopen(filename,"rb"))==NULL) /*打开文件*/
{ printf("\t\t\tcann't open the file\n"); /*打开失败信息*/
printf("\t\t\t");
system("pause");
return(n);
}
fscanf(fp,"%d",&num); /*读入总记录量*/
while(i {
fscanf(fp,"%s%s%d",stud[n+i].num,stud[n+i].name,&stud[n+i].score);
i++;
}
n+=num;
fclose(fp); /*关闭文件*/
printf("\t\t\tSuccessed!\n");
printf("\t\t\t");
system("pause");
return(n);
}
void WritetoText(Student stud[],int n) /*将所有记录写入文件*/
{
int i=0;
FILE *fp; /*定义文件指针*/
char filename[20]; /*定义文件名*/
printf("\t\t\tWrite Records to a Text File\n"); /*输入文件名*/
printf("\t\t\tInput the filename:");
scanf("\t\t\t%s",filename);
if((fp=fopen(filename,"w"))==NULL) /*打开文件*/
{
printf("\t\t\tcann't open the file\n");
system("pause");
return;
}
fprintf(fp,"%d\n",n); /*循环写入数据*/
while(i {
fprintf(fp,"%-16s%-15s%d\n",stud[i].num,stud[i].name,stud[i].score);
i++;
}
fclose(fp); /*关闭文件*/
printf("Successed!\n"); /*返回成功信息*/
}
void main() /*主函数*/
{
int n=0;
for(;;)
{
switch(menu_select()) /*选择判断*/
{
case 1:
printf("\t\t\tInput Records\n"); /*输入若干条记录*/
n=Input(stu,n);
break;
case 2:
printf("\t\t\tDisplay All Records\n"); /*显示所有记录*/
Display(stu,n);
break;
case 3:
printf("\t\t\tSort\n");
Sort_by_num(stu,n); /*按学号排序*/
printf("\t\t\tSort Suceessed!\n");
printf("\t\t\t");
system("pause");
break;
case 4:
printf("\t\t\tInsert a Record\n");
n=Insert_a_record(stu,n); /*插入一条记录*/
printf("\t\t\t");
system("pause");
break;
case 5:
printf("\t\t\tDelete a Record\n");
n=Delete_a_record(stu,n); /*按姓名查找，删除一条记录*/
printf("\t\t\t");
system("pause");
break;
case 6:
printf("\t\t\tQuery\n");
Query_a_record(stu,n); /*查找并显示一个记录*/
printf("\t\t\t");
system("pause");
break;
case 7:
printf("\t\t\tStatistic\n");
Statistic(stu,n); /*新增功能，输出统计信息*/
printf("\t\t\t");
system("pause");
break;
case 8:
printf("\t\t\tAdd Records from a Text File\n");
n=AddfromText(stu,n); /*新增功能，输出统计信息*/
break;
case 9:
printf("\t\t\tWrite to a Text file\n");
WritetoText(stu,n); /*循环写入数据*/
printf("\t\t\t");
system("pause");
break;
case 0:
printf("\t\t\tHave a Good Luck,Bye-bye!\n"); /*结束程序*/
printf("\t\t\t");
system("pause");
exit(0);
}
}
}

四、函数调用关系图
注：“→”代表调用
Input函数
打印链表记录
Display函数
输入若干条记录
menu_select()函数
选择菜单
Sort_by_num函数
显示所有记录
Delete_a_record函数
按姓名查找，删除一条记录
Query_a_record查找并显示一条记录
Statistic函数
输出统计信息 （新增）
AddfromText函数
从正文中添加数据到结构体数组中
Main函数
Insert_a_record插入一条记录
WritetoText函数 将所有数据写入文件中
退出程序
Reverse(head)函数
按学号排序
五、设计测试流程
1、进入界面
2、输入选项1，回车；
按提示输入数据：
3、回到主菜单；
输入选项7，回车；
输入文件名：data.txt，回车；
出现成功提示，则读入文件操作成功。
4、回到主菜单，输入2，回车
每10个暂停显示数据
5、回到主菜单，输入3，回车
出

#include
#include
#include
#include

struct student
{ char num[10];
char name[20];
char sex[5];
float grade[3];
float v;
float sum;
}stu[50];
int k=0;

void input();
void display();
void lookandchange();
void average();
void paixu();
void save();

void main()
{
int a;
do
{

printf("\n\n ******************************************************************\n");
printf(" *"); printf("\t\twelcome enter the student management system"); printf("\t*");
printf("\n ******************************************************************\n");

printf(" *"); printf("\t 1.Access student information"); printf("\t\t\t\t*\n");
printf(" *"); printf("\t 2.Display student information"); printf("\t\t\t\t*\n");
printf(" *"); printf("\t 3.LookandChange student information"); printf("\t\t\t*\n");
printf(" *"); printf("\t 4.By sum Sort student information and output"); printf("\t\t*\n");
printf(" *"); printf("\t 5.save the student information"); printf("\t\t\t*\n");
printf(" *"); printf("\t 6. exit "); printf("\t\t\t\t\t*\n");
printf(" ******************************************************************\n");

printf(" Enter you choice : ");
scanf("%d",&a);

switch(a)
{

case 1:printf("\n");input();break;
case 2:printf("\n");display();break;
case 3:printf("\n");lookandchange();break;
case 4:printf("\n");paixu();break;
case 5:printf("\n");save();break;
case 6:printf("\n");exit(0);break;
default:printf("\nThe choice is between 1 to 6.\n");
}
}while(a!=0);

}

void input()
{ int j;
char ch[20];
printf("\nenter student information:\n");
do
{ printf("\nnum: ");
scanf("%s",stu[k].num);
printf("\nname: ");
scanf("%s",stu[k].name);
printf("\nsex: ");
scanf("%s",stu[k].sex);
for(j=0;j<3;j++)
{ printf("\ngrade%d: ",j+1);
scanf("%f",&stu[k].grade[j]); }
k++;
printf("\nif want continue input student information(y/n): ");
scanf("%s",ch);
}while(strcmp(ch,"y")==0||strcmp(ch,"Y")==0);
average();
display();
}

void display()
{ int i;
printf(" the student information is:\n");
for(i=0;i { printf("%-10s %-10s %-5s %.2f %.2f %.2f %8f %8f\n",stu[i].num,stu[i].name,stu[i].sex,stu[i].grade[0],stu[i].grade[1],stu[i].grade[2],stu[i].sum,stu[i].v);
printf("\n"); }
}

void average()
{ int i,j;
for(i=0;i { stu[i].sum=0;
for(j=0;j<3;j++)
stu[i].sum=stu[i].sum+stu[i].grade[j] ;
stu[i].v=stu[i].sum/5; }
}

void lookandchange()

{ int pass[4]; int i,j,l,flag;
char a[20],ch[10],c[20];
printf("This is a database management system:\n");
for(l=0;l<3;l++)
{ flag=0;
printf(" please enter the password: ");
scanf("%1d%1d%1d%1d",&pass[0],&pass[1],&pass[2],&pass[3]);
for(i=0;i<4;i++)
if(pass[i]==i+1) flag=flag+1;
if(flag==4)
{ printf("\nenter you want look student num:");
scanf("%s",a);
for(i=0;i if(strcmp(stu[i].num,a)==0) printf("%-10s %-10s %-5s %.2f %.2f %.2f %8f %8f\n",stu[i].num,stu[i].name,stu[i].sex,stu[i].grade[0],stu[i].grade[1],stu[i].grade[2],stu[i].sum,stu[i].v);
printf("\nenter you want look student name:");
scanf("%s",a);
for(i=0;i if(strcmp(stu[i].name,a)==0) printf("%-10s %-10s %-5s %.2f %.2f %.2f %8f %8f\n",stu[i].num,stu[i].name,stu[i].sex,stu[i].grade[0],stu[i].grade[1],stu[i].grade[2],stu[i].sum,stu[i].v);
printf("\nenter you want change student num:");
scanf("%s",a);
for(i=0;i {
if(strcmp(stu[i].num,a)==0)
{ printf("\nyou sure want change student num(y/n): ");
scanf("%s",ch);
if(strcmp(ch,"y")==0||strcmp(ch,"Y")==0) { printf("\nnum:"); scanf("%s",stu[i].num);}
printf("\nyou sure want change student name(y/n): ");
scanf("%s",ch);
if(strcmp(ch,"y")==0||strcmp(ch,"Y")==0) { printf("\nname:"); scanf("%s",stu[i].name);}
printf("\nyou sure want change student sex(y/n): ");
scanf("%s",ch);
if(strcmp(ch,"y")==0||strcmp(ch,"Y")==0) { printf("\nsex:"); scanf("%s",stu[i].sex);}
printf("\nyou sure want change student grade(y/n): ");
scanf("%s",ch);
if(strcmp(ch,"y")==0||strcmp(ch,"Y")==0)
for(j=0;j<3;j++)
{ printf("grade%d：",j+1); scanf("%f",&stu[i].grade[j]); printf("\n"); }
stu[i].sum=0;
for(j=0;j<5;j++)
stu[i].sum=stu[i].sum+stu[i].grade[j] ;
stu[i].v=stu[i].sum/5;
}
} printf("\nyou sure want delete student information(y/n): ");
scanf("%s",ch);
if(strcmp(ch,"y")==0||strcmp(ch,"Y")==0)
{ printf("\nenter you want delete num ：\n");
printf("num：");
scanf("%s",&c);
for(i=0;i if(strcmp(c,stu[i].num)==0) break;
for(j=i;j<=2;j++)
stu[j]=stu[j+1];
printf("\t\t\tyou had delete %s\n",c);
k--; }
}
else printf("\nyou enter password is wrong.\n"); }
display();
}

void paixu()
{ struct student temp;
int i,j;
for(i=0;i{
for(j=i+1;j {
if(stu[i].sum {
temp=stu[i];
stu[i]=stu[j];
stu[j]=temp;
}
} }
display();
}

void save()
{ FILE *fp; int i;
if((fp=fopen("xinxi.txt","w"))==NULL)
{ printf("cannot write the file.\n");
exit(0);}
for(i=0;strlen(stu[i].num)!=0;i++)
fprintf(fp,"%-10s %-10s %-5s %.2f %.2f %.2f %8f %8f\n",stu[i].num,stu[i].name,stu[i].sex,stu[i].grade[0],stu[i].grade[1],stu[i].grade[2],stu[i].sum,stu[i].v);
fclose(fp);
}