用C语言实现一个学生成绩管理系统 实现学生信息管理。包括：录入、查询、排序等功能。 要求： 用数据文件保存学生基本信息(学号 姓名 课程1 课程2 课程3…) ,利用菜单可以循环实现各个功能。

用C语言实现一个学生成绩管理系统
题目： 学生成绩管理系统
功能： 实现学生信息管理。包括：录入、查询、排序等功能。
要求： 用数据文件保存学生基本信息(学号 姓名 课程1 课程2 课程3…) ,利用菜单可以循环实现各个功能。
进一步要求*： (1) 能够实现增加、删除、修改功能；
(2) 能够实现统计功能等。
思路简介： 要采用模块化思想，对不同的功能编写不同的函数进行实现
不足之处： 没有查重处理，需要进一步完善
比如此结构体中，定义有学号，在函数查找、修改等功能中也是通过学号来查找。
没有查重则对结果影响比较大。举例来说，原本数据存有学号为 20190156 的学生
。当你选择增加数据且再次输入一个学号为 20190518 的学生数据时，程序并不会
报错，只是默默的存在在数据文件中。所以这就带来了很大的隐患。当你继续选择
查找功能时，假如你输入的学号是 20190518 ，这时候计算机就不知道怎么处理了
。在实际生活中情况可能更复杂，带来更大的隐患。所以应该增加查重环节并对数
据进一步处理。

#include <stdio.h>
#include <string.h>
#include <stdlib.h>   //提供 exit() 函数支持
#define SIZE 100000
//#include"conio.h"

//声明函数原型
void finput();    //存入数据
void flist();     //输出数据
void fsearch();   //查找数据
void fadden();    //增加数据
void fchange();   //修改数据
void ftaxis();    //数据排序
void stat();      //统计数据

//定义结构体
struct student
{
int num;        //存放
char name[10];  //定义名字数组变量
int C;          //C 语言成绩
int Maths;      //数学课成绩
int En;         //英语课成绩
float ave;      //三门课平均成绩
} stu[SIZE];        //在定义结构体时同时声明结构体变量

int main()
{
int n;
for(;;)          //使程序能够循环，在循环内部判断何时结束
{
printf("\n\n");        //与上次的输出结果保持间隔，便于美观
printf("	_________________________________\n");//菜单输出
printf("	|           MENU                |\n");
printf("	|       1.Input data            |\n");
printf("	|       2.Output data           |\n");
printf("	|       3.Search data           |\n");
printf("	|       4.Add data              |\n");
printf("	|       5.Revise data           |\n");
printf("	|       6.Sort data             |\n");
printf("	|       7.Statistics            |\n");
printf("	|       8.  quit                |\n");
printf("	|_______________________________|\n");
printf("  Please choose your function:(1-7):");          //功能选择
scanf("%d",&n);
printf("\n");
if(n>0&&n<8) {
switch(n) {
case 1:
finput();
break;
case 2:
flist();
break;
case 3:
fsearch();
break;
case 4:
fadden();
break;
case 5:
fchange();
break;
case 6:
ftaxis();
break;
case 7:
stat();
case 8:
printf("\n    ~~~~~~~~~~~~~~~~~~~~~~~~~~\n");     //退出提示
printf("             Goodbye!         \n");
printf("    ~~~~~~~~~~~~~~~~~~~~~~~~~~\n");
exit(0);//将程序退出
}
} else //没有按规范选择功能，要进行错误提示     //错误提示
{
printf("\n    ~~~~~~~~~~~~~~~~~~~~~~~~~~\n");
printf("           error input!       \n");
printf("    ~~~~~~~~~~~~~~~~~~~~~~~~~~\n");
//			break; //应该将这一句话去掉才能使在输错的情况下也进行菜单循环
}
}
return 0;
}
/*
主函数部分结束
*/

/*
下面是模块化设计
每个功能对应一个函数
*/

//part 1 : 进行信息录入
void finput()
{
FILE *fp;            //声明指针变量
int i,p;
fp=fopen("grades","wb");          //首次打开文件， 若没有文件将会自动创建新文件
for(i=0; i<SIZE; i+1)
{
printf("1 to continue and 0 to end input: ");        //询问是否继续输入
scanf("%d",&i);
if(i==0)
{
fclose(fp);
return;
}
else {
printf("Please inut your school number, C grade, Math grade, English grade:\n");
scanf("%d%s%d%d%d",&stu[i].num,stu[i].name,&stu[i].C,&stu[i].Maths,&stu[i].En);
stu[i].ave=(stu[i].C+stu[i].Maths+stu[i].En)/3.0;
fwrite(&stu[i],sizeof(struct student),1,fp);
}
}
fclose(fp);         //记得关闭文件，这是一个好习惯！
}

//part 2: 将结果输出
void flist()
{
FILE *fp;
int i;
fp=fopen("grades","rb");
printf("____________________________________________________________________________________________________\n");
printf("|                                                  Report                                           |\n");
printf("|~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~|\n");
printf("|        ID      |    name   |    C grade    |    Math grade   |   English grade   |    Average     |\n");
printf("|~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~|\n");
for(i=0; fread(&stu[i],sizeof(struct student),1,fp)==1; i++)
printf("|%11d%15s%13d%17d%18d%19.2f\n",stu[i].num,stu[i].name,stu[i].C,stu[i].Maths,stu[i].En,stu[i].ave);
/*
此处采用字宽输入比加空格更好， 因为若是使用空格输入，当学号或者名字前后输入的长度不一致时，格式会乱掉，导致无法对其格式
*/
printf("|___________________________________________________________________________________________________|\n\n");
fclose(fp);
}

//part 3：查找数据
void fsearch()
{
FILE *fp;
int i,num,flag=0;//flag 用来判断是否需要进行错误提示
fp=fopen("grades","rb");
rewind(fp);
printf("Which one are you searching? Input the School number: ");
scanf("%d",&num);

for(i=0; i<=SIZE; i++)
{
if(stu[i].num==num)
{
printf("____________________________________________________________________________________________________\n");//与上文采用相同的输出格式，会显得统一整洁
printf(" Here are the rusults                                                                               \n");
printf("|~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~|\n");
printf("|        ID      |    name   |    C grade    |    Math grade   |   English grade   |    Average     \n");
printf("|~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~|\n");
printf("|%11d%15s%13d%17d%18d%19.2f\n",stu[i].num,stu[i].name,stu[i].C,stu[i].Maths,stu[i].En,stu[i].ave);
printf("|__________________________________________________________________________________________________|\n\n");
flag+=1;
}
}
if(flag==0)
{
printf("\n    ~~~~~~~~~~~~~~~~~~~~~~~~~~\n");
printf("           error input!       \n");
printf("    ~~~~~~~~~~~~~~~~~~~~~~~~~~\n");
}
//	printf("___________________________________________________________________________________________________________\n\n");
fclose(fp);
}

//part 4：增加数据
void fadden()
{
int i,s;
FILE *fp;
fp=fopen("grades","ab+");
rewind(fp);
printf("___________________________________________________________________________ ________________________\n");
printf("|                                                  Report                                          |\n");
printf("|~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~|\n");
printf("|        ID      |    name   |    C grade    |    Math grade   |   English grade   |    Average     \n");
printf("|~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~|\n");
for(i=0; fread(&stu[i],sizeof(struct student),1,fp)==1; i++)
printf("|%11d%15s%13d%17d%18d%19.2f\n",stu[i].num,stu[i].name,stu[i].C,stu[i].Maths,stu[i].En,stu[i].ave);
printf("____________________________________________________________________________________________________\n");
s=i;	         //记录学号位置，从此处开始增加新的数据
for(i=s; i<SIZE; i++) {
printf("1 to continue and 0 to end input: ");
scanf("%d",&i);
if(i==0)
{
fclose(fp);
return;
} else
{
printf("Please inut your school number, C grade, Math grade, English grade:\n");
scanf("%d%s%d%d%d",&stu[i].num,stu[i].name,&stu[i].C,&stu[i].Maths,&stu[i].En);
stu[i].ave=(stu[i].C+stu[i].Maths+stu[i].En)/3.0;
fwrite(&stu[i],sizeof(struct student),1,fp);
}
}
fclose(fp);
}

//part 5：修改数据
void fchange()
{
FILE *fp;
int i,num,n;
int flag=0;
printf("Which one are you searching? Input the School number: ");
scanf("%d",&num);
printf("\n");
for(i=0; i<=SIZE; i++)
if(stu[i].num==num)
{
printf("____________________________________________________________________________________________________\n");
printf("|                                                  Report                                           |\n");
printf("|~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~|\n");
printf("|        ID      |    name   |    C grade    |    Math grade   |   English grade   |    Average     |\n");
printf("|~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~|\n");
printf("|%11d%15s%13d%17d%18d%19.2f\n",stu[i].num,stu[i].name,stu[i].C,stu[i].Maths,stu[i].En,stu[i].ave);
printf("|___________________________________________________________________________________________________|\n\n");
n=i;
flag=1;
break;
}
if(flag==0) {
printf("\n    ~~~~~~~~~~~~~~~~~~~~~~~~~~\n");
printf("           error input!       \n");
printf("    ~~~~~~~~~~~~~~~~~~~~~~~~~~\n");
return;
}
printf("\n\n");
fp=fopen("grades","rb+");
fseek(fp,n*sizeof(struct student),0);
printf("Please inut your school number, C grade, Math grade, English grade:\n");
scanf("%d%s%d%d%d",&stu[i].num,stu[i].name,&stu[i].C,&stu[i].Maths,&stu[i].En);
stu[i].ave=(stu[i].C+stu[i].Maths+stu[i].En)/3.0;
fwrite(&stu[i],sizeof(struct student),1,fp);
fclose(fp);
fp=fopen("grades","rb");
printf("_______________________________________________________________________________ _____________________\n");
printf("|                                                  Report                                           |\n");
printf("|~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~|\n");
printf("|        ID      |    name   |    C grade    |    Math grade   |   English grade   |    Average     |\n");
printf("|~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~|\n");
for(i=0; fread(&stu[i],sizeof(struct student),1,fp)==1; i++)
{
printf("|%11d%15s%13d%17d%18d%19.2f\n",stu[i].num,stu[i].name,stu[i].C,stu[i].Maths,stu[i].En,stu[i].ave);
}
printf("|___________________________________________________________________________________________________|\n");
fclose(fp);
}

//part 6：按平均成绩进行排序
void ftaxis()
{
int i,j,n;
FILE *fp;
struct student t;
fp=fopen("grades","rb");
printf("____________________________________________________________________________________________________ \n");
printf("|                                                  Report                                           |\n");
printf("|~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~|\n");
printf("|        ID      |    name   |    C grade    |    Math grade   |   English grade   |    Average     |\n");
printf("|~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~|\n");
for(i=0; fread(&stu[i],sizeof(struct student),1,fp)==1; i++)
printf("|%11d%15s%13d%17d%18d%19.2f\n",stu[i].num,stu[i].name,stu[i].C,stu[i].Maths,stu[i].En,stu[i].ave);
printf("|___________________________________________________________________________________________________|\n\n");
fclose(fp);
n=i;
for(i=0; i<n; i++)
for(j=i+1; j<n; j++)
if(stu[i].ave<stu[j].ave) {
t=stu[i];
stu[i]=stu[j];
stu[j]=t;
}
fp=fopen("grades","wb");
printf("\n\n\n");
printf("_____________________________________________________________________________________________________\n");
printf("|                                                  Report                                           |\n");
printf("|~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~|\n");
printf("|        ID      |    name   |    C grade    |    Math grade   |   English grade   |    Average     |\n");
printf("|~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~|\n");
for(i=0; i<n; i++) {
fwrite(&stu[i],sizeof(struct student),1,fp);
printf("|%11d%15s%13d%17d%18d%19.2f\n",stu[i].num,stu[i].name,stu[i].C,stu[i].Maths,stu[i].En,stu[i].ave);
}
printf("|___________________________________________________________________________________________________|\n");
fclose(fp);
}

//part 6: 统计指定分数之上的人数
void stat()
{
FILE *fp;
int i,num,flag=0,count=0;//flag 用来判断是否需要进行错误提示, count用来统计个数
float score_;
fp=fopen("grades","rb");
rewind(fp);
printf("Do you want to know the percentage of the total score?\nEnter your number: ");
scanf("%f",&score_);

for(i=0; i<=SIZE; i++)
{
if(score_ < stu[i].ave )
{
count++;
flag=1;
}
}
if(flag == 1)
printf("%d in total above your number\n",count);
if(flag==0)
{
printf("\n    ~~~~~~~~~~~~~~~~~~~~~~~~~~\n");
printf("           error input!       \n");
printf("    ~~~~~~~~~~~~~~~~~~~~~~~~~~\n");
}
//	printf("___________________________________________________________________________________________________________\n\n");
fclose(fp);
}

欢迎大家交流指正~