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);
}

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