（C）学生成绩管理系统

 #include <stdio.h>
 #include <string.h>
 #include <stdlib.h>
 #include <unistd.h>

 struct Student
 {
     char id[];
     char name[];
     int score;
 };

 typedef struct User
 {
     char userName[];
     char userPassword[];
 }UserInfo;

 void inputNameAndPassword();
 void logon();
 void creatDataBace();
 void selectServe();
 void checkAchievement();
 void addAchievement();
 void delectAchievement();
 void changeAchievement();
 void sortAchievement();
 void start();

 int main(int argc, const char * argv[])
 {
     start();
     //清屏未实现
     system("clear");

     FILE *file;
     file=fopen("/Users/5000/Desktop/C:OC作业/Final Project/achievement.txt", "r+");
     struct Student aStudent;
     if (fread(&aStudent, sizeof(struct Student), , file)==) {
         creatDataBace();
     }
     fclose(file);
     //清屏未实现

     selectServe();

     return ;
 }

 void start()
 {
     int land;
     printf("1.注册\n2.登陆\n");
     scanf("%d",&land);
     if (land==) {
         logon();
     }else
     {
         if (land==)
             inputNameAndPassword();
         else
         {
             printf("输入有误，请重新选择\n");
             start();
         }
      }
 }

 void logon()
 {
     UserInfo userInput;
     printf("\n------------------注册用户------------------");
     printf("\n请输入注册用户名：");
     scanf("%s",userInput.userName);
     printf("请输入密码：");
     scanf("%s",userInput.userPassword);
     FILE *fp;
     if((fp=fopen("/Users/5000/Desktop/C:OC作业/Final Project/user_password.txt", "a+"))==NULL)
     {
         printf("注册失败！");
         exit();
     }
     if ((fwrite(&userInput, sizeof(UserInfo), , fp))!=) {
         printf("注册失败！");
         exit();
     }
     fclose(fp);
     inputNameAndPassword();
 }

 void inputNameAndPassword()
 {
     UserInfo userInput,userBase[];
     int i=,count=,chance=;

     FILE *fp;
     if((fp=fopen("/Users/5000/Desktop/C:OC作业/Final Project/user_password.txt", "r"))==NULL)
     {
         printf("登陆失败！");
         exit();
     }

     while(fread(&userBase[i], sizeof(UserInfo), , fp)!=)
         i++;
     count=i;
     fclose(fp);

     printf("\n------------------用户登陆------------------\n");
     while ()
     {
         printf("用户名：");
         scanf("%s",userInput.userName);
         printf("密码：");
         scanf("%s",userInput.userPassword); //密码用星号代替未实现

         for (i=; i<count; i++) {
             if((strcmp(userInput.userName, userBase[i].userName)==)&&(strcmp(userInput.userPassword, userBase[i].userPassword)==))
                 return;
         }
         if (chance!=)
             printf("\n用户名或密码输入错误，请重新输入（还有 %d 次机会）：\n",-chance);
         chance++;
         if (chance>=) {
             printf("\n尝试超出次数！退出程序。");
             exit();
         }
     }
 }

 void selectServe()
 {
     int serveNumber;
     printf("\n------------------操作菜单------------------");
     printf("\n1.查询学生成绩\n2.添加学生成绩\n3.删除学生成绩\n4.修改学生成绩\n5.查看成绩排名\n");
     printf("\n请选择您需要的操作(输入序号选择，输入其它退出程序）:");
     scanf("%d",&serveNumber);
     switch (serveNumber) {
         case :
             checkAchievement();
             break;
         case :
             addAchievement();
             break;
         case :
             delectAchievement();
             break;
         case :
             changeAchievement();
             break;
         case :
             sortAchievement();
             break;
         default:
             break;
     }
     printf("\n ^^ 再见.....");
 }

 void creatDataBace()
 {
     FILE *fp;
     struct Student student[];
     int flag=;
     int i=;
     int k=;
     int count=;
     int m=;
     char ch;

     if((fp=fopen("/Users/5000/Desktop/C:OC作业/Final Project/achievement.txt", "r"))==NULL)
     {
         printf("打开文件错误！");
         exit();
     }

     for (i=;fread(&student[i], sizeof(struct Student), , fp)!=;i++);
     count=i;
     fclose(fp);

     printf("\n------------------初始化数据库------------------");
     i=;
     while () {
         printf("\n请输入学生的基本信息:\n");
         do
         {
             printf("第 %d 个学生的ID号：",i+);
             scanf("%s",student[i].id);

             for (k=i-; k>=; k--) {
                 if(strcmp(student[i].id, student[k].id)==)
                 {
                     printf("\nID号已存在，请重新输入\n");
                     flag=;
                     break;
                 }
             }

             for (k=; k<count; k++) {
                 if(strcmp(student[i].id, student[k].id)==)
                 {
                     printf("\nID号在整个数据库中已存在，请重新输入\n");
                     flag=;
                     break;
                 }
             }
         }while(flag);

         do
         {
             flag=;
             printf("学生名称：");
             scanf("%s",student[i].name);
         }while (flag);

         do
         {
             flag=;
             printf("学生成绩：");
             scanf("%d",&student[i].score);
             if (student[i].score>||student[i].score<) {
                 flag=;
                 continue;
             }
         }while (flag);

         i++;
         m++;
         printf("\n是否继续创建学生成绩信息？输入'y'或'Y'继续，输入其它进入下一步：");
         getchar();
         scanf("%c",&ch);
         if (ch!='Y'&&ch!='y')
             break;
     }

     if((fp=fopen("/Users/5000/Desktop/C:OC作业/Final Project/achievement.txt", "a"))==NULL)
     {
         printf("打开文件错误！");
         exit();
     }

     for (i=; i<m; i++) {
         if (fwrite(&student[i], sizeof(struct Student), , fp)!=)
             printf("数据保存失败");
     }

     fclose(fp);
 }

 void checkAchievement()
 {
     struct Student student;
     char id[];
     FILE *fp;

     printf("\n------------------查询学生成绩------------------\n");
     printf("请输入需要查询的学生ID：");
     scanf("%s",id);
     while ()
     {
         if ((fp=fopen("/Users/5000/Desktop/C:OC作业/Final Project/achievement.txt","r"))==NULL)
         {
             printf("打开文件错误！");
             selectServe();
         }

         while (fread(&student, sizeof(struct Student), , fp)!=) {
             if (strcmp(id,student.id)==) {
                 printf("ID:%s  姓名:%s  分数:%d\n",student.id,student.name,student.score);
                 break;
             }
         }

         if (strcmp(id,student.id)!=)
             printf("没查找到ID为 %s 的学生信息。\n",id);

         printf("\n请输入需要查询的学生ID（输入n返回操作菜单）：");
         scanf("%s",id);
         if (strcmp(id,"n")==||strcmp(id,"N")==) {
             fclose(fp);
             selectServe();
         }
         fclose(fp);
     }
 }

 void addAchievement()
 {
     FILE *fp;
     struct Student student[];
     int i=;
     int count=;
     char ch;

     if((fp=fopen("/Users/5000/Desktop/C:OC作业/Final Project/achievement.txt", "r"))==NULL)
     {
         printf("打开文件错误！");
         selectServe();
     }

     for (i=;fread(&student[i], sizeof(struct Student), , fp)!=;i++);
     count=i;
     fclose(fp);

     if((fp=fopen("/Users/5000/Desktop/C:OC作业/Final Project/achievement.txt", "a+"))==NULL)
     {
         printf("打开文件错误！");
         selectServe();
     }

     printf("\n------------------添加学生成绩------------------");
     while ()
     {
         int flag;
         do {
             flag=;
             printf("\n请输入需要添加的学生ID：");
             scanf("%s",student[count].id);
             for (int k=; k<count; k++) {
                 if(strcmp(student[count].id, student[k].id)==)
                 {
                     printf("ID号在数据库中已存在，请重新输入。\n");
                     flag=;
                     break;
                 }
             }
         } while (flag);
         printf("请输入需要添加的学生姓名：");
         scanf("%s",student[count].name);
         printf("请输入需要添加的学生分数：");
         scanf("%d",&student[count].score);
         if (fwrite(&student[count], sizeof(struct Student), , fp)!=) {
             printf("添加失败！");
         }
         printf("添加成功！\n");
         printf("\n是否继续添加学生成绩信息？输入y继续，输入其它返回操作菜单：");
         getchar();
         scanf("%c",&ch);
         if (ch!='y'&&ch!='Y') {
             fclose(fp);
             selectServe();
         }
         count++;
     }
 }

 void delectAchievement()
 {
     char id[];
     char sure;
     FILE *infile,*outfile;
     struct Student students[];
     int i=,flag=-,count=;

     printf("\n------------------删除学生成绩------------------");

     if ((infile=fopen("/Users/5000/Desktop/C:OC作业/Final Project/achievement.txt","r"))==NULL)
     {
         printf("打开文件错误！");
         selectServe();
     }

     while (fread(&students[i], sizeof(struct Student), , infile)!=) i++;
     count=i;
     fclose(infile);

     printf("\n请输入需要删除的学生ID：");
     scanf("%s",id);
     while ()
     {
         for (i=; i<count; i++) {
             if (strcmp(id,students[i].id)==) {
                 flag=i;
                 break;
             }
         }

         if (flag==-)
             printf("没查找到ID为 %s 的学生信息。",id);
         else
         {
             printf("确认要删除ID为 %s 的学生信息吗？（y确定 n取消）",id);
             getchar();
             scanf("%c",&sure);
             if (sure=='y')
             {
                 for (i=flag; i<count-; i++) {
                     students[i]=students[i+];
                 }
                 count--;

                 outfile=fopen("/Users/5000/Desktop/C:OC作业/Final Project/temp.txt","w+");
                 for (i=; i<count; i++) {
                     if(fwrite(&students[i], sizeof(struct Student), , outfile)!=)
                     {
                         printf("删除失败！");
                         selectServe();
                     }
                 }
                 fclose(outfile);
             }
             printf("删除成功！\n");
         }

         printf("\n请输入需要删除的学生ID（输入n返回操作菜单）：");
         scanf("%s",id);

         if (strcmp(id,"n")==||strcmp(id,"N")==) {
             /*其实用w打开原来文件就可以直接写入原来的文件，w打开会清空原来文件的内容*/
             unlink("/Users/5000/Desktop/C:OC作业/Final Project/achievement.txt");//#include <unistd.h>
             rename( "/Users/5000/Desktop/C:OC作业/Final Project/temp.txt","/Users/5000/Desktop/C:OC作业/Final Project/achievement.txt");//#include <unistd.h>
             selectServe();
         }
     }
 }

 void changeAchievement()
 {
     FILE *fp;
     char id[],ch;
     int score=,count=,flag=;
     int i=;
     struct Student students[];

     if ((fp=fopen("/Users/5000/Desktop/C:OC作业/Final Project/achievement.txt","r"))==NULL)
     {
         printf("打开文件错误！");
         selectServe();
     }
     while (fread(&students[i], sizeof(struct Student), , fp)!=) i++;
     count=i;
     fclose(fp);

     printf("\n------------------学生成绩排名------------------\n");
     while ()
     {
         printf("请输入需要修改成绩的学生ID：");
         scanf("%s",id);

         for (i=;i<count;i++) {
             if (strcmp(id,students[i].id)==) {
                 printf("ID为 %s 的%s同学，分数为:%d\n",students[i].id,students[i].name,students[i].score);
                 printf("更改%s同学的分数值为：",students[i].name);
                 scanf("%d",&score);
                 students[i].score=score;
                 flag=;
                 break;
             }
         }

         if (flag)
             printf("没查找到ID为 %s 的学生信息。\n",id);

         if ((fp=fopen("/Users/5000/Desktop/C:OC作业/Final Project/achievement.txt","w+"))==NULL)
         {
             printf("打开文件错误！");
             selectServe();
         }
         for (i=; i<count; i++) {
             if(fwrite(&students[i], sizeof(struct Student), , fp)!=)
             {
                 printf("修改失败！");
                 selectServe();
             }
         }

         printf("\n是否继续查询学生成绩信息？输入'y'或'Y'继续，输入其它返回操作菜单：");
         getchar();
         scanf("%c",&ch);
         if (ch!='y'&&ch!='Y') {
             fclose(fp);
             selectServe();
         }
     }
 }

 void sortAchievement()
 {
     char ch;
     FILE *fp;
     struct Student students[],temp;
     int i=,j=,count=;

     if ((fp=fopen("/Users/5000/Desktop/C:OC作业/Final Project/achievement.txt","r"))==NULL)
     {
         printf("打开文件错误！");
         selectServe();
     }

     while (fread(&students[i], sizeof(struct Student), , fp)!=) i++;
     fclose(fp);
     count=i;

     printf("\n------------------学生成绩排名------------------\n");
     for(i=;i<count-;i++)
         for(j=;j<count--i;j++)
         {
             if (students[j].score<students[j+].score) {
                 temp=students[j];
                 students[j]=students[j+];
                 students[j+]=temp;
             }
         }
     printf("ID    Name      Score\n"); //Id****Name******Score
     for (i=; i<count; i++) {
         printf("%s",students[i].id);
         for (j=; j<-strlen(students[i].id); j++)
             printf(" ");

         printf("%s",students[i].name);
         for (j=; j<-strlen(students[i].name); j++)
             printf(" ");

         printf("%d\n",students[i].score);
     }

     printf("\n输入任意键返回操作菜单：");
     getchar(); //接收选择操作4时输入的回车
     scanf("%c",&ch);
     selectServe();

 }

运行截图：