用c语言设计一个简单的学生成绩管理系统。设有学生成绩文件student.txt，每位学生成绩信息包含学号（num）、姓名（name）、性别（）、出生日期（birthday，包括年、月、日，分别表示为年、月、日）、3门功课的成绩（高数、C语言、大学物理）、总分和平均分。设计程序，要求从文件student.txt中读出学生成绩表，之后参对成绩表进行如下操作： （1）建立学生成绩信息结构数组（从student.txt读入数据） （2）显示。即输出出所有成绩。（3）添加。可添加一条或多条记录。（4）排序。分为两个方面，按学号递增排序和按总分递减排序。（5）查找。分为三方面：按学号查找、按姓名查找和按分数查找。（6）计算。计算各门课的平均分数。（7）保存。退出程序前将结果保存到studeng.txt。2）要求 （1）设计一个简单的界面 （2）每一个功能设为一个模块

很好，下面是一个简单的学生成绩管理系统的C语言程序，共包含七个模块，分别实现了题目要求的七个功能。其中，使用了结构体数组存储学生成绩信息，文件IO读写学生成绩信息，以及对学生成绩信息进行排序、查找、计算等操作。

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

#define MAX_STUDENT_NUM 100  // 最大学生数
#define MAX_NAME_LEN 20  // 最大姓名长度
#define MAX_DATE_LEN 11  // 最大日期长度

// 学生信息结构体
typedef struct {
    int num;  // 学号
    char name[MAX_NAME_LEN];  // 姓名
    char gender;  // 性别
    char birthday[MAX_DATE_LEN];  // 出生日期
    float score[3];  // 三门功课成绩
    float total_score;  // 总分
    float average_score;  // 平均分
} Student;

// 函数声明
void read_file(Student *students, int *student_num, const char *filename);
void show(Student *students, int student_num);
void add(Student *students, int *student_num);
void sort_by_num(Student *students, int student_num);
void sort_by_score(Student *students, int student_num);
void search_by_num(Student *students, int student_num);
void search_by_name(Student *students, int student_num);
void search_by_score(Student *students, int student_num);
void calculate_average_score(Student *students, int student_num);
void save_file(Student *students, int student_num, const char *filename);

// 主函数
int main() {
    Student students[MAX_STUDENT_NUM];  // 学生信息数组
    int student_num = 0;  // 学生数目
    char filename[] = "student.txt";  // 学生成绩信息文件名
    int choice;  // 用户选择的操作

    while (1) {
        // 打印菜单
        printf("=============================================\n");
        printf("=           学生成绩管理系统                =\n");
        printf("=============================================\n");
        printf("= 1. 显示所有学生信息                       =\n");
        printf("= 2. 添加学生信息                           =\n");
        printf("= 3. 按学号递增排序                         =\n");
        printf("= 4. 按总分递减排序                         =\n");
        printf("= 5. 按学号查找                             =\n");
        printf("= 6. 按姓名查找                             =\n");
        printf("= 7. 按分数查找                             =\n");
        printf("= 8. 计算各门课的平均分数                   =\n");
        printf("= 9. 保存学生成绩信息到文件student.txt      =\n");
        printf("= 0. 退出程序                               =\n");
        printf("=============================================\n");
        printf("请输入您的选择（0-9）：");
        scanf("%d", &choice);

        switch (choice) {
            case 0:
                // 退出程序
                printf("谢谢使用，再见！\n");
                exit(0);
            case 1:
                // 显示所有学生信息
                show(students, student_num);
                break;
            case 2:
                // 添加学生信息
                add(students, &student_num);
                break;
            case 3:
                // 按学号递增排序
                sort_by_num(students, student_num);
                break;
            case 4:
                // 按总分递减排序
                sort_by_score(students, student_num);
                break;
            case 5:
                // 按学号查找
                search_by_num(students, student_num);
                break;
            case 6:
                // 按姓名查找
                search_by_name(students, student_num);
                break;
            case 7:
                // 按分数查找
                search_by_score(students, student_num);
                break;
            case 8:
                // 计算各门课的平均分数
                calculate_average_score(students, student_num);
                break;
            case 9:
                // 保存学生成绩信息到文件student.txt
                save_file(students, student_num, filename);
                break;
            default:
                printf("输入有误，请重新输入！\n");
                break;
        }
    }

    return 0;
}

// 从文件中读取学生成绩信息
void read_file(Student *students, int *student_num, const char *filename) {
    FILE *fp;

    if ((fp = fopen(filename, "r")) == NULL) {
        printf("无法打开文件%s！\n", filename);
        exit(-1);
    }

    while (!feof(fp)) {
        fscanf(fp, "%d %s %c %s %f %f %f\n",
               &students[*student_num].num, students[*student_num].name,
               &students[*student_num].gender, students[*student_num].birthday,
               &students[*student_num].score[0], &students[*student_num].score[1],
               &students[*student_num].score[2]);
        students[*student_num].total_score = students[*student_num].score[0] +
                                             students[*student_num].score[1] +
                                             students[*student_num].score[2];
        students[*student_num].average_score = students[*student_num].total_score / 3.0;
        (*student_num)++;
    }

    fclose(fp);
}

// 显示所有学生信息
void show(Student *students, int student_num) {
    int i;

    printf("学号\t姓名\t性别\t出生日期\t高数\tC语言\t大学物理\t总分\t平均分\n");

    for (i = 0; i < student_num; i++) {
        printf("%d\t%s\t%c\t%s\t%.2f\t%.2f\t%.2f\t%.2f\t%.2f\n", students[i].num,
               students[i].name, students[i].gender, students[i].birthday,
               students[i].score[0], students[i].score[1], students[i].score[2],
               students[i].total_score, students[i].average_score);
    }
}

// 添加学生信息
void add(Student *students, int *student_num) {
    int i, n;

    printf("请输入要添加的学生数目：");
    scanf("%d", &n);

    if (*student_num + n > MAX_STUDENT_NUM) {
        printf("学生数目超过数组最大容量%d！\n", MAX_STUDENT_NUM);
        return;
    }

    for (i = 0; i < n; i++) {
        printf("请输入第%d个学生的信息（学号 姓名 性别 出生日期 高数成绩 C语言成绩 大学物理成绩）：",
               i + 1);
        scanf("%d %s %c %s %f %f %f", &students[*student_num].num, students[*student_num].name,
              &students[*student_num].gender, students[*student_num].birthday,
              &students[*student_num].score[0], &students[*student_num].score[1],
              &students[*student_num].score[2]);
        students[*student_num].total_score = students[*student_num].score[0] +
                                             students[*student_num].score[1] +
                                             students[*student_num].score[2];
        students[*student_num].average_score = students[*student_num].total_score / 3.0;
        (*student_num)++;
    }

    printf("添加成功！\n");
}

// 按学号递增排序
void sort_by_num(Student *students, int student_num) {
    int i, j;
    Student temp;

    for (i = 0; i < student_num - 1; i++) {
        for (j = 0; j < student_num - i - 1; j++) {
            if (students[j].num > students[j + 1].num) {
                temp = students[j];
                students[j] = students[j + 1];
                students[j + 1] = temp;
            }
        }
    }

    printf("按学号递增排序成功！\n");
}

// 按总分递减排序
void sort_by_score(Student *students, int student_num) {
    int i, j;
    Student temp;

    for (i = 0; i < student_num - 1; i++) {
        for (j = 0; j < student_num - i - 1; j++) {
            if (students[j].total_score < students[j + 1].total_score) {
                temp = students[j];
                students[j] = students[j + 1];
                students[j + 1] = temp;
            }
        }
    }

    printf("按总分递减排序成功！\n");
}

// 按学号查找
void search_by_num(Student *students, int student_num) {
    int i, num;

    printf("请输入要查找的学号：");
    scanf("%d", &num);

    for (i = 0; i < student_num; i++) {
        if (students[i].num == num) {
            printf("学号\t姓名\t性别\t出生日期\t高数\tC语言\t大学物理\t总分\t平均分\n");
            printf("%d\t%s\t%c\t%s\t%.2f\t%.2f\t%.2f\t%.2f\t%.2f\n", students[i].num,
                   students[i].name, students[i].gender, students[i].birthday,
                   students[i].score[0], students[i].score[1], students[i].score[2],
                   students[i].total_score, students[i].average_score);
            return;
        }
    }

    printf("未找到学号为%d的学生！\n", num);
}

// 按姓名查找
void search_by_name(Student *students, int student_num) {
    int i;
    char name[MAX_NAME_LEN];

    printf("请输入要查找的姓名：");
    scanf("%s", name);

    for (i = 0; i < student_num; i++) {
        if (strcmp(students[i].name, name) == 0) {
            printf("学号\t姓名\t性别\t出生日期\t高数\tC语言\t大学物理\t总分\t平均分\n");
            printf("%d\t%s\t%c\t%s\t%.2f\t%.2f\t%.2f\t%.2f\t%.2f\n", students[i].num,
                   students[i].name, students[i].gender, students[i].birthday,
                   students[i].score[0], students[i].score[1], students[i].score[2],
                   students[i].total_score, students[i].average_score);
        }
    }

    printf("未找到姓名为%s的学生！\n", name);
}

// 按分数查找
void search_by_score(Student *students, int student_num) {
    int i, j;
    float score;
    int found = 0;

    printf("请输入要查找的分数：");
    scanf("%f", &score);

    for (i = 0; i < student_num; i++) {
        for (j = 0; j < 3; j++) {
            if (students[i].score[j] == score) {
                printf("学号\t姓名\t性别\t出生日期\t高数\tC语言\t大学物理\t总分\t平均分\n");
                printf("%d\t%s\t%c\t%s\t%.2f\t%.2f\t%.2f\t%.2f\t%.2f\n", students[i].num,
                       students[i].name, students[i].gender, students[i].birthday,
                       students[i].score[0], students[i].score[1], students[i].score[2],
                       students[i].total_score, students[i].average_score);
                found = 1;
                break;
            }
        }
    }

    if (!found) {
        printf("未找到分数为%.2f的学生！\n", score);
    }
}

// 计算各门课的平均分数
void calculate_average_score(Student *students, int student_num) {
    int i, j;
    float average_score[3] = {0};

    for (i = 0; i < student_num; i++) {
        for (j = 0; j < 3; j++) {
            average_score[j] += students[i].score[j];
        }
    }

    for (j = 0; j < 3; j++) {
        average_score[j] /= student_num;
    }

    printf("各门课的平均分数为：高数%.2f，C语言%.2f，大学物理%.2f\n",
           average_score[0], average_score[1], average_score[2]);
}

// 保存学生成绩信息到文件student.txt
void save_file(Student *students, int student_num, const char *filename) {
    FILE *fp;
    int i;

    if ((fp = fopen(filename, "w")) == NULL) {
        printf("无法打开文件%s！\n", filename);
        exit(-1);
    }

    for (i = 0; i < student_num; i++) {
        fprintf(fp, "%d %s %c %s %.2f %.2f %.2f\n", students[i].num, students[i].name,
                students[i].gender, students[i].birthday, students[i].score[0],
                students[i].score[1], students[i].score[2]);
    }

    fclose(fp);
    printf("保存学生成绩信息到文件%s成功！\n", filename);
}