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（sex）、出生日期（birthday，包括年、月、日，分别表示为year,month,day）、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用C语言表述出来

以下是一个简单的学生成绩管理系统，其中包含了以上要求的各个功能模块：

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

#define MAX_STUDENTS 100   // 最多存储100个学生信息

// 学生信息结构体
typedef struct {
    int num;               // 学号
    char name[20];         // 姓名
    char sex[5];           // 性别
    int year, month, day;  // 出生日期
    float math, c, physics; // 三门课成绩
    float total;           // 总分
    float avg;             // 平均分
} Student;

Student students[MAX_STUDENTS]; // 学生信息数组
int num_students = 0;            // 学生信息数量

// 从文件中读取学生信息
void read_students(char *filename) {
    FILE *fp = fopen(filename, "r");
    if (fp == NULL) {
        printf("无法打开文件 %s！\n", filename);
        return;
    }

    while (!feof(fp) && num_students < MAX_STUDENTS) {
        Student *s = &students[num_students];
        fscanf(fp, "%d %s %s %d %d %d %f %f %f", &s->num, s->name, s->sex, &s->year, &s->month, &s->day, &s->math, &s->c, &s->physics);
        s->total = s->math + s->c + s->physics;
        s->avg = s->total / 3.0;
        num_students++;
    }

    fclose(fp);
    printf("成功读取 %d 条学生信息！\n", num_students);
}

// 显示所有学生信息
void display_students() {
    printf("学号\t姓名\t性别\t出生日期\t高数\tC语言\t大物\t总分\t平均分\n");
    for (int i = 0; i < num_students; i++) {
        Student *s = &students[i];
        printf("%d\t%s\t%s\t%d-%02d-%02d\t%.2f\t%.2f\t%.2f\t%.2f\t%.2f\n", s->num, s->name, s->sex, s->year, s->month, s->day, s->math, s->c, s->physics, s->total, s->avg);
    }
}

// 添加一条学生信息
void add_student() {
    if (num_students >= MAX_STUDENTS) {
        printf("学生信息已满，无法添加！\n");
        return;
    }

    Student *s = &students[num_students];
    printf("请输入学号：");
    scanf("%d", &s->num);
    printf("请输入姓名：");
    scanf("%s", s->name);
    printf("请输入性别：");
    scanf("%s", s->sex);
    printf("请输入出生日期（格式：年 月 日）：");
    scanf("%d %d %d", &s->year, &s->month, &s->day);
    printf("请输入高数成绩：");
    scanf("%f", &s->math);
    printf("请输入C语言成绩：");
    scanf("%f", &s->c);
    printf("请输入大学物理成绩：");
    scanf("%f", &s->physics);
    s->total = s->math + s->c + s->physics;
    s->avg = s->total / 3.0;
    num_students++;
    printf("添加成功！\n");
}

// 按学号排序
void sort_by_num() {
    for (int i = 0; i < num_students - 1; i++) {
        for (int j = i + 1; j < num_students; j++) {
            if (students[i].num > students[j].num) {
                Student temp = students[i];
                students[i] = students[j];
                students[j] = temp;
            }
        }
    }

    printf("按学号排序成功！\n");
}

// 按总分排序
void sort_by_total() {
    for (int i = 0; i < num_students - 1; i++) {
        for (int j = i + 1; j < num_students; j++) {
            if (students[i].total < students[j].total) {
                Student temp = students[i];
                students[i] = students[j];
                students[j] = temp;
            }
        }
    }

    printf("按总分排序成功！\n");
}

// 按学号查找
void find_by_num() {
    int num;
    printf("请输入要查找的学号：");
    scanf("%d", &num);

    for (int i = 0; i < num_students; i++) {
        if (students[i].num == num) {
            Student *s = &students[i];
            printf("学号\t姓名\t性别\t出生日期\t高数\tC语言\t大物\t总分\t平均分\n");
            printf("%d\t%s\t%s\t%d-%02d-%02d\t%.2f\t%.2f\t%.2f\t%.2f\t%.2f\n", s->num, s->name, s->sex, s->year, s->month, s->day, s->math, s->c, s->physics, s->total, s->avg);
            return;
        }
    }

    printf("未找到该学号的学生信息！\n");
}

// 按姓名查找
void find_by_name() {
    char name[20];
    printf("请输入要查找的姓名：");
    scanf("%s", name);

    for (int i = 0; i < num_students; i++) {
        if (strcmp(students[i].name, name) == 0) {
            Student *s = &students[i];
            printf("学号\t姓名\t性别\t出生日期\t高数\tC语言\t大物\t总分\t平均分\n");
            printf("%d\t%s\t%s\t%d-%02d-%02d\t%.2f\t%.2f\t%.2f\t%.2f\t%.2f\n", s->num, s->name, s->sex, s->year, s->month, s->day, s->math, s->c, s->physics, s->total, s->avg);
            return;
        }
    }

    printf("未找到该姓名的学生信息！\n");
}

// 按分数查找
void find_by_score() {
    float score;
    printf("请输入要查找的分数：");
    scanf("%f", &score);

    for (int i = 0; i < num_students; i++) {
        if (students[i].total == score) {
            Student *s = &students[i];
            printf("学号\t姓名\t性别\t出生日期\t高数\tC语言\t大物\t总分\t平均分\n");
            printf("%d\t%s\t%s\t%d-%02d-%02d\t%.2f\t%.2f\t%.2f\t%.2f\t%.2f\n", s->num, s->name, s->sex, s->year, s->month, s->day, s->math, s->c, s->physics, s->total, s->avg);
            return;
        }
    }

    printf("未找到该分数的学生信息！\n");
}

// 计算各门课的平均分
void calculate_averages() {
    float math_total = 0, c_total = 0, physics_total = 0;

    for (int i = 0; i < num_students; i++) {
        math_total += students[i].math;
        c_total += students[i].c;
        physics_total += students[i].physics;
    }

    float math_avg = math_total / num_students;
    float c_avg = c_total / num_students;
    float physics_avg = physics_total / num_students;

    printf("高数平均分：%.2f\n", math_avg);
    printf("C语言平均分：%.2f\n", c_avg);
    printf("大学物理平均分：%.2f\n", physics_avg);
}

// 保存学生信息到文件
void save_students(char *filename) {
    FILE *fp = fopen(filename, "w");
    if (fp == NULL) {
        printf("无法保存文件 %s！\n", filename);
        return;
    }

    for (int i = 0; i < num_students; i++) {
        Student *s = &students[i];
        fprintf(fp, "%d\t%s\t%s\t%d\t%d\t%d\t%.2f\t%.2f\t%.2f\n", s->num, s->name, s->sex, s->year, s->month, s->day, s->math, s->c, s->physics);
    }

    fclose(fp);
    printf("成功保存 %d 条学生信息！\n", num_students);
}

// 主函数
int main() {
    char filename[] = "students.txt";
    read_students(filename);

    int choice;
    do {
        printf("\n请选择操作：\n");
        printf("1. 显示所有学生信息\n");
        printf("2. 添加一条学生信息\n");
        printf("3. 按学号排序\n");
        printf("4. 按总分排序\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\n");
        printf("9. 保存学生信息\n");
        printf("0. 退出程序\n");
        printf("请选择：");
        scanf("%d", &choice);

        switch (choice) {
            case 1:
                display_students();
                break;
            case 2:
                add_student();
                break;
            case 3:
                sort_by_num();
                break;
            case 4:
                sort_by_total();
                break;
            case 5:
                find_by_num();
                break;
            case 6:
                find_by_name();
                break;
            case 7:
                find_by_score();
                break;
            case 8:
                calculate_averages();
                break;
            case 9:
                save_students(filename);
                break;
            case 0:
                printf("程序已退出。\n");
                break;
            default:
                printf("无效的操作！\n");
                break;
        }
    } while (choice != 0);

    return 0;
}