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（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

以下是一个简单的学生成绩管理系统的C语言实现，包括了所有要求的功能：

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

#define MAX_NUM 100 // 最大学生数

// 学生信息结构体
typedef struct {
    char num[20]; // 学号
    char name[20]; // 姓名
    char sex[10]; // 性别
    int year; // 出生年份
    int month; // 出生月份
    int day; // 出生日期
    int math; // 高数成绩
    int c; // C语言成绩
    int phys; // 大学物理成绩
    int total; // 总分
    float avg; // 平均分
} Student;

// 学生数组
Student students[MAX_NUM];
int num_of_students = 0; // 学生数

// 读取学生信息文件
void read_student_file() {
    FILE *fp;
    fp = fopen("student.txt", "r");
    if (fp == NULL) {
        printf("无法打开文件！\n");
        return;
    }
    while (!feof(fp)) {
        fscanf(fp, "%s%s%s%d%d%d%d%d%d%d", students[num_of_students].num, students[num_of_students].name, students[num_of_students].sex, &students[num_of_students].year, &students[num_of_students].month, &students[num_of_students].day, &students[num_of_students].math, &students[num_of_students].c, &students[num_of_students].phys);
        students[num_of_students].total = students[num_of_students].math + students[num_of_students].c + students[num_of_students].phys;
        students[num_of_students].avg = students[num_of_students].total / 3.0;
        num_of_students++;
    }
    fclose(fp);
    printf("读取学生信息成功！\n");
}

// 显示所有学生信息
void show_all_students() {
    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 (int i = 0; i < num_of_students; i++) {
        printf("%s\t%s\t%s\t%d-%d-%d\t%d\t%d\t%d\t%d\t%.2f\n", students[i].num, students[i].name, students[i].sex, students[i].year, students[i].month, students[i].day, students[i].math, students[i].c, students[i].phys, students[i].total, students[i].avg);
    }
}

// 添加学生信息
void add_student() {
    int n;
    printf("请输入要添加的学生数：");
    scanf("%d", &n);
    if (num_of_students + n > MAX_NUM) {
        printf("学生数已达到最大值！\n");
        return;
    }
    for (int i = 0; i < n; i++) {
        printf("请输入第%d个学生的信息（学号 姓名 性别 出生年月日 高数成绩 C语言成绩 大学物理成绩）：", i + 1);
        scanf("%s%s%s%d%d%d%d%d%d", students[num_of_students].num, students[num_of_students].name, students[num_of_students].sex, &students[num_of_students].year, &students[num_of_students].month, &students[num_of_students].day, &students[num_of_students].math, &students[num_of_students].c, &students[num_of_students].phys);
        students[num_of_students].total = students[num_of_students].math + students[num_of_students].c + students[num_of_students].phys;
        students[num_of_students].avg = students[num_of_students].total / 3.0;
        num_of_students++;
    }
    printf("添加学生信息成功！\n");
}

// 按学号递增排序
void sort_by_num() {
    for (int i = 0; i < num_of_students - 1; i++) {
        for (int j = i + 1; j < num_of_students; j++) {
            if (strcmp(students[i].num, students[j].num) > 0) {
                Student temp = students[i];
                students[i] = students[j];
                students[j] = temp;
            }
        }
    }
    printf("按学号递增排序成功！\n");
}

// 按总分递减排序
void sort_by_total() {
    for (int i = 0; i < num_of_students - 1; i++) {
        for (int j = i + 1; j < num_of_students; j++) {
            if (students[i].total < students[j].total) {
                Student temp = students[i];
                students[i] = students[j];
                students[j] = temp;
            }
        }
    }
    printf("按总分递减排序成功！\n");
}

// 按学号查找
void search_by_num() {
    char num[20];
    printf("请输入要查找的学生学号：");
    scanf("%s", num);
    for (int i = 0; i < num_of_students; i++) {
        if (strcmp(students[i].num, num) == 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("%s\t%s\t%s\t%d-%d-%d\t%d\t%d\t%d\t%d\t%.2f\n", students[i].num, students[i].name, students[i].sex, students[i].year, students[i].month, students[i].day, students[i].math, students[i].c, students[i].phys, students[i].total, students[i].avg);
            return;
        }
    }
    printf("没有找到该学生！\n");
}

// 按姓名查找
void search_by_name() {
    char name[20];
    printf("请输入要查找的学生姓名：");
    scanf("%s", name);
    for (int i = 0; i < num_of_students; 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("%s\t%s\t%s\t%d-%d-%d\t%d\t%d\t%d\t%d\t%.2f\n", students[i].num, students[i].name, students[i].sex, students[i].year, students[i].month, students[i].day, students[i].math, students[i].c, students[i].phys, students[i].total, students[i].avg);
            return;
        }
    }
    printf("没有找到该学生！\n");
}

// 按分数查找
void search_by_score() {
    int score;
    printf("请输入要查找的分数：");
    scanf("%d", &score);
    int found = 0;
    for (int i = 0; i < num_of_students; i++) {
        if (students[i].total == 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("%s\t%s\t%s\t%d-%d-%d\t%d\t%d\t%d\t%d\t%.2f\n", students[i].num, students[i].name, students[i].sex, students[i].year, students[i].month, students[i].day, students[i].math, students[i].c, students[i].phys, students[i].total, students[i].avg);
            found = 1;
        }
    }
    if (!found) {
        printf("没有找到该分数的学生！\n");
    }
}

// 计算各门课平均分
void calculate_avg() {
    float math_sum = 0, c_sum = 0, phys_sum = 0;
    for (int i = 0; i < num_of_students; i++) {
        math_sum += students[i].math;
        c_sum += students[i].c;
        phys_sum += students[i].phys;
    }
    float math_avg = math_sum / num_of_students;
    float c_avg = c_sum / num_of_students;
    float phys_avg = phys_sum / num_of_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", phys_avg);
}

// 保存学生信息到文件
void save_student_file() {
    FILE *fp;
    fp = fopen("student.txt", "w");
    if (fp == NULL) {
        printf("无法打开文件！\n");
        return;
    }
    for (int i = 0; i < num_of_students; i++) {
        fprintf(fp, "%s\t%s\t%s\t%d\t%d\t%d\t%d\t%d\t%d\n", students[i].num, students[i].name, students[i].sex, students[i].year, students[i].month, students[i].day, students[i].math, students[i].c, students[i].phys);
    }
    fclose(fp);
    printf("保存学生信息成功！\n");
}

// 显示菜单
void show_menu() {
    printf("\n");
    printf("***********************************\n");
    printf("                菜单               \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. 计算各门课平均分\n");
    printf("9. 保存学生信息到文件\n");
    printf("0. 退出程序\n");
    printf("***********************************\n");
}

int main() {
    read_student_file();
    while (1) {
        show_menu();
        int choice;
        printf("请输入操作编号：");
        scanf("%d", &choice);
        switch (choice) {
            case 1:
                show_all_students();
                break;
            case 2:
                add_student();
                break;
            case 3:
                sort_by_num();
                break;
            case 4:
                sort_by_total();
                break;
            case 5:
                search_by_num();
                break;
            case 6:
                search_by_name();
                break;
            case 7:
                search_by_score();
                break;
            case 8:
                calculate_avg();
                break;
            case 9:
                save_student_file();
                break;
            case 0:
                printf("程序已退出！\n");
                return 0;
            default:
                printf("输入有误，请重新输入！\n");
                break;
        }
    }
    return 0;
}