用c语言实现 学生成绩管理系统 实现功能：输入、输出、插入、删除、查找、追加、读入、显示、保存、排序、分类统计、退出。

以下是用C语言实现学生成绩管理系统的示例代码：

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

#define MAX_STUDENTS 100

struct Student {
    int id;
    char name[50];
    float scores[3];
    float average;
};

struct Student students[MAX_STUDENTS];
int numStudents = 0;

void inputStudent() {
    struct Student newStudent;
    printf("请输入学生的学号：");
    scanf("%d", &newStudent.id);
    printf("请输入学生的姓名：");
    scanf("%s", newStudent.name);
    printf("请输入学生的3门课成绩：");
    for (int i = 0; i < 3; i++) {
        scanf("%f", &newStudent.scores[i]);
    }
    newStudent.average = (newStudent.scores[0] + newStudent.scores[1] + newStudent.scores[2]) / 3;
    students[numStudents++] = newStudent;
    printf("学生信息已添加。\n");
}

void outputStudent(struct Student student) {
    printf("学号：%d\n", student.id);
    printf("姓名：%s\n", student.name);
    printf("成绩：");
    for (int i = 0; i < 3; i++) {
        printf("%.2f ", student.scores[i]);
    }
    printf("\n");
    printf("平均成绩：%.2f\n", student.average);
}

void displayStudents() {
    if (numStudents == 0) {
        printf("没有学生信息。\n");
        return;
    }
    for (int i = 0; i < numStudents; i++) {
        printf("第%d个学生信息：\n", i + 1);
        outputStudent(students[i]);
    }
}

void deleteStudent() {
    int studentId;
    printf("请输入要删除的学生的学号：");
    scanf("%d", &studentId);
    int index = -1;
    for (int i = 0; i < numStudents; i++) {
        if (students[i].id == studentId) {
            index = i;
            break;
        }
    }
    if (index == -1) {
        printf("找不到该学生。\n");
        return;
    }
    for (int i = index; i < numStudents - 1; i++) {
        students[i] = students[i + 1];
    }
    numStudents--;
    printf("学生信息已删除。\n");
}

void searchStudent() {
    int studentId;
    printf("请输入要查找的学生的学号：");
    scanf("%d", &studentId);
    int index = -1;
    for (int i = 0; i < numStudents; i++) {
        if (students[i].id == studentId) {
            index = i;
            break;
        }
    }
    if (index == -1) {
        printf("找不到该学生。\n");
        return;
    }
    printf("找到该学生的信息：\n");
    outputStudent(students[index]);
}

void saveStudents() {
    FILE *file = fopen("students.txt", "w");
    if (file == NULL) {
        printf("保存失败。\n");
        return;
    }
    for (int i = 0; i < numStudents; i++) {
        fprintf(file, "%d %s %.2f %.2f %.2f\n", students[i].id, students[i].name, students[i].scores[0], students[i].scores[1], students[i].scores[2]);
    }
    fclose(file);
    printf("学生信息已保存。\n");
}

void loadStudents() {
    FILE *file = fopen("students.txt", "r");
    if (file == NULL) {
        printf("加载失败。\n");
        return;
    }
    numStudents = 0;
    while (fscanf(file, "%d %s %f %f %f", &students[numStudents].id, students[numStudents].name, &students[numStudents].scores[0], &students[numStudents].scores[1], &students[numStudents].scores[2]) != EOF) {
        students[numStudents].average = (students[numStudents].scores[0] + students[numStudents].scores[1] + students[numStudents].scores[2]) / 3;
        numStudents++;
    }
    fclose(file);
    printf("学生信息已加载。\n");
}

void sortStudents() {
    for (int i = 0; i < numStudents - 1; i++) {
        for (int j = 0; j < numStudents - i - 1; j++) {
            if (students[j].average < students[j + 1].average) {
                struct Student temp = students[j];
                students[j] = students[j + 1];
                students[j + 1] = temp;
            }
        }
    }
    printf("学生信息已排序。\n");
}

void calculateAverage() {
    for (int i = 0; i < numStudents; i++) {
        students[i].average = (students[i].scores[0] + students[i].scores[1] + students[i].scores[2]) / 3;
    }
    printf("学生平均成绩已计算。\n");
}

int main() {
    int choice;
    while (1) {
        printf("学生成绩管理系统\n");
        printf("1. 输入学生信息\n");
        printf("2. 显示学生信息\n");
        printf("3. 删除学生信息\n");
        printf("4. 查找学生信息\n");
        printf("5. 保存学生信息\n");
        printf("6. 加载学生信息\n");
        printf("7. 排序学生信息\n");
        printf("8. 计算学生平均成绩\n");
        printf("9. 退出\n");
        printf("请输入您的选择：");
        scanf("%d", &choice);
        switch (choice) {
            case 1:
                inputStudent();
                break;
            case 2:
                displayStudents();
                break;
            case 3:
                deleteStudent();
                break;
            case 4:
                searchStudent();
                break;
            case 5:
                saveStudents();
                break;
            case 6:
                loadStudents();
                break;
            case 7:
                sortStudents();
                break;
            case 8:
                calculateAverage();
                break;
            case 9:
                printf("谢谢使用，再见！\n");
                exit(0);
            default:
                printf("无效的选择。\n");
                break;
        }
    }
    return 0;
}