用c语言做一个学生成绩管理系统，功能包含添加，删除，修改，查询，按平均分大小排序，最后存档

好的，下面是一个简单的学生成绩管理系统的 C 语言代码：

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

#define MAX_STUDENTS 100

typedef struct {
    char name[20];
    int id;
    float score;
} Student;

void add_student(Student students[], int *num_students) {
    if (*num_students >= MAX_STUDENTS) {
        printf("The maximum number of students has been reached.\n");
        return;
    }
    Student new_student;
    printf("Enter the name of the student: ");
    scanf("%s", new_student.name);
    printf("Enter the ID of the student: ");
    scanf("%d", &new_student.id);
    printf("Enter the score of the student: ");
    scanf("%f", &new_student.score);
    students[*num_students] = new_student;
    (*num_students)++;
    printf("The student has been added.\n");
}

void delete_student(Student students[], int *num_students) {
    int id;
    printf("Enter the ID of the student you want to delete: ");
    scanf("%d", &id);
    for (int i = 0; i < *num_students; i++) {
        if (students[i].id == id) {
            for (int j = i; j < *num_students - 1; j++) {
                students[j] = students[j + 1];
            }
            (*num_students)--;
            printf("The student has been deleted.\n");
            return;
        }
    }
    printf("Student not found.\n");
}

void modify_student(Student students[], int num_students) {
    int id;
    printf("Enter the ID of the student you want to modify: ");
    scanf("%d", &id);
    for (int i = 0; i < num_students; i++) {
        if (students[i].id == id) {
            printf("Enter the new name of the student: ");
            scanf("%s", students[i].name);
            printf("Enter the new score of the student: ");
            scanf("%f", &students[i].score);
            printf("The student has been modified.\n");
            return;
        }
    }
    printf("Student not found.\n");
}

void query_student(Student students[], int num_students) {
    int id;
    printf("Enter the ID of the student you want to query: ");
    scanf("%d", &id);
    for (int i = 0; i < num_students; i++) {
        if (students[i].id == id) {
            printf("Name: %s\nID: %d\nScore: %.2f\n", students[i].name, students[i].id, students[i].score);
            return;
        }
    }
    printf("Student not found.\n");
}

void sort_students(Student students[], int num_students) {
    for (int i = 0; i < num_students - 1; i++) {
        for (int j = i + 1; j < num_students; j++) {
            if (students[i].score < students[j].score) {
                Student temp = students[i];
                students[i] = students[j];
                students[j] = temp;
            }
        }
    }
    printf("The students have been sorted by score.\n");
}

void save_students(Student students[], int num_students) {
    FILE *fp = fopen("students.txt", "w");
    if (fp == NULL) {
        printf("Error opening file.\n");
        return;
    }
    for (int i = 0; i < num_students; i++) {
        fprintf(fp, "%s %d %.2f\n", students[i].name, students[i].id, students[i].score);
    }
    fclose(fp);
    printf("The students have been saved to the file.\n");
}

int main() {
    Student students[MAX_STUDENTS];
    int num_students = 0;
    int choice;
    while (1) {
        printf("1. Add a new student\n");
        printf("2. Delete a student\n");
        printf("3. Modify a student\n");
        printf("4. Query a student\n");
        printf("5. Sort the students by score\n");
        printf("6. Save the students to a file\n");
        printf("7. Exit\n");
        printf("Enter your choice: ");
        scanf("%d", &choice);
        switch (choice) {
            case 1:
                add_student(students, &num_students);
                break;
            case 2:
                delete_student(students, &num_students);
                break;
            case 3:
                modify_student(students, num_students);
                break;
            case 4:
                query_student(students, num_students);
                break;
            case 5:
                sort_students(students, num_students);
                break;
            case 6:
                save_students(students, num_students);
                break;
            case 7:
                printf("Goodbye!\n");
                exit(0);
            default:
                printf("Invalid choice.\n");
                break;
        }
    }
    return 0;
}

这个程序使用了一个 `Student` 结构体来存储每个学生的信息，包括姓名、学号和分数。在主函数中，使用一个 `while` 循环来不断显示菜单，根据用户的选择执行相应的功能。其中，函数 `add_student` 用于添加学生，函数 `delete_student` 用于删除学生，函数 `modify_student` 用于修改学生信息，函数 `query_student` 用于查询学生信息，函数 `sort_students` 用于按照分数大小对学生进行排序，函数 `save_students` 用于将学生信息保存到文件中。

这是一个简单的学生成绩管理系统，可以根据实际需要进行修改和扩展。