应用《C语言程序设计》和《数据结构》课程的内容，编写一个完整的学生成绩管理系统程序，实现以下题目的要求： 1.学生信息包括学号、姓名、3 门考试成绩 2.学生成绩录入功能(成绩信息用文件保存) 3.统计所有学生的总分及平均分 4.统计所有课程的平均分 5.按平均分进行排序 6.输入一个学生学号输出其各科成绩及平均成绩 7.修改、删除学生信息

好的，这是一个比较复杂的程序，需要涉及到文件的读写、数据结构的使用等内容。下面是一个简单的示例程序，可以供您参考：

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

#define MAX_NAME_LEN 20
#define MAX_STUDENTS 100

typedef struct {
    int id;
    char name[MAX_NAME_LEN];
    int scores[3];
    float total_score;
    float avg_score;
} Student;

int read_students(Student students[]) {
    FILE *fp;
    int i = 0;
    char filename[] = "students.dat";
    fp = fopen(filename, "rb");
    if (fp == NULL) {
        printf("Cannot open file %s\n", filename);
        return 0;
    }
    while (fread(&students[i], sizeof(Student), 1, fp) == 1) {
        i++;
    }
    fclose(fp);
    return i;
}

void write_students(Student students[], int num_students) {
    FILE *fp;
    char filename[] = "students.dat";
    fp = fopen(filename, "wb");
    if (fp == NULL) {
        printf("Cannot open file %s\n", filename);
        return;
    }
    fwrite(students, sizeof(Student), num_students, fp);
    fclose(fp);
}

void add_student(Student students[], int *num_students) {
    if (*num_students >= MAX_STUDENTS) {
        printf("Cannot add more students\n");
        return;
    }
    printf("Enter student ID: ");
    scanf("%d", &students[*num_students].id);
    printf("Enter student name: ");
    scanf("%s", students[*num_students].name);
    printf("Enter scores for three exams:\n");
    scanf("%d %d %d", &students[*num_students].scores[0], &students[*num_students].scores[1], &students[*num_students].scores[2]);
    students[*num_students].total_score = students[*num_students].scores[0] + students[*num_students].scores[1] + students[*num_students].scores[2];
    students[*num_students].avg_score = students[*num_students].total_score / 3.0;
    (*num_students)++;
    write_students(students, *num_students);
}

void print_student(Student student) {
    printf("%d\t%s\t%d\t%d\t%d\t%.2f\t%.2f\n", student.id, student.name, student.scores[0], student.scores[1], student.scores[2], student.total_score, student.avg_score);
}

void print_all_students(Student students[], int num_students) {
    int i;
    printf("ID\tName\tExam 1\tExam 2\tExam 3\tTotal\tAverage\n");
    for (i = 0; i < num_students; i++) {
        print_student(students[i]);
    }
}

void compute_scores(Student students[], int num_students) {
    int i, j;
    float exam_totals[3] = {0.0};
    float class_total = 0.0;
    for (i = 0; i < num_students; i++) {
        class_total += students[i].total_score;
        for (j = 0; j < 3; j++) {
            exam_totals[j] += students[i].scores[j];
        }
    }
    printf("Class average:\n");
    for (j = 0; j < 3; j++) {
        printf("Exam %d: %.2f\n", j+1, exam_totals[j] / num_students);
    }
    printf("Total: %.2f\n", class_total / num_students);
}

void sort_by_average(Student students[], int num_students) {
    int i, j;
    Student temp;
    for (i = 0; i < num_students-1; i++) {
        for (j = i+1; j < num_students; j++) {
            if (students[i].avg_score < students[j].avg_score) {
                temp = students[i];
                students[i] = students[j];
                students[j] = temp;
            }
        }
    }
}

void find_student(Student students[], int num_students) {
    int id, i;
    printf("Enter student ID: ");
    scanf("%d", &id);
    for (i = 0; i < num_students; i++) {
        if (students[i].id == id) {
            printf("ID\tName\tExam 1\tExam 2\tExam 3\tTotal\tAverage\n");
            print_student(students[i]);
            return;
        }
    }
    printf("No student with ID %d found\n", id);
}

void modify_student(Student students[], int num_students) {
    int id, i;
    printf("Enter student ID: ");
    scanf("%d", &id);
    for (i = 0; i < num_students; i++) {
        if (students[i].id == id) {
            printf("Enter new scores for three exams:\n");
            scanf("%d %d %d", &students[i].scores[0], &students[i].scores[1], &students[i].scores[2]);
            students[i].total_score = students[i].scores[0] + students[i].scores[1] + students[i].scores[2];
            students[i].avg_score = students[i].total_score / 3.0;
            write_students(students, num_students);
            printf("Student %d updated\n", id);
            return;
        }
    }
    printf("No student with ID %d found\n", id);
}

void delete_student(Student students[], int *num_students) {
    int id, i, j;
    printf("Enter student ID: ");
    scanf("%d", &id);
    for (i = 0; i < *num_students; i++) {
        if (students[i].id == id) {
            for (j = i; j < *num_students-1; j++) {
                students[j] = students[j+1];
            }
            (*num_students)--;
            write_students(students, *num_students);
            printf("Student %d deleted\n", id);
            return;
        }
    }
    printf("No student with ID %d found\n", id);
}

int main() {
    Student students[MAX_STUDENTS];
    int num_students = 0;
    int choice;
    num_students = read_students(students);
    while (1) {
        printf("Choose an option:\n");
        printf("1. Add a student\n");
        printf("2. Print all students\n");
        printf("3. Compute scores\n");
        printf("4. Sort by average\n");
        printf("5. Find a student\n");
        printf("6. Modify a student\n");
        printf("7. Delete a student\n");
        printf("8. Exit\n");
        scanf("%d", &choice);
        switch (choice) {
            case 1:
                add_student(students, &num_students);
                break;
            case 2:
                print_all_students(students, num_students);
                break;
            case 3:
                compute_scores(students, num_students);
                break;
            case 4:
                sort_by_average(students, num_students);
                print_all_students(students, num_students);
                break;
            case 5:
                find_student(students, num_students);
                break;
            case 6:
                modify_student(students, num_students);
                break;
            case 7:
                delete_student(students, &num_students);
                break;
            case 8:
                write_students(students, num_students);
                exit(0);
            default:
                printf("Invalid choice\n");
                break;
        }
    }
    return 0;
}

这段代码实现了一个简单的学生成绩管理系统，包含了添加学生、打印所有学生、统计所有学生的总分及平均分、按平均分进行排序、输入一个学生学号输出其各科成绩及平均成绩、修改、删除学生信息等功能。代码中使用了结构体来存储学生信息，使用了文件来保存数据，并且使用了一些简单的数据结构和算法来实现排序等功能。