定义一个结构体表示学生成绩，包含学生学号、姓名、数学成绩、语文成绩、英语成绩等信息。然后定义一个数组，存储多个学生的成绩信息。实现查找可以遍历数组，根据姓名查找对应学生的成绩信息。插入可以在数组末尾添加一个新的学生成绩信息。删除可以根据学号或姓名查找到对应学生的成绩信息，然后将其从数组中删除。修改可以根据姓名查找到对应学生的成绩信息，然后修改其数学成绩、语文成绩、英语成绩等信息。使用代码实现

以下是代码实现：

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

#define MAX_STUDENT_NUM 100

struct Student {
    char id[20];
    char name[20];
    float math_score;
    float chinese_score;
    float english_score;
};

int find_student_by_name(struct Student students[], int num_students, char name[]) {
    for (int i = 0; i < num_students; i++) {
        if (strcmp(students[i].name, name) == 0) {
            return i;
        }
    }
    return -1;
}

void print_student(struct Student student) {
    printf("ID: %s, Name: %s, Math: %.2f, Chinese: %.2f, English: %.2f\n",
           student.id, student.name, student.math_score, student.chinese_score, student.english_score);
}

void print_students(struct Student students[], int num_students) {
    for (int i = 0; i < num_students; i++) {
        print_student(students[i]);
    }
}

void insert_student(struct Student students[], int *num_students, struct Student new_student) {
    if (*num_students >= MAX_STUDENT_NUM) {
        printf("Error: too many students.\n");
        return;
    }
    students[*num_students] = new_student;
    (*num_students)++;
}

void delete_student_by_id(struct Student students[], int *num_students, char id[]) {
    int index = -1;
    for (int i = 0; i < *num_students; i++) {
        if (strcmp(students[i].id, id) == 0) {
            index = i;
            break;
        }
    }
    if (index == -1) {
        printf("Error: student not found.\n");
        return;
    }
    for (int i = index; i < *num_students - 1; i++) {
        students[i] = students[i + 1];
    }
    (*num_students)--;
}

void delete_student_by_name(struct Student students[], int *num_students, char name[]) {
    int index = find_student_by_name(students, *num_students, name);
    if (index == -1) {
        printf("Error: student not found.\n");
        return;
    }
    for (int i = index; i < *num_students - 1; i++) {
        students[i] = students[i + 1];
    }
    (*num_students)--;
}

void modify_student(struct Student students[], int num_students, char name[], float math_score, float chinese_score, float english_score) {
    int index = find_student_by_name(students, num_students, name);
    if (index == -1) {
        printf("Error: student not found.\n");
        return;
    }
    students[index].math_score = math_score;
    students[index].chinese_score = chinese_score;
    students[index].english_score = english_score;
}

int main() {
    struct Student students[MAX_STUDENT_NUM];
    int num_students = 0;

    // insert some students
    insert_student(students, &num_students, (struct Student){"001", "Alice", 90, 80, 85});
    insert_student(students, &num_students, (struct Student){"002", "Bob", 85, 90, 95});
    insert_student(students, &num_students, (struct Student){"003", "Charlie", 95, 95, 90});

    // print all students
    printf("All students:\n");
    print_students(students, num_students);

    // find a student by name
    char name_to_find[] = "Bob";
    int index = find_student_by_name(students, num_students, name_to_find);
    if (index != -1) {
        printf("Found student by name '%s':\n", name_to_find);
        print_student(students[index]);
    } else {
        printf("Student not found by name '%s'.\n", name_to_find);
    }

    // insert a new student
    insert_student(students, &num_students, (struct Student){"004", "David", 80, 85, 90});
    printf("After inserting a new student:\n");
    print_students(students, num_students);

    // delete a student by id
    char id_to_delete[] = "002";
    delete_student_by_id(students, &num_students, id_to_delete);
    printf("After deleting a student by id '%s':\n", id_to_delete);
    print_students(students, num_students);

    // delete a student by name
    char name_to_delete[] = "Charlie";
    delete_student_by_name(students, &num_students, name_to_delete);
    printf("After deleting a student by name '%s':\n", name_to_delete);
    print_students(students, num_students);

    // modify a student
    char name_to_modify[] = "Alice";
    float new_math_score = 95;
    float new_chinese_score = 90;
    float new_english_score = 80;
    modify_student(students, num_students, name_to_modify, new_math_score, new_chinese_score, new_english_score);
    printf("After modifying a student by name '%s':\n", name_to_modify);
    print_students(students, num_students);

    return 0;
}