C语言设置一个学生系统，可以学生成绩录入，学生成绩信息删除，学生成绩修改，学生成绩信息查找，学生信息插入，统计学生人数

好的，这是一个比较复杂的问题，需要设计一个学生结构体来存储学生信息，并且需要用文件来保存学生信息，下面是一个简单的实现：

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

#define MAX_NAME_LEN 50
#define MAX_STUDENT_NUM 100

struct student {
    char name[MAX_NAME_LEN];
    int id;
    float grade;
};

void add_student(struct student *students, int *num_students);
void delete_student(struct student *students, int *num_students);
void modify_student(struct student *students, int *num_students);
void search_student(struct student *students, int num_students);
void insert_student(struct student *students, int *num_students);
void count_student(int num_students);

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

    while (1) {
        printf("What do you want to do?\n");
        printf("1. Add student\n");
        printf("2. Delete student\n");
        printf("3. Modify student\n");
        printf("4. Search student\n");
        printf("5. Insert student\n");
        printf("6. Count student\n");
        printf("7. Exit\n");

        int 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:
                search_student(students, num_students);
                break;
            case 5:
                insert_student(students, &num_students);
                break;
            case 6:
                count_student(num_students);
                break;
            case 7:
                exit(0);
            default:
                printf("Invalid choice.\n");
        }
    }

    return 0;
}

void add_student(struct student *students, int *num_students) {
    if (*num_students >= MAX_STUDENT_NUM) {
        printf("Too many students.\n");
        return;
    }

    struct student new_student;
    printf("Enter name: ");
    scanf("%s", new_student.name);
    printf("Enter id: ");
    scanf("%d", &new_student.id);
    printf("Enter grade: ");
    scanf("%f", &new_student.grade);

    students[*num_students] = new_student;
    (*num_students)++;

    printf("Student added.\n");
}

void delete_student(struct student *students, int *num_students) {
    int id;
    printf("Enter student id 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("Student deleted.\n");
            return;
        }
    }

    printf("Student not found.\n");
}

void modify_student(struct student *students, int *num_students) {
    int id;
    printf("Enter student id to modify: ");
    scanf("%d", &id);

    for (int i = 0; i < *num_students; i++) {
        if (students[i].id == id) {
            printf("Enter new name (or press enter to keep current name): ");
            char new_name[MAX_NAME_LEN];
            fgets(new_name, MAX_NAME_LEN, stdin);
            new_name[strcspn(new_name, "\n")] = 0;
            if (strlen(new_name) > 0) {
                strcpy(students[i].name, new_name);
            }

            printf("Enter new grade (or press enter to keep current grade): ");
            char new_grade_str[10];
            fgets(new_grade_str, 10, stdin);
            new_grade_str[strcspn(new_grade_str, "\n")] = 0;
            if (strlen(new_grade_str) > 0) {
                sscanf(new_grade_str, "%f", &students[i].grade);
            }

            printf("Student modified.\n");
            return;
        }
    }

    printf("Student not found.\n");
}

void search_student(struct student *students, int num_students) {
    int id;
    printf("Enter student id to search: ");
    scanf("%d", &id);

    for (int i = 0; i < num_students; i++) {
        if (students[i].id == id) {
            printf("Name: %s\n", students[i].name);
            printf("Grade: %.1f\n", students[i].grade);
            return;
        }
    }

    printf("Student not found.\n");
}

void insert_student(struct student *students, int *num_students) {
    if (*num_students >= MAX_STUDENT_NUM) {
        printf("Too many students.\n");
        return;
    }

    int index;
    printf("Enter the index to insert the student (starting from 0): ");
    scanf("%d", &index);

    if (index < 0 || index > *num_students) {
        printf("Invalid index.\n");
        return;
    }

    struct student new_student;
    printf("Enter name: ");
    scanf("%s", new_student.name);
    printf("Enter id: ");
    scanf("%d", &new_student.id);
    printf("Enter grade: ");
    scanf("%f", &new_student.grade);

    for (int i = *num_students; i > index; i--) {
        students[i] = students[i-1];
    }
    students[index] = new_student;
    (*num_students)++;

    printf("Student inserted.\n");
}

void count_student(int num_students) {
    printf("Number of students: %d\n", num_students);
}

这个程序用了一个循环来提供菜单，其中每个菜单选项都对应一个函数，可以实现增加、删除、修改、查找和插入学生，以及统计学生人数。注意，这个程序只是一个简单的实现，实际情况中可能还需要考虑更多的细节和异常情况。