用C语言写学生信息管理系统其功能包括，学生信息的录入，显示，删除（按学号删除），查找，增加（插入），统计功能（平均分的统计，成绩的统计，成绩排序）保存和文件读写，学生信息包括学生的学号，姓名，三科成绩（math，English，program），菜单的人机交互设计（选择的功能完成后清屏并回到功能选择菜单）

好的，下面是一个简单的学生信息管理系统的 C 代码：

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

#define MAX_NAME_LEN 20
#define MAX_STU_NUM 100

typedef struct student{
    int id;
    char name[MAX_NAME_LEN];
    float math;
    float english;
    float program;
} Student;

int num = 0;
Student students[MAX_STU_NUM];

void clear_input_buffer()
{
    char c;
    while((c = getchar()) != '\n' && c != EOF);
}

void add_student()
{
    if(num >= MAX_STU_NUM){
        printf("The number of students exceeds the maximum limit.\n");
        return;
    }

    Student s;
    printf("Please enter student's ID, name and three grades (math, english, program):\n");
    scanf("%d%s%f%f%f", &s.id, s.name, &s.math, &s.english, &s.program);
    students[num++] = s;
    printf("Student added successfully.\n");
}

void display_students()
{
    if(num == 0){
        printf("No student information.\n");
        return;
    }

    printf("ID\tName\t\tMath\tEnglish\tProgram\tTotal\n");
    for(int i = 0; i < num; i++){
        printf("%d\t%-10s\t%.2f\t%.2f\t%.2f\t%.2f\n", students[i].id, students[i].name, students[i].math, students[i].english, students[i].program, students[i].math + students[i].english + students[i].program);
    }
}

void search_student()
{
    if(num == 0){
        printf("No student information.\n");
        return;
    }

    int id;
    printf("Please enter the ID of the student to be searched:\n");
    scanf("%d", &id);

    for(int i = 0; i < num; i++){
        if(students[i].id == id){
            printf("ID\tName\t\tMath\tEnglish\tProgram\tTotal\n");
            printf("%d\t%-10s\t%.2f\t%.2f\t%.2f\t%.2f\n", students[i].id, students[i].name, students[i].math, students[i].english, students[i].program, students[i].math + students[i].english + students[i].program);
            return;
        }
    }

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

void delete_student()
{
    if(num == 0){
        printf("No student information.\n");
        return;
    }

    int id;
    printf("Please enter the ID of the student to be deleted:\n");
    scanf("%d", &id);

    for(int i = 0; i < num; i++){
        if(students[i].id == id){
            for(int j = i; j < num - 1; j++){
                students[j] = students[j + 1];
            }
            num--;
            printf("Student deleted successfully.\n");
            return;
        }
    }

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

void insert_student()
{
    if(num >= MAX_STU_NUM){
        printf("The number of students exceeds the maximum limit.\n");
        return;
    }

    int pos;
    printf("Please enter the position to insert the student (0 - %d):\n", num);
    scanf("%d", &pos);

    if(pos < 0 || pos > num){
        printf("Invalid position.\n");
        return;
    }

    Student s;
    printf("Please enter student's ID, name and three grades (math, english, program):\n");
    scanf("%d%s%f%f%f", &s.id, s.name, &s.math, &s.english, &s.program);

    for(int i = num; i > pos; i--){
        students[i] = students[i - 1];
    }
    students[pos] = s;
    num++;
    printf("Student inserted successfully.\n");
}

void sort_students()
{
    if(num == 0){
        printf("No student information.\n");
        return;
    }

    for(int i = 0; i < num - 1; i++){
        for(int j = 0; j < num - i - 1; j++){
            if(students[j].math + students[j].english + students[j].program < students[j + 1].math + students[j + 1].english + students[j + 1].program){
                Student temp = students[j];
                students[j] = students[j + 1];
                students[j + 1] = temp;
            }
        }
    }

    printf("ID\tName\t\tMath\tEnglish\tProgram\tTotal\n");
    for(int i = 0; i < num; i++){
        printf("%d\t%-10s\t%.2f\t%.2f\t%.2f\t%.2f\n", students[i].id, students[i].name, students[i].math, students[i].english, students[i].program, students[i].math + students[i].english + students[i].program);
    }
}

void calculate_average()
{
    if(num == 0){
        printf("No student information.\n");
        return;
    }

    float math_sum = 0, english_sum = 0, program_sum = 0;
    for(int i = 0; i < num; i++){
        math_sum += students[i].math;
        english_sum += students[i].english;
        program_sum += students[i].program;
    }

    printf("Average Math: %.2f\n", math_sum / num);
    printf("Average English: %.2f\n", english_sum / num);
    printf("Average Program: %.2f\n", program_sum / num);
}

void calculate_total()
{
    if(num == 0){
        printf("No student information.\n");
        return;
    }

    float total_sum = 0;
    for(int i = 0; i < num; i++){
        total_sum += students[i].math + students[i].english + students[i].program;
    }

    printf("Total Score: %.2f\n", total_sum);
}

void save_students()
{
    if(num == 0){
        printf("No student information.\n");
        return;
    }

    FILE *fp;
    fp = fopen("students.txt", "w");

    fprintf(fp, "ID\tName\tMath\tEnglish\tProgram\n");
    for(int i = 0; i < num; i++){
        fprintf(fp, "%d\t%s\t%.2f\t%.2f\t%.2f\n", students[i].id, students[i].name, students[i].math, students[i].english, students[i].program);
    }

    fclose(fp);
    printf("Student information saved successfully.\n");
}

void read_students()
{
    FILE *fp;
    fp = fopen("students.txt", "r");

    if(fp == NULL){
        printf("Student information file does not exist.\n");
        return;
    }

    fscanf(fp, "%*[^\n]\n");  // skip the first line

    while(!feof(fp) && num < MAX_STU_NUM){
        Student s;
        fscanf(fp, "%d%s%f%f%f\n", &s.id, s.name, &s.math, &s.english, &s.program);
        students[num++] = s;
    }

    fclose(fp);
    printf("Student information loaded successfully.\n");
}

void show_menu()
{
    printf("*********************\n");
    printf("* 1. Add student     *\n");
    printf("* 2. Display students*\n");
    printf("* 3. Search student  *\n");
    printf("* 4. Delete student  *\n");
    printf("* 5. Insert student  *\n");
    printf("* 6. Sort students   *\n");
    printf("* 7. Calculate average*\n");
    printf("* 8. Calculate total *\n");
    printf("* 9. Save students   *\n");
    printf("* 10. Read students  *\n");
    printf("* 0. Exit            *\n");
    printf("*********************\n");
}

int main()
{
    int choice;
    while(1){
        show_menu();
        printf("Please enter your choice:\n");
        scanf("%d", &choice);
        clear_input_buffer();

        switch(choice){
            case 0:
                printf("Goodbye!\n");
                exit(0);
            case 1:
                add_student();
                break;
            case 2:
                display_students();
                break;
            case 3:
                search_student();
                break;
            case 4:
                delete_student();
                break;
            case 5:
                insert_student();
                break;
            case 6:
                sort_students();
                break;
            case 7:
                calculate_average();
                break;
            case 8:
                calculate_total();
                break;
            case 9:
                save_students();
                break;
            case 10:
                read_students();
                break;
            default:
                printf("Invalid choice.\n");
        }

        printf("Press Enter to continue.\n");
        getchar();
        system("clear");
    }

    return 0;
}

这个程序的功能包括：学生信息的录入、显示、删除、查找、插入、排序、平均分的统计、成绩的统计、保存和文件读写，同时还有一个简单的菜单界面。