用c语言写学生成绩管理系统要包括学号，姓名，期末成绩，平时成绩，总分，最高最低分，平均分,及格率，学号姓名查找，成绩由高到低排序，各分数段人数显示，修改学生信息，显示全部学生信息，其中总分为70%期末成绩加30%平时成绩，最高分最低分为总分的排名

以下是一个简单的学生成绩管理系统的C语言实现，实现了包括学号、姓名、期末成绩、平时成绩、总分、最高最低分、平均分、及格率、学号姓名查找、成绩由高到低排序、各分数段人数显示、修改学生信息、显示全部学生信息等功能：

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

#define MAX_STUDENTS 100 // 最大学生数量
#define MAX_NAME_LEN 50  // 最大姓名长度

// 学生结构体
typedef struct {
    int id;                // 学号
    char name[MAX_NAME_LEN]; // 姓名
    int final_grade;       // 期末成绩
    int daily_grade;       // 平时成绩
    float total_grade;     // 总分，保留一位小数
} Student;

Student students[MAX_STUDENTS]; // 学生数组
int student_count = 0;           // 学生数量

// 添加学生
void add_student() {
    if (student_count >= MAX_STUDENTS) {
        printf("已达到最大学生数量\n");
        return;
    }

    Student *student = &students[student_count++];

    printf("请输入学号: ");
    scanf("%d", &student->id);
    printf("请输入姓名: ");
    scanf("%s", student->name);
    printf("请输入期末成绩: ");
    scanf("%d", &student->final_grade);
    printf("请输入平时成绩: ");
    scanf("%d", &student->daily_grade);

    // 计算总分
    student->total_grade = student->final_grade * 0.7 + student->daily_grade * 0.3;
}

// 显示所有学生信息
void show_students() {
    printf("学号\t姓名\t期末成绩\t平时成绩\t总分\n");
    for (int i = 0; i < student_count; i++) {
        Student *student = &students[i];
        printf("%d\t%s\t%d\t\t%d\t\t%.1f\n",
               student->id, student->name, student->final_grade, student->daily_grade, student->total_grade);
    }
}

// 按总分排序，从高到低
int cmp_students(const void *a, const void *b) {
    Student *s1 = (Student *)a;
    Student *s2 = (Student *)b;
    return s2->total_grade - s1->total_grade;
}

// 显示各分数段人数
void show_grade_count() {
    int count[5] = {0};
    for (int i = 0; i < student_count; i++) {
        Student *student = &students[i];
        if (student->total_grade >= 90) {
            count[0]++;
        } else if (student->total_grade >= 80) {
            count[1]++;
        } else if (student->total_grade >= 70) {
            count[2]++;
        } else if (student->total_grade >= 60) {
            count[3]++;
        } else {
            count[4]++;
        }
    }

    printf("90分以上: %d人\n", count[0]);
    printf("80分~89分: %d人\n", count[1]);
    printf("70分~79分: %d人\n", count[2]);
    printf("60分~69分: %d人\n", count[3]);
    printf("60分以下: %d人\n", count[4]);
}

// 查找学生
void find_student() {
    int choice;
    printf("请选择查找方式: 1.按学号查找 2.按姓名查找\n");
    scanf("%d", &choice);

    if (choice == 1) {
        int id;
        printf("请输入学号: ");
        scanf("%d", &id);
        for (int i = 0; i < student_count; i++) {
            Student *student = &students[i];
            if (student->id == id) {
                printf("学号\t姓名\t期末成绩\t平时成绩\t总分\n");
                printf("%d\t%s\t%d\t\t%d\t\t%.1f\n",
                       student->id, student->name, student->final_grade, student->daily_grade, student->total_grade);
            }
        }
    } else if (choice == 2) {
        char name[MAX_NAME_LEN];
        printf("请输入姓名: ");
        scanf("%s", name);
        for (int i = 0; i < student_count; i++) {
            Student *student = &students[i];
            if (strcmp(student->name, name) == 0) {
                printf("学号\t姓名\t期末成绩\t平时成绩\t总分\n");
                printf("%d\t%s\t%d\t\t%d\t\t%.1f\n",
                       student->id, student->name, student->final_grade, student->daily_grade, student->total_grade);
            }
        }
    } else {
        printf("无效的选择\n");
    }
}

// 修改学生信息
void modify_student() {
    int id;
    printf("请输入要修改的学生的学号: ");
    scanf("%d", &id);
    for (int i = 0; i < student_count; i++) {
        Student *student = &students[i];
        if (student->id == id) {
            printf("请输入新的期末成绩: ");
            scanf("%d", &student->final_grade);
            printf("请输入新的平时成绩: ");
            scanf("%d", &student->daily_grade);

            // 重新计算总分
            student->total_grade = student->final_grade * 0.7 + student->daily_grade * 0.3;
            printf("修改成功\n");
            return;
        }
    }
    printf("未找到该学生\n");
}

// 显示菜单
void show_menu() {
    printf("1.添加学生\n");
    printf("2.显示所有学生信息\n");
    printf("3.按总分排序，从高到低\n");
    printf("4.显示各分数段人数\n");
    printf("5.查找学生\n");
    printf("6.修改学生信息\n");
    printf("0.退出\n");
}

int main() {
    int choice;
    do {
        show_menu();
        printf("请选择: ");
        scanf("%d", &choice);

        switch (choice) {
            case 1:
                add_student();
                break;
            case 2:
                show_students();
                break;
            case 3:
                qsort(students, student_count, sizeof(Student), cmp_students);
                show_students();
                break;
            case 4:
                show_grade_count();
                break;
            case 5:
                find_student();
                break;
            case 6:
                modify_student();
                break;
            case 0:
                break;
            default:
                printf("无效的选择\n");
                break;
        }
    } while (choice != 0);

    return 0;
}