班有5名同学，建立一个学生的简单信息表，包括学号、姓名、3门课程的成绩，编写程序，计算每名学生的平均成绩及名次。（注：定义一个结构体类型，用结构指针作为函数参数）用c语言编写

好的，以下是一个简单的实现：

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

#define MAX_STUDENTS 5
#define MAX_NAME_LENGTH 20

typedef struct {
    int id;
    char name[MAX_NAME_LENGTH];
    int grades[3];
    float average;
    int rank;
} Student;

void calculate_average(Student *students, int num_students);
void calculate_rank(Student *students, int num_students);
void print_students(Student *students, int num_students);

int main() {
    Student students[MAX_STUDENTS] = {
        {1, "Alice", {85, 90, 95}},
        {2, "Bob", {75, 80, 85}},
        {3, "Charlie", {90, 95, 100}},
        {4, "David", {60, 65, 70}},
        {5, "Eve", {80, 85, 90}}
    };

    calculate_average(students, MAX_STUDENTS);
    calculate_rank(students, MAX_STUDENTS);
    print_students(students, MAX_STUDENTS);

    return 0;
}

void calculate_average(Student *students, int num_students) {
    for (int i = 0; i < num_students; i++) {
        float sum = 0;
        for (int j = 0; j < 3; j++) {
            sum += students[i].grades[j];
        }
        students[i].average = sum / 3;
    }
}

void calculate_rank(Student *students, int num_students) {
    // sort students by average grade
    for (int i = 0; i < num_students; i++) {
        for (int j = 0; j < num_students - 1; j++) {
            if (students[j].average < students[j+1].average) {
                Student temp = students[j];
                students[j] = students[j+1];
                students[j+1] = temp;
            }
        }
    }

    // assign ranks
    int rank = 1;
    for (int i = 0; i < num_students; i++) {
        if (i > 0 && students[i].average < students[i-1].average) {
            rank++;
        }
        students[i].rank = rank;
    }
}

void print_students(Student *students, int num_students) {
    printf("%-5s%-10s%-7s%-7s%-7s%-7s\n", "ID", "Name", "Grade1", "Grade2", "Grade3", "Avg");
    for (int i = 0; i < num_students; i++) {
        printf("%-5d%-10s%-7d%-7d%-7d%-7.2f%d\n", students[i].id, students[i].name, students[i].grades[0], students[i].grades[1], students[i].grades[2], students[i].average, students[i].rank);
    }
}

这个程序首先定义了一个 `Student` 结构体，包含每个学生的学号、姓名、成绩、平均成绩和名次。然后在 `main` 函数中定义了一个包含 5 个学生信息的数组，并调用了 `calculate_average` 函数和 `calculate_rank` 函数来计算每个学生的平均成绩和名次。最后调用 `print_students` 函数打印出所有学生的信息。