用C语言输入4个学生3门课的成绩，分别用函数实现下列各项功能： 1）计算出每个学生的平均分； 2）计算出每门课程的平均分； 3）找出所有12个分数中最高分数所对应的学生和课程

在C语言中，我们可以设计一个结构体`Student`存储学生信息，同时用三个数组分别存储三门课的成绩。接下来，我会展示如何编写几个函数来实现这些功能。

#include <stdio.h>

typedef struct {
    char name[50];
    float score[3]; // 学生的三科成绩
} Student;

void input_scores(Student* students, int num_students) {
    for (int i = 0; i < num_students; i++) {
        scanf("Name: %s", students[i].name);
        for (int j = 0; j < 3; j++) {
            scanf("%f", &students[i].score[j]);
        }
    }
}

float average_score(Student student) {
    float sum = 0;
    for (int i = 0; i < 3; i++) {
        sum += student.score[i];
    }
    return sum / 3;
}

float course_average(float scores[], int num_courses) {
    float sum = 0;
    for (int i = 0; i < num_courses; i++) {
        sum += scores[i];
    }
    return sum / num_courses;
}

void find_highest_score(Student students[], int num_students) {
    int max_index = 0;
    float highest_score = students[0].score[0];

    for (int i = 1; i < num_students; i++) {
        for (int j = 0; j < 3; j++) {
            if (students[i].score[j] > highest_score) {
                highest_score = students[i].score[j];
                max_index = i;
            }
        }
    }

    printf("Highest score is %.2f, achieved by student %s in Course %d.\n", 
           highest_score, students[max_index].name, max_index % 3 + 1); // 课程编号从1开始
}

int main() {
    int num_students = 4;
    Student students[num_students];

    input_scores(students, num_students);

    printf("Average scores of each student:\n");
    for (int i = 0; i < num_students; i++) {
        printf("%s: %.2f\n", students[i].name, average_score(students[i]));
    }

    printf("Average scores of each course:\n");
    float course_scores[3] = {students[0].score[0], students[1].score[1], students[2].score[2]};
    printf("Course 1: %.2f\nCourse 2: %.2f\nCourse 3: %.2f\n", course_average(course_scores, 3));

    find_highest_score(students, num_students);

    return 0;
}

上述代码实现了所需的功能，包括输入学生成绩、计算平均分、课程平均分以及找出最高分及其对应的课程。请注意，课程编号在这里是按数组索引（1, 2, 3）表示的。