用c语言写一个学生选修课程系统

好的，我可以为您提供一个简单的学生选修课程系统的代码示例，基于C语言实现。以下是代码：

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

#define MAX_COURSES 5
#define MAX_NAME_LEN 20

typedef struct {
    char name[MAX_NAME_LEN];
    int credits;
    float grade;
} Course;

typedef struct {
    char name[MAX_NAME_LEN];
    int id;
    int num_courses;
    Course courses[MAX_COURSES];
} Student;

void add_course(Student* student);
void print_courses(Student student);
void print_gpa(Student student);

int main() {
    Student student;
    student.num_courses = 0;
    printf("Enter student name: ");
    scanf("%s", student.name);
    printf("Enter student ID: ");
    scanf("%d", &student.id);

    int choice = 0;
    do {
        printf("\n1. Add course\n");
        printf("2. Print courses taken\n");
        printf("3. Print GPA\n");
        printf("4. Quit\n");
        printf("Enter your choice: ");
        scanf("%d", &choice);

        switch(choice) {
            case 1:
                add_course(&student);
                break;
            case 2:
                print_courses(student);
                break;
            case 3:
                print_gpa(student);
                break;
            case 4:
                printf("Quitting program...\n");
                break;
            default:
                printf("Invalid choice. Try again.\n");
                break;
        }
    } while(choice != 4);

    return 0;
}

void add_course(Student* student) {
    if(student->num_courses >= MAX_COURSES) {
        printf("Cannot add more courses. Maximum limit reached.\n");
        return;
    }

    Course course;
    printf("\nEnter course name: ");
    scanf("%s", course.name);
    printf("Enter credits for course: ");
    scanf("%d", &course.credits);
    printf("Enter grade for course (out of 4.0): ");
    scanf("%f", &course.grade);
    student->courses[student->num_courses++] = course;
}

void print_courses(Student student) {
    if(student.num_courses == 0) {
        printf("No courses taken yet.\n");
        return;
    }

    printf("\nCourses taken by %s:\n", student.name);
    for(int i = 0; i < student.num_courses; i++) {
        printf("%s (%d credits) - Grade: %.2f\n", student.courses[i].name, student.courses[i].credits, student.courses[i].grade);
    }
}

void print_gpa(Student student) {
    if(student.num_courses == 0) {
        printf("No courses taken yet.\n");
        return;
    }

    float total_credits = 0, total_grade_points = 0;
    for(int i = 0; i < student.num_courses; i++) {
        total_credits += student.courses[i].credits;
        total_grade_points += student.courses[i].credits * student.courses[i].grade;
    }

    printf("\nGPA for %s (ID: %d) is %.2f\n", student.name, student.id, total_grade_points/total_credits);
}

这个程序定义了两个结构体，`Course` 和 `Student`，`Course` 结构体表示一个课程，包含课程名称、学分和成绩；`Student` 结构体表示一个学生，包含学生姓名、学号、选修的课程数量和课程列表。程序主要通过一个菜单驱动式的界面与用户交互，提供添加课程、打印选修课程和计算 GPA 等功能。