刚学习C不久，自己写了个动态单行链表的程序，于是对return更加茫然了，求解答，求喷，求打击
代码：
# include <stdio.h>
# include <malloc.h>
# define null 0

struct Student
{
    char name[20];
    int age;
    float score;
    struct Student * pnext;
};

struct Student * creat(void)
{
    int i,n;
    struct Student * p2;
    printf("请输入学生人数：\n");
    scanf("%d",&n);

    struct Student * phead = (struct Student *)malloc(sizeof(struct Student));
    if (null == phead)
    {
        printf("内存分配失败！退出程序\n");
        return 0;              //函数的返回类型是struct Student * ，这里为什么返回0是正确的？
    }                            //而换成了其他整数报错？# include <stdlib.h> 头文件中的exit()
                                //是否是强制退出函数？
    phead->pnext = null;
    p2 = phead;
    p2->pnext = null;
   

    for (i=0;i<n;i++)
    {
        struct Student * p1 = (struct Student *)malloc(sizeof(struct Student));
        if (null == p1)
        {
            printf("内存分配失败！退出程序\n");
            return 0;
        }
        printf("请输入第%d个学生的名字：\n",i+1);
        scanf("%s",p1->name);
        printf("请输入第%d个学生的年纪：\n",i+1);
        scanf("%d",&p1->age);
        printf("请输入第%d个学生的成绩：\n",i+1);
        scanf("%f",&p1->score);
        p2->pnext = p1;
        p1->pnext = null;
        p2 = p1;
    }

    p2->pnext = null;

    return phead;
}

int  main(void)
{
    struct Student * phead = null;
   
    phead = creat();   
   
    return 0;
}