struct students
{
    int Number;
    char Name[20];
    float English;
    float Maths;
    float Cprogram;
    float Average;
    struct students *next;
};
struct students *head, *p1, *p2;
int n;
void ipt(void)
{
    n = 0;
    p1 = p2 = (struct students*)malloc(sizeof(struct students));
    printf("Input students' record:Number Name English Maths Cprogram:");
    scanf("%d%s%f%f%f", &p1->Number, &p1->Name, &p1->English, &p1->Maths, &p1->Cprogram);
    head = NULL;
    while(p1->Number!=0)
    {
        n++;
        if (n = 1)
            head = p1;
        else    p2->next = p1;
        p2 = p1;
        p1 = (struct students*)malloc(sizeof(struct students));
        scanf("%d%s%f%f%f", &p1->Number, &p1->Name, &p1->English, &p1->Maths, &p1->Cprogram);
    }
    p2->next = NULL;
    return;
}

主函数运行没有问题.问题出在：scanf("%d%s%f%f%f", &p1->Number, &p1->Name, &p1->English, &p1->Maths, &p1->Cprogram);
上。
今天猛然想起老师讲的不能这样写，会出问题的。
改成这样就没问题了。
struct students
{
    int Number;
    char Name[20];
    int English;
    int Maths;
    int Cprogram;
    float Average;
    struct students *next;
};
struct students *head, *p1, *p2;
int n;
void ipt(void)
{
    n = 0;
    p1 = p2 = (struct students*)malloc(sizeof(struct students));
    printf("Input students' record:Number Name English Maths Cprogram:");
    scanf("%d%s%d%d%d", &p1->Number, &p1->Name, &p1->English, &p1->Maths, &p1->Cprogram);
    head = NULL;
    while(p1->Number!=0)
    {
        n++;
        if (n = 1)
            head = p1;
        else    p2->next = p1;
        p2 = p1;
        p1 = (struct students*)malloc(sizeof(struct students));
        scanf("%d%s%d%d %d", &p1->Number, &p1->Name, &p1->English, &p1->Maths, &p1->Cprogram);
    }
    p2->next = NULL;
    return;
}

为什么这么说？