C语言未定义标识符及各种错误

问题遇到的现象和发生背景

VS2022下编译不通过，NULL显示的是未定义标识符，已经定义的结构体显示的是未定义标识符，各种错误都有

用代码块功能插入代码，请勿粘贴截图

#include 
#include 


struct Node
{
    int data;
    struct Node* next; // C++中只需要写Node*
};
struct Node* head;
void Insert(int x)
{
    struct Node* temp = (Node*)malloc(sizeof(struct Node));
    temp->data = x;
    temp->next = head;
    head = temp;
}
void Print()
{
    struct Node* temp = head;
    printf("List is:");
    while (temp != NULL)
    {
        printf(" %d", temp->next);
        temp = temp->next;
    }
    printf("\n");
}
int main(void)
{
    int n, x;
    head = NULL;
    printf("How many numbers?\n");
    
    scanf("%d\n", &n);
    for (int i = 0; i < n; i++)
    {
        printf("Enter the number:\n");
        scanf("%d", &x);
        Insert(x);
        Print(x);
    }

    return 0;
}

运行结果及报错内容

• 可以看下c语言参考手册中的 c语言-未定义行为

修改见注释，供参考：

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

struct Node
{
    int data;
    struct Node* next; // C++中只需要写Node*
};
struct Node* head;
void Insert(int x)
{
    struct Node* temp = (struct Node*)malloc(sizeof(struct Node));//修改
    //struct Node* temp = (Node*)malloc(sizeof(struct Node));
    temp->data = x;
    temp->next = head;
    head = temp;
}
void Print()
{
    struct Node* temp = head;
    printf("List is:");
    while (temp != NULL)
    {
        printf(" %d", temp->data); //修改
        // printf(" %d", temp->next);
        temp = temp->next;
    }
    printf("\n");
}
int main(void)
{
    int n, x;
    head = NULL;
    printf("How many numbers?\n");

    scanf("%d", &n); //scanf("%d\n", &n);//修改
    for (int i = 0; i < n; i++)
    {
        printf("Enter the number:\n");
        scanf("%d", &x);
        Insert(x);
        Print();    //Print(x); //修改
    }
    return 0;
}