#include <iostream>

using namespace std;

int main()

{

    cout << "Hello, world!" << endl;//endl 换行
　　int a;
    cin>>a;

    return ;

}

#include <iostream>

using namespace std;

int main()

{

    cout << "Hello, world!" << endl;

    return 0;

}

文件A.cpp

#include <iostream>

extern int count;

void write_extern(void) //（void）表示无输入参数  也可以不填写

{

   std::cout << "Count is " << count << std::endl;

}

文件main.cpp

int count ;

extern void write_extern();

void main()

{

     count =1;

      write_extern();

}

	#pragma region 类的使用

	   Student *pStu = new Student; //在堆中 需要手动回收

	   pStu -> name = "小明";

	   pStu -> age = 15;

	   pStu -> score = 92.5f;

	   pStu -> say();

	   delete pStu;  //删除对象

	   Student s;	//在栈中 自动回收

	   s.name="1111";

	   s.age=23;

	   s.score=22;

	   s.say();

	 Student stu;

	 stu.name="2";

	   stu.age=2;

	   stu.score=2;

	   stu.say();

	   cout<<&s<<";"<<&stu<<endl;

	#pragma endregion