头文件和源文件定义之C++基础

头文件

#ifndef C_LEARNING_02_HEAD_H_
#define C_LEARNING_02_HEAD_H_

int age = 18;

#endif

源文件

#include "02_head.h"
#include<iostream>
using namespace std;
int main(){
    cout<<age<<endl;
}

CmakeLists

cmake_minimum_required("VERSION 3.15")
project(c_learning)
set(CMAKE_CXX_STANDARD 14)
add_executable(02_head chapter03/02_head.cpp)