n的自增

main.cpp

#include<iostream>
using namespace std;
void fn1();
int n;
int main()
{
	n=100;
	fn1();
	cout<<n<<endl;
	return 0;
}

fn1.cpp

#include<iostream>
#include<cmath>
using namespace std;
extern int n;
void fn1()
{
	n++;
}