C++怎样设置可读写的全局变量

怎么样定义一个可读写的全局变量，比如我代码中的变量yu

#include<iostream>
#define yu;
int day(int);
int hour(int);
int minute(int);
int second(int);
const int stom = 60;
const int mtoh = 60;
const int htod = 24;

int main(){
    using namespace std;
    cout << "Enter the number of seconds: ";
    long seconds;
    cin >> seconds;
    cout << seconds << " seconds = " << day(seconds) << " days, "
    << hour(seconds) << " hours, " << minute(seconds) 
    << " minutes, " << second(seconds) << " seconds." << endl;
    return 0; 
}
int day(int s){
    int d;
    d = s /stom / mtoh / htod;
    return d;
}
int hour(int s){
    int h;
    yu = s %(stom * mtoh * htod);
    h = yu / stom / mtoh;
    return h;
}
int minute(int s){
    int m;
    yu = yu %(stom * mtoh);
    m = yu / stom;
    return 0;
}
int second(int s){
    int se;
    se = yu % stom;
    return se;
}

求大神指教

这是纯C的问题吧，虽然不知道你想做什么，定义一个全局yu
#define yu; 请替换为
int yu = 0;
另外建议改
const int stom = 60;
const int mtoh = 60;
const int htod = 24;
为
#define STOM 60