#include <iostream>
using namespace std;
class renlei
{
public:
    void huodeshengao(){cout<<shengao;}
    void shezhishengao(int x){shengao=x;}
    void huodetizhong();
    void shezhitizhong(int x);
private:
    int shengao;
    int tizhong;
};
void renlei::shezhitizhong(int x)
{
    tizhong=x;
}
void renlei::huodetizhong()
{
    cout<<tizhong;
}
void main()
{
    renlei kangqiu;
    kangqiu.shezhishengao(8);
    kangqiu.huodeshengao();
    cout<<endl;
    kangqiu.shezhitizhong(80);            //为什么无法输出这个80.
    kangqiu.huodetizhong;
}

最后一行少个参数括号吧，试试。

kangqiu.huodetizhong;
这句应该为 kangqiu.huodetizhong();吧！

粗心了。以为数不出值是上面赋值问题、没看下面。诶~~~~~

warming都不看么

#include <iostream>
using namespace std;
class renlei
{
public:
    void huodeshengao()
    {
        cout<<shengao;
    }

    void shezhishengao(int x)

    {
        shengao=x;
    }

    void huodetizhong();

    void shezhitizhong(int x);

private:
    int shengao;
    int tizhong;
};
void renlei::shezhitizhong(int x)
{
    tizhong=x;
}
void renlei::huodetizhong()
{
    cout<<tizhong;
}
void main()
{
    renlei kangqiu;
    kangqiu.shezhishengao(8);
    kangqiu.huodeshengao();
    cout<<endl;
    kangqiu.shezhitizhong(80);            //为什么无法输出这个80.
    kangqiu.huodetizhong();
    cout<<endl;
}