也可以使用三元运算符，更为简单：

#include <iostream>
using namespace std;
int main(){
    int a,b,c,MAX;
    cout<<"please enter three number";
    cin>>a>>b>>c;
    MAX=a?b:a,b;
    MAX=MAX?c:MAX,c;
    cout<<"big number is"<<MAX;
    return 0;
} 

可以使用临时变量记录最大值:

#include <iostream>
using namespace std;
 
int main()
{
    float n1, n2, n3, max;
 
    cout << "请输入三个数: ";
    cin >> n1 >> n2 >> n3;
 
    if(n1 >= n2)
    {
        max = n1;
    }else{
        max = n2;
    }
 
    if(n3 >= max)
    {
        max = n3;
    }
 
    cout << "最大数为: " << max;
 
    return 0;
}

可以用与运算判断：

#include <iostream>
using namespace std;
 
int main()
{
    int n = 1;
 
    cout << "输入一个整数: ";
    cin >> n;
 
    if ( ( n & 1 ) == 0)
        cout << n << " 为偶数。";
    else
        cout << n << " 为奇数。";
 
    return 0;
}

改进了下上面的列子：

#include<iostream>
using namespace std;
class Student1 {
public:
    int a=0;
    int b=0;
    void fprint() {
        cout << " a = " << a << " " << "b = " << b << "\n"<<endl;
    }
    Student1()
    {
        cout << "无参构造函数Student1" << endl;
    }
    Student1(int i):a(i),b(a)
    { 
        cout << "有参参构造函数Student1" << endl;
    } 
    Student1(const Student1& t1)
    {
        cout << "拷贝构造函数Student1" << endl;
        this->a = t1.a;
        this->b = t1.b;
    }
    Student1& operator = (const Student1& t1) // 重载赋值运算符
    {
        cout << "赋值函数Student1" << endl;
        this->a = t1.a;
        this->b = t1.b;
        return *this;
    }
};
class Student2
{
public:
    Student1 test;
    Student2(Student1& t1) {
        t1.fprint();
        cout << "D: ";
        test = t1;
    }
    //     Student2(Student1 &t1):test(t1){}
};
int main()
{
    cout << "A: ";
    Student1 A;
    A.fprint();
    cout << "B: ";
    Student1 B(2); 
    B.fprint();
    cout << "C: ";
    Student1 C(B); 
    C.fprint(); 
    cout << "D: ";
    Student2 D(C);
    D.test.fprint();
}

教程里面举的例子可能不太好理解，下面是我写的一个例子：

int &changevalue()
{
    static int a_return =-29;
    return a_return;
}
int main()
{
    int &a_return=changevalue();
    a_return =20;
    cout<<changevalue()<<endl;
    system("pause");
}

最终，屏幕上打印的结果是：20