Part-One

#include<iostream>
using namespace std;
int main()
{
    cout<<"Hello!"<<endl;
    cout<<"Welcome to C++"<<endl;
    return 0;
 } 

#include<iostream> 
using namespace std;
int main()
{
    int year;
    bool isLeapYear;
    
    cout<<"Enter the year:";
    cin>>year;
     //能被4整除且不能被一百整除，或者能被四百整除的年份是闰年
    isLeapYear=((year%4==0&&year%100!=0)||(year%400==0)); //新的代码结构！！！！ 它可以起到类似于常量的作用，一改全改，如果以后用到相同的条件，不用再写那么多的代码
    
    if(isLeapYear)
    {
        cout<<year<<" is a leap year"<<endl; 
     } 
    else{
        cout<<year<<" is a leap year"<<endl;
    }
    return 0;
}

驼峰命名法：
        大驼峰：如ZhongHuaRenMinGongHeGuo
        小驼峰：如zhongHuaRenMinGongHeGuo
匈牙利命名法： 
        Int   iNum:以i开头的变量存储整数
        Float  fNum:以f开头的变量存储小数
        Boolean  bBoo:以b或bo开头的变量存储布尔变量
        String  sStr:以s开头的变量存储一个字符串
        Char  cCh:以c开头的变量存储一个字符
        Object  obj:以o开头的变量存储对象
        Array  arr:以arr开头的变量存储数组
        Function  fn:以fn开头的变量存储函数

#include<iostream>
using namespace std;
int main()
{
    int day;
    
    cin>>day;
    switch(day){
        case 0:
            cout<<"Sunday"<<endl;
            break;
        case 1:
            cout<<"Monday"<<endl;
            break;
        case 2:
            cout<<"Tuesday"<<endl;
            break;
        case 3:
            cout<<"Wednesday"<<endl;
            break;
        case 4:
            cout<<"Thursday"<<endl;
            break;
        case 5:
            cout<<"Friday"<<endl;
            break;
        case 6:
            cout<<"Saturday"<<endl;
            break;
        default:
            cout<<"Day out of range Sunday…Saturday"<<endl;
            break;
            
    }
    return 0;
 }