About character arrays and strings

@C++

#include<bits/stdc++.h>
using namespace std;
int main(){
	char a[5];
	for(int i=0;i<5;i++){
		cin>>a[i];
	}
	cout<<strlen(a)<<endl;
	a[2]='\0';
	for(int i=0;i<5;i++){
		cout<<a[i]<<endl;
	}
	cout<<a[4]<<endl; 
	cout<<strlen(a)<<endl;
	cout<<sizeof(a)<<endl;
	//cout<<a.length()<<endl;报错 
	cout<<"xxxxxxxxxxxx"<<endl;
	string b;
	cin>>b;
	cout<<b<<endl;
	cout<<sizeof(b)<<endl;
	//cout<<strlen(b)<<endl;报错 
	cout<<b.length()<<endl;
}