#include<iostream>
using namespace std;
int main()
{
	int sum;
  
	sum=0;
	cout<<"sum="<<sum<<endl;
	
	sum=sum+1;
	cout<<"sum="<<sum<<endl;
	//sum+=1;
	
	sum=sum+2;
	cout<<"sum="<<sum<<endl;
	//sum+=2;
	
	sum=sum+3;
	cout<<"sum="<<sum<<endl;
	
	sum=sum+4;
	cout<<"1+2+3+4="<<sum<<endl;  
	
	return 0;
}

scratch2代码

 

scratch3代码