关于移位操作的一点重要说明

#include <iostream>
using namespace std;


int main()
{
  int num1=7;
  cout<<"num1(7)<<2: "<<(num1<<2)<<endl;
  cout<<"num1(7)>>2: "<<(num1>>2)<<endl;
  int num2=-7;
  cout<<"num2(-7)<<2: "<<(num2<<2)<<endl;
  cout<<"num2(-7)>>1: "<<(num2>>1)<<endl;
  cout<<"num2(-7)>>2: "<<(num2>>2)<<endl;
  return 0;
}