判断成绩.cpp

我已经调试过了

//判断成绩等级程序
#include <iostream>
using namespace std;
int main()
{
  cout<<"please enter your score ,please! ?\n";
  int score;
  cin>>score;
  if(score>100||score<0){
    cout<<"the score you entered is invalidate!" <<endl;
    cout<<"input again ?\b";
  }
  if(score==100)
    cout<<'A'<<endl;
  else if(score>=90&&score<100)
    cout<<'B'<<endl;
  else if(score>=75&&score<90)
    cout<<'C'<<endl;
  else if(score>=60&&score<=75) //60<=score<=75 呢???!!!
    cout<<'D'<<endl;
  else
    cout<<'E'<<endl;
}


/*if(score>=60&&score<=75)   写作60<=score<=75是错误的,因为按照逻辑
运算符从左到有的运算顺序,60<=score的结果只能是0或者1,即假或者真,0或
1小于等于75恒为真,即无论score取多大的数,f(条件)恒成立.*/