我哪里做错了？ 程序未读取“未完成”和“不满意”变量

Question

When I run it's not reading outstanding and unsatisfactory . The grade and everything seem to work fine.

a. Write a program to read in a collection of exam scores ranging in value from 0 to 100. Your program should display the category of each score. It should also count and display the number of outstanding scores (90 to 100), the number of satisfactory scores (60 to 89), and the number of unsatisfactory scores(0 to 59).

b.Modify your program so it also displays the average score at the end of the run.

using namespace std;

void displayGrade(int);


int main()
{
   const int SENTINEL = -1;    
   int score, sum = 0, count = 0, outstanding = 0, satisfactory = 0, unsatisfactory  =0;                                
   double average;              

   cout << "Enter scores one at a time as requested." << endl;
   cout << "When done, enter " << SENTINEL << " to finish entering scores." << endl;
   cout << "Enter the first score: ";
   cin >> score;
   while (score != SENTINEL)
   {
      sum += score;
      count++;
      displayGrade(score); 
      cout << endl<< "Enter the next score: ";
      cin >> score;
      if (score >= 90)
          outstanding++;
      else if (score >=60){
          satisfactory++;
          if (score >= 0 && score <= 59)
              unsatisfactory++;
      }
   } 

   cout << endl << endl; 
   cout << "Number of scores processed is " << count << endl;
   cout << "Sum of exam scores is " << sum << endl;
   cout << "The number of Outstanding scores is: " << outstanding << endl;
   cout << "The number of Satisfactory scores is: " << satisfactory << endl;
   cout << "The number of Unsatisfactory scores is: " << unsatisfactory << endl;
   if (count > 0)
   {
      average = sum / count;
      cout << "Average score is " << average << endl;
   }
   system("PAUSE");
   return 0;
}   

void displayGrade(int score)
{
   if (score >= 90)
       cout << "Grade is A" << endl;
   else if (score >= 80)
       cout << "Grade is B" << endl;
   else if (score >= 70)
       cout << "Grade is C" << endl;
   else if (score >= 60)
       cout << "Grade is`enter code here` D" << endl;
   else
       cout << "Grade is F" << endl;
}

Answer 1

else if (score >=60){
  satisfactory++;

  if(score >= 0 && score <= 59)
    unsatisfactory++;
}

Can you see whats going wrong ? Rethink the logic for a score of 75. It will do satis++. Fine. But what about 45 ? It will never pass the else if in the first place, so it will never reach unsatis++ (it doesnt even reach the inner if-statement).

What you want is more like

else if (score >=60){
  satisfactory++;
} else if(score >= 0 && score <= 59) {
  unsatisfactory++;
}

or even shorter (if scores can be safely assumed to be between 0-100 all the time. :

else if (score >=60){
  satisfactory++;
} else {
  unsatisfactory++;
}

I will leave the outstanding part up to you, since this is obviously a homework. We are glad to help you understand things, but we won't do your schoolwork so you would never learn it. A good way of finding bugs is "stepping" through it with a debugger. You can tell your IDE to stop at the moment of entering the while-loop and then go though it line by line. On every line-halt you can see which line its at (and which got skipped..) and what the variable contents are at that particular point in time.