For loop not letting me change input

Question

The point of this program is for the user to enter the grade of a certain amount of students up to 50, from a range of grades A,B,C,D, or F. At the end, the program is then supposed to show how many students got each grade. Whenever I test the following code, whatever I input for the for loop repeats every time, such that if I input for it to do the grades 3 students, whatever letter I enter for student 1 will be the same grade for every student, so if one student has an A, they all will have an A. I also have to use arrays for this program because it's for college. Sorry if there's not enough information, this is my first time posting.

#include<iostream>
#include<iomanip>
#include<string>
void gradeTotals();
using namespace std;
int x,z,a=0,b=0,c=0,d=0,f=0,i=0;
char grade[50];
int main()
{

cout<<"Please enter the number of students"<<endl;
cin>>x;
for (i=0;i<x;i++)
{
    int y;
    y=i+1;
    cout<<"Please enter a letter grade of A,B,C,D, or F for student "<<y<<endl;
    cout<<"All grades must be uppercase"<<endl;
    cin>>z;
    grade[i]=z;
    gradeTotals();
}
}
void gradeTotals()
{
    if (grade[i]=='A')
    {
        a++;
    }
    else if (grade[i]=='B')
    {
        b++;
    }
    else if (grade[i]=='C')
    {
        c++;
    }
    else if (grade[i]=='D')
    {
        d++;
    }
    else if (grade[i]=='F')
    {
        f++;
    }
cout<<a<<endl;
cout<<b<<endl;
cout<<c<<endl;
cout<<d<<endl;
cout<<f<<endl;
}

You forgot to ask a question. You told a story, showed some code, and then just stopped. The button is labelled "Ask Question" for a reason. — David Schwartz, Nov 24 '14 at 04:02
`z` is an int. How are you expecting it to hold letter grades? — David Schwartz, Nov 24 '14 at 04:03
Sorry, my question is how to make it so my for loop lets me input a new value for each subscript. — Nick Hannmann, Nov 24 '14 at 04:04
OK that fixed everything. I just added the z to the list of values I already had without thinking. Thanks. — Nick Hannmann, Nov 24 '14 at 04:09

therealrootuser · Accepted Answer · 2014-11-24T04:12:40.137

0

It looks like your if statements are not doing what you expect. For instance:

if (grade[i]='B')
{
    // This code will *always* execute
}

You ought to be using the double equals == to compare a value, and a single equals = to assign a value.

(Edit after additional code change)

Inside the for-loop, you are trying to use cin to read in a single character. However, since the z is an integer, cin is looking for a valid integer, which does not happen to include 'A' or 'B', etc.

Perhaps you should try using a getline() or get().

edited Nov 24 '14 at 04:12

answered Nov 24 '14 at 03:56

therealrootuser

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I changed that but then none of the values at the end were increasing, which made me realize there might be more of my code that's messed up. But I still haven't had any help with my main problem, the for loop. – Nick Hannmann Nov 24 '14 at 03:59

score 0 · Answer 2 · edited May 23 '17 at 11:57

The problem lies in having your input variable as an int, take in a char.

What happens is that when you perform cin >> z;, the character that was input by the user is recognized as an invalid input by the >> operator and therefore does not extract the character.

As such, z does not get any value, the character stays in the stream, and the >> operator continues to fail to extract the character until the loop ends.

Therefore, you can solve your problem by making your input variable a char instead.

Here's a link to help you better understand how to avoid such problems in the future.

Thank you for reading.

For loop not letting me change input

2 Answers2