Thread: Grades program has me lost

This one is a review for a final exam which I will be taking in about 13 hours. Supposively, my instructor insist that if we can do this program we should be able to do the final. I'm big in trouble. I started the program but I'm stumped. I just started back attending my classes 2 1/2 weeks ago after being out for 8 weeks ( was put on bed rest by doctor due to complication with pregnancy). Should've withdrew from my classes, but I didn't so now I'm trying to catchup on what I missed in four classes and attempt to take the finals. The only thing that my program does is displays the number of all grades entered including valid and non valid. I need it to display total number of grades included in the average; the average grade; and total number of A’s, B’s, C’s, D’s, and F’s. Right now it displays the average but the average includes grades of 0 which it shouldn't.
Would someone please advise me on what to do. I really want to know how to count the number of letter grades. I missed so much of class and am very lost, tired, and stressed out. I hope I don't go into early labor over this class. I've included a copy of the program description and the code that I have so far.

PROGRAM DESCRIPTION

You task is to write an interactive program that determines a student’s letter grade from the numeric grade (an integer), computes the average of all valid grades entered, and displays statistics about the grades entered.

SPECIFIC DIRECTIONS

Ask the user for one numeric grade at a time, and display the appropriate letter grade. You must use a separate function to request and input the grade, then return the grade to main.

The numeric ranges for grades are as follows:

91 – 100: A
81 – 90: B
71 – 80: C
65 – 70: D
Below 65: F

Use another function to test the numeric grade and return the letter equivalent to main .

You need to determine the average of all valid grades entered: any nonzero grade is valid, but any grades of zero should not be included in the average, since this means the student didn’t even take the test (you get 2 points for writing your name!). So, you don’t want to lower the average by including grades of Ø. When the user wants to quit, display the following: total number of all grades entered, including valid grades and grades of Ø; total number of grades included in the average; the average grade; and total number of A’s, B’s, C’s, D’s, and F’s.

Program
__________________________________________________
#include <iostream>
using namespace std;

//function prototypes
int getAvgGrade();
char assignGrade(float);

int main()
{
//declare variables

char grade = ' ';
float n_grade = 0.0;
float total_n_grade= 0.0;
float avg =0.0;
//get average grade
n_grade = getAvgGrade();
//assign grade
grade = assignGrade(n_grade);
//display grade
cout << "Average Grade: " << grade << endl;


return 0;
} //end of main function

//*****program-defined functions*****
int getAvgGrade()
{
//gets and accumulates the scores, then returns the average
int total_n_grade = 0;
int total_grades = 0;
float n_grade = 0.0;
char letterGrade = ' ';
char grade = ' ' ;
cout << "Pleae enter the first numeric grade: ";
cin >> n_grade;

while (n_grade > 0)
{

total_grades = total_grades + 1;

total_n_grade = total_n_grade + n_grade;

cout << "please enter the next numeric grade: ";
cin >> n_grade;

}//end while
if (total_grades >=0)
n_grade = total_n_grade/ total_grades;
cout << "Total number of all grades entered: " << total_grades << endl;

return n_grade;

} //end of getAvGrade function


char assignGrade(float n_grade)
{
//assigns the letter grade
char letterGrade = ' ';

if (n_grade>= 91)
letterGrade = 'A';
else if (n_grade >= 81)
letterGrade = 'B';
else if (n_grade >= 71)
letterGrade = 'C';
else if (n_grade >= 65)
letterGrade = 'D';
else letterGrade = 'F';
//end ifs
return letterGrade;
} //end of assignGrade function

Hi adrea-

I don't see the problem you are describing. The logic appears to be okay, except that as soon as you enter a zero the loop stops and the average is computed; you aren't giving it the option to consider zero grades. One way to fix this is to use a negative grade as the flag to stop counting:

Code:

int getAvgGrade()
{
    //gets and accumulates the scores, then returns the average
    int total_n_grade = 0;
    int total_grades = 0;
    int zero_grades = 0;  // Added this
    float n_grade = 0.0;
    char letterGrade = ' ';
    char grade = ' ' ;
    cout << "Pleae enter the first numeric grade: ";
    cin >> n_grade;

    while (n_grade >= 0)  // Changed this here
        {
        if (n_grade > 0) { // Added this if-else
            total_grades++;
            total_n_grade += n_grade;
        } else
            zero_grades++;

        cout << "please enter the next numeric grade: ";
        cin >> n_grade;

    }//end while
    if (total_grades >=0)
        n_grade = total_n_grade/ total_grades;

    cout << "Total number of all grades entered: " 
         << total_grades + zero_grades << endl;  // Changed this
    cout << "Total number of valid grades entered: " 
         << total_grades << endl;  // Added this
    return n_grade;
} //end of getAvGrade function

Also, you may want to have something else that deals with the special case where the average ends up being zero (in other words the student didn't take any tests at all. The program with the revisions to the getAvGrade function produced the following run:

Code:

akua% a.out
Pleae enter the first numeric grade: 100
please enter the next numeric grade: 100
please enter the next numeric grade: 100
please enter the next numeric grade: 0
please enter the next numeric grade: 100
please enter the next numeric grade: 100
please enter the next numeric grade: 0
please enter the next numeric grade: 0
please enter the next numeric grade: 100
please enter the next numeric grade: -1
Total number of all grades entered: 9
Total number of valid grades entered: 6
Average Grade: A

Hope this isn't too late, good luck on your final.