Test scores average coming out incorrectly

[cloudwolf]

Hey guys, I saw that someone posted a question about this program earlier but they are having a different issue than I am. When I compile the code and input the values, the average keeps returning as "-71582760.00," no matter what I put in.

After that, the program doesn't return a letter grade at all. I've worked on it for a while and also confirmed that the find average function was exactly like one I previously made in another program that worked properly. Thanks in advance for any help!

  #include <iostream>
#include <iomanip>

using namespace std;

const	int MAXGRADE = 25;	// maximum number of grades per student 
const	int MAXCHAR = 30;	// maximum characters used in a name

typedef char StringType30[MAXCHAR + 1];	// character array data type for names
										// having 30 characters or less.

typedef	float GradeType[MAXGRADE];		// one dimensional integer array data type

float findGradeAvg(GradeType, int);		// finds grade average by taking array of
										// grades and number of grades as parameters

char findLetterGrade(float);			// finds letter grade from average given
										// to it as a parameter 
int main()
{
	StringType30 firstname, lastname;	// two arrays of characters defined
	int numOfGrades;					// holds the number of grades
	GradeType grades;					// grades defined as a one dimensional array
	float average;						// holds the average of a student's grade
	char moreInput;						// determines if there is more input
	char grade;

	cout << setprecision(2) << fixed << showpoint;

	// Input the number of grades for each student
	cout << "Please input the number of grades each student will receive." << endl
		<< "This must be a number between 1 and " << MAXGRADE << " inclusive"
		<< endl;
	cin >> numOfGrades;

	while (numOfGrades > MAXGRADE || numOfGrades < 1)
	{
		cout << "Please input the number of grades for each student." << endl
			<< "This must be a number between 1 and " << MAXGRADE
			<< " inclusive\n";
		cin >> numOfGrades;
	}

	// Input names and grades for each student
	cout << "Please input a y if you want to input more students"
		<< " any other character will stop the input" << endl;
	cin >> moreInput;

	while (moreInput == 'y' || moreInput == 'Y')
	{
		cout << "Please input the first name of the student" << endl;
		cin >> firstname;

		cout << endl << "Please input the last name of the student" << endl;
		cin >> lastname;

		for (int count = 0; count < numOfGrades; count++)
		{
			cout << endl << "Please input a grade" << endl;

			cin >> grades[0]; // Fill in the input statement to place grade in the array
		}

		cout << firstname << " " << lastname << " has an average of " ;

		average = findGradeAvg(grades, numOfGrades); // Fill in code to get and print average of student to screen
		cout << fixed << setprecision(2) << average << endl;

		grade = findLetterGrade(average);			 // Fill in call to get and print letter grade of student to screen
		

		cout << "This student's letter grade is " << grade << endl;

		cout << endl << endl << endl;

		cout << "Please input a y if you want to input more students"
			<< " any other character will stop the input" << endl;
		cin >> moreInput;
	}

	return 0;
}

//***********************************************************************
// findGradeAvg
//
// task:	      This function finds the average of the
//                numbers stored in an array.
//
// data in:	      an array of integer numbers
// data returned: the average of all numbers in the array
//
//***********************************************************************

float findGradeAvg(GradeType array, int numGrades)

{
	float sum = 0;
	
	    
	for (int count = 0; count < numGrades; count++)

	{
		sum += array[count];
	}

	return (sum / numGrades);

}

//***********************************************************************
// findLetterGrade
//
// task:	      This function finds the letter grade for the number
//                passed to it by the calling function
//
// data in:	      a floating point number
// data returned: the grade (based on a 10 point spread) based on the 
//                number passed to the function
//
//***********************************************************************

char findLetterGrade(float numGrade)
{
	char grade = 0;
	
	if (numGrade >= 90)
	{
		grade = 'A'; // Fill in the code for this function
	}
	else if (numGrade >= 80 && numGrade < 90)
	{
		grade = 'B';
	}
	else if (numGrade >= 70 && numGrade < 80)
	{
		grade = 'C';
	}
	else if (numGrade >= 60 && numGrade < 70)
	{
		grade = 'D';
	}
	if (numGrade < 60 && numGrade >= 0)
	{
		grade = 'F';
	}
	return grade;
}

[Ganado]

		for (int count = 0; count < numOfGrades; count++)
		{
			cout << endl << "Please input a grade" << endl;

			cin >> grades[0]; // Fill in the input statement to place grade in the array
		}

What value is grades[1] set to here?

"GradeType" is a confusing typedef for an array.
"StringType30" encodes the magic number 30 into the name of the typedef itself.
If I were you I wouldn't use either of these typedefs, but maybe that's just me.

[cloudwolf]

Yeah the GradeType and StringType30 were included in the skeleton code that we were provided. I don't mess with that stuff because I got docked some points once for modifying it.

Doesn't the grades input need to be written that way to accept user input into the array?

[Ganado]

Your grades array is an array of 25 floats (although you don't necessarily use all these indices).
That is, grades[0] is a float, grades[1] is a float, ..., grades[24] is a float.

Your loop (lines 57 to 62) only ever puts user input into grades[0] (line 61).

You need to put values into grades indices beyond grades[0] as well.

[cloudwolf]

Awesome, that did it. Thanks a lot, that was driving me insane!

Is there an explanation for why it kept returning the same number everytime? Like what was the program doing to keep getting that number?

[Ganado]

The -71582760.00 number is just the result of using uninitialized values in your calculations. Essentially, junk values, and junk in = junk out.