Program wont run properly

[adeclue]

Heres what the program is supposed to do:
Write a program that will read data from the file "p6.dat". The file (that you will create) always contains 15 test scores (whole numbers between 0 and 100). The test scores are scores for 5 students taking 3 tests, and are arranged, in the file, by the student - that is the first 3 numbers are the test scores for test 1, 2, and 3 for the first student, etc.
The program will print:
- average per student (5 averages), on a single line, with 2 decimals
- average per test (3 averages), on a single line, with 2 decimals
- overall best score on a single line
- how many scores were As (out of the 15, how many were at least 90) on a single line

To simplify the code, no validations are needed. That is, assume the file is successfully opened, and that all data are 0-100, and that there are exactly 15 numbers in the file.
Note that the program reads the filename

  #include <iostream>
#include <string>
#include <fstream>
#include <iomanip>

using namespace std;

int main()
{
    const int num_students = 5;
    const int num_tests = 3;
    double testScores[num_students][num_tests];
    string filename;
    ifstream inputFile;


    cout << "Enter name of file to read: ";
        cin >> filename;

    // Open the file.
    inputFile.open(filename);

    // Read the test scores from the file into the array.
    for(int i = 0; i < num_students; i++)
    {
        for(int j = 0; j < num_tests; j++)
        {
            inputFile >> testScores[i][j];
        }
    }

    // Close the file
    inputFile.close();

    // Average per student
    cout << "\nAverage per student:  ";
    for(int i = 0; i < num_students; i++)
    {
        double sumForStudent = 0;
        for (int j = 0; j < num_tests; j++)
        {
            sumForStudent = sumForStudent + testScores[i][j];
        }
        double avgOfStudent = sumForStudent / num_tests;
        cout << "\t" << setiosflags(ios::fixed) << setprecision(2) << avgOfStudent;
    }

    // Average per test
    cout << "\n\nAverage per test:  ";
    for(int i = 0; i < num_tests; i++)
    {
        double sumForTest = 0;
        for (int j = 0; j < num_students; j++)
        {
            sumForTest = sumForTest + testScores[j][i];
        }
        double avgOfTest = sumForTest / num_students;
        cout << "\t" << setiosflags(ios::fixed) << setprecision(2) << avgOfTest;
    }

    // Overall Best Score and number of A's
    double max = 0, countOfA = 0;
    for(int i = 0; i < num_students; i++)
    {
        for (int j = 0; j < num_tests; j++)
        {
            if(testScores[i][j] > max)
                max = testScores[i][j];

            if(testScores[i][j] >= 90)
                ++countOfA;
        }
    }

    cout << "\n\nOverall best score:  " << max;
    cout << "\n\nNumber of A's:  " << countOfA << "\n\n";

    system("pause");
    return 0;
}

And all I get when I run is:
Average per student: 0.00 0.00 nan 0.00 0.00

Average per test: 0.00 0.00 nan

Overall best score: 0.00

Number of A's: 0.00

[lastchance]

Your results give the impression that the program didn't find the data file (or, just possibly, it wasn't in the correct format).

Try the code below (I made minor adjustments to accommodate the C++98 standard: you probably don't need to). You should check that the file opened correctly (as in the code).

#include <iostream>
#include <string>
#include <fstream>
#include <iomanip>
#include <cstdlib>                             // <==== Minor quibble for C++98

using namespace std;

int main()
{
    const int num_students = 5;
    const int num_tests = 3;
    double testScores[num_students][num_tests];
    string filename;
    ifstream inputFile;


    cout << "Enter name of file to read: ";
        cin >> filename;

    // Open the file.
    inputFile.open(filename.c_str());               // <==== Minor change to accommodate C++98
    if ( !inputFile )                               // <==== CHECK WHETHER FILE OPENED CORRECTLY
    {                                               //
       cout << "Can't open file " + filename +"\n"; //
       system("pause");                             //
       return 1;                                    //
    }                                               //


    // Read the test scores from the file into the array.
    for(int i = 0; i < num_students; i++)
    {
        for(int j = 0; j < num_tests; j++)
        {
            inputFile >> testScores[i][j];
        }
    }

    // Close the file
    inputFile.close();

    // Average per student
    cout << "\nAverage per student:  ";
    for(int i = 0; i < num_students; i++)
    {
        double sumForStudent = 0;
        for (int j = 0; j < num_tests; j++)
        {
            sumForStudent = sumForStudent + testScores[i][j];
        }
        double avgOfStudent = sumForStudent / num_tests;
        cout << "\t" << setiosflags(ios::fixed) << setprecision(2) << avgOfStudent;
    }

    // Average per test
    cout << "\n\nAverage per test:  ";
    for(int i = 0; i < num_tests; i++)
    {
        double sumForTest = 0;
        for (int j = 0; j < num_students; j++)
        {
            sumForTest = sumForTest + testScores[j][i];
        }
        double avgOfTest = sumForTest / num_students;
        cout << "\t" << setiosflags(ios::fixed) << setprecision(2) << avgOfTest;
    }

    // Overall Best Score and number of A's
    double max = 0, countOfA = 0;
    for(int i = 0; i < num_students; i++)
    {
        for (int j = 0; j < num_tests; j++)
        {
            if(testScores[i][j] > max)
                max = testScores[i][j];

            if(testScores[i][j] >= 90)
                ++countOfA;
        }
    }

    cout << "\n\nOverall best score:  " << max;
    cout << "\n\nNumber of A's:  " << countOfA << "\n\n";

    system("pause");
    return 0;
}

When I used the following input file p6.dat:

10   20  30
90   80  70
40   50  60
60   50  40
70   70  70

I obtained output

Average per student:  	20.00	80.00	50.00	50.00	70.00

Average per test:  	54.00	54.00	54.00

Overall best score:  90.00

Number of A's:  1.00

Apart from some minor formatting issues (e.g. make countOfA an int) it seems reasonable.

While debugging it would also be sensible to output each value of testScores[i][j] immediately after reading it.