Populating arrays from files.

[wharp2]

@Chervil

So I think I am getting closer and wonted you to take a look at what I have. It still is not working but I have the whole thing written and have been working on it I have seem to hit a wall tho. can you help me out?

When I Run it I get

5 5 5 5
5 5 5 5
5 5 5 5
5 5 5 5
5 5 5 5
Letter grade is F!
Class average is: 0.4

//  main.cpp
//  Program 8
//  Created by William Blake Harp on 7/16/14.

#include <iostream>
#include <fstream>
#include <iomanip>
#include <cmath>
#include <vector>

int size;
int sum_of_test_scores;
double average;
double class_average;
int r = 0;


using namespace std;

int main()
{
    ifstream inputFile;
    
    string data = "Student Data.txt";
    
    // Open the file
    inputFile.open("data.c_str");
    
    //2D Array.
    const int students = 5;
    const int test_scores = 4;
    int s[students][test_scores];
    
    //Arrays on the heap.
    int* arrayNames = nullptr;
    arrayNames = new int[size];
    
    int* arrayID = nullptr;
    arrayID = new int[size];
    
    int* arrayAverage = nullptr;
    arrayAverage = new int[size];
    
    int* arrayLetterGrade = nullptr;
    arrayLetterGrade = new int[size];
    
    // Populating 2D array test_scores.
    for (int i = 0; i < r; i++)
    {
        for (int j = 0; j < test_scores; j++)
        {
            cin >> s[i][j];
        }
    }
    
    // Displaying 2D array test_scores.
    for (int i = 0; i < r; i++)
    {
        for(int j = 0; j < test_scores; j++)
        {
            cout << s[i][j];
        }
        cout << endl;
    }
    
    // Populating array on the heap arrayNames
    for (int i = 0; i != size; i++)
    {
        cin >> arrayNames[i];
    }
    
    // Displaying array on the heap arrayNames
    for (int i = 0; i != size; i++)
    {
        cout << arrayNames[i];
    }
    
    // Populating array on the heap arrayID
    for (int i = 0; i != size; i++)
    {
        cin >> arrayID[i];
    }
    
    // Displaying array on the heap arrayID
    for (int i = 0; i != size; i++)
    {
        cout << arrayID[i];
    }

    // Populating array on the heap arrayAverage
    for (int i = 0; i != size; i++)
    {
        cin >> arrayAverage[i];
    }
    
    // Displaying array on the heap arrayAverage
    for (int i = 0; i != size; i++)
    {
        cout << arrayAverage[i];
    }

    // Populating array on the heap arrayLetterGrade
    for (int i = 0; i != size; i++)
    {
        cin >> arrayLetterGrade[i];
    }
    
    // Displaying array on the heap arrayLetterGrade
    for (int i = 0; i != size; i++)
    {
        cout << arrayLetterGrade[i];
    }

    do {
        // Average
        sum_of_test_scores += test_scores;
        average = sum_of_test_scores / 4;
    
        for(int i=0; i<students; i++)
        {
            for(int j=0; j<test_scores; j++)
                cout << s[students][test_scores] <<" "; cout<<endl;
        }
    
        // Geting a letter grade.
        if (average >= 90)
        {
            cout << "Letter grade is A!" << endl;
        }
        else if (average >= 89 && average <= 80)
        {
            cout << "Letter grade is B" << endl;
        }
        else if (average >= 79 && average <= 70)
        {
            cout << "Letter grade is C" << endl;
        }
        else if (average >= 79 && average <= 60)
        {
            cout << "Letter grade is D" << endl;
        }
        else (average < 60);
        {
            cout << "Letter grade is F!" << endl;
        }
    } while (students < 5);
    
    // Geting the class average
    class_average = (++average) / 5;
    cout << "Class average in: " << class_average << endl;

    // Close the file.
    inputFile.close();
    
    // releasing memory block on the heap.
    delete [] arrayNames;
    arrayNames = 0;
    delete [] arrayID;
    arrayID = 0;
    delete [] arrayAverage;
    arrayAverage = 0;
    delete [] arrayLetterGrade;
    arrayLetterGrade = 0;
    
    return 0;
}// End Code. 

[Chervil]

As you know, cin and cout are used for input and output respectively, to/from the console. cin is a type of input stream. When you use a file for input, then you use an ifstream - that is another type of input stream.

In most cases the streams share common behaviour.
for example you can do this such things as cin >> x, or getline(cin, y)

or equally, you can do something like this,
ifstream inputFile("Student Data.txt");
then inputFile >> x, or getline(inputFile, y)

Notice how cin can simply be replaced by inputFile, that's because both are input streams. I hope this helps a little, I'm trying to illustrate at least a little bit, how these things fit together.

[wharp2]

No that is very helpful I am going to see what I can do with this.