Program that shows sum of even numbers

Question

I have a problem for my CS class that I'm just not getting. I have to read an unspecified amount of integers in a text file. From there on I have to find the integers that are divisible by 5 and then add them up. Say I have a text file containing 1, 5, 7, 10, and 11, so my answer should be 15. The instructor says we have to use a while loop to read until End-Of-File.

Here is what I have, which is completely wrong:

#include <iostream>
#include <fstream>

using namespace std;

int main()
{
    int sum, even;
    sum = 0;
    ifstream inFile;

    inFile.open("numbers.txt");

    inFile >> even;

    do
    {
        if (even % 5 == 0)
        {
            sum = sum + even;
            cout << "\nThe sum of the numbers is:" << sum << endl;
        }

        else
        {
            cout << "\nNo numbers divisible by 5." << endl;
        }
    } 
    while (!inFile.eof());

    inFile.close();

    system("pause");

    return 0;
}

Something does happen; an endless loop that goes through large negative numbers.

Can anyone point me into the right direction?

Thanks,

Tobi

Update: I have this so far, but it prints out 4 answers.

#include <iostream> 
#include <fstream> 

using namespace std;

int main()
{
    int num, sum, count;
    sum = 0;
    ifstream inFile;

    inFile.open ("numbers2.txt");

    if (!inFile)
    {
        cout << "Can't open the input file.\n" << endl;
        system("pause");
        return 1;
     }

     inFile >> num;

     while (!inFile.eof())
     {
        inFile >> num;

        if (num % 5 == 0)
        {
            sum += num;
            cout << "Sum is: " << sum << endl;
        }

        else
        {
            cout << "Is not divisible by 5." << endl;
        }
     }

    inFile.close();

    system("pause");

    return 0;
}

My output looks like this:

1. sum is: 5
2. sum is: 25 (What I want as the output)
3. Is not divisible by 5.
4. Is not divisible by 5

I'll keep trying until I get this.

Thanks to everyone who has answered so far.

Answer 1

You can try something like this...not perfect, but just something you can use to understand and improve upon.

C++ example - program.cpp

#include <iostream> // provides cout, endl etc.
#include <fstream>  // provides file stream functionality
#include <string>   // provides string
#include <stdlib.h> // provides atoi functionality

using namespace std;

int main()
{
    int sum = 0;
    int num = 0;
    bool multiple_of_5_found = false;

    std::ifstream file("numbers.txt");
    std::string str;

    // while begins
    while(std::getline(file, str))
    {
        // convert string to number
        num = atoi(str.c_str());
        if (num % 5 == 0)
        {
            multiple_of_5_found = true;
            sum += num;
        }
    }
    // while ends

    // based on what we observed/calculated, print info
    if (multiple_of_5_found)
    {
        cout << "The sum of numbers divisible by  5 is "
             << sum << endl;
    }
    else
    {
        cout << "No number divisible by 5" << endl;
    }

    return 0;
}

GCC version

$> g++ --version
g++-4.7.real (Debian 4.7.2-5) 4.7.2

numbers.txt

$ cat numbers.txt
1
5
7
10
11
15

compile and run

$ g++ program.cpp && ./a.out
The sum of numbers divisible by  5 is 30

Visual Studio 2013 screenshot of numbers.txt resource

Visual Studio 2013 screenshot of Source.cpp

Visual Studio 2013 screenshot after pressing F7 and clicking on Local Windows Debugger