Getting Input to fill an array

I don't quite understand how to get an input file to fill an array. It's part of a much bigger program, and I need this file (filled with 20 numbers) to be read in it's entirety (an eof?) to an array.

So what have you tried? Do you know anything about arrays?

I understand arrays pretty well. It's combining one with an input file that confuses me.
Here is what I have so far:

Code:

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void fill_array(int a[],int size, int& number_used)

{
    int next,index =0;
    using namespace std;
    ifstream in_stream;
    in_stream.open("SUPERNUMBERS.txt");
    if(in_stream.fail( ))
        {
            cout << "In stream failed.\n";
            exit (1);
        }
    in_stream.get(next);
    while (! in_stream.eof( ))
    {
          a[index] = next;
          index ++;
          cin >> next;
    }
    number_used = index;
}

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