Question

I have been trying to figure out how to mirror the programs output to a .txt file as well as the console. I am relatively new to this, so I’m lost.. Please help, here is what I have so far.

#include <iostream>
#include <fstream>
#include <cmath>
#include <cstdlib>

using namespace std;

bool isPrime (int);

int main ()
{
    int numbers;
    ifstream inputFile;
    //open the file
    inputFile.open("22.txt");
    //output to file
    ofstream outFile;
    outFile.open("PrimeNumbers.txt");
    while(inputFile >> numbers)
        if(isPrime(numbers))
            outFile << numbers << endl;
            cout << numbers << " is a prime number." << endl;
} //end of main function
//function formula
bool isPrime (int num)
{
    int count=0;
    for (int numb=2; 
        numb<=num/2; 
        numb++)
    {
        if(num%numb==0)
            count++;
    }
    if (count>0)
        return false;
    else
        return true;
}

Answer 1

One error that stands out to me is:

while(inputFile >> numbers)
    if(isPrime(numbers))
        outFile << numbers << endl;
        cout << numbers << " is a prime number." << endl;

You don’t have any blocks (defined by curly brackets) so this snippet is equivalent to:

while(inputFile >> numbers)
{
    if(isPrime(numbers))
    {
        outFile << numbers << endl;
    }
    cout << numbers << " is a prime number." << endl;
}

See how the “cout” statement isn’t affected by the condition? What you wanted to write is:

while(inputFile >> numbers)
{
    if(isPrime(numbers))
    {
        outFile << numbers << endl;
        cout << numbers << " is a prime number." << endl;
    }
}

(Also, see my comment underneath your question requesting a more precise definition of the problem if you want more help)