Writing to a program to a file

[cheagle5]

So my assignment is to write to a file prime numbers from 1 to 100.
Here is my code, but i can't seem to get it to write to my specified file

  
#include <iostream>
#include <fstream>
using namespace std;


int main(int argc, const char * argv[])
{
    //tell user what program is doing
    cout << "This program stores all prime numbers from 1 to 100 in a file." << endl;
    
    //declare and open an output file for writing to
    ofstream outputFile;
    outputFile.open("primeNumbers.txt");
    
    //for loop to go through every number up to 100
    for (int i = 1; i <= 100; i++)
    {
        int ans = 1;
    
        //for loop to determine if prime
        for (int x = 2;i <= i/2; x++)
            {
                //if statement determines a not prime number
                if (i % x == 0)
                    ans = 0;
                //else it is prime
                else
                    //writes to file the prime number
                    outputFile << i << endl;
            }
    }
    
    //closes file
    outputFile.close();
        return 0;
}

[ak16]

Try this-

#include <iostream>
#include <fstream>
using namespace std;


int main(int argc, const char * argv[])
{
          //tell user what program is doing
    cout << "This program stores all prime numbers from 1 to 100 in a file." << endl;
    
    ofstream outputFile;						//declare and open an output file for writing to
    outputFile.open("primeNumbers.txt");
    
	if(outputFile.is_open())					//You should check weather file opened or not
	{
									
		for (int i = 1; i <= 100; i++)			//for loop to go through every number up to 100
		{
			int ans = 1;
			for(int x=2;x<=i/2;++i)
			{
				if(i%x==0)
				{
					break;				//If divide by any other than 1/itself then break loop
				}
				else
				{
					cout<<i<<"	";		//write on Console
					outputFile<<i<<" ";		//write on file
				}
			}
  
		}

	}

    outputFile.close();							//closes file

	return 0;
}

[ak16]

your file related code is correct.
but problem is in calculating prime number,
check this -

 
  for (int x = 2;i <= i/2; x++)

[cheagle5]

I just tried this code, and it seems to be displaying just the odd numbers from 5 to 100

[Computergeek01]

I just tried this code, and it seems to be displaying just the odd numbers from 5 to 100

That's because you're outputting after each integer test. You have to iterate through the entire second for loop before you know if the number you are testing is prime or not, so the output code should be outside of the second for loop.

[cheagle5]

ok i think i figured it out
here is what I've got

#include <iostream>
#include <fstream>
using namespace std;


int main(int argc, const char * argv[])
{
    //tell user what program is doing
    cout << "This program stores all prime numbers from 1 to 100 in a file." << endl;
    
    ofstream outputFile;						
    outputFile.open("primeNumbers.txt");
    
	if(outputFile.is_open())					
	{
        
		for (int i = 1; i <= 100; i++)			
		{
            bool prime = true;
            
			for(int x=2;x<=i/2;x++)
			{
				if(i%x==0)
				{
					prime = false;				
				}
				
			}
            
            if (prime == true)
            {
                outputFile << i;
                cout << i << "   ";
		
            }
        }
	}
    
    outputFile.close();							//closes file
    
	return 0;
}

[ak16]

#include "stdafx.h"
#include "conio.h"
#include "iostream"
#include <fstream>
using namespace std;



int _tmain(int argc, _TCHAR* argv[])
{
    //tell user what program is doing
    cout << "This program stores all prime numbers from 1 to 100 in a file." << endl;
    
    ofstream outputFile;						//declare and open an output file for writing to
    outputFile.open("primeNumbers.txt");
    
	if(outputFile.is_open())					//You should check weather file opened or not
	{
									
		for (int i = 1; i <= 100; i++)
		{
			int ans = 1;
			int x;
    
			//for loop to determine if prime
			for (x = 2;x <= i/2; x++)
			{
				//if statement determines a not prime number
				if (i % x == 0)
					break;
                
			}
			if(x>i/2)
			{
				outputFile <<i<<"  ";
				cout<<"\t"<<i;
			}

		}

	}

    outputFile.close();							//closes file
	getch();
	return 0;
}