Question

1. Create a program named Lab14B. You will create a nested loop in this program by putting Lab14A’s for loop inside a while loop. In the new while loop, you will read integers from the file, Lab14B.txt, and determine if the number is prime (using the copied loop from Lab14A). Stop the while loop when you reach the end of file.

• Copy your code from Lab14A into your new program
• Add a while not eof loop around that code, and also change the code to read the input number from a text file instead of from the user. (Lab 12 has an eof controlled while loop.)
• Don’t forget to reset your count variable to 0 every time you read a new number.

For each number, print both the number itself and a statement saying if it is prime or not.

My code is below. I'm mainly confused with what to leave from my original code and what to take out for the eof while loop

int main()
{
    int num, i, count = 0;
    ifstream infile;
    infile.open("Lab14B.txt");
    while (!infile.eof())
    cout << "Please enter a number : ";
    cin >> num;
    if (num == 0)
    {
        cout << " is not prime ";
    }
    else
    {
        for (i = 2; i < num; i++)
            if (num % i == 0)
                count++;
    }
    if (count > 1)
        cout << " Number is not prime ";
    else
        cout << " Number is prime ";
    return 0;
}

Answer 1

Lab14B.cpp:

#include <fstream>
#include<iostream>
using namespace std;
int main()
{
int num, i, count = 0;
ifstream infile;
infile.open("Lab14B.txt"); //opening given text file
   //here we wont use !infile.eof() condition in while loop
   // because it doesnt read text file properly .If we use that condition then last line will be read twice
while (infile >> num) //reading until lines exist
   {
       count=0;
       if (num == 0 || num == 1) //if number is 0 or 1
       {
       cout <<num<< " is not prime\n"; //they are not prime
           continue; //skipping the next statments of loop
       }
       else
       {
       for (i = 2; i < num; i++) //iterating upto that number
       if (num % i == 0){ //if it is divisible by any number
       count++; //increment count variable
                   break; //coming out of the for loop
               }
       }
       if (count == 1) //if count is 1 then it is not prime
       cout <<num<< " Number is not prime\n";
       else
       cout <<num<< " Number is prime\n";
   }
return 0;
}

OUTPUT:
my file Lab14B.txt contents:

1
2
3
4
5
6
7
8
9
10

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