Question

a prime number is a number that is only evenly divisible by itself and 1. for example the number 5 is prime because it can only be evenly divided by 1 and 5 the number 6 however is not prime because it can be divided evenly by 1,2,3 and 6.

write a function name isPrime which takes an integer as an argument and returns true if the argument is a prime number, or false otherwise.

use this functuion in a program to store a list of all the prime numbers from 1 throuhg 300 in a file

recall that the% operator divides one number by another and returns the reminder of the division in an expression such as num1 % num2 the % operator will return 0 if num 1 is evenly divisible by num2

c plus plus

Answer 1

Solution:

Function isPrime()

bool isPrime(int num)
{
    for(int i = 2; i <= num / 2; i++) 
        {
       if(num % i == 0) 
           {
          return false;
       }
    }
    return true;
}

Complete program:

Note: Please specify the correct filename and path inside main.

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

//Function to check if a number is prime
bool isPrime(int num)
{
    for(int i = 2; i <= num / 2; i++) 
        {
       if(num % i == 0) 
           {
          return false;
       }
    }
    return true;
}

int main()
{
        fstream newfile;
        //Provide the correct file name and path here
        newfile.open("primeList.txt");
        int x;
        //Loop is from 2 to 300 since 1 is not a prime number
        for(x=2;x<=300;x++) 
        {
                if(isPrime(x))
                {
                        //writing the number to the file
                        newfile << x <<endl;
                }
                
        }
        //Freeing unused memory of array q

        return 0;
        
}

After execution the following text will be stored to the file specified in the main function of the program

2
3
5
7
11
13
17
19
23
29
31
37
41
43
47
53
59
61
67
71
73
79
83
89
97
101
103
107
109
113
127
131
137
139
149
151
157
163
167
173
179
181
191
193
197
199
211
223
227
229
233
239
241
251
257
263
269
271
277
281
283
293