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  1. #1
    Join Date
    Nov 2011
    Posts
    3

    can someone explain whats going on

    here is a full working program to check a number for primeness

    i need an expert who can explain it for me particularly the section //print results

    what is if(is_prime) mean.

    #include <iostream>
    #include <cmath>
    using namespace std;
    int main() {
    int n; // Number to test for prime-ness
    int i; // Loop counter
    int is_prime = true; // Boolean flag...
    // Assume true for now.
    // Get a number from the keyboard.
    cout << "Enter a number and press ENTER: ";
    cin >> n;
    // Test for prime by checking for divisibility
    // by all whole numbers from 2 to sqrt(n).
    i = 2;
    while (i <= sqrt(n)) { // While i is <= sqrt(n),
    if (n % i == 0) // If i divides n,
    is_prime = false; // n is not prime.
    i++; // Add 1 to i.
    }
    // Print results
    if (is_prime)
    cout << "Number is prime." << endl;
    else
    cout << "Number is not prime." << endl;
    system("PAUSE");
    return 0;
    }

  2. #2
    Join Date
    Apr 1999
    Posts
    27,449

    Re: can someone explain whats going on

    Quote Originally Posted by TalkTime View Post
    here is a full working program to check a number for primeness
    Next time, please use code tags when posting code. Your code is almost unreadable without using them.
    i need an expert who can explain it for me particularly the section //print results

    what is if(is_prime) mean.
    What part of that statement is confusing you? The if()? The is_prime? The is_prime is either true or false, and the if() statement executes if it is true.

    Regards,

    Paul McKenzie

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