prime number cpp code code example

Example 1: c++ prime number program

#include <iostream>
using namespace std;

int main() {
    int i, n;
    bool isPrime = true;

    cout << "Enter a positive integer: ";
    cin >> n;

    // 0 and 1 are not prime numbers
    if (n == 0 || n == 1) {
        isPrime = false;
    }
    else {
        for (i = 2; i <= n / 2; ++i) {
            if (n % i == 0) {
                isPrime = false;
                break;
            }
        }
    }
    if (isPrime)
        cout << n << " is a prime number";
    else
        cout << n << " is not a prime number";

    return 0;
}

Example 2: c++ program to generate prime numbers

#include <iostream>
using namespace std;

int main() {
    int low, high, i;
    bool isPrime = true;

    cout << "Enter two numbers (intervals): ";
    cin >> low >> high;

    cout << "\nPrime numbers between " << low << " and " << high << " are: " << endl;

    while (low < high) {
        isPrime = true;
        if (low == 0 || low == 1) {
            isPrime = false;
        }
        else {
            for (i = 2; i <= low / 2; ++i) {
                if (low % i == 0) {
                    isPrime = false;
                    break;
                }
            }
        }
        
        if (isPrime)
            cout << low << " ";

        ++low;
    }

    return 0;
}