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Program to Check if Given Number is Prime or Not using While loop

Program to Check if Given Number is Prime or Not using While loop

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  • Write a program to Check if Given Number is Prime or Not using While loop in C
  • Write a program to Check if Given Number is Prime or Not using While loop in C++
  • Write a program to Check if Given Number is Prime or Not using While loop in Python
  • Write a program to Check if Given Number is Prime or Not using While loop in PHP
  • Write a program to Check if Given Number is Prime or Not using While loop in Java
  • Write a program to Check if Given Number is Prime or Not using While loop in Java Script
  • Write a program to Check if Given Number is Prime or Not using While loop in C#

Explanation:

To check if a given number is prime or not using a for loop, follow these steps:

Steps:

  • Take the input number n.
  • Prime number check: A prime number is a number greater than 1 that is divisible only by 1 and itself.
  • Loop from 2 to sqrt(n) (you can stop at sqrt(n) because a larger factor of n must be paired with a smaller factor that has already been checked).
  • If any number divides n evenly (i.e., n % i == 0), then n is not prime.
  • If no such number divides n, then n is prime.

Logic:

  • If the number is less than 2, it is not prime.
  • For numbers greater than 2, check if they are divisible by any number from 2 to sqrt(n).
  • If divisible, it is not prime, otherwise, it is prime.

Explanation:

  • For input n = 7:
  • Loop iterates through numbers 2 to sqrt(7) (approximately 2.65), checking if 7 is divisible by any of these numbers.
  • Since no number divides 7 evenly, 7 is a prime number.

Why Looping Until sqrt(n)?

  • Any divisor of n greater than sqrt(n) must have a corresponding smaller divisor (less than sqrt(n)). So, by checking divisibility up to sqrt(n), you reduce unnecessary checks, improving efficiency.

Program to Check if Given Number is Prime or Not using While loop

#include <stdio.h>

int main() {
    int num, i = 2, isPrime = 1;

    printf("Enter a number: ");
    scanf("%d", &num);

    // Check if number is prime using a while loop
    while (i <= num / 2) {
        if (num % i == 0) {
            isPrime = 0;
            break;
        }
        i++;
    }

    if (isPrime == 1 && num > 1) {
        printf("%d is a prime number.\n", num);
    } else {
        printf("%d is not a prime number.\n", num);
    }

    return 0;
}

#include <iostream>
using namespace std;

int main() {
    int num, i = 2, isPrime = 1;

    cout << "Enter a number: ";
    cin >> num;

    // Check if number is prime using a while loop
    while (i <= num / 2) {
        if (num % i == 0) {
            isPrime = 0;
            break;
        }
        i++;
    }

    if (isPrime == 1 && num > 1) {
        cout << num << " is a prime number." << endl;
    } else {
        cout << num << " is not a prime number." << endl;
    }

    return 0;
}

num = int(input("Enter a number: "))
i = 2
is_prime = True

# Check if number is prime using a while loop
while i <= num // 2:
    if num % i == 0:
        is_prime = False
        break
    i += 1

if is_prime and num > 1:
    print(f"{num} is a prime number.")
else:
    print(f"{num} is not a prime number.")


<?php
$num = (int)readline("Enter a number: ");
$i = 2;
$isPrime = true;

# Check if number is prime using a while loop
while ($i <= $num / 2) {
    if ($num % $i == 0) {
        $isPrime = false;
        break;
    }
    $i++;
}

if ($isPrime && $num > 1) {
    echo "$num is a prime number.\n";
} else {
    echo "$num is not a prime number.\n";
}
?>


import java.util.Scanner;

public class PrimeNumber {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        System.out.print("Enter a number: ");
        int num = sc.nextInt();
        int i = 2;
        boolean isPrime = true;

        // Check if number is prime using a while loop
        while (i <= num / 2) {
            if (num % i == 0) {
                isPrime = false;
                break;
            }
            i++;
        }

        if (isPrime && num > 1) {
            System.out.println(num + " is a prime number.");
        } else {
            System.out.println(num + " is not a prime number.");
        }

        sc.close();
    }
}


let num = parseInt(prompt("Enter a number: "));
let i = 2;
let isPrime = true;

while (i <= num / 2) {
    if (num % i === 0) {
        isPrime = false;
        break;
    }
    i++;
}

if (isPrime && num > 1) {
    console.log(`${num} is a prime number.`);
} else {
    console.log(`${num} is not a prime number.`);
}


using System;

class Program {
    static void Main() {
        Console.Write("Enter a number: ");
        int num = int.Parse(Console.ReadLine());
        int i = 2;
        bool isPrime = true;

        // Check if number is prime using a while loop
        while (i <= num / 2) {
            if (num % i == 0) {
                isPrime = false;
                break;
            }
            i++;
        }

        if (isPrime && num > 1) {
            Console.WriteLine($"{num} is a prime number.");
        } else {
            Console.WriteLine($"{num} is not a prime number.");
        }
    }
}

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