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Program to Print All Prime Numbers Between 1 and n using For loop

Program to Print All Prime Numbers Between 1 and n using For loop

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  • Write a program to Print All Prime Numbers Between 1 and n using For loop in C
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  • Write a program to Print All Prime Numbers Between 1 and n using For loop in C#

Explanation:

Steps

  1. Input: Take the upper limit n.
  2. Prime number check:
    • A prime number is greater than 1 and divisible only by 1 and itself.
    • For each number i from 2 to n, check if it is prime:
      • Loop through numbers from 2 to sqrt(i) to see if any number divides i.
      • If no number divides i, it is prime.
  3. Print primes: Display all numbers identified as prime.

Logic

  • Use a loop to iterate from 2 to n.
  • For each number, check divisibility up to its square root.
  • Print the number if it is prime.

Explanation

  • For n = 20:
    • Check numbers 2 through 20.
    • Primes are: 2, 3, 5, 7, 11, 13, 17.

Efficiency Tip

  • By checking divisibility only up to sqrt(num), the program reduces unnecessary checks for larger divisors, making it more efficient.

Program to Print All Prime Numbers Between 1 and n using For loop

#include <stdio.h>

int is_prime(int num) {
    for (int i = 2; i * i <= num; i++) {
        if (num % i == 0) {
            return 0;  // Not prime
        }
    }
    return 1;  // Prime
}

int main() {
    int n;

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

    printf("Prime numbers between 1 and %d are:\n", n);

    for (int num = 2; num <= n; num++) {
        if (is_prime(num)) {
            printf("%d ", num);
        }
    }

    return 0;
}

#include <iostream>
using namespace std;

bool is_prime(int num) {
    for (int i = 2; i * i <= num; i++) {
        if (num % i == 0) {
            return false;  // Not prime
        }
    }
    return true;  // Prime
}

int main() {
    int n;

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

    cout << "Prime numbers between 1 and " << n << " are:" << endl;

    for (int num = 2; num <= n; num++) {
        if (is_prime(num)) {
            cout << num << " ";
        }
    }

    return 0;
}

def is_prime(num):
    for i in range(2, int(num ** 0.5) + 1):
        if num % i == 0:
            return False  # Not prime
    return True  # Prime

n = int(input("Enter a number: "))

print(f"Prime numbers between 1 and {n} are:")

for num in range(2, n + 1):
    if is_prime(num):
        print(num, end=" ")


<?php
function is_prime($num) {
    for ($i = 2; $i * $i <= $num; $i++) {
        if ($num % $i == 0) {
            return false;  // Not prime
        }
    }
    return true;  // Prime
}

$n = (int)readline("Enter a number: ");

echo "Prime numbers between 1 and $n are:\n";

for ($num = 2; $num <= $n; $num++) {
    if (is_prime($num)) {
        echo "$num ";
    }
}
?>


import java.util.Scanner;

public class PrimeNumbers {
    public static boolean isPrime(int num) {
        for (int i = 2; i * i <= num; i++) {
            if (num % i == 0) {
                return false;  // Not prime
            }
        }
        return true;  // Prime
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("Enter a number: ");
        int n = scanner.nextInt();

        System.out.println("Prime numbers between 1 and " + n + " are:");

        for (int num = 2; num <= n; num++) {
            if (isPrime(num)) {
                System.out.print(num + " ");
            }
        }

        scanner.close();
    }
}


function isPrime(num) {
    for (let i = 2; i * i <= num; i++) {
        if (num % i === 0) {
            return false;  // Not prime
        }
    }
    return true;  // Prime
}

let n = parseInt(prompt("Enter a number:"));

console.log(`Prime numbers between 1 and ${n} are:`);

for (let num = 2; num <= n; num++) {
    if (isPrime(num)) {
        console.log(num);
    }
}


using System;

class Program {
    static bool IsPrime(int num) {
        for (int i = 2; i * i <= num; i++) {
            if (num % i == 0) {
                return false;  // Not prime
            }
        }
        return true;  // Prime
    }

    static void Main() {
        Console.Write("Enter a number: ");
        int n = int.Parse(Console.ReadLine());

        Console.WriteLine($"Prime numbers between 1 and {n} are:");

        for (int num = 2; num <= n; num++) {
            if (IsPrime(num)) {
                Console.Write(num + " ");
            }
        }
    }
}

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