Prime number C# Exercise - C# Programming Course

using System;  // Import the System namespace, which contains fundamental classes like Console

class Program  // Define the Program class
{
    static void Main()  // The entry point of the program
    {
        // Ask the user to enter an integer
        Console.Write("Enter an integer: ");
        int number = int.Parse(Console.ReadLine());  // Read and convert the user input to an integer

        // Check if the number is less than 2, as prime numbers are greater than 1
        if (number < 2)  
        {
            Console.WriteLine("The number is not prime.");  // If the number is less than 2, it's not prime
        }
        else  
        {
            bool isPrime = true;  // Assume the number is prime unless proven otherwise

            // Check divisibility from 2 to the square root of the number
            for (int i = 2; i <= Math.Sqrt(number); i++)  
            {
                if (number % i == 0)  // If the number is divisible by i, it's not prime
                {
                    isPrime = false;  // Set isPrime to false if a divisor is found
                    break;  // Exit the loop as we've found a divisor
                }
            }

            // Display whether the number is prime or not
            if (isPrime)  
            {
                Console.WriteLine("The number is prime.");  // If no divisors were found, it's prime
            }
            else  
            {
                Console.WriteLine("The number is not prime.");  // If a divisor was found, it's not prime
            }
        }
    }
}