C#: Find the prime numbers within a range of numbers

C# Sharp For Loop: Exercise-34 with Solution

Write a program in C# Sharp to find prime numbers within a range of numbers.

Visual Presentation:

Sample Solution:

C# Sharp Code:

using System;  // Importing necessary namespace

public class Exercise34  // Declaration of the Exercise34 class
{  
    public static void Main()  // Main method, entry point of the program
    {
        int num, i, ctr, stno, enno;  // Declaration of variables

        Console.Write("\n\n");  // Displaying new lines
        Console.Write("Find the prime numbers within a range of numbers:\n");  // Displaying the purpose of the program
        Console.Write("---------------------------------------------------\n\n");  // Displaying a separator and new lines

        Console.Write("Input starting number of range: ");  // Prompting the user to input the starting number of the range
        stno = Convert.ToInt32(Console.ReadLine());  // Reading the starting number entered by the user

        Console.Write("Input ending number of range : ");  // Prompting the user to input the ending number of the range
        enno = Convert.ToInt32(Console.ReadLine());  // Reading the ending number entered by the user

        Console.Write("The prime numbers between {0} and {1} are : \n", stno, enno);  // Displaying the range for which primes are being found

        // Loop to find and display prime numbers within the given range
        for (num = stno; num <= enno; num++)
        {
            ctr = 0;  // Counter to check for factors of each number

            // Loop to check if the number is prime or not
            for (i = 2; i <= num / 2; i++)
            {
                if (num % i == 0)
                {
                    ctr++;  // Incrementing the counter if the number has factors other than 1 and itself
                    break;  // Exiting the loop if a factor is found
                }
            }

            // If the counter is 0 and the number is not 1, it's a prime number
            if (ctr == 0 && num != 1)
            {
                Console.Write("{0} ", num);  // Displaying the prime number
            }
        }
        Console.Write("\n");  // Moving to the next line for better readability
    }
}

Sample Output:

Find the prime numbers within a range of numbers:                                                                                                         
---------------------------------------------------                                                                                                         
Input starting number of range: 1                                                                                                         
Input ending number of range : 50                                                                                                         
The prime numbers between 1 and 50 are :                                                                                                         
2 3 5 7 11 13 17 19 23 29 31 37 41 43 47  

Flowchart:

C# Sharp Code Editor:

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