Ruby program to check whether the given number is prime or not

Checking prime number in Ruby: Here, we are going to learn how to check whether a given number is a prime number or not in Ruby programming language?
Submitted by Hrithik Chandra Prasad, on August 07, 2019

Checking prime number

Before getting into writing the code, let us understand what exactly the prime numbers are? So that we could easily design its logic and implement it in the code. Prime numbers are those numbers which can only be divisible by itself or 1. So, we will design a code which can fulfill the property of prime numbers.

Methods used:

puts: For giving the output as well as a message to the user.
gets: For taking the input from the user.
.to_i: For converting strings into integers.

Operators used:

%: For retrieving the remainder.
==: Used for comparing two values.
< and >: These are comparison operators.
+: Generally used in the code for incrementing the loop variable.

Variables used:

num: It is storing the user inputted integer value.
count: Initialised with 0 and used as a counter variable.

Ruby code to check weather a number is prime or not

=begin 
Ruby program to check whether the given number is 
prime or not.
=end

puts "Enter the number:"
num=gets.chomp.to_i
count=0
if (num==0)
	puts "0 is not prime"
else
	
	i=2
	while(i<num)
		if (num%i==0)
			count+=1
		end
		i+=1
	end
	
end
	if count>1
		puts "#{num} is not a prime number"
	else
		puts "#{num} is a prime number"
	end

Output

RUN 1 : 
Enter the number:
13
13 is a prime number

RUN 2:
Enter the number:
890
890 is not a prime number

Code explanation:

This program checks whether the integer input is prime or not. The input is checked using the while loop and conditions. Based on the condition check the code prints the required output.