Trying to debug this error

#!/usr/bin/env ruby
# frozen_string_literal: true

# Created by Paul A.Gureghian in May 2020. #
# This Ruby program demos the creation of a class and the generation of instances of the class. #

# Start of program. #

# Create the class. #
class Computer
  @@users = {}  

  def initialize(username, password)
    @username = username
    @password = password
    @@users[username] = password
    @files = {}

  def create(filename)

    time =
    @files[filename] = time
    puts "#{filename} was created by #{username} at #{time}."


  def Computer.get_users



# Instantiate the class. #
paul_computer ='paul', 'monkey123')

# Call the "create" class method and create a file. #

# Print out user(s) name(s). #
puts "User(s): #{Computer.get_users}."

# End of program. #

Hello @paulgureghian. In this line:

Are you using the correct scope of the variable? When you don’t have @ in front of a variable, you are referring to a local variable; one that only exists within its block. When you use @, you are referring to an instance variable; it is available in all of the methods within a class:

class someclass

  def somemethod()
     vara = "somevalue"

  def anothermethod()
     @varb = "anothervalue"

vara can only be accessed from the somemethod function, whereas @varb can be accessed from any method in the function. Here is a website that explains it quite well.
I hope this helps!