Binary converter free 2.0 with Ruby

main.rb

def num2bin(num)

  build_reverse = ""
  eax = num
  while eax != 0

    build_reverse += (eax%2).to_s
    eax = eax/2.to_i

  end

  return build_reverse.reverse

end

def bin2num(bin)

  build = 0

  for idx in (0...bin.to_s.size)

    idx_r = bin.to_s.size-idx-1

    pchar = bin.to_s[idx_r].to_i

    build += pchar * 2**idx

  end

  return build

end

def main()
  puts "Welcome to Ruby Binary converter by 0rbianta"
  puts "SELECT AN OPTION: \n1)DEC2BIN\n2)BIN2DEC\n3)Exit\n\n"

  print("USER>> ")
  usr_select = gets.chomp

  case usr_select

  when "1"

    print("USER>> ")
    usr = gets.chomp
    bin = num2bin(usr.to_i)
    puts "OUTPUT: "+bin

  when "2"

    print("USER>> ")
    usr = gets.chomp
    num = bin2num(usr)
    puts "OUTPUT: "+num.to_s

  when "3"
    exit()
  else
    puts "Unknown option selected. Exiting..."
    exit()

  end

end


main()