input: Write a function to convert a given number into its binary format string representation. If the given number is 0, return '0'.
  def convert_to_binary(num):
      if num == 0:
          return '0'
  
      binary = ''
      while num != 0:
          remainder = num % 2
          binary = str(remainder) + binary
          num = num // 2
  
      return binary
  
  assert convert_to_binary(10) == '1010'
  assert convert_to_binary(0) == '0'
  assert convert_to_binary(7) == '111'
  assert convert_to_binary(255) == '11111111'
  assert convert_to_binary(42) == '101010'
output: def convert_to_binary(num):
      if num == 0:
          return '0'
  
      binary = ''
      while num != 0:
          remainder = num % 2
          binary = str(remainder) + binary
          num = num // 2
  
      return binary