Patent ID: 6995861

Claim:
A method of determining whether a storage unit included in an ink cartridge is normal, wherein the ink cartridge is configured to be detachably attached to a printer, the method comprising the steps of: (a) reading a piece of decision information that has been registered in advance in a predetermined format, from the storage unit; and (b) identifying whether the read-out piece of decision information satisfies the predetermined format, so as to determine whether the storage unit is normal, wherein the step (b) determines that the storage unit is not normal in the case where the read-out piece of decision information does not satisfy the predetermined format, wherein the step (b) uses a piece of information relating to a month of manufacture of the ink cartridge as the piece of decision information, wherein the piece of information relating to the month of manufacture of the ink cartridge is expressed by a data length of four bits, and the step (b) determines that the storage unit is not normal in the case where all the four bits have an identical digit, that is, either one of ‘0’ and ‘1’.