A printer chip, comprising a chip control circuit, a data storage unit used for storing data, and a communication unit used for communication with a printer, wherein the data storage unit and the communication unit are electrically connected with the chip control circuit respectively; wherein: the data storage unit comprises an authorization flag bit which causes the whole data storage unit to switch between an unauthorized state and an authorized state according to different numerical values of the authorization flag bit; when the data storage unit is in the unauthorized state, the data storage unit comprises a non-protected part allowing data to be read or written therein by the control circuit, and a protected part allowing data to be read by the control circuit, and a disposable part allowing data to be read by the control circuit and only allowing disposable data to be written therein by the control circuit; when the data storage unit is in the authorized state, the whole data storage unit is converted into the non-protected part; the control circuit comprises a key unit, an operation unit and a reading and writing unit; the operation unit is used for operating input data sent from a printer main body through key data stored in the key unit so as to obtain a first check code; the operation unit is also used for comparing a second check code sent from the printer main body with the first check code and changing the numerical value of the authorization flag bit in the data storage unit; wherein, when the data storage unit is in an unauthorized state: - data in the protected part are writable by the control circuit only when it is used for the first time, and cannot be modified once being written in, - data in the disposable part are writeable by the control circuit on each data bit only once, - the data are writeable in the disposable part from 0 to 1 and, once data are written as 1, the data cannot be written as 0 anymore, - the data written in the disposable part include multiple bits, wherein each bit corresponds to part of the ink of the ink cartridge, and - the data are written in the disposable part as 1 from 0 when the part of ink is used up, so that a user is enabled working out residual ink quantity data according to data of the part. the data storage unit comprises an authorization flag bit which causes the whole data storage unit to switch between an unauthorized state and an authorized state according to different numerical values of the authorization flag bit; when the data storage unit is in the unauthorized state, the data storage unit comprises a non-protected part allowing data to be read or written therein by the control circuit, and a protected part allowing data to be read by the control circuit, and a disposable part allowing data to be read by the control circuit and only allowing disposable data to be written therein by the control circuit; when the data storage unit is in the authorized state, the whole data storage unit is converted into the non-protected part; the control circuit comprises a key unit, an operation unit and a reading and writing unit; the operation unit is used for operating input data sent from a printer main body through key data stored in the key unit so as to obtain a first check code; the operation unit is also used for comparing a second check code sent from the printer main body with the first check code and changing the numerical value of the authorization flag bit in the data storage unit; wherein, when the data storage unit is in an unauthorized state: - data in the protected part are writable by the control circuit only when it is used for the first time, and cannot be modified once being written in, - data in the disposable part are writeable by the control circuit on each data bit only once, - the data are writeable in the disposable part from 0 to 1 and, once data are written as 1, the data cannot be written as 0 anymore, - the data written in the disposable part include multiple bits, wherein each bit corresponds to part of the ink of the ink cartridge, and - the data are written in the disposable part as 1 from 0 when the part of ink is used up, so that a user is enabled working out residual ink quantity data according to data of the part. - data in the protected part are writable by the control circuit only when it is used for the first time, and cannot be modified once being written in, - data in the disposable part are writeable by the control circuit on each data bit only once, - the data are writeable in the disposable part from 0 to 1 and, once data are written as 1, the data cannot be written as 0 anymore, - the data written in the disposable part include multiple bits, wherein each bit corresponds to part of the ink of the ink cartridge, and - the data are written in the disposable part as 1 from 0 when the part of ink is used up, so that a user is enabled working out residual ink quantity data according to data of the part.