To provide an apparatus unit, an image forming apparatus, and its managing system which can be used with ease by a user by always operating under the best condition regardless of the type of the apparatus unit, genuine or non-genuine, recycle or non-recycle, which is exchanged for the image forming apparatus main body.

The apparatus unit 20 is attachably and detachably installed on the image forming apparatus provided with a control part 100. Furthermore, the apparatus unit 20 is provided with an non-volatile memory 157 retaining information to be exchanged with a control part 100. The non-volatile memory 157 is provided with a writing forbidding range 157a, forbidding overwriting of information over existing information and a writing possible range 157b, to which information can be written.

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