Using two or more developer replenishing units, each of which has a first
storage for storing identification information related to developer and a
second storage for storing history information related to the developer,
if the identification information read out from each developing
replenishing unit accords with unique information stored in an image
forming main body, the history information is read out from the developing
replenishing unit and analyzed to judge whether the utilization amount of
the developing replenishing unit is at the end of its life. If the
developing replenishing unit is not at the end of its life, the discharge
amount of the developer replenished from the developer replenishing unit
is controlled according to the history information and image output
results formed by means of the image forming main body.
