An image forming apparatus or a cartridge detachably attachable to the image
forming
apparatus is provided, wherein the apparatus comprises a developer container for
containing developer, a developer amount detector for detecting an amount of the
developer contained in the developer container, a memory for memorizing information
concerning the amount of the developer detected by the detector and an output unit
for outputting the information concerning the amount of the developer. The output
unit outputs the information concerning the developer memorized in the memory until
the detection result of the detector is confirmed.