Image forming apparatus having a detachably mounted processing unit

An image forming apparatus for performing an image forming operation during a service life, to form an image corresponding to data received from a host unit on an image bearing member, the image forming apparatus comprising:

• a processing unit having both the image bearing member and a processing means for acting on the image bearing member to perform the image forming operation;
• a main body to which the processing unit is detachably mounted, wherein the processing unit mounted on the main body may be replaced with a new processing unit when the service life of the mounted processing unit expires;
• first memory means for storing the amount of use of the processing unit mounted on the main body;
• second memory means for storing maintenance message information containing instruction for replacing the processing unit mounted on the main body with the new processing unit when the service life of the mounted processing unit expires;
• first detecting means for detecting when an amount of use stored in the first memory means reaches a predetermined value and outputting a detecting signal;
• second detecting means responsive to the detecting signal received from the first detecting means for detecting that the image forming operation in response to data received from a host unit is completely performed;
• means for causing the processing means to form the maintenance message information stored in the second memory means on the image bearing member in response to the second detecting means;
• and
• means for printing the maintenance message information formed on the image bearing member on a recording medium.