Patent ID: 7430961

Claim:
An image forming system comprising a residue data obtaining means which obtains residue data representing a residue of an expendable, a residue data recording means which records in a storage means the residue data obtained by the residue data obtaining means, a read out means which reads out the residue data recorded in the storage means by the residue data recording means, and a control means which controls operation of a predetermined object to be controlled operation of which is to be controlled in relation to the residue of the expendable on the basis of the residue data read out by the read out means, thereby causing the predetermined object to be controlled to operate on the basis of the residue data by the control means, wherein the improvement comprises that the residue of the expendable is divided into n(n standing for an integer not smaller than 2) residue ranges Hi (i=1 to n), and n storage areas, which correspond to the respective residue ranges and in which pieces of residue data for the corresponding residue ranges are recorded, are set in the storage means, and the residue data recording means records pieces of residue data in sequence in the storage areas corresponding to the residue of the expendable as reduction of residue of the expendable while, when the residue is shifted from a predetermined residue range Hi to the next residue range Hi+1, the residue data recording means makes unwritable the storage area corresponding to the former residue range Hi, and when the residue data read out from a storage area which has not been made unwritable yet is determined to be not regular, the read out means reads out the residue data recorded in the storage area which has been made unwritable last.