Patent ID: 8917410

Claim:
An image forming apparatus, comprising: pluralities of sheet storage units; a printing unit; a sheet driving unit that feeds a sheet of paper from the sheet storage units to the printing unit; a group setting maintaining unit that forms a group of the sheet storage units; a residual sheet amount detecting unit that detects sheet empty on any of the sheet storage units in the group; a sheet storage switching control unit that controls the sheet driving unit to select another one of the sheet storage units in the same group for feeding a sheet, if the residual sheet amount detecting unit detects the sheet empty; said sheet driving unit to select one of the sheet storage units that has the least number of residual sheets in the same group next a sheet empty warning unit that warns a user of the sheet empty detected by the residual sheet amount detecting unit; and the sheet empty warning unit issues a first warning that warns that one of the sheet storage units is empty and issues a second warning that warns a user that only one of the sheet storage units in a group has a sheet; a sheet attribution detecting unit that detects one or more sheet attributions of sheets stored in the sheet storage units; an attribution consistency determining unit that determines whether or not a sheet attribution of a sheet stored in one of the sheet storage units in the group is same as a sheet attribution of a sheet stored in other ones of the sheet storage units; and wherein said group setting unit automatically forms the group according to a sheet attribution of sheets stored in the sheet storage units and removes a sheet storage unit with an inconsistent sheet attribution from the group.