1. An image forming apparatus comprising: a registering device configured to register a plurality of jobs; an image forming device configured to form images corresponding to the plurality of jobs registered by the registering device; a discriminating device configured to discriminate between first items for which maintenance for internal mechanical parts of the image forming apparatus is required and second items for which the maintenance is not required among maintenance items; a permitting device configured to permit start of execution of the plurality of jobs registered by the registering device upon completion of maintenance on the first items; a setting device configured to set an allowable range of ambient environment for each of a plurality of image forming modes; and a display device configured to display the first items and the second items in different display manners according to the results of discrimination by the discriminating device, wherein the display device displays, in different display manners, an image forming mode in which the ambient environment is within the allowable range and another image forming mode in which the ambient environment is not within the allowable range.