6. An image forming apparatus comprising: document sheet recirculating means for separating document sheets from a stack of document sheets, feeding the separated document sheets onto a document table, and returning the document sheets from the document table to the stack, thereby recirculating the document sheets; exposure means for scanning and exposing the document sheets fed onto the document table by said document recirculating means, said exposure means operating in one of a first exposure mode in which said document recirculating means temporarily stations each document sheet on the document table while said exposure means is moved to scan and expose the stationary document sheet and a second exposure mode in which said exposure means remains stationary while said document recirculating means moves each document sheet across the document table to cause the document to be scanned and exposed; image forming means for forming images on recording sheets from the document sheets that have been scanned and exposed by said exposure means; sheet receiving means for receiving and storing the recording sheets carrying images formed by said image forming means, said receiving means having a plurality of sheet receiving portions and operating in one of the first exposure mode and the second exposure mode; selecting means for selecting one of a first receiving mode in which a set of recording medium sheets having images corresponding to those on the stack of document sheets are received and stored in each of a plurality of sheet receiving portions of said sheet receiving means and a second receiving mode in which each sheet receiving portion of said sheet receiving means receives and stores a plurality of recording medium sheets having images corresponding to that on one of said document sheets; and control means for controlling each combination of the first and second exposure modes and the first and second receiving modes.
6. An image forming apparatus comprising: document sheet recirculating means for separating document sheets from a stack of document sheets, feeding the separated document sheets onto a document table, and returning the document sheets from the document table to the stack, thereby recirculating the document sheets; exposure means for scanning and exposing the document sheets fed onto the document table by said document recirculating means, said exposure means operating in one of a first exposure mode in which said document recirculating means temporarily stations each document sheet on the document table while said exposure means is moved to scan and expose the stationary document sheet and a second exposure mode in which said exposure means remains stationary while said document recirculating means moves each document sheet across the document table to cause the document to be scanned and exposed; image forming means for forming images on recording sheets from the document sheets that have been scanned and exposed by said exposure means; sheet receiving means for receiving and storing the recording sheets carrying images formed by said image forming means, said receiving means having a plurality of sheet receiving portions and operating in one of the first exposure mode and the second exposure mode; selecting means for selecting one of a first receiving mode in which a set of recording medium sheets having images corresponding to those on the stack of document sheets are received and stored in each of a plurality of sheet receiving portions of said sheet receiving means and a second receiving mode in which each sheet receiving portion of said sheet receiving means receives and stores a plurality of recording medium sheets having images corresponding to that on one of said document sheets; and control means for controlling each combination of the first and second exposure modes and the first and second receiving modes. 9. An image forming apparatus according to claim 6, wherein said control means controls said sheet receiving means so as to change the sheet receiving portion into which sheets are received each time the document sheets on said document table are replaced by said document recirculating means whenever said sheet receiving means is operating in the first exposure mode and the second receiving mode has been selected by said selecting means.