1. An image forming apparatus comprising: a plurality of microprocessors; a plurality of storage units storing control programs respectively provided in association with the plurality of microprocessors; an update unit configured to update the control programs stored in the respective storage units; a selection unit configured to enable manual selection of functions to be used in an image forming job caused to be executed by the image forming apparatus; and a control unit configured to control, during execution of update of a control program targeted for update by said update unit, the selection unit so as to prevent selection of a function which uses a microprocessor associated with the control program targeted for update, and so as to enable selection of a function which does not use the microprocessor associated with the control program targeted for update.