An object of the present invention is to provide a data processing apparatus in which, merely by an arbitrary indicator being specified by a user from the array of indicators representing plural types of instructive information which is acceptable during the execution of an application, an operation allotted to the indicator is executed. In the present invention, a CPU recognizes a mark on a paper sheet specified by a user through the analysis of an image of the paper sheet photographed by a document camera, and after reading out a command corresponding to the mark with reference to a mark table based on the mark, instructs the currently executed application to perform an operation corresponding to the command.