A data generating apparatus includes a controller to perform a first process to generate and store into a work area n pieces of first-layer object data representing n objects having earlier orders than a combined object in a combining sequence, a second process to generate and store into the work area M pieces of second-layer object data representing M second-layer objects of the combined object, a third process to generate first bitmap data representing an image obtained by combining the n first-layer objects, using the n pieces of first-layer object data, and a fourth process to generate second bitmap data representing the combined object. When a free space is less than a reference value during the second process, the controller interrupts the second process, performs the third process or a part of the fourth process, releases a storage area for object data, and thereafter resumes and completes the second process.