An image forming apparatus includes a storage area used as a work area of programs for implementing functions, the programs including a basic function program configured to implement a basic function and an extension function program configured to implement an extension function, wherein the entire storage area is used in the event that the basic function program is executed to implement a specified maximum function of the basic function; a detecting unit configured to detect a usage state of the storage area; a storage unit configured to store information indicating an allocation mode defining a method of allocating the work area to the programs; and an allocation unit configured to allocate the work area to each of the programs that is to be executed, according to the usage state of the storage area detected by the detecting unit and the allocation mode stored in the storage unit.