An image forming apparatus in which a control program can be loaded, the control program providing a service for image forming processing, said apparatus comprising: a memory unit configured to store (i) an operating system, (ii) an interpreter which provides an execution environment to execute the control program, runs on the operating system, and interprets the control program, (iii) a driver program for controlling image forming processing, and (iv) a function program, wherein the driver program operates a hardware resource unit which includes at least one of a printing unit and an image pickup unit, and wherein the function program (a) serves as an API (Application Programming Interface), (b) is defined between the control program and the driver program, and (c) is used by the control program.