1. An image forming apparatus having a plurality of functions related to an image forming process, the image forming apparatus comprising: a user-interface unit that receives a request from a user; a control unit that performs an execution control in response to the request received by the user-interface unit, and during an execution process, performs an interruption process and an authentication process; an application-logic unit that provides the functions related to the image forming process; and a device-service unit that provides a shared service for the application-logic unit.