A method for providing an image forming device with a user-friendly application program. A program of the image forming device includes a basic service program and a simple text language processing program. The basic service program has an operation panel control module, image input and image output modules. If a command string in a source code is a control string, the simple text language processing program passes a parameter of a button description included in the control string to the operation panel control module as an argument to cause a button to be displayed and pressing of the button when pressed. In response to the detection, corresponding modules are activated. Accordingly, different multiple modules can be easily processed. Additionally, any size of buttons can be displayed anywhere on the panel. The image forming device alone can realize the method to allow many more users to easily use the application.