The invention provides a portable terminal, a program therefor, an apparatus, and an operation display system that are capable of easily changing a screen displayed on the portable terminal to a screen displayed on an operating panel of another apparatus. An operation display system includes a portable terminal (40) and an image processing apparatus (10) having an operating panel (30). The portable terminal (40) is a portable information processing apparatus such as a tablet. In the operation display system (5), when a user displaces the portable terminal (40) such that the image processing apparatus (10) and the portable terminal (40) have a predetermined positional relationship, a screen displayed on the portable terminal (40) changes to a screen displayed on the operating panel (30) of the image processing apparatus (10), enabling the portable terminal (40) to operate as a remote operating panel of the image processing apparatus (10).