Displaying device which can receive pinch out operation

An image forming apparatus as a displaying device receives a pinch out operation on a touch panel of a portable telecommunication terminal device, when displaying the operation screen on the touch panel of the portable telecommunication terminal device. The image forming apparatus determines whether there is an identified area in the operation screen or not when receiving the pinch out operation. The image forming apparatus enlarges the image around a center of the enlargement in the identified area, in case that there is the identified area in the operation screen. The image forming apparatus enlarges the image around a center of the enlargement as a point moved from a midpoint of the pinch out operation in a direction determined based on displacement of the two contact points, a distance of the movement is determined based on displacement of the two contact points, in case that there is not the identified area in the operation screen.