1. A projector, comprising: a projection part that projects a menu image including at least one part according to an image signal, the menu image being an interface that enables a user to interactively adjust parameters of images projected by the projector; a selection part that causes the user to select a language type of the menu image; a menu image processing part that generates the image signal so that a character array of the selected language type can appear in the menu image as a part, the menu image processing part comprising: a first interface unit; an additional function part that outputs an image data set to a network line, the additional function part comprising: a second interface unit connected to the first interface unit, and a network interface unit connected to the network line; a data defining part including plural memory areas that store respectively character array data of respective language types, in which plural indexes are assigned to the plural memory areas one by one; a first index storing part that stores one of the plural indexes according to the selection by the user; a first CPU which takes out, according to the stored index, the character array data from the corresponding memory area in case that a command for projecting the menu image is given; and an image generating part that generates the image signal according to the taken-out character array data so that the character array can appear in the menu image as the part, the additional function part outputting the image data set corresponding to the selected language type to the network line, so that a computer connected to the additional function part through the network line can display data relating to the projector on a monitor screen of the computer, with the selected language type, the displayed data including a user interface image for setting a parameter of the projector.