An array of parameter setting images corresponding to a plurality of parameters, and a plurality of tab images for selecting any one of a plurality of groups formed by grouping the plurality of parameters. The tab images are displayed on a screen in an arrangement associated with the array of the parameter setting images corresponding to the parameters belonging to corresponding ones of the groups. The grouping of the parameters is made such that a portion of the parameters included in a given one of the groups is shared with another of the groups, and a portion of the tab image corresponding to the portion of the parameters shared with the other group is displayed in a display style to indicate the sharing. Upon selecting a tab image, the parameters corresponding to the selected tab image are allocated to individual ones of the plurality of operators.