Abstract: When display data having a smaller vertical number of pixels than a vertical number of pixels of a display is to be displayed, a display status can be switched during the execution of any application software. When a display selection switch receives a switch command, it outputs a selection signal directly to a display controller, an address generator in the display controller selects one of display modes to the display in accordance with the selection signal. When the display data having the smaller vertical number of pixels than the vertical number of pixels of the display is to be displayed, a user can freely select the display mode without interruption of a CPU during the execution of any application software.

Abstract: A gradation conversion system comprising: a plurality of gradation conversion devices for converting color display data into gradation display data by different gradation conversion methods, respectively; and switching device for selectively activating one of the plurality of graduation conversion device. Accordingly, if a number of different colors are to be displayed in the same number of gradations when converting multi-color display data into gradation display data, it is possible to perform this gradation conversion. On the other hand, if different colors are to be displayed in gradations as exact to the brightnesses of colors as possible, it is possible to select one of plural gradation conversion methods so as to carry out this gradation conversion.