A display device capable of analog and digital image display has a retaining circuit holding an image signal disposed for each of the pixel elements. In the memory operation mode, an output from an oscillation unit formed inside the display panel is supplied to the pixel element electrodes of the display. The on-resistance of an output transistor for the pixel electrode is higher than the on-resistance of thin film transistors of the inverters in the oscillation unit. In the memory operation mode, gate and drain lines are set at predetermined voltages and an output of a voltage booster circuit formed in the display panel is used as a reference voltage of the retaining circuit and used for switching a selection circuit selecting image display circuits.