A display device includes a vertical driver for applying to row electrodes a set of row signals represented by a set of orthogonal functions supplied by an orthogonal function generator at each selection period by group-sequential scanning within one frame. A dot product processor successively carries out a dot product computation between the set of orthogonal functions and a set of pixel data. A horizontal driver applies to column electrodes column signals having voltage levels determined by the results of the dot product computation at each selection period in synchronization with the group-sequential scanning. A frame memory stores the pixel data for each frame in divided bit form. The dot product processor reads out the set of stored pixel data in divided bit form and executes the dot product computation to produce a column signal component for each respective bit. The horizontal driver arranges a plurality of column signal components corresponding to the respective bits subjected to either pulse modulation or frame-rate modulation within one frame period to produce the column signal that is applied to the column electrodes. A memory controller controls the writing of the pixel data into the frame memory. Bit data subjected to the pulse modulation are written to the frame memory for every frame, while bit data subjected to frame-rate modulation are selectively written to the frame memory only at frames specified by the frame-rate modulation.