A display device of high definition, multiple colors and low power consumption includes a display panel having a pixel section in which pixels are arrayed in the form of a matrix at the cross points of a plurality of data lines and a plurality of scanning lines, a scanning circuit for applying voltage sequentially to the plurality of scanning lines, and a data-line driver, which receives display data supplied by a host device, for applying signals corresponding to the display data to the plurality of data lines. Provided external to the display panel is a controller IC having a display memory for storing display data corresponding to the pixel section, an output buffer for reading data out of the display memory and outputting this data to the display panel, and a controller for controlling the display memory and output buffer and communication with the host device. The display panel is provided with a digital/analog converter, which forms part of the data-line driver, for converting display data represented by a digital signal to an analog signal. The width of a bus for data transfer between the controller IC and data-line driver of the display panel is such that data of a greater number of bits is transferred in parallel by a single transfer than is transferred by the bus between the controller and the host device. This allows the operating frequency of the data-line driver to be reduced.