A driving device drives a liquid crystal display device or the like to achieve screen display. This driving device has a driver integrated circuit device for feeding a driving signal to a display, a read-only memory having characters stored therein, and a microcomputer for feeding the driver integrated circuit device with bit-mapped data used to achieve graphic display and address data used to specify characters. The driver integrated circuit device, on receiving bit-mapped data, produces a driving signal in accordance with the received bit-mapped data, and, on receiving address data, reads the characters corresponding to the received address data from the read-only memory and produces a driving signal for character-based display.

There is disclosed a display system for outputting image data of a bit map to be displayed on a raster scan type display and a pattern of font corresponding to a code of a character, symbol or graphics having the predetermined code assigned thereto to the display for displaying the image and the character, symbol or graphics corresponding to the code on the display, comprising the steps of adding identification data for discriminating the code from the image data to the code and storing the code in a memory together with the image data, sequentially reading the code together with the image data from the memory, and outputting a pattern of the font corresponding to the code having the identification data added thereto to the display when the identification data is detected.

A character and graphic signal generating apparatus of the type suitable for use with a personal computer for displaying characters and graphic patterns in a superposed relation according to a raster scan method comprises a frame buffer for storing coded character data, a DMA control unit for controlling DMA transfer of coded character data from a display RAM to the frame buffer in a non-display cycle, and units for reading out the data from the display RAM and the frame buffer in parallel relation in a display cycle so as to simultaneously derive the graphic data and the coded character data in each display cycle, whereby more display data can be read out in a unit time, and high-density display can be achieved without the sacrifice of the scanning speed.

This invention provides a RAM data selection circuit in which the screen data from the graphic display RAM and the text display RAM incorporated in the personal computer are simultaneously outputted and a data selection means adapted to output either of the two screen data preferentially by the dot unit to the monitor TV is provided, thereby rapidly enabling the superimposing of graphic and text data on the screen.

In order to reduce the capacity of a character ROM without reducing the character information, n-bit bit pattern data and sequence data having information necessary for composing n-bit m components are stored in first memory means (character ROM). Second memory means has addresses corresponding to each display position on the screen and holds addresses for the first memory means as a data. In accordance with the address from the second memory means and the sequence data from the first memory means, address modifying means produces an address of a scanning line with respect to pertinent character for the first memory means. According to this address, the bit pattern data is read out from the first memory means.