PURPOSE: To write and read picture element data instantaneously in both normal and 90° rotation modes by performing arithmetic for an address and a data bus and arranging the picture element data which continue in both raster scanning directions of the normal and 90° rotation modes on different device.

CONSTITUTION: The address bus and data bus are provided with arithmetic units 4 and 5 and the picture element data continue in the raster scan data directions of both the normal and 90° rotation modes. The picture element data are arranged dispersedly in dot addresses of a memory device 1 so that the one-bit picture element data can be written and read on the different data buses. The picture element data which are read out continuously are stored on different memory devices in the memory device 1. Consequently, a raster scan display is easily made while turned by 90° and the processing time up to the output of 90°-rotated raster scan data is shortened.