Abstract: Data to be sent to a frame buffer memory keeping output data in a bit map form is subdivided into square blocks. The words arranged in the row direction are rotated in a column direction by a bit each time the row address is increased. The rotation amount is attained by adding the row and column addresses associated with the square block.

Abstract: A control apparatus for a raster scan printer has a bit map memory for storing bit information corresponding to print dots, input means for writing the bit information into the bit map memory, sending means for reading the bit information from the bit map memory and sending it to the raster scan printer, and a central processing unit for controlling the apparatus. The address of the bit map memory ascends in a sheet feed direction and is consecutive in a raster scan direction. A control method includes the steps of storing bit information corresponding to print dots in a bit map memory sequentially in a sheet feed direction and consecutively in a raster scan direction, reading the bit information from the bit map memory in the raster scan direction and sending it to the raster scan printer, storing bit information corresponding to print dots into an area of the bit map memory from which the bit information has been read, and reading the latter bit information and sending it to the raster scan printer.