PURPOSE: To reduce the fatigue of eyes by determining the height of a character cell in response to a font select command and inverting white and black by the height of the character cell.

CONSTITUTION: A first processor 3 receives a character code information, contains it in a page buffer 2 and extracts data corresponding to one line, varies them into parameters for processing, and transmits them over a mailbox 4. A character data row corresponding to one line is arranged in order of a completion code LF in a pre-line, line-dot height (b), a line-base position (c) and a font select command (d, e). Figures, each represent the shapes and size of character patterns. A character pattern ROM5 contains informations representing character-cell height corresponding to figures, and the informations are used on reverse printing (f). A second processor 6 executes processing by employing data in the mailbox 4, and conducts reverse printing at the height dot height of inversion character cells in one line. A process is repeated at every line, and characters in which only reverse characters are printed in a white-black inversion manner are printed. Minimum inversion printing is conducted on inversion printing, fine printing is obtained, and characters are not white-black inverted extending over the whole width of the line, thus resulting in little fatigue of eyes.