PURPOSE: To insert and print out a page and lines to be referred into/on a reference indicating unit at the time of printing by calculating the position of a reference indicating sentence on the basis of prescribed printing parameters.

CONSTITUTION: To print out a document, the size of paper, right and left margines, a character pitch, etc. are stored in a printing parameter register 8. When printing has started, a character generator 4 is accessed in accordance with the character codes in the contents of addresses of a data buffer memory 5 successively from location "0" to print out characters on a printing device 7 successively. Every time when a character code to be printed out is detected, a printing character number counter 13 counts up. At the detection of a line feed code, a printing line counter 10 counts up, and at the detection of a page feed code, a printing page number counter 9 counts up. When the address in the memory reaches the address to be referred, the page and lines to be referred are inserted and printed out to the reference indicating unit.