Abstract: Printing is effected in units of data of a band that includes a plurality of line data while a recording head is moved perpendicularly to the movement direction of a recording medium. An output interface receives compressed data from an external apparatus. An output buffer retains data of the nth band even after printing of those data. An output processing section judges whether each line data of the (n+1)th band is compressed data, empty data, or non-compressed data. For the compressed data, the output processing section restores the line data of the (n+1)th band using differences from corresponding line data of the nth band, and updates the corresponding line data of the output buffer. For the empty data, the output processing section erases the corresponding line data of the output buffer. For the non-compressed data, the output processing section overwrites the line data of the (n+1)th band on the corresponding line data of the output buffer.

Abstract: Disclosed herein is a dot matrix printer capable of recording character strings with a high quality at high speeds. The dot matrix printer includes an output processor for obtaining the numbers of effective dots of character patterns in a character string with respect to a character string reference line designating a print position of font of the character string according to information of the font and information of the character string reference line, comparing the numbers of effective dots with the number of printable dots of the print head, determining whether or not another character string in addition to the character string is admitted within the width of the print head if a maximum value of the numbers of effective dots is smaller than the width of the print head, and setting a print position of at least one of the character strings admitted within the width of the print head.

Abstract: A movement distance monitoring pulse counter counts drive pulses being applied to a carriage-moving pulse motor, and produces a count value M. An optical sensor attached to a head carriage detects slits of a slit encoder passed by the head carriage. A slit counter counts output pulses of the optical sensor, and produces a reset signal every time the count reaches a preset number of output pulses corresponding to a monitoring carriage movement distance. The count value M is reset in response to the reset signal. When the count value M exceeds a preset number of drive pulses corresponding to the monitoring carriage movement distance, an abnormality detection signal is produced.