PURPOSE: To perform printing operations by averagely varying pins to be used by a method in which pins used in a dot printer are altered on the signals of a controller.

CONSTITUTION: In printing operation using a dot printer, when lines such as under line or upper line rules are printed, the positions of pins of dots to be used are automatically altered. Concentration of only specific pins on preparation of lines can thus be avoided, and troubles with shortening of life due to abrasion of only specific pins in the early period can be prevented. The lengthening of the life of the dot printer can be attained.