and b are added and it is checked whether or not the addition result is greater than 0 if yes in step s21 step s22 is executed in which data c is updated to data b data d is read from memory 2 by cpu 10 in step s25 and data c determined in step s22 is added thereto data d is then stored again in memory 2 by cpu 10 in step s26 data a is read from memory 2 by cpu 10 and data c is added thereto data a is then stored again in memory 2 by cpu 10 data a is updated in this manner without executing the paper feed operation from a printing instruction when a printing instruction is not input and paper feed instructions are input sequentially these steps are repeated therefore data a represents not the line position at which the latest printing instruction was executed but substantially represents the number of lines from the first line of the fanfold paper to a predicted line position after the input paper feed instruction was executed thus when paper feed instructions are repeatedly supplied data a can become 0 if no in step s21 step s23 is executed and data c is set to be equal to readout data a step s25 is then executed in this case step s24 can be executed in place of step s23.