PURPOSE: To perform simple and accurate data write to ROM writer, by assembling a program to pick up data to be written in an ROM out of a data list.

CONSTITUTION: A program to pick up a data to be written in an ROM is assembled out of a data list transmitted to a printer with a specified communication system from a computer, into an ROM writer in advance (before purchased by a user). When the user purchases thi ROM writer and uses it, this ROM writer 2' is connected on the way of a line 5 transmitting the data list from the computer 1 to the printer 4, the data required to be written in the ROM 3 is picked up and written in the ROM 3. In connecting the ROM writer 2' to the line 5, connection terminals are not necessarily required and as a simple method, soldering connection can be made on the way of the line 5.