PURPOSE: To prevent the redundancy of a job program by making the file input/ output of a host side executed through a communication circuit and a host side file driver when the job program issues an input/output requiring message to a terminal side file driver.

CONSTITUTION: A terminal side file driver 3 to execute on-line procedure and data conversion is provided independently of terminal equipment 1 and a job program 2, the on-line processing of the terminal equipment 1 and a host computer 7, Japanese code conversion, the data conversion such as the conversion of an internal decimal number to an external decimal number and the input/ output function of a host file are integrated and file drivers 3 and 8 of a terminal 1 side and a host 7 side are bear them. Thus, since the job program 2 can input/output the file of the host side as it inputs/outputs the file of the terminal, the simplification of the program is attained.