PURPOSE: To dynamically change the data communication rules by providing a table storing the data communication rules and a means updating the content of the table corresponding to a terminal equipment to a host computer.

CONSTITUTION: The information relating to the data communication rules between an on-line information processing program 9 and a terminal equipment 5 is stored in a terminal control table on a host computer 11 at the connection processing between the terminal equipment 5 and an on-line information processing program 9. Thus, even when the necessity of data communication between the on-line information processing program 9 and the terminal equipment 5 takes place, before the terminal equipment 5 is connected to the on-line information processing program 9, the information relating to the data communication rule stored in the data communication rule storage means 3 in the terminal equipment 5 has only to be changed by using a data communication registration means 4, then the communication is started easily. Thus, the data communication rule is changed dynamically.