PURPOSE: To prevent an undesired trouble by detecting a trouble of dissidence between a communication control software and a system generation of a line adaptor.

CONSTITUTION: Upon the receipt of a line open processing request from a host software, a communication control software reads the content of a line adaptor class display register from a line adaptor to obtain the line adaptor class code. Then a control management table (MCT) 3 corresponding to a line number is acquired succeedingly through the structure of line number ascending order 6 and line takeover information 8 is obtained corresponding to the communication procedure and the line class from the MCT 3. Then a line adaptor class identification table (LAT) 5 is acquired through the structure of the line adaptor class dependent code and a line adaptor class code ascending order 7. Since the line takeover information 8 is assigned in the ascending order from the head of the LAT 5 by one byte each, the communication control software acquires adaptive information 9 from an area corresponding to the line takeover information 8 obtained by the MCT 3. Thus, the mount dissidence between the communication control software and the line adaptor is recognized.