PURPOSE: To always display real-time communication log information by displaying the communication log information in an idle time of execution of various communication processing tasks in multitask processing.

CONSTITUTION: Based on a multitask monitor 3, various communication processing tasks 3a perform respective data communications and record protocol data used for transmission and reception as communication log information. After termination of macro processings, various communication tasks are in the holding state until being started from the outside. When all processing tasks are set to the holding state, the processing of a dummy task 3b is started. A macro call is started for the purpose of getting communication log information for display in the dummy task 3b. When this macro processing has communication log information to be displayed, this information is displayed.