PURPOSE: To obtain a check function which ensures the on-line business processing program AP circularity in view of an AP interface by adding a data base DB/data communication DC interface correspondence check function developed originally by a user to a language checker.

CONSTITUTION: A means 1 is provided to add a check function related to a DB/DC interface together with the means 21-25 which decide and extract the information needed for the check related to the DB/DC interface out of an object program at the side of a checker 2, and the means 27 and 28 which transfer the information and the control to an additional part 3 which attains the check function related to the DB/DC interface. Thus a user selects a language checker in accordance with the operating environment and at the same time a DB/DC interface correspondence check function developed originally by the user is added to the language checker. Thus it is possible to obtain a check function which ensures the AP circularity in view of the AP interface.