PURPOSE: To prevent the breakage of a library main body when the processing is discontinued by exchanging the library file names after a library file is updated.

CONSTITUTION: An updating means 11 shifting a member to an updating library file 3 from a library file 2 to be updated and at the same time updates the member. A file name changing means 13 exchanges the name of the library 2 with the name of the file 3 after the updating is carried out by the means 11. Then a file name control means 14 performs the control so as to evade the duplication of the file names which are exchanged by the means 13. Thus, a library main body is never broken even with discontinuation of the processing.