PURPOSE: To detect a failure generated at the time of compiling by listing source code parts, marking it with a preparing state mark, operating repeated scanning, trying to compile, and replacing it with a compiling normal end mark at a normal time.

CONSTITUTION: A part A is checked and complied, and a scheduling state mark is set as BUILT. Next, a part B depends on the previous compiling of a part C which is not processed, and the part B can not be compiled and the state mark is not changed. Next, a part C is complied and the state mark is set as BUILT. As a result, the flags of the parts A and C are changed from TO-BE- BUILT to BUILT and a scheduler is returned to the head of the list. The part A is checked again, nothing is executed, the part B is checked and complied, and the scheduling state mark is set as BUILT. The part C is checked, and the state mark is set as BUILT from the previous scanning, and the compiling is not executed.