according to the importance levels of bugs and information for progress of correction for the bugs , a bug for which priority in problem solution is to be given is chosen . in an original source code , a search is performed to the whole original source code for a character sting written in a bug form and expressing the bug , thereby identifying locations in which bugs in the same type might exist . furthermore , a search for a correction location in a corrected source code is performed and correction contents are verified with reference to the bug form and the retrieved correction location in the corrected source code .