Checking multiple choice question exams

the aim of this study is to explain an algorithm for identifying checked choices in multiple choices question exam. The target is considered, finding numbers of correct checked tests and recognizing students ID for each answer sheet, base on Black Square. This algorithm uses Morphological operations to eliminate noises and to find distinctive features of image in answer sheet. To identify checked choices, it uses the apparent properties of answer sheet. In final analysis section, system is tested in different situation and it shows that system is resistant to few image rotation and intensity changing, however it is sensitive to state of checking (square must be completely checked in black).