(a) Mark sensing is often used for machine-scoring multiple choice
examinations. The student uses a heavy lead pencil to mark his answer. The marks
are sensed by an optical mark page reader as the document passes under a light
source. The presence of marks in specific locations is then translated into machine
language. Up to 2000 forms of the same type can be read and processed in a few
Figure 2-21. Optical mark recognition on exam answer sheets.