"omr, ocr, and micr are all types of "

OMR, OCR and MICR are all types of character and mark recognition devices. They are scanners that are able to recognize special characters and marks.
OMR stands for Optical Mark Recognition,which senses the presence or absence of a mark.
OCR stands for Optical Character recognition, which reads special preprinted characters by light source.
MICR stands for Magnetic Ink Character Recognition, where  machine reads character made of ink containing magnetized particles.

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