Yours truly, writing for Typekit:
OCR-A Std and OCR-B Std are two takes on machine-readable typeface standardization. OCR stands for Optical Character Recognition (a very different kind of “optical” typeface than the optical styles of Chaparral!). These typefaces were designed to be read by a machine. OCR-B, originally designed by Adrian Frutiger, pushes the limits of the optical reader but is easier for people to read.