This application note explains the design of an optical character recognition engine called the Optical Character Associator (OCA). Optical character recognition systems must classify optical inputs as specific letters, numbers, or other charcters, and are thus ideal candidates for fuzzy logic implementation. OCA is a classification engine that recognizes the set of 14 characters used by the US banking industry to encode account numbers along the lower edge of cheques. The engine is implemented using an MC68HC11E9 8-bit micro-controller, although it could have been implemented using devices from the M68HC05, M68HC16 or M68300 MCU families.