This document provides a literature review of optical character recognition. It discusses early uses of OCR by the US postal service in the 1960s. In the 1970s, work on OCR for Hindi language began in India. Researchers at IIT Delhi developed one of the first commercial Hindi OCR systems called "Chitrankan" in the late 1990s. The document also briefly outlines some early techniques for estimating text slant, including methods using shirorekha analysis and mathematical approaches.