This document provides a review of optical character recognition (OCR) technologies. It discusses research that has been conducted on OCR for English, Arabic, and Devanagari characters. For English characters, various studies that used techniques like neural networks, support vector machines, and nearest neighbor classification are summarized. For Arabic characters, research using neural networks, Haar-like feature extraction and boosting classifiers achieved recognition rates from 87% to 99%. Studies on Devanagari characters employed techniques such as curvelet transforms, neural networks, k-means clustering and support vector machines and achieved recognition rates from 90% to 98.5%. In general, the document reviews past work on OCR and the techniques researchers have used to recognize