HE was an Arab mathematician (c. 980–1037) from Baghdad who is best known for his treatise “Al-Takmila Fi'l-Hisab.” It contains results in number theory, and comments on works by Al-Khwarizmi which are now lost. (His several works were translated into Latin.) The influence of this book lasted until the 17th century, when the leading Jesuit mathematician Christoph Clavius, from the famous Collegio Romano, made use of it in his Practical Geometry. Among his writings, Al-Takmila Fi'l-Hisab, is a work of major importance in the history of mathematics in which Al-Baghdadi considers different systems of arithmetic. These systems derive from counting on the fingers, the sexagesimal system, and the arithmetic of the Indian numerals and fractions. He also considers the arithmetic of irrational numbers and business arithmetic. He further stresses the benefits of each of the systems but seems to favour the Indian numerals.
