Baghdadi HE was an Arab mathematician (980–1037 CE) 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. Influence of some of his books translated into Latin 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 favor the Indian numerals.
