Al-Uqlidisi

Abu'l-Hasan Ahmad ibn Ibrahim al-Uqlidisi was born around 920 CE in Damascus, Syria. His name, meaning "the Euclidean," suggests he was a copyist or seller of Euclid's works, though he became a highly original mathematician in his own right. He is primarily celebrated for the earliest known use of decimal fractions in arithmetic, a contribution of foundational importance to mathematics.

Al-Uqlidisi wrote his major work, Kitab al-Fusul fi al-Hisab al-Hindi (Chapters on Hindu Arithmetic), in Damascus in 952 CE. This treatise was one of the earliest and most comprehensive accounts of the Hindu-Arabic numeral system written in Arabic. Unlike earlier authors who merely described the system, al-Uqlidisi deeply explored its computational potential, introducing modifications that made arithmetic more practical and powerful.

His most revolutionary contribution was the explicit use of decimal fractions, representing parts of a unit using the positional decimal system extended to the right of a marker. He used a vertical stroke to separate the integer part from the fractional part, an ancestor of the modern decimal point. This allowed him to halve odd numbers in decimal notation, perform operations that had previously required cumbersome fractions, and carry out calculations with a fluency and precision that earlier methods could not match.

Al-Uqlidisi also eliminated the need for the dustboard — a sand tray used for calculation — by developing methods suited to pen and paper, making arithmetic more accessible and permanent. He died around 980 CE in Damascus. His Kitab al-Fusul survived in a single manuscript and was rediscovered by modern scholars, who recognized it as a milestone in the history of mathematics and the precursor to the decimal notation the entire modern world relies upon.