Numerical digit
From India, the thriving trade between Islamic sultans and Africa carried the concept to Cairo. Arabic mathematicians extended the system to include decimal fractions, and Muḥammad ibn Mūsā al-Ḵwārizmī wrote an important work about it in the 9th  century. The modern Arabic numerals were introduced to Europe with the translation of this work in the 12th century in Spain and Leonardo of Pisa's "Liber Abaci" of 1201. In Europe, the complete Indian system with the zero was derived from the Arabs in the 12th century.
Eastern Arabic numerals
The numeral system originates from an ancient Indian numeral system, which was re-introduced in the book "On the Calculation with Hindu Numerals" written by the medieval-era Iranian mathematician and engineer Khwarazmi, whose name was Latinized as "Algoritmi".