Adelard of Bath
Adelard of Bath (; 1080 1152 AD) was a 12th-century English natural philosopher. He is known both for his original works and for translating many important Arabic and Greek scientific works of astrology, astronomy, philosophy and mathematics into Latin from Arabic versions, which were then introduced to Western Europe. He is known as one of the first to introduce the Arabic numeral system to Europe. He stands at the convergence of three intellectual schools: the traditional learning of French schools, the Greek culture of Southern Italy, and the Arabic science of the East.
Pope Sylvester II
Gerbert learned of Hindu–Arabic digits and applied this knowledge to the abacus, but probably without the numeral zero. According to the 12th-century historian William of Malmesbury, Gerbert got the idea of the computing device of the abacus from a Spanish Arab. The abacus that Gerbert reintroduced into Europe had its length divided into 27 parts with 9 number symbols (this would exclude zero, which was represented by an empty column) and 1,000 characters in all, crafted out of animal horn by a shieldmaker of Rheims. According to his pupil Richer, Gerbert could perform speedy calculations with his abacus that were extremely difficult for people in his day to think through in using only Roman numerals. Due to Gerbert's reintroduction, the abacus became widely used in Europe once again during the 11th century.