Excerpts from Books and Wikipedia
"In 967, his superiors sent him [Gerbert d'Aurillac, the future Pope Sylvester II] for three years of advanced studies at the monastery of Vich in Catalonia, then a distant Christian frontier outpost abutting the scientific and cultural powerhouse of Muslim Spain." [Lyons: House of Wisdom, p. 36] ". . . He learned to use the numbering system of the Arabs, discovered by them in their forays into India. Unlike the cumbersome Roman system, these numbers (generally now known as Hindu-Arabic numerals) relied on place for their value. . . . 'Seeing the abundance of books in Arabic on every subject,' one of his students later wrote, 'he learned the Arabic language in order to be able to translate.'" [Bauer: Renaissance World, p. 46-7]