Fibonacci grew up in Algeria, the son of a Pisan customs officer, and he encountered an extraordinary system of writing used by the Arabs. He introduced Hindu-Arabic numerals to Italy. In 1202, he wrote a book called Liber Abaci (Book of Calculation), in which he explained that the Hindus contributed the numbers 1-9, and the Arabs contributed the zero. He used his famous Fibonacci sequence to explain the practical uses of the number system.