Excerpts from Books and Wikipedia
"Fibonacci was born around 1170 to Guglielmo, an Italian merchant and customs official. Guglielmo directed a trading post in Bugia, Algeria. Fibonacci travelled with him as a young boy, and it was in Bugia that he learned about the Hindu–Arabic numeral system. . . . Fibonacci became a guest of Emperor Frederick II, who enjoyed mathematics and science. . . .The book advocated numeration with the digits 0–9 and place value. The book showed the practical use and value of the new Hindu-Arabic numeral system by applying the numerals to commercial bookkeeping, converting weights and measures, calculation of interest, money-changing, and other applications." [Wikipedia] "The use of this Arabic system did not, however, become common-place until it was popularized by the Liber abaci, or book of the Abacus, written in the early thirteenth century by the famous mathematician Leonardo Fibonacci, a thoroughly Arabized merchant from Pisa who had studied accounting methods in north Africa (present-day Algeria), where his father had been a Pisan diplomat." [Menocal: Ornament of the World, p. 181n]