"The Spanish forms of the numerals were called the hurūf al-ģobār, the ģobār or dust numerals, as distinguished from the hurūf aljumal or alphabetic numerals. Probably the latter... were also used by the Arabs. ...[D]oubtless ...these numerals were written on the dust abacus, this plan being distinct from the counter method ...Al-Bīrūnī states that the Hindus often performed numerical computations in the sand. ...The system has nine characters, but no zero. A dot above a character indicates tens, two dots hundreds, and so on, \dot{5} meaning 50, and [\ddot{5} meaning 500]."