A place-value system is a number system in which the value of a number symbol depends not only on the symbol itself but also on the position it occurs. The sexagesimal system of the Babylonians, with base 60, our own decimal system, with base 10, and the binary system (base 2), used in computers, are examples. Each place-value system has a positive integral base and as many different number-symbols as this base allows.

A sexagesimal system must thus have 60 number-symbols; the decimal system uses the symbols 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9; a binary system can use the symbols 0 and 1.