The counting rods (籌 chou2) were used by ancient China before the invention of the Abacus. The way that a number is presented by counting rods is called the rod numeral system. The rod numeral system is a decimal place value system, where the digits 1 to 9 are represented in two ways:

depending on their positions. For example 126 is represented by |=⊤ instead of |∥⊤ which could be confused with 36. Usually black rods are for positive numbers and red rods are for negative numbers.

The counting rods could be used for a wide range of calculations, including finding the value of !

Before the introduction of 0, there was no way to separate 10007 and 107 except inserting a bigger space between 1 and 7, and so rod numerals were used only for doing calculations with counting rods. Once 0 came into play, the rod numerals had become independent and their use indeed outlives the counting rods. One variation of rod numerals is still in use, see the article on Chinese numerals.

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