The quipu was invented by Andean people in the 9th century and was used to store information. It was a device that used cotton or animal fibers to make strings and the knots in those strings symbolize decimal or numerical values (Fiveash). The Inca did not have a writing system like the other Bronze Age civilizations of the time (Mann pg. 1650).

People nowadays know that the quipu was used for mathematical purposes such as where the Inca read the number of knots in descending decimal order top to bottom (Christensen pg. 39, Zepp pgs. 43 and 45). The other uses of the quipu are less certain however. The way quipus carried information was through the chasqui, runners that carried the quipu across the empire so that the Quipucamayocs, the people that made and interpreted the Quipu, could read them  (Fiveash).

The quipu could have been used as some sort of bureaucratic tool or an accounting tool (not money, but history) in the Inca empire (Christensen pg. 39, Mann pg. 1650, Yeakel pg. 39). We know the Inca used the quipu to record mathematical information, but there is still debate about the other purposes of the quipu like the narrative use where not a single one has been decisively decoded (Mann pg. 1650).

Most of our information about the Inca comes from a Spanish conquistador named Guaman Poma de Ayala who wrote about the Inca using a base ten-system on something akin to an abacus to record numerical information (Zepp pg. 42). Although many quipu were destroyed by the Spanish that subdued the Inca, some still remain like the quipu numbering around 100 in the American Museum of Natural History in New York City (Fiveash, Mann pg. 1650). 

Even though the main user of the quipu, the Inca, has been gone for about a half-millennium, some people still use the quipu in the Andean region of South America.