The Inca device that used knotted strings for record-keeping was the quipu, also spelled khipu.
A quipu consisted of a main cord with attached pendant cords made from cotton or camelid fiber. Meaning could be encoded through the number, position, color, and type of knots. Inca administrators used a decimal system, allowing them to record quantities such as population counts, tribute, crop stores, and military supplies.
Quipus were managed by specialists known as quipucamayocs. These trained officials maintained records for provinces and reported information to the imperial administration. Some historical sources suggest that quipus may also have preserved narrative or historical information, although scholars still cannot fully decipher every aspect of the system.
Quipus were not simply an abacus, calendar, or alphabetic writing system. Their strongest and clearest documented use was administrative record-keeping, especially for numerical data. Archaeological evidence shows that knotted-cord recording traditions existed in the Andes before the Inca Empire, including during the Wari period.