How did the Inca use quipu to send messages and keep records?

The Inca utilized the quipu—a system of knotted, colored cords—as a sophisticated tool for bookkeeping, historical record-keeping, and communication across their empire.123

How Quipu Functioned

• Structure: A quipu consisted of a primary cord with various pendant cords attached, which could further feature smaller "subsidiary" cords. Meaning was derived from the cord's color, length, composition, ply, and the spacing between them.1
• Numeric Records: Knots tied at specific positions on the pendant cords represented numeric values based on a decimal system. Simple knots represented powers of 10, long knots (wrapped 2–9 times) represented digits 2–9, and figure-8 knots represented 1. A space indicated zero.1
• Communication: Because the Inca lacked a traditional writing system, quipus served as vital administrative records. They were maintained by officials at every level of the bureaucracy, from the capital of Cuzco to regional village headmen, to track labor obligations, census data, and military logistics. These records were transported across the vast Inca highway system by relay runners.2314

While quipus were highly effective for quantitative data, some "narrative quipus" are believed to have encoded non-numeric information, though these remain largely undeciphered.13