it's quipu
Knotted string communication is called "khipu" (or "quipu"). It was an ancient Inca method of record-keeping and communication that used variously colored strings and knots to convey information, such as numerical data and possibly narrative content. Khipus served as a sophisticated system for managing administrative and economic records in the Inca Empire.
Quipu or khipu (sometimes called talking knots) were recording devices used in the Inca Empire and its predecessor societies in the Andean region.
Different cultures may have the same word, or very similar ones, for different things. In the Culture of the North-West coast of North America a potlatch was a communal party where participants impressed each other in the amount of stuff they could give away.
macrame
String can be reused if it is in good condition and not too tangled or knotted.
Macrame
it is used in an Inca method for keeping records. it is a vertical string with knots on it that varies in size, color, and placement on the string.
struct student { std::string id; std::string first_name; std::string last_name; // ... }; student students[10];
Jute is a strong, heavy fiber-like string, which comes in a loosely coiled roll called a skein. When the string comes loose from the roll, it can become knotted and tangled.
Quipus
Type 8 cotton string works good, and it can be colored to if you want.
Tie several knots...mess with it a little...tie a few more knots...mess with it some more...