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The Quipu
Disk Drive of the Ancient Inca

Sellam Ismail ( )
Vintage Computer Festival

June 14, 2000






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Many civilizations of the past have left behind some form of written record for modern man to discover. The Incas, despite a traditional form of writing using symbols either printed or impressed upon a medium, nonetheless did leave behind a record of their civilization. The Incas recorded the quantities of their daily lives upon the Quipu (pronounced kee-poo). The Quipu is a mnemonic knot record that uses a heirarchical system of knotted strings made of wool or cotton to express mostly numeric data, but other information as well.

That the Incas used cloth to stored their records should not be surprising. Cloth played an important role in Inca culture, both ceremonially and socially. The Quipu reflects the heirarchical social structure of Inca society. Every Quipu features a main cord with several pendant cords hanging from this cord, with further cords attached to those cords and so on. One might wonder why the Incas never devised a system of writing in our own sense. It is helpful to understand that the Inca society was a very portable one because of the mountainous terrain. Items carried had to be light weight and easily transportable. Records stored as knots on pieces of string provide an ideal solution. The resulting record is lightweight and easily tucked in a sack, taking up little space.

All that we know about the Quipu today is derived from research done on the relatively few Quipus still in existence. The Spaniards made an effort to destroy every last vestige of the Inca society, and the Inca’s form of record keeping was not spared this fate. Most of the Quipus found in museums were recovered from gravesites in the lower desert regions along the western coast of South America, where the dry environment preserved them.

The artifacts found in the graves along with the Quipus give us some insight into the life of the Quipucamayoc or Quipu-maker. While they enjoyed some privelege in the Inca heirarchy, they still were among the lower ranking officials. The Quipucamayocs were most likely individuals picked from villages and then brought to Cusco to be trained in the art of Quipu making. They were then returned to their village to carry out the record keeping functions.

Much of what is currently known about the Quipu comes from the work of Leland Locke in his book The Ancient Quipu (1923) and the more recent Mathematics of the Incas: Code of the Quipu (1981) by Marcia and Robert Ascher. Locke was responsible for first realizing that the knots on the Quipus represented stored numeric data in a base ten numbering system. The Ascher’s took Locke’s research further and expanded upon it.

A Quipu is generally thought to be merely a mnemonic memory aid, but it is actually quite a bit more sophisticated. It was used to store multiple dimensioned tables of numeric data with summary information. It is also speculated (and alluded to by the Spanish chroniclers) that the Quipu also played a role in storing songs, calendar information, and even encoded the laws of Incan society in some manner. The data generally believed to be stored on Quipus includes census information, crop figures, herd counts, etc., all the typical things a primitive society would want to keep track of.

The construction of a Quipu is relatively simple, yet extremely complex structures could be built using the basic system of cords and knots. The material used is either wool or cotton, though wool is what was normally used in construction. Each cord in a Quipu is a double ply piece of string that is spun to create a loop on one end and tied off in a knot on the other. The cord can then be made to attach to another cord by looping the cord through itself and then drawn tight over the cord it is attached to. The main cord is always the thickest, and all the other cords either hang from the main cord or from cords attached to the main cord. No information in the form of knots is ever encoded on the main cord. Its sole purpose is to form the “root” of the Quipu.

The “pendant” cords that hang from the main cord contain the majority of the information encoded on the Quipu. Cords that hang from pendant cords are called “subsidiary” cords, and can either contain information supplementary to that stored on the cord it is hanging from, or might contain summation information for a group of cords. Such a cord is also called a “top” cord, because it extends from the top of a group of cords and “hangs” in the opposite direction of the pendant cords. A top cord is looped through a series of other cords that contain information to be summed, to indicate visually that the collective information stored on the cords it encompasses are summed on this one cord. Finally, a cord that contains summation or identifying information for an entire Quipu is dubbed a “dangle” cord, as it dangles from the loop of the main cord.

Encoding of information on the Quipu is implemented in several different ways. First and foremost, the colors of the cords are generally believed to symbolically represent the category of encoded data. For instance, yellow might represent corn or gold, white might represent cotton, or a certain color might repesent men and another women, etc. Basic colors were often combined to produce more color variations with which to encode numbers or data.

The spacing of the cords on a Quipu also play a significant role in the encoding of the data. Spacing was used to separate or group data. These groupings could have been used to represent disparate crops among various fields, or perhaps population counts in various villages. Another method for grouping data is to place a bare pendant containing no knots in between pendants with information.

Interestingly, the numeric figures recorded on the pendants were represented in the decimal numbering system, and included all the digits from one through nine, as well as zero. Grouped knots are used to indicate the digits in the overall figure. Anywhere from one to nine knots are created on the cord to represent ‘1’ through ‘9’ respectively for each digit in the number. The only exception is a one digit in the one’s place, which is represented by a “long” knot (a knot tied in a figure eight). Finally, no knots represents zero (that the Incas indepentently discovered the concept of zero demonstrates their scientific acumen).

Digits are recorded from the top of the cord to the bottom, with the highest order digit in the number appearing at the top, and the lowest order digit (the one’s place) appearing at the bottom. The digits for each number on an individual cord are generally in alignment with the digits for all other cords on the Quipu, including top cords and any subsidiary cords. This obviously facilitated in the reading of the Quipu.

Despite our technical understanding of the Quipu, the nature of the information actually encoded on the Quipu remains mostly a mystery. No written record is available that explains the process of encoding information on the Quipu beyond what modern day research has speculated. Only educated guesses have been made as to what is encoded on the relatively few Quipus that have been discovered. Furthermore, evidence suggests that individual Quipucamayocs used their own color schemes for recording information, and thus the context of those Quipus in existence is lost entirely to time.

Most of what we now know about what may actually have been encoded on the Quipu comes from the descriptions in the chronicles of the early Spanish Conquistadores. The Chronicles indicate that, besides numeric data, other information that was encoded on the Quipu may have included dates and times, or codes which represented the various cities and provinces in the Inca empire. There are also references to the recording of calendar informaion, refrains of songs, and Inca laws.

Other uses for the Quipu have been deduced from their structure. Some Quipus seem to be tables of numbers, perhaps used as ledgers or even spreadsheets. Analysis of some Quipus has revealed a rhythmic and repetetive structure, suggesting Quipus may have been used to record weaving patterns for textiles. It has also been suggested that Quipus could contain directional information for navigating the thousands of miles of Inca highways; in other words, maps.

Unfortunately, we will most likely never be know for sure what is encoded on the Quipu. Without any other written record left by the Incas, the few clues available for analysis offer little insight into the actual data that was recorded.

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