Sam wrote on the fascinating quipu:

> It also shows that a computer does not have to be electrical based

i cannot make sense of this comment.

i saw some nice examples of quipu at an exhibit this winter:

  http://www.peabody.yale.edu/exhibits/inca/

from what i could tell there and have read since then, the quipu was a
quite elaborate "coded spreadsheet", but i havent heard anything
calculational about it yet.

but perhaps there is something about the construction of the knot
system that aids in calculating sums??? i would like to hear more
about the quipu's construction before considering this more than what
the Independent article called a "textile abacus".

some links i collected after i saw the exhibit at Yale:

 1. http://www-gap.dcs.st-and.ac.uk/~history/HistTopics/Inca_mathematics.html
 2  http://www.archaeology.org/9611/abstracts/inka.html
 3. http://mathforum.org/library/drmath/view/57577.html
 4. http://hemi.ps.tsoa.nyu.edu/eng/newsletter/issue5/Lear,Scabies_and_Quipus.htm
 5. http://nordbotten.ifi.uib.no/ADM/ADM_text/F1-data-types.htm
 6. http://www.nasm.edu/nasm/dsh/LDC/ldc_part2.html
 7. http://ripley.wo.sbc.edu/departmental/spanish/www/MMLatAm/Quipus.html
 8. http://wiscinfo.doit.wisc.edu/chaysimire/titulo2/khipus/what.htm
 9. http://www.cs.uidaho.edu/~casey931/seminar/quipu.html
10. http://agutie.homestead.com/files/Quipu_B.htm
11. http://www.sfu.ca/archaeology/museum/laarch/inca/quipue.html
12. http://www.incasgroup.com/?pk_pagina=44&lang=E
13. http://www.indianreader.com/Studies/Quipu.html
14. http://www.science-frontiers.com/sf022/sf022p02.htm
15. http://cse.ssl.berkeley.edu/lessons/indiv/nellie/quipu.html
16. http://www.crd.rca.ac.uk/alumni/00-02/jez/HTML/crd1/quipu_01.htm
17. http://www.wowessays.com/dbase/ad1/avw104.shtml
18. http://exchanges.state.gov/culprop/1peru/fi/00000031.htm


the ninth and tenth links calls the Quipu an Incan data structure. i
like that characterization. and the parallel "threads" of the quipu
reminded me a lot of modern spreadsheets.  link 13 also refers to
quipu as an early computer, but also discusses briefly the training of
Incan mathematicians. link 15 shows how a modern day electromagnetic
spectrum could be displayed using quipu knots.  link 16 uses ideas of
quipu as a modern PIM (Personal Information Manager).

les schaffer