The THROBAC and Jim’s MacAbacus are great - but more seriously, there is a useful discussion on the origins of the abacus in Williams, M. R. 1985. A History of Computing Technology. Englewood Cliffs: Prentice-Hall, Inc. - pp 53-66. Williams focuses mainly on the table abacus used by the Greeks and Romans - not the hand abacus discussed in this intriguing blog post, which I did not know about. On p 56, Williams reproduces a drawing of the Greek abacus in use, copied from an ancient vase. Williams is referring to the obvious table abacus in the drawing — but the man in that same drawing is holding something in one hand that might conceivably be a hand abacus like the one Herbert identifies. No further information is given. Herbert, please let us know what you find out! Best, Paul On Feb 20, 2019, at 12:36, herbert.bruderer@bluewin.ch<mailto:herbert.bruderer@bluewin.ch> wrote: How did the Romans calculate? https://cacm.acm.org/blogs/blog-cacm/234881-how-did-the-romans-calculate/ful... Hi all: Does anyone know how the Romans calculated with the Roman numeral system? What is the meaning of the right-most slot of the Roman hand abacus? Do you have Roman hand abaci (original devices or replicas) in your collection? Thank you very much for your help. Best wishes, Herbert Bruderer _______________________________________________ This email is relayed from members at sigcis.org<http://sigcis.org>, the email discussion list of SHOT SIGCIS. Opinions expressed here are those of the member posting and are not reviewed, edited, or endorsed by SIGCIS. The list archives are at http://lists.sigcis.org/pipermail/members-sigcis.org/ and you can change your subscription options at http://lists.sigcis.org/listinfo.cgi/members-sigcis.org ___________________________ Paul N. Edwards William J. Perry Fellow in International Security Center for International Security and Cooperation<http://cisac.fsi.stanford.edu/> Stanford University Professor of Information<http://www.si.umich.edu/> and History<http://www.lsa.umich.edu/history/> (Emeritus) University of Michigan Contact: m: pedwards@stanford.edu<mailto:pedwards@stanford.edu> w: pne.people.si.umich.edu<http://pne.people.si.umich.edu> t: @AVastMachine