Dear colleagues: The Romans used the abacus for calculations and recorded the results with Roman numerals. The Incas recorded the values with quipus and calculated with yupanas. Does anyone know how they calculated with these tools? Many thanks. Best wishes, Herbert Bruderer -- Bruderer Informatik Seehaldenstrasse 26 Postfach 47 CH-9401 Rorschach Switzerland Telefon +41 71 855 77 11 Bruderer, Herbert [2020a]: Milestones in Analog and Digital Computing, Springer Nature Switzerland AG, Cham, 3rd edition 2020, 2 volumes, 2113 pages, 715 illustrations, 151 tables, https://www.springer.com/de/book/9783030409739 Bruderer, Herbert [2020b]: Meilensteine der Rechentechnik, De Gruyter Oldenbourg, Berlin/Boston, 3. Auflage 2020, Band 1, 970 Seiten, 577 Abbildungen, 114 Tabellen, https://www.degruyter.com/view/title/567028?rskey=xoRERF&result=7 Bruderer, Herbert [2020c]: Meilensteine der Rechentechnik, De Gruyter Oldenbourg, Berlin/Boston, 3. Auflage 2020, Band 2, 1055 Seiten, 138 Abbildungen, 37 Tabellen, https://www.degruyter.com/view/title/567221?rskey=A8Y4Gb&result=4