and meteorology. Many of his works are believed to have been part of the K'nnikon (Քննիկոն, from "canon", Greek: Kanonikon), completed circa 666, and used as the standard science textbook in medieval Armenia. According to Greenwood, the K'nnikon was a "fluid compilation, whose contents fluctuated over time, reflecting the interests and resources of different teachers and practitioners." Modern scholars have praised Anania's writing as concise, simple, and to the point, retaining the reader's attention and citing examples to illustrate his point. Mathematical Anania was primarily devoted to mathematics, which he considered the "mother of all knowledge." His mathematical books were used as textbooks in Armenia. Of Anania's several mathematical works, the most important is the book of arithmetic (Hamaroghut’iun, Համարողութիւն; or T'vabanut'iun, Թւաբանութիւն), a comprehensive collection of tables on the four basic operations. It is the earliest extant known work of its kind. The operations reach up to a total of 80 million, which is the highest number. A possible theoretical part is believed lost. Problems and Solutions (alternatively translated as On Questions and Answers), a collection of 24 arithmetical problems and their solutions, is based on the application of fractions; it is the earliest such work in Armenian. Many of its problems allude to real-world situations: six connect to the princely house of Shirak, the Kamsarakans, and at least three to Iran. Greenwood calls the problems "a rich source for seventh-century history whose value has not been sufficiently recognized." The third work, probably an appendix of the book of arithmetic, is titled Xraxc'anakank (Խրախճանականք), literally "things for festive occasions". It has been translated into English as Mathematical Pastimes, Fun with Arithmetic or Problems for Amusement. It also contains 24 problems "intended for mathematical entertainment in social gatherings." According to Mathews this may be the oldest extant text of its kind. Numerical notation For his mathematical works, Anania developed a unique numerical notation based on 12 letters of the Armenian alphabet. For the units, he used the first nine letters of the Armenian script (Ա, Բ, Գ, Դ, Ե, Զ, Է, Ը, Թ), similar to the standard traditional Armenian numerical system. The letters used for 10, 100, and 1000 were also identical to the traditional Armenian system (Ժ, Ճ, Ռ), but all other numbers up to 10,000 were written using these 12 letters. For instance, 50 would be written ԵԺ (5×10) and not Ծ as in the standard system. Thus,