Editing Binary number (section)

===Egypt===
{{See also|Ancient Egyptian mathematics}}
[[File:Oudjat.SVG|thumb|240px|left|Arithmetic values thought to have been represented by parts of the [[Eye of Horus]]]]
The scribes of ancient Egypt used two different systems for their fractions, [[Egyptian fraction]]s (not related to the binary number system) and [[Eye of Horus|Horus-Eye]] fractions (so called because many historians of mathematics believe that the symbols used for this system could be arranged to form the eye of [[Horus]], although this has been disputed).<ref>{{citation|title=The Oxford Handbook of the History of Mathematics|editor1-first=Eleanor|editor1-last=Robson|editor1-link=Eleanor Robson|editor2-first=Jacqueline|editor2-last=Stedall|editor2-link=Jackie Stedall|publisher=Oxford University Press|year=2009|isbn=9780199213122|page=790|url=https://books.google.com/books?id=xZMSDAAAQBAJ&pg=PA790|contribution=Myth No. 2: the Horus eye fractions}}</ref> Horus-Eye fractions are a binary numbering system for fractional quantities of grain, liquids, or other measures, in which a fraction of a [[hekat]] is expressed as a sum of the binary fractions 1/2, 1/4, 1/8, 1/16, 1/32, and 1/64. Early forms of this system can be found in documents from the [[Fifth Dynasty of Egypt]], approximately 2400 BC, and its fully developed hieroglyphic form dates to the [[Nineteenth Dynasty of Egypt]], approximately 1200 BC.<ref>{{citation|title=Numerical Notation: A Comparative History|first=Stephen|last=Chrisomalis|publisher=Cambridge University Press|year=2010|isbn=9780521878180|pages=42–43|url=https://books.google.com/books?id=ux--OWgWvBQC&pg=PA42}}.</ref>

The method used for [[ancient Egyptian multiplication]] is also closely related to binary numbers. In this method, multiplying one number by a second is performed by a sequence of steps in which a value (initially the first of the two numbers) is either doubled or has the first number added back into it; the order in which these steps are to be performed is given by the binary representation of the second number. This method can be seen in use, for instance, in the [[Rhind Mathematical Papyrus]], which dates to around 1650 BC.<ref>{{citation|title=How Mathematics Happened: The First 50,000 Years|first=Peter Strom|last=Rudman|publisher=Prometheus Books|year=2007|isbn=9781615921768|pages=135–136|url=https://books.google.com/books?id=BtcQq4RUfkUC&pg=PA135}}.</ref>