Editing Endianness (section)

=== Numbers ===
[[Positional notation|Positional number systems]] (mostly base 2, or less often base 10) are the predominant way of representing and particularly of manipulating [[Integer (computer science)|integer data]] by computers. In pure form this is valid for moderate sized non-negative integers, e.g. of C data type <code>[[Signedness|unsigned]]</code>. In such a number system, the ''value'' of a digit that contributes to the whole number is determined not only by its value as a single digit, but also by the position it holds in the complete number, called its significance. These positions can be mapped to memory mainly in two ways:<ref name="TanenbaumAustin2012">{{cite book |first1=Andrew S. |last1=Tanenbaum |first2=Todd M. |last2=Austin |title=Structured Computer Organization |url=https://books.google.com/books?id=m0HHygAACAAJ |access-date=18 May 2013 |date=4 August 2012 |publisher=Prentice Hall PTR |isbn=978-0-13-291652-3}} </ref>
* Decreasing numeric significance with increasing memory addresses, known as ''big-endian'' and
* Increasing numeric significance with increasing memory addresses, known as ''little-endian''.

In ''big-endian'' and ''little-endian'', the ''end'' is the extremity where the ''big'' or ''little'' significance is written in the location indexed by the lowest memory address.

The integer data that are directly supported by the [[Arithmetic logic unit|computer hardware]] have a fixed width of a low power of 2, e.g. 8 bits ≙ 1 byte, 16 bits ≙ 2 bytes, 32 bits ≙ 4 bytes, 64 bits ≙ 8 bytes, 128 bits ≙ 16 bytes. The low-level access sequence to the bytes of such a field depends on the operation to be performed. The least-significant byte is accessed first for [[addition]], [[subtraction]] and [[multiplication]]. The most-significant byte is accessed first for [[Division (mathematics)|division]] and [[Natural number# Order|comparison]]. See {{section link||Calculation order}}.