Editing Signed number representations (section)

{{Short description|Encoding of negative numbers in binary number systems}}
{{Refimprove|date=April 2013}}
{{distinguish|Signed-digit representation}}

In [[computing]], '''signed number representations''' are required to encode [[negative number]]s in binary number systems.

In [[mathematics]], negative numbers in any base are represented by prefixing them with a minus sign ("−"). However, in [[RAM]] or CPU [[Processor register|registers]], numbers are represented only as sequences of [[bit]]s, without extra symbols. The four best-known methods of extending the [[binary numeral system]] to represent [[signed number]]s are: [[#Sign–magnitude|sign–magnitude]], [[#Ones' complement|ones' complement]], [[#Two's complement|two's complement]], and [[#Excess-K|offset binary]]. Some of the alternative methods use implicit instead of explicit signs, such as negative binary, using the [[#Base −2|base −2]]. Corresponding methods can be devised for [[positional notation|other bases]], whether positive, negative, fractional, or other elaborations on such themes.

There is no definitive criterion by which any of the representations is universally superior. For integers, the representation used in most current computing devices is two's complement, although the [[UNIVAC 1100/2200 series|Unisys ClearPath Dorado series]] mainframes use ones' complement.
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