Editing Sign bit (section)

{{Refimprove|date=December 2009}}
In [[computer science]], the '''sign bit''' is a [[bit]] in a [[signed number representation]] that indicates the [[sign (mathematics)|sign]] of a number.  Although only [[signedness|signed]] numeric data types have a sign bit, it is invariably located in the [[most significant bit]] position,<ref name=":0">{{Cite web |title=Intel® 64 and IA-32 Architectures Software Developer's Manual Combined Volumes: 1, 2A, 2B, 2C, 2D, 3A, 3B, 3C, 3D, and 4 |url=https://www.intel.com/content/www/us/en/content-details/782158/intel-64-and-ia-32-architectures-software-developer-s-manual-combined-volumes-1-2a-2b-2c-2d-3a-3b-3c-3d-and-4.html |access-date=2024-03-13 |website=Intel}}</ref> so the term may be used interchangeably with "most significant bit" in some contexts.

Almost always, if the sign bit is 0, the number is non-negative (positive or zero).<ref name=":0" />  If the sign bit is 1 then the number is negative. Formats other than [[two's complement]] integers allow a [[signed zero]]: distinct "positive zero" and "negative zero" representations, the latter of which does not correspond to the mathematical concept of a [[negative number]].

When using a complement representation, to convert a signed number to a wider format the additional bits must be filled with copies of the sign bit in order to preserve its numerical value,<ref name="Bryant" />{{Rp|61–62}} a process called ''[[sign extension]]'' or ''sign propagation''.<ref>{{Cite web |url=http://www.adrc.com/glossary/s1.html |title=Data Dictionary (Glossary and Algorithms) |website=Adroit Data Recovery Centre Pte Ltd |access-date=2014-12-15 |archive-date=2017-04-19 |archive-url=https://web.archive.org/web/20170419101741/http://www.adrc.com/glossary/s1.html |url-status=dead }}</ref>