Integer overflow: Difference between revisions

Revision as of 09:59, 28 February 2013

Revision as of 08:30, 27 May 2013

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: 32 bits: maximum representable value 2³² − 1 = 4,294,967,295 (the most common width for personal computers {{As of|2005|lc=on}}),

: 64 bits: maximum representable value 2⁶⁴ − 1 = 18,446,744,073,709,551,615 (the most common width for personal computers, but not necessarily their [[Operating system|operating systems]], {{As of|2012|lc=on}}),

: 128 bits: maximum representable value 2¹²⁸ − 1 = 340,282,366,920,938,463,463,374,607,431,768,211,4553.4028236692093846346337460743177e+38

Since an arithmetic operation may produce a result larger than the maximum representable value, a potential error condition may result. In the [[C (programming language)|C programming language]], signed integer overflow causes [[undefined behavior]], while unsigned integer overflow causes the number to be reduced [[modular arithmetic|modulo a power of two]], meaning that unsigned integers "wrap around" on overflow. This "wrap around" is the cause of the famous "[[kill screen|Split Screen]]" in Pac-Man.<ref>{{cite web|url=http://home.comcast.net/~jpittman2/pacman/pacmandossier.html|title=The Pac-Man Dossier|author=Pittman, Jamey}}</ref>