Integer overflow: Difference between revisions

Revision as of 01:47, 26 April 2010

Revision as of 02:40, 26 April 2010

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The [[register width]] of a processor determines the range of values that can be represented. Typical [[Binary numeral system|binary]] register widths include:

: 8 bits: (maximum representable value 2⁸ − 1 = 255),

: 16 bits: (maximum representable value 2¹⁶ − 1 = 65,535),

: 32 bits (the most common width for personal computers {{As of|2005|lc=on}},: 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),

: 128 bits: (maximum representable value 2¹²⁸ − 1 = 340,282,366,920,938,463,463,374,607,431,768,211,455)

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.