Integer overflow: Difference between revisions

Revision as of 03:04, 22 November 2007

Revision as of 09:25, 2 December 2007

Line 4:

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]], maximum representable value 2³² - 1 = 4,294,967,295),

: 64 bits (maximum representable value 2⁶⁴ - 1 = 18,446,744,073,709,551,615),

: 128 bits (maximum representable value approx. 10³⁸ — actually, 2¹²⁸ - 1 = 340,282,366,920,938,463,463,374,607,431,768,211,456)

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.