Editing Arithmetic underflow (section)

{{Short description|Computer programming condition}}
{{Redirect|Underflow|the condition of attempting to read an empty buffer|Buffer underrun}}
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The term '''arithmetic underflow''' (also '''floating-point underflow''', or just '''underflow''') is a condition in a [[computer program]] where the result of a calculation is a number of more precise absolute value than the computer can actually represent in [[Computer memory|memory]] on its [[central processing unit]] (CPU).

Arithmetic underflow can occur when the true result of a [[Floating-point arithmetic|floating-point operation]] is smaller in magnitude (that is, closer to zero) than the smallest value representable as a [[normal number (computing)|normal]] floating-point number in the target [[Data type|datatype]].<ref>{{cite journal |last1=Coonen |first1=Jerome T. |s2cid=206445847 |title=An implementation guide to a proposed standard for floating-point arithmetic |journal=Computer |date=1980 |volume=13 |issue=1 |pages=68–79 |doi=10.1109/mc.1980.1653344}}</ref> Underflow can in part be regarded as negative [[Arithmetic overflow|overflow]] of the [[exponent]] of the floating-point value. For example, if the exponent part can represent values from &minus;128 to 127, then a result with a value less than &minus;128 may cause underflow.

For integers, the term "integer underflow" typically refers to a special kind of [[integer overflow]] or ''integer wraparound'' condition whereby the result of subtraction would result in a value less than the minimum allowed for a given integer type, i.e. the ideal result was closer to negative infinity than the output type's representable value closest to negative infinity.<ref>{{cite web |url=https://cwe.mitre.org/data/definitions/191.html |title=CWE-191: Integer Underflow (Wrap or Wraparound) (3.1) |website=Common Weakness Enumeration}}</ref><ref>{{cite web |url=https://dzone.com/articles/overflow-and-underflow-data |title=Overflow And Underflow of Data Types in Java |website=DZone}}</ref><ref>{{cite web |url=https://medium.com/@taabishm2/integer-overflow-underflow-and-floating-point-imprecision-6ba869a99033 |title=Integer Overflow/Underflow and Floating Point Imprecision |last=Mir |first=Tabish |date=4 April 2017 |website=Medium}}</ref><ref>{{cite web |url=https://www.mozilla.org/en-US/security/advisories/mfsa2015-147/ |title=Integer underflow and buffer overflow processing MP4 metadata in libstagefright |website=Mozilla}}</ref><ref>{{cite web |url=https://developer.apple.com/library/content/documentation/Security/Conceptual/SecureCodingGuide/Articles/BufferOverflows.html#//apple_ref/doc/uid/TP40002577-SW7 |title=Avoiding Buffer Overflows and Underflows |website=Apple Developer}}</ref>