Editing Logic error

{{Short description|A bug in a program that causes it to operate incorrectly, but not to terminate abnormally}}
{{for|an error in logical reasoning|logical fallacy}}
{{More citations needed|date=March 2025}}
In [[computer programming]], a '''logic error'''  is a [[Software bug|bug]] in a program that causes it to operate incorrectly, but not to terminate abnormally (or [[crash (computing)|crash]]).<ref>{{cite book |last1=Breedlove |first1=Todd W. |last2=Albert |first2=Randal L. |title=C++: An Active Learning Approach |date=22 October 2010 |publisher=Jones & Bartlett Publishers |isbn=978-1-4496-1283-2 |page=44 |url=https://books.google.com/books?id=FgnnQ8Gqx1wC&pg=PA44 |access-date=20 March 2025 |language=en}}</ref> A logic error produces unintended or undesired output or other behaviour, although it may not immediately be recognized as such.

Logic errors occur in both [[Compiler|compiled]] and [[Interpreter (computing)|interpreted]] languages. Unlike a program with a [[syntax error]], a program with a logic error is a valid program in the language, though it does not behave as intended. Often the only clue to the existence of logic errors is the production of wrong solutions, though [[Static program analysis|static analysis]] may sometimes spot them.

==Debugging logic errors==

One of the ways to find this type of error is to put out the program's [[Variable (programming)|variables]] to a file or on the screen in order to determine the error's location in code. Although this will not work in all cases, for example when calling the wrong [[subroutine]], it is the easiest way to find the problem if the program uses the incorrect results of a bad [[Algorithm|mathematical calculation]].

==Examples==

This example function in [[C (programming language)|C]] to calculate the [[Arithmetic mean|average]] of two numbers contains a logic error. It is missing parentheses in the calculation, so it compiles and runs but does not give the expected answer due to [[Operator precedence in C|operator precedence]] (division is evaluated before addition).
<syntaxhighlight lang="c">
float average(float a, float b)
{
    return a + b / 2;  // should be (a + b) / 2
}
</syntaxhighlight>

==See also==

*[[Syntax error]]
*[[Off-by-one error]]

==References==
{{Reflist}}

[[Category:Computer errors]]
[[Category:Programming language theory]]


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[[bg:Логическа грешка]]
[[de:Logischer Fehler]]