halting problem
halting problem A decision problem that was discovered and investigated by Alan Turing in 1936. Suppose M is a Turing machine and let x be an input to M. If we start the machine running two things might happen: after a finite number of steps the machine might stop, or it might run on forever. Is there any way to test, given M and x, which of these two situations will occur? This is the halting problem. In fact there is no algorithm or effective procedure that, given any Turing machine and its input, will decide whether or not the calculation ever terminates.
Assuming the Church–Turing thesis, the halting problem is algorithmically unsolvable or undecidable. It is one example of many unsolvable problems in mathematics and computer science. It has profound practical implications: if it were solvable it would be possible to write a program tester that, given (say) any Pascal program and its input, would print “yes” if the program terminated after a finite number of steps and “no” if it did not. For any programming language that can define the recursive functions, no such termination program exists.
Cite this article
Pick a style below, and copy the text for your bibliography.

MLA

Chicago

APA
"halting problem." A Dictionary of Computing. . Encyclopedia.com. 16 Oct. 2018 <http://www.encyclopedia.com>.
"halting problem." A Dictionary of Computing. . Encyclopedia.com. (October 16, 2018). http://www.encyclopedia.com/computing/dictionariesthesaurusespicturesandpressreleases/haltingproblem
"halting problem." A Dictionary of Computing. . Retrieved October 16, 2018 from Encyclopedia.com: http://www.encyclopedia.com/computing/dictionariesthesaurusespicturesandpressreleases/haltingproblem
Citation styles
Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).
Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.
Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the mostrecent information available at these sites:
Modern Language Association
The Chicago Manual of Style
http://www.chicagomanualofstyle.org/tools_citationguide.html
American Psychological Association
Notes:
 Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
 In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.