Skip to main content

cyclic redundancy check

cyclic redundancy check (cyclic redundancy code; CRC) The most widely used error-detecting code. Extra digits are appended to each block in order to provide a means of checking the data for errors that may have occurred, say, during transmission or due to recording and readback processes: the digits are calculated from the contents of the block on input, and recalculated by the receiver or during readback.

A CRC is a type of polynomial code. In principle, each block, regarded as a polynomial A, is multiplied in the encoder by a generating polynomial G to form AG. This is affected during transmission or recording by the addition of an error polynomial E, to form AG + E

In the decoder this is divided by the same generating polynomial G to give a residue, which is examined to see if it is zero. If it is nonzero, an error is recorded and appropriate action is taken (see backward error correction). In practice, the code is made systematic by encoding A as Axr + R

where r is the degree of G and R is the residue on dividing Axr by G. In either case, the only errors that escape detection are those for which E has G as a factor: the system designer chooses G to make this as unlikely as possible. Usually, in the binary case, G is the product of (x + 1) and a primitive factor of suitable degree.

A binary code for which G = x + 1

is known as a simple parity check (or simple parity code). When applied across each character of, say, a magnetic tape record, this is called a horizontal check; when applied along each track of the record, it is called a vertical check. Simple checks (horizontal and/or vertical) are much less secure against burst errors than a nontrivial CRC with G of degree (typically) 16. The term longitudinal redundancy check (LRC) usually refers to a nontrivial CRC, but may apply to a simple vertical check.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"cyclic redundancy check." A Dictionary of Computing. . Encyclopedia.com. 16 Aug. 2018 <http://www.encyclopedia.com>.

"cyclic redundancy check." A Dictionary of Computing. . Encyclopedia.com. (August 16, 2018). http://www.encyclopedia.com/computing/dictionaries-thesauruses-pictures-and-press-releases/cyclic-redundancy-check

"cyclic redundancy check." A Dictionary of Computing. . Retrieved August 16, 2018 from Encyclopedia.com: http://www.encyclopedia.com/computing/dictionaries-thesauruses-pictures-and-press-releases/cyclic-redundancy-check

Learn more about citation styles

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 most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

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.