Computer Science - 0478 CIE

Methods Of Error Detection

Gbogbo ọrọ náà

When data travels down a cable or through the air, it can be damaged on the way. Electrical interference can flip a 1 to a 0, lose a bit entirely, or add one that should not be there. A single flipped bit can ruin a bank transfer or a downloaded file, so computers need ways to notice that something has gone wrong.

In this lesson you will meet the main error detection methods on the syllabus: the parity check, the checksum, the echo check, the check digit and the automatic repeat query. You will learn how each one works, what kind of error it catches, and how a system can ask for the data to be sent again when an error is found.

Ebumnobi

  1. 1 Understand the need to check for errors after data transmission and how these errors can occur
  2. 2 Describe the processes involved in each of the following error detection methods for detecting errors in data after transmission: parity check (odd and even), checksum and echo check
  3. 3 Describe how a check digit is used to detect errors in data entry and identify examples of when a check digit is used, including international standard book numbers (ISBN) and bar codes
  4. 4 Describe how an automatic repeat query (ARQ) can be used to establish that data is received without error

Nkuzi Olu

Gee ntị na nkuzi a na ngwa

Maapụ uche

E seela isiokwu a ka ị hụ otu echiche si ejikọta.

Mepee maapụ uche na ngwa

Kaadị ncheta

Omume ncheta ngwa ngwa n'ihe a na-anwale n'isiokwu a.

Mee omume kaadị ndị a na ngwa

Akwụkwọ Ọmụmụ

No transmission is perfectly safe. As data moves between devices, interference (sometimes called noise) can change the bits. Three things can go wrong: a bit can be changed (a 1 becomes a 0 or the other way round), data can be lost, or extra data can be gained. Because we cannot always stop these errors, the next best thing is to detect them, so the data can be checked and, if needed, sent again. Every method below is a way of adding or comparing information so the receiver can tell whether the data arrived as it left.

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Nnyocha Ọmụmụ

Ekele diri gi maka imecha ihe karịrị na Methods Of Error Detection. Ugbu a na ị na-enyochakwa isi echiche na echiche ndị dị mkpa, ọ bụ oge iji nwalee ihe ị ma. Ngwa a na-enye ụdị ajụjụ ọmụmụ dị iche iche emebere iji kwado nghọta gị wee nyere gị aka ịmata otú ị ghọtara ihe ndị a kụziri.

Ị ga-ahụ ngwakọta nke ụdị ajụjụ dị iche iche, gụnyere ajụjụ chọrọ ịhọrọ otu n’ime ọtụtụ azịza, ajụjụ chọrọ mkpirisi azịza, na ajụjụ ede ede. A na-arụpụta ajụjụ ọ bụla nke ọma iji nwalee akụkụ dị iche iche nke ihe ọmụma gị na nkà nke ịtụgharị uche.

Jiri akụkụ a nke nyocha ka ohere iji kụziere ihe ị matara banyere isiokwu ahụ ma chọpụta ebe ọ bụla ị nwere ike ịchọ ọmụmụ ihe ọzọ. Ekwela ka nsogbu ọ bụla ị na-eche ihu mee ka ị daa mba; kama, lee ha anya dị ka ohere maka ịzụlite onwe gị na imeziwanye.

  1. An extra bit added to a byte to make the number of 1s odd or even is called a: A. check digit B. parity bit C. checksum D. stop bit Answer: B
  2. Which method detects errors during data entry rather than transmission? A. echo check B. parity check C. check digit D. checksum Answer: C
  3. In a positive acknowledgement ARQ, the sender re-sends a packet when: A. a positive acknowledgement arrives B. no acknowledgement arrives before the timeout C. the checksum matches D. the parity is even Answer: B
  4. A weakness of a single parity check is that it may not detect: A. a single changed bit B. two changed bits in the same byte C. an odd number of 1s D. an even number of 1s Answer: B
  5. Where is a check digit commonly used? A. RAM addressing B. an ISBN on a book C. a logical shift D. virtual memory Answer: B

Rue ajuju ndi a n'ime ngwa ahu

Rue ajuju ndi a n'ime ngwa ahu

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