Error detection and correction
Cambridge IGCSE Computer Science (0478) · Unit 2: Data transmission · 9 flashcards
Error detection and correction is topic 2.2 in the Cambridge IGCSE Computer Science (0478) syllabus , positioned in Unit 2 — Data transmission , alongside Types and methods of data transmission and Encryption. In one line: Parity refers to a method used to detect errors during data transmission. It involves adding an extra bit (the parity bit) to a string of binary data to indicate whether the number of 1s in the string is even or odd.
This topic is examined in Paper 1 (computer systems theory) and Paper 2 (algorithms, programming and logic).
The deck below contains 9 flashcards — 5 definitions, 2 key concepts and 1 application card — covering the precise wording mark schemes reward. Use the 5 definition cards to lock down command-word answers (define, state), then move on to the concept and application cards to handle explain, describe and compare questions.
The term 'parity' in the context of data transmission
Parity refers to a method used to detect errors during data transmission. It involves adding an extra bit (the parity bit) to a string of binary data to indicate whether the number of 1s in the string is even or odd.
What the Cambridge 0478 syllabus says
Official 2026-2028 specThese are the exact learning objectives Cambridge sets for this topic. Match the command word (Describe, Explain, State, etc.) in your answer to score full marks.
- Understand Understand the need to check for errors after data transmission and how these errors can occur
- Describe Describe the processes involved in parity check (odd and even), checksum and echo check for detecting errors in data after transmission
- Describe Describe how a check digit is used to detect errors in data entry and identify examples including ISBN and bar codes
- Describe Describe how an automatic repeat query (ARQ) can be used to establish that data is received without error
Define the term 'parity' in the context of data transmission.
Parity refers to a method used to detect errors during data transmission. It involves adding an extra bit (the parity bit) to a string of binary data to indicate whether the number of 1s in the string is even or odd.
Explain the difference between even and odd parity.
Even parity ensures the total number of 1s (including the parity bit) is even. Odd parity ensures the total number of 1s (including the parity bit) is odd.
Describe how a checksum is used for error detection.
A checksum is a calculated value that summarizes the contents of a block of data. The sender calculates the checksum and sends it along with the data. The receiver recalculates the checksum, and if the two values don't match, an error is detected.
Explain the purpose of a check digit and provide an example.
A check digit is a single digit added to a number (e.g., an account number or ISBN) that is calculated based on the other digits. It's used to detect errors made when manually entering the number.
Outline the process of an echo check for error detection.
In an echo check, the receiver sends back the data it received to the sender. The sender then compares the sent data with the received data. If they match, the transmission is considered error-free; otherwise, an error has occurred.
Describe what ARQ stands for and how it works for error correction.
ARQ stands for Automatic Repeat reQuest. It is an error-control method where the receiver automatically requests retransmission of a data packet if it detects an error, ensuring reliable data delivery.
Give a scenario where using error correction is more appropriate than just error detection.
Error correction is more appropriate in scenarios where retransmission is impractical or costly, such as data transmission from satellites or deep space probes, as re-requesting lost data packets causes major time delays.
A data packet '1100101' is sent using even parity. What parity bit would be added to the end of the data?
The parity bit would be '0' because the original data already has an even number of 1s (four). Adding '0' keeps the total count of 1s even.
Explain why parity checks can only detect, but not correct, errors.
Parity checks can detect errors by identifying if the number of 1s is inconsistent with the defined parity (even or odd). However, they cannot identify which bit is incorrect, making it impossible to correct the error without retransmission.
Key Questions: Error detection and correction
Define the term 'parity' in the context of data transmission.
Parity refers to a method used to detect errors during data transmission. It involves adding an extra bit (the parity bit) to a string of binary data to indicate whether the number of 1s in the string is even or odd.
Describe how a checksum is used for error detection.
A checksum is a calculated value that summarizes the contents of a block of data. The sender calculates the checksum and sends it along with the data. The receiver recalculates the checksum, and if the two values don't match, an error is detected.
Explain the purpose of a check digit and provide an example.
A check digit is a single digit added to a number (e.g., an account number or ISBN) that is calculated based on the other digits. It's used to detect errors made when manually entering the number.
Outline the process of an echo check for error detection.
In an echo check, the receiver sends back the data it received to the sender. The sender then compares the sent data with the received data. If they match, the transmission is considered error-free; otherwise, an error has occurred.
Describe what ARQ stands for and how it works for error correction.
ARQ stands for Automatic Repeat reQuest. It is an error-control method where the receiver automatically requests retransmission of a data packet if it detects an error, ensuring reliable data delivery.
More topics in Unit 2 — Data transmission
Error detection and correction sits alongside these Computer Science decks in the same syllabus unit. Each uses the same spaced-repetition system, so progress in one informs the next.
Cambridge syllabus keywords to use in your answers
These are the official Cambridge 0478 terms tagged to this section. Mark schemes credit responses that use the exact term — weave them into your answers verbatim rather than paraphrasing.
Key terms covered in this Error detection and correction deck
Every term below is defined in the flashcards above. Use the list as a quick recall test before your exam — if you can't define one of these in your own words, flip back to that card.
How to study this Error detection and correction deck
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