Computer Science • Data Transmission

Parity Check

Simple Parity

Your best in this mode: 0 · 60 seconds · 5 lives

Parity Check — Explanation

When data is sent, a bit can be flipped on the way: a 0 arrives as a 1, or a 1 as a 0. A parity bit is one extra bit added to each group of bits, so the receiver can check whether one has changed.

The receiver counts the 1s again. If the count no longer matches the rule, at least one bit has changed. Parity can't tell which bit changed, and if two bits flip, the count matches again and the error goes unnoticed.

Simple Parity

You're given 7 data bits and the rule (even or odd). Choose the parity bit, 0 or 1, that makes the count of 1s fit the rule. A right answer scores 10 points and adds 3 seconds; a wrong one costs a life and 5 seconds.

Example, even parity: 1011001 has four 1s, which is already even, so the parity bit is 0. With odd parity it would be 1.

Parity Block

A parity block (a 2D parity check) arranges the data in rows. Each row has a parity bit at its end (the last column), each column has one at its foot (the last row), and the bit in the corner is the parity bit for the parity bits. Check every row and every column against the rule:

A right decision scores 25 points and adds 5 seconds; a wrong one costs a life and 8 seconds. After each answer, a ✓ or ✗ beside every row and under every column shows which passed.

You start with 60 seconds and 5 lives. The game ends when either runs out.

Objective: explain how a parity bit (even or odd) detects an error in transmission, work out a parity bit, and use a parity block to find and correct a single flipped bit (for example, Cambridge IGCSE Computer Science 0478, 2.2 methods of error detection).

Where this fits

  • AQA: AQA A Level Computer Science (7517) Goes beyond AQA A Level Computer Science (7517): Parity blocks (finding and fixing the flipped bit) go beyond AQA's parity bits.
  • Cambridge: Cambridge IGCSE Computer Science (0478); Cambridge A Level Computer Science (9618); Cambridge AS Level Computer Science (9618)

Parity Check — Key Terms

Key concepts in English, with te reo Māori, Chinese (Simplified) and Korean.

EnglishTe reo Māori中文（简体）한국어What it means on this page
Parity bitmoka pūrite校验位패리티 비트An extra bit added to a binary code to ensure the total number of 1s is even or odd.
Even parityno attested term偶校验짝수 패리티A system where the parity bit is chosen so that the total number of 1-bits is even.
Odd parityno attested term奇校验홀수 패리티A system where the parity bit is chosen so that the total number of 1-bits is odd.
Parity blockno attested term校验块패리티 블록A 2D array of bits with parity bits calculated for every row and column.
Error detectionno attested term错误检测오류 검출The ability to identify that a data corruption error has occurred during transmission.
Error correctionno attested term错误纠正오류 정정The ability to locate and reverse a corrupted bit back to its original state.

On the te reo Māori column. Terms marked as gaps have no attested equivalent in the sources checked — Karaitiana Taiuru's Dictionary of Māori Computer and Social Media Terms, Paekupu, the Reserve Bank's te reo financial glossary, NZQA and Te Aka. No coinage is printed as though it were established; where a class needs one, commission it from Te Taura Whiri i te Reo Māori and credit the translator. Te reo Māori is not italicised and takes no plural "s".