Parity Check: Bits & Blocks

Section

A single parity bit can tell you a bit stream has an error, but not which bit is wrong. Arrange bits in a block — with a parity bit on every row and every column — and one flipped bit can be pinpointed and repaired. Two or more flips can be detected but not safely trusted, so the block must be rejected instead.

Simple parity

Score: 0 / 0

A 7-bit chunk arrives. Choose the parity bit (0 or 1) that must be appended to satisfy the required parity.

Required parity: EVEN

Your parity bit:

Method reference

Simple (single) parity — one extra bit is appended to a chunk of data so that the total count of 1-bits matches the required parity:

Required parity	What the parity bit must make true
Even	The total number of 1-bits (data + parity bit) is even.
Odd	The total number of 1-bits (data + parity bit) is odd.

A single parity bit can tell you that a chunk has been corrupted (if the count no longer matches), but never which bit — and it misses any even number of flipped bits entirely.

Parity block (two-dimensional parity) — arrange data as a 7×7 grid, add a parity bit to the end of every row, and a parity bit under every column (including a corner bit, which is the parity of the parity bits). Checking every row and every column tells you far more:

Failing checks	What it means
No rows, no columns fail	The block is internally consistent — accept it.
Exactly one row and one column fail	Their intersection is the single flipped bit — repair it by clicking that cell (which flips it back).
Any other pattern of failing rows/columns	Two or more bits have been corrupted and cannot be safely pinpointed — reject the block.

Two-dimensional parity is much stronger than single parity, but it is not perfect: certain rare 3-bit error patterns (three corners of a rectangle within the grid) can still look exactly like a single-bit error and point to the wrong cell. This is a genuine, known limitation of the method, not a flaw in this tool.

Key terms · Ngā kupu matua

English	Māori	What it means

Māori translations are only shown where a term is attested in Te Aka Māori Dictionary (maoridictionary.co.nz). Where no widely-used term could be verified, that is shown honestly rather than guessed at.