Parity checks

Parity checks

Parity bits and parity blocks, including finding and fixing a flipped bit.

Transcript

Parity checking counts the number of one bits in a byte. The parity is either even, or odd.

One bit, usually the left most, is reserved as the parity bit. For even parity, it is set so the total number of ones is even.

Four ones is already even, so the parity bit is zero. With three ones, the parity bit must be one.

A parity block adds a parity byte after a block of bytes. Every column gets a parity bit too.

If one bit flips, one row and one column fail. The wrong bit sits where they cross, so it can be corrected.

A parity bit for each byte, a parity byte for each block. Errors found, and even fixed.

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