A parity bit adds a simple consistency check to a group of data bits. Even parity makes the total number of ones even; odd parity makes it odd. A receiver recomputes the parity to detect a changed relationship between the data and check bit.
Worked example
Data 1011 contains three ones. Its even-parity bit must be 1, making four ones in total. If one transmitted data bit changes, the received group has odd parity and the receiver flags an error.
What to watch for
Parity detects any odd number of bit flips. Two flipped bits can preserve parity, and one parity bit cannot identify which bit was wrong.
Try it yourself
Find the odd-parity bit for data 1100.
Answer: The data has two ones. Add parity bit 1 to make three ones, which is odd.
How to study this topic
Treat a code as a mapping with an explicit convention. Write the input, encoded bits and decoded result side by side. For error-checking examples, distinguish detecting an error from locating and correcting it.
Explore related programmes
These recorded programmes are upcoming. This article is general educational content, not a syllabus or course sample.
Digital Electronics