Error Detection Simulator
Explore four error detection methods interactively: parity bits, majority voting, checksums, and check digits. Matches AQA A Level CS (7517) specification §4.5.5.3.
📖 Learn Step-by-StepClick data bits to toggle them. The parity bit is calculated automatically. Use “Introduce Error” to flip a bit during transmission.
Data bits (click to toggle)
Introduce a single-bit error
Working
- Data bits: 01101001
- Count of 1s in data: 4
- Even parity: total 1s (including parity bit) must be even → parity bit = 0
- Transmitted: 011010010
Error Detection Practice Questions
Even parity bit
Data bits:
Parity type: even
What is the parity bit?
Majority voting
Apply majority voting to each group:
Checksum calculation
Data bytes:
Calculate the checksum byte (mod 256):
ISBN-13 check digit
Given digits:
Calculate the check digit:
Odd parity bit
Data bits:
Parity type: odd
What is the parity bit?
Quick reference — error detection methods
Parity bits
An extra bit is appended so the total number of 1s is even (even parity) or odd (odd parity). Detects single-bit errors but not two-bit errors.
Majority voting
Each bit is transmitted an odd number of times (e.g. 3). The receiver takes the majority value. Can correct errors as long as fewer than half the copies are corrupted.
Checksums
All data bytes are summed and a checksum byte is appended so the total (mod 256) equals 0. The receiver re-sums; a non-zero result indicates an error.
Check digits
A digit calculated from the others using a weighted formula — e.g. ISBN-13 alternates weights of 1 and 3. Catches single-digit errors and most transpositions.