Summary
When data is transmitted from a source to a destination, errors can occur due to factors like electrical interference or packet loss. Error detection methods help identify these errors to ensure data integrity.
- Parity Check — A method that involves adding a parity bit to data to ensure the number of 1s is even or odd. Example: If using even parity, the data 0110 would have a parity bit added to make it 01101.
- Checksum — A value calculated from a data set that is sent along with the data to verify integrity. Example: A checksum is calculated and appended to data; if recalculated checksum matches at the destination, data is error-free.
- Echo Check — A method where data is sent back to the sender to verify if it matches the original data. Example: Data is sent from sender to receiver and then back to sender to check for errors.
Exam Tips
Key Definitions to Remember
- Parity Check
- Checksum
- Echo Check
Common Confusions
- Parity checks cannot locate the exact position of an error.
- Echo checks do not identify which stage the error occurred.
Typical Exam Questions
- What is a parity check? A method of error detection using parity bits to ensure even or odd numbers of 1s.
- How does a checksum work? It calculates a value from data and compares it at the destination to check for errors.
- What is the purpose of an echo check? To verify data integrity by sending it back to the sender.
What Examiners Usually Test
- Understanding of different error detection methods
- Ability to explain how each method works