Which term is described by 'number to verify entry'?

• A. Echo check
• B. Check digit
• C. Parity check
• D. Checksum

Answer: (A)

A check digit is a number added to a code that is calculated from the rest of the digits to help verify entry. The idea is simple: when the full number is entered, the system recomputes the check digit from the data and checks it against the attached digit. If they don’t match, a mistake in typing or transcription is detected. This makes check digits a direct way to catch common input errors for codes like identification numbers, credit card numbers, or ISBNs.

Other terms describe different error-detection ideas. A parity check uses a single parity bit to detect bit errors in data, not a specific decimal digit attached to a number. A checksum covers larger blocks of data to detect corruption in transmission or storage, not a single entry. Echo check isn’t a standard term used for verifying a single entered number. So the phrase describes the check digit concept.