03. Validation, verification, check digits and testing - revision mindmap
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Validation versus verification
- Validation: specified acceptable-data rules
- Verification: faithful copying or repeated entry
- Both can accept data from an incorrect original source
- true 72 → typed 27 → range check passes
Choose a validation check
- Presence versus existence
- Type versus range
- Length versus format
- State field → exact rule → reason; preserve textual identifiers
Check-digit calculation
- Identify data digits and check character
- Order, weights, weighted sum, modulus
- Complement and special mappings: 0 or X where specified
- Append or compare; follow the question’s exact scheme
Validation algorithm
- Establish length before indexing
- Check characters before numeric conversion
- Calculate expected check character
- Distinguish invalid format from incorrect check digit
Testing and debugging
- Normal, boundary, erroneous inputs
- Input → expected outcome → test purpose
- Syntax versus runtime versus logic errors
- Trace variables and conditions; handle expected exceptions
Worked example & exam traps
- 12345 with weights 6,5,4,3,2: weighted sum = 50.
- 50 mod 11 = 6; check character = 11 - 6 = 5 → 123455.
- Marks 0–100: 0 and 100 accepted; -1 and 101 rejected.
- Avoid: check digit corrects errors or detects every error
Sources and reading
This map condenses Chapter 03 and its source trail. Use the self-learning reading guide for the corresponding VJC pages and A notes. It does not add topics to the stated promo scope.