Verify entered data with visual and double-entry checks
Compare input with a source or require independent re-entry to reduce transcription mistakes.
Section 7 · Algorithm design and problem-solving
This sequence follows Cambridge IGCSE Computer Science 0478, 2026–2028 syllabus Version 6. It covers subject content Topic 7 only. The separately published 2029–2031 syllabus is not mapped here. Practice is original, self-checked and does not award an official Cambridge grade. Full timed papers and human subject-teacher review remain outstanding.
Before you begin
- No programming language is required. Be comfortable with place value and multiplication; each lesson introduces the computer-science notation it uses.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which method compares typed data with its original document?
What you will learn
- Explain visual verification
- Explain double-entry verification
- Distinguish verification from validation
Verification checks fidelity to a source
Visual verification asks a person to compare entered data with the original source, such as checking a typed address against a form. It can catch differences but depends on careful attention.
Apply and check the rule
Double-entry verification asks for the same data to be entered twice, often by different people or in separate steps. The entries are compared; a mismatch is flagged. Verification checks that the data matches the source, while validation checks that it meets rules.
Pause and explain
A program checks that an entered age is 0–120. Is that verification?
Worked example
A clerk types a phone number from a form and then compares it with the form. Is that validation or verification?
Show the worked solution
- The source is the completed form.
- The clerk compares the entered number with that source.
- This is visual verification.
Answer Visual verification.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Describe how double-entry verification can detect a mistyped bank account number.
Give me a hint
Explain the two entries and comparison.
Compare my reasoning
- The number is entered twice independently.
- The system compares the entries.
- If they differ, the user must review them against the source.
Enter the account number twice, compare the entries, and flag a mismatch for correction against the original details.
Look for these in your work
- Two entries
- Comparison
- Mismatch action
A date passes the required format check. What separate verification could confirm it matches the source form?
Give me a hint
Use the original record, not just the date pattern.
Compare my reasoning
- The format check confirms the date shape.
- Compare each entered digit with the source form.
- Correct any mismatch.
Visually compare the entered date with the source or use double entry and review any difference.
Look for these in your work
- Validation result
- Source comparison
- Correction
A form has a valid-looking address that was copied from the wrong customer record. Explain why both validation and verification may still need the original source.
Give me a hint
A plausible value can still belong to another person.
Compare my reasoning
- Validation can confirm presence, type or format.
- Verification compares data with the source record.
- Staff must also ensure the selected source belongs to the intended customer.
The address can pass validation yet still be assigned to the wrong customer. Verify it against the correct source record and confirm the record selection.
Look for these in your work
- Validation scope
- Verification role
- Correct source
Common mistakes
- Calling an in-range value verified
- Assuming retyping guarantees the original source was accurate
What can you explain now?
What does double-entry verification compare?
Compare with the explanation
Two independent entries of the same data
A mismatch indicates that the entries need review against the source.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
How do visual and double-entry verification differ from validation?
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.