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S3 ICT: Algorithms and Flowcharts (Paper 4: mistake clinic)
S3 ICT: Algorithms and Flowcharts (Paper 4: mistake clinic)
S3 ICT algorithms and flowcharts paper four, mistake clinic: ten questions fixing symbol confusion, step loop counts, linear against binary search comparisons and uninitialised variables.
Direct answers Answers in order: the diamond, the parallelogram, span divided by step plus one, 7, three times, 200 comparisons, 55, five rounds with x equal to 2, about ten comparisons, and an uninitialised variable is unpredictable.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 |
| Suggested time | 20 |
| Difficulty mix | Foundation 3 · Intermediate 3 · Challenge 3 · Error redo 1 |
| Chapter | Chapter: S3 ICT: Algorithms and Flowcharts |
| Level | S3 |
02 Questions (10 items)
- FoundationWhich flowchart symbol is used for a decision?
- FoundationWhich symbol is used for input and output?
- FoundationHow is the number of FOR rounds computed?
- IntermediateAfter x = 5, y = x * 2 and y = y – 3, what is y?
- IntermediateHow many times does FOR i = 3 TO 9 STEP 3 run?
- IntermediateSearching for an absent value among 200 items with linear search, how many comparisons at most?
- ChallengeWith sum = 0 and FOR i = 1 TO 5 adding i times i, what is the final sum?
- ChallengeWith x = 64 and WHILE x > 2 halving x each round, how many rounds run and what is the final x?
- ChallengeIn the worst case, about how many comparisons does binary search use on 1 000 sorted items?
- Error redoA student says an unset sum starts at zero automatically. What is wrong?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | The diamond | The diamond is reserved for decisions and its exits carry yes and no. |
| 2 | The parallelogram | Reading data and printing results both use it, so do not mix it with the diamond. |
| 3 | Upper bound minus lower bound, divided by the step, plus one | Work out the span, divide by the step and add one to get the count. |
| 4 | 7 | Five times two is ten and ten minus three is seven. |
| 5 | Three times | The counter takes three, six and nine. |
| 6 | 200 | An absent value forces a comparison with every one of the two hundred items. |
| 7 | 55 | Adding one, four, nine, sixteen and twenty five gives fifty five. |
| 8 | Five rounds and the final x is 2 | The value falls through 32, 16, 8 and 4 to 2, where the condition fails. |
| 9 | About ten | Halving the range ten times narrows a thousand items to one, since two to the tenth power exceeds it. |
| 10 | An uninitialised variable holds an unpredictable value, so the total is wrong | Initialise with sum = 0 before accumulating, otherwise an unknown old value is added in. |
04 What to do after marking
- After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
- Repeat the same item two days later; move to the next paper only when both attempts are correct.
- Parents only need the answer and note columns; there is no need to explain every item.
An algorithm is a finite and unambiguous list of steps; flowcharts use a diamond for decisions and a parallelogram for input or output, combined through sequence, selection and iteration.Tutor Registration →
Questions and answers are written originally by the TutorZone team and are not taken from any school, publisher or examination authority paper. Every value is checked by computer.