IGCSE Computer Science Paper 2 Definitions Worksheet: 7c Pseudocode and Flowcharts (Modules 232–241)
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Key terms
Write what each term means, in your own words.
1
Explaining a flowchart
2
error in an algorithm
3
Total ← 0
4
ENDIF NEXT ENDWHILE UNTIL
5
Age >= 18
6
Mark < 0 OR Mark > 100
7
off-by-one error
8
infinite loop
9
wrong loop type
Answer Key
IGCSE Computer Science Paper 2 · Modules 232–241 · Student wording will vary for definitions
1Explaining a flowchart — Follow the flow lines from Start, say what each symbol does and what each decision tests (Yes and No paths), then state the overall purpose.
2error in an algorithm — A mistake that breaks pseudocode rules or gives wrong results. Find it by reading the code, then trace it with test values and compare the actual output with the expected output.
3Total ← 0 — Use ← to store a value, so write Total ← 0, not Total = 0. Use = only to compare, as in IF Score = 5, not IF Score ← 5. Swapping them is an error.
4ENDIF NEXT ENDWHILE UNTIL — Closing keywords that end IF, FOR, WHILE and REPEAT. Each one must match its opening statement. A missing or mismatched closing keyword is an error.
5Age >= 18 — Using > instead of >= (or < instead of <=) is a logic error: the boundary value, such as Age 18, is wrongly rejected. Test the boundary value, then correct the operator.
6Mark < 0 OR Mark > 100 — Use OR, not AND, to catch an invalid mark. A mark cannot be below 0 and above 100 at once, so AND is never TRUE. OR is TRUE when either part is TRUE.
7off-by-one error — A FOR loop with the wrong start or end value runs one time too many or too few, e.g. TO 9 instead of TO 10, or starting at 0 for a 1-based array. Check the bounds with a trace table.
8infinite loop — A loop that never ends because nothing in the body changes the tested variable, or the condition can never reach its exit value.
9wrong loop type — Using REPEAT when the body must sometimes not run, or WHILE when it must run at least once. REPEAT always runs once; WHILE may run zero times.