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Ready to begin
Press Next Step to start executing the code line by line.
algorithm.py
Trace Table 0 rows
numberremaindertotalOutput
Rows will appear as code executes…
Variable Watch
NUM —
number undef
remainder undef
total undef
✓ Complete — output is 12
0 / 0
Q = NOT S AND T means (NOT S) AND T — the NOT applies only to S, not the whole expression. Derive S and T by spotting patterns in A, B, C. Then compute Q row by row.
Expression for S
? — click Reveal
Expression for T
? — click Reveal
Given: Q
NOT S AND T
0 / 8 revealed
ABC ST Q = NOT S AND T
⚠ Bracket trap: NOT S AND T = (NOT S) AND T. If S=1 then NOT S = 0, so Q = 0 regardless of T. If S=0 then Q simply equals T.
Mark Scheme — 3 marks
✓1 mark: S = A AND C (correct logical expression)
✓1 mark: T = B OR C (correct logical expression)
✓1 mark: All 8 Q values correct
✗Common error: writing NOT(S AND T) instead of (NOT S) AND T
▶
Ready — target: 78
Array: [11, 22, 33, 44, 55, 66, 77, 88, 99, 100, 101]. Press Next Step to begin.
Array Visualiser — yellow = mid-point blue = search range grey = discarded
✓ Complete — 78 not found
0 / 4
Start index End index Calculation of mid-point Found Y or N Discard lower, higher or none
Click Next Step to walk through the binary search. The array is sorted so we can halve the search space each time.
⚠ Mid-point rule: Always write the full calculation (start + end) // 2 — the mark scheme awards the working, not just the result. Integer division floors the result: (6+7)//2 = 6, not 6.5.
Mark Scheme — 6 marks
✓1 mark per correct row (4 rows needed)
✓Mid-point calculation must show the arithmetic, not just the result
✓All Found values must be N (78 is not in the array)
✓Final Discard = "none" — search exhausted, start = end
✗Common error: writing only the result of (start+end)//2, not the full sum
✗Common error: writing "lower" or "higher" on the final row instead of "none"