| OCR |
GCSE (9-1) Computer Science
Mark Scheme
J277/02: Unit 2.4 Boolean Logic
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| Question | Answer | Marks | Guidance |
|---|---|---|---|
| 1 |
(i) 0 (1) (ii) 0 (1) (iii) 1 (1) |
3 |
Tests familiarity with ¬ (NOT), ∧ (AND), and ∨ (OR).
|
| 2 |
P = ¬(A ∧ B)
|
2 |
1 mark for correct symbols (¬ and ∧).
1 mark for correct placement of brackets/grouping.
|
| 3 |
1 mark for every correct row: 0 0 -> 0 0 1 -> 1 1 0 -> 0 1 1 -> 0 |
4 |
Ghost Topic: The student must "trace" the circuit mentally. The logic is (NOT A) AND B.
|
| 4 | 4 |
1 mark for Inputs S, T, O correctly labeled.
1 mark for OR gate combining T and O.
1 mark for AND gate combining S and the result.
1 mark for correct shapes.
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| 5 |
(A OR B) Column: 0, 0, 1, 1, 1, 1, 1, 1 (1) Q Column Rows 1-4: 0, 0, 0, 1 (1) Q Column Rows 5-8: 0, 1, 0, 1 (1) (2 marks for fully correct table with no errors) |
5 |
NO FOLLOW THROUGH: If the intermediate column is wrong, final marks cannot be awarded.
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| 6 | A triangle without a circle represents a Buffer (1), which passes the signal unchanged / does not invert the signal (1). | 2 |
Targets feedback regarding "pointed AND gates" and "triangles without circles".
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| 7 |
(a) AND First: (0 AND 1) = 0 -> (0 OR 1) = 1 (1) (b) OR First: (1 OR 1) = 1 -> (0 AND 1) = 0 (1) (c) Precedence: NOT, then AND, then OR. (1) |
3 |
Order of operations (BODMAS for Logic) is a Ghost Topic discriminator.
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