| OCR |
GCSE (9-1) Computer Science
Mark Scheme
J277/02: Unit 2.4 Boolean Logic (Maths & Circuits)
|
| Question | Answer | Marks | Guidance |
|---|---|---|---|
| 1 |
Column ¬A: 1, 1, 0, 0 (1) Column Q: 1, 1, 0, 1 (2 for all correct, 1 for 2/4 correct) |
4 |
Tests ∨ (OR) symbol. If ¬A is wrong, allow follow-through for Q if OR logic is applied correctly to their numbers.
|
| 2 |
A -> 2 (AND) B -> 3 (NOT) C -> 1 (OR) |
3 |
All 3 lines must be correct.
|
| 3 |
Intermediate (A AND B): Last 4 rows: 0, 0, 1, 1 (1) Final P (Rows 1-4): 0, 1, 0, 1 (1) Final P (Rows 5-8): 0, 1, 1, 1 (1) (Award 2 additional marks if table is perfectly correct). |
5 |
CRITICAL: If Intermediate Column is wrong, do not award marks for final column rows that depend on it. (No Follow Through).
|
| 4 |
(i) Row 3 (Input A=1, B=0, A OR B should be 1). (1) (ii) The student calculated NOT(0) to get 1. They lose the mark because the logic gate A OR B was processed incorrectly first. (1) (iii) Correct Output: 0 (1) |
3 |
Because 1 OR 0 is 1, and NOT(1) is 0.
|
| 5 |
(i) NO (1) (ii) The table shows an OR gate (Light on if M OR N is true). The scenario requires an AND gate (Light on ONLY if M AND N are true). (2) |
3 |
Tests ability to read the meaning of the table, not just fill boxes.
|
| 6 |
Row (1, 1, 0): A OR B = 1. Final Output = 0 (1 AND 0). (2) Row (1, 1, 1): A OR B = 1. Final Output = 1 (1 AND 1). (2) |
4 |
Forces student to derive
(A OR B) AND C logic mentally. |