This exam tips covers Exam Tips - Logic Gates within Logic Gates for GCSE Computer Science. Revise Logic Gates in 3.4 Computer Systems for GCSE Computer Science with 16 exam-style questions and 20 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 8 of 9 in this topic. Treat this as a marking guide for what examiners are looking for, not just a fact list.
Exam Tips - Logic Gates
Drawing gate symbols:
- AND gate: Draw a D-shape (flat back, curved front)
- OR gate: Draw a pointed shape (curved back, pointed front)
- NOT gate: Draw a triangle with a small circle (bubble) at the output
- The bubble ALWAYS means NOT (inversion)
Common exam mistakes to avoid:
- Forgetting that AND requires ALL inputs to be 1 - not just one!
- Confusing AND and OR symbols - remember AND is D-shaped, OR is pointed
- Missing the NOT bubble - it's essential for showing inversion
- Wrong truth table: AND has only ONE 1 (bottom row), OR has only ONE 0 (top row)
Quick truth table memory tricks:
- AND: Think "strict gate" - only 1,1 passes through → gives 1
- OR: Think "generous gate" - only 0,0 blocks → gives 0
- NOT: Think "flip gate" - whatever goes in, opposite comes out
Practice questions for Logic Gates
An AND gate has inputs A=1 and B=0. What is the output?
Complete the truth table for an OR gate with two inputs A and B. | A | B | Output | |---|---|--------| | 0 | 0 | | | 0 | 1 | | | 1 | 0 | | | 1 | 1 | |