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Flip to reveal answersWhat is a logic gate?
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All 5 Flashcards — Logic gates
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Question
What is a logic gate?
Answer
A component that takes one or two bits in and gives one bit out, always the same way for the same inputs. Gates wired together are what a CPU is physically built from.
Question
When does each basic gate output 1?
Answer
AND: only when both inputs are 1. OR: when at least one input is 1. NOT: when the single input is 0. XOR: when the two inputs are different.
Question
What does a circle on a gate's output mean?
Answer
Invert the output. AND with a circle is NAND, OR with a circle is NOR, XOR with a circle is XNOR — each is the original table with every output flipped.
Question
What is the difference between OR and XOR?
Answer
When both inputs are 1, OR gives 1 but XOR gives 0. XOR means the inputs are different, so it rules out the both-on case. A rule saying 'one or the other but not both' is XOR.
Question
Give a real use for AND and for OR.
Answer
AND: a microwave runs only if the door is closed and the timer is running — the rule says 'both'. OR: a car alarm sounds if any one of several doors opens — the rule says 'any'.
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Topic 1.2 hub
Data representation and logic
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Computer Science exam skills
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