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Flip to reveal answersHow many rows does a truth table need?
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All 5 Flashcards — Truth tables
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Question
How many rows does a truth table need?
Answer
Two to the power of the number of inputs: 2 inputs give 4 rows, 3 give 8, 4 give 16. The rows are counted upwards in binary, so no combination is missed.
Question
How do you build a truth table from a logic circuit?
Answer
Give every gate its own column and work left to right. Fill the input columns first, then each gate column using only its own inputs, then combine those for the final output.
Question
How do you write a circuit as a Boolean expression?
Answer
Use · for AND, + for OR and NOT for inversion. A circuit where an AND of A and B feeds an OR alongside an inverted C is X = (A·B) + NOT C.
Question
How does a Karnaugh map simplify an expression?
Answer
The outputs are arranged so neighbouring squares differ by one variable only. Circle the largest groups of adjacent 1s in sizes 1, 2, 4 or 8; for each circle keep the variables that stay constant and drop those that change.
Question
Why simplify a Boolean expression?
Answer
A shorter expression is a circuit built from fewer gates — less hardware, less power consumption and fewer things to fail. For example A·B + A·(NOT B) simplifies to just A, needing no gates at all.
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Topic 1.2 hub
Data representation and logic
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