The full adder adds the Kth bits of two numbers to the
Answer: C
Correct answer: carry from ( K - 1 )TH bit
A full adder at bit position k adds the two operand bits of that position together with the carry produced by position \(k-1\). It is that third input that distinguishes it from a half adder.
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A 2-input gate that can be used to pass a digital waveform unchanged at certain times and inverted at other times is a(n) ________.
Answer: D
Correct answer: XOR gate
Holding one XOR input at 0 passes the other input unchanged, since \( 0\oplus X = X \); holding it at 1 inverts it, since \( 1\oplus X = X' \). That makes the XOR a controlled inverter, which no other two-input gate provides.
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The basic types of programmable arrays are made up of ________.
Answer: D
Correct answer: AND gates and OR gates
Programmable arrays implement sum-of-products expressions, so they consist of an AND plane forming the product terms and an OR plane summing them. Whether one plane, the other, or both are programmable is what distinguishes PROM, PAL and PLA.
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An OR array is programmed by blowing fuses to eliminate selected variables from the output functions.
Answer: A
Correct answer: True
In a programmable OR array each product term reaches the output through a fuse, and blowing a fuse removes that term from the function, leaving only the terms wanted.
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A combinational logic circuit which generates a particular binary word or number is
Answer: A
Correct answer: Encoder
An encoder takes an active input line and produces the binary code that identifies it, so it is the circuit that generates a binary word. A decoder performs the inverse operation: it takes the binary word and activates the one output line it names.
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The output of a NOT gate is HIGH when ________.
Answer: A
Correct answer: the input is LOW
A NOT gate produces the complement of its input, so its output is HIGH exactly when the input is LOW. The presence of supply power is a precondition for the gate working at all, not a logical input.
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Logically, the output of a NOR gate would have the same Boolean expression as a(n):
Answer: B
Correct answer: OR gate immediately followed by an inverter
NOR means NOT-OR: \( (A+B)' \). Inverting the output of an OR gate produces exactly that expression.
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Good troubleshooting is done by looking at the input signal and how it interacts with the circuits.
Answer: B
Correct answer: False
Troubleshooting works from the output backwards: the output tells you whether the circuit is doing what it should, and the inputs are then checked to find why not. Watching the input alone shows nothing about the fault.
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If a signal passing through a gate is inhibited by sending a LOW into one of the inputs, and the output is HIGH, the gate is a(n):
Answer: B
Correct answer: NAND
Holding one input of an AND or NAND gate LOW forces the AND function to 0, which blocks the signal on the other input. If the output is then HIGH, the gate must be inverting the blocked 0 - so it is a NAND.
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When used with an IC, what does the term "QUAD" indicate?
Answer: B
Correct answer: 4 circuits
The prefixes count the independent gates in the package: dual two, triple three, quad four, hex six. A quad two-input NAND, the 7400, holds four separate gates.
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