EEE 120 Quiz 5 Requires Respondus LockDown Browser +
Webcam Q&A | Graded A+ | Fall Update 2026-2027
1. Which of the following best describes the primary function of a multiplexer in a digital
system?
A) To convert serial data to parallel data
B) To select one of several input signals and route it to a single output
C) To perform binary addition of two numbers
D) To store multiple bits of data permanently
Correct Answer: To select one of several input signals and route it to a single output
Rationale: A multiplexer is a combinational circuit that selects one of 2^n data inputs based on
n select lines and routes the selected input to a single output. It is commonly used for data
routing and signal selection. It does not perform addition, store data, or convert data formats.
2. What is the primary purpose of a decoder in a digital circuit?
A) To select one of several inputs and route it to an output
B) To convert an n-bit binary input into one of 2^n unique output lines
C) To store data temporarily during computation
D) To perform arithmetic operations on binary numbers
Correct Answer: To convert an n-bit binary input into one of 2^n unique output lines
Rationale: A decoder takes an n-bit binary input and activates exactly one of its 2^n output lines
based on the input value. It is the functional opposite of a multiplexer. It does not store data,
perform arithmetic, or select inputs.
3. Which of the following best describes the primary characteristic of a PROM
(Programmable Read-Only Memory)?
A) Data can be erased with ultraviolet light and reprogrammed
B) Both the inputs and outputs are fixed, and data can only be programmed once
C) It is a volatile memory that loses data when power is removed
D) It has a programmable AND array and a fixed OR array
Correct Answer: Both the inputs and outputs are fixed, and data can only be programmed once
Rationale: A PROM is a type of read-only memory that is programmed once by the user after
manufacturing. The inputs (address lines) and outputs (data lines) are fixed, and once
programmed, the data cannot be changed. It is non-volatile.
, 4. How many select lines are required for a 16-to-1 multiplexer?
A) 2
B) 3
C) 4
D) 5
Correct Answer: 4
Rationale: A multiplexer with 2^n data inputs requires n select lines. For 16 inputs, 2^4 = 16, so
4 select lines are needed.
5. What is the minimum number of 2:1 multiplexers required to build a 16:1 multiplexer?
A) 4
B) 8
C) 15
D) 16
Correct Answer: 15
Rationale: A 16:1 MUX requires 15 2:1 MUXes arranged as a tree: 8 in the first stage, 4 in the
second stage, 2 in the third stage, and 1 in the final stage. The total is 8 + 4 + 2 + 1 = 15.
6. What is the primary function of a look-up table (LUT) in an FPGA?
A) To implement combinational logic functions of its inputs
B) To store program code and constant data
C) To perform arithmetic operations such as addition and subtraction
D) To generate clock signals for the FPGA
Correct Answer: To implement combinational logic functions of its inputs
Rationale: In an FPGA, a LUT is a small memory that can implement any combinational logic
function of its inputs. It is the fundamental building block of FPGA logic. It does not store
program code, perform arithmetic, or generate clocks.
7. Which of the following is a characteristic of a programmable logic array (PLA)?
A) It has a fixed AND array and a programmable OR array
B) It has a programmable AND array and a programmable OR array
C) It has a programmable AND array and a fixed OR array
D) It has no programmable elements and is fixed at manufacture
Correct Answer: It has a programmable AND array and a programmable OR array
, Rationale: A PLA has both a programmable AND array and a programmable OR array, allowing it
to implement complex sum-of-products expressions. A PAL has a programmable AND array and
a fixed OR array.
8. How many output lines does a 3-to-8 decoder have?
A) 3
B) 6
C) 8
D) 16
Correct Answer: 8
Rationale: An n-to-2^n decoder has 2^n output lines. For a 3-to-8 decoder, n=3, so there are
2^3 = 8 output lines.
9. Which of the following can be used to implement an arbitrary Boolean function?
A) Decoder with OR gates
B) Multiplexer
C) PROM
D) All of the above
Correct Answer: All of the above
Rationale: Any Boolean function can be implemented using a decoder with OR gates (sum of
minterms), a multiplexer (MUX), or a PROM. NAND gates are also universal and can implement
any function.
10. What is the primary purpose of a tri-state buffer in a digital system?
A) To perform three-input logic operations
B) To allow an output to be in a high-impedance state, disconnecting it from a shared bus
C) To store three bits of data
D) To generate three-phase clock signals
Correct Answer: To allow an output to be in a high-impedance state, disconnecting it from a
shared bus
Rationale: A tri-state buffer has three output states: high (1), low (0), and high-impedance (Z).
The high-impedance state effectively disconnects the output from a shared bus, allowing
multiple devices to share the same bus.
11. What is the decimal equivalent of the unsigned binary number (1101)₂?
A) 11
B) 12
Webcam Q&A | Graded A+ | Fall Update 2026-2027
1. Which of the following best describes the primary function of a multiplexer in a digital
system?
A) To convert serial data to parallel data
B) To select one of several input signals and route it to a single output
C) To perform binary addition of two numbers
D) To store multiple bits of data permanently
Correct Answer: To select one of several input signals and route it to a single output
Rationale: A multiplexer is a combinational circuit that selects one of 2^n data inputs based on
n select lines and routes the selected input to a single output. It is commonly used for data
routing and signal selection. It does not perform addition, store data, or convert data formats.
2. What is the primary purpose of a decoder in a digital circuit?
A) To select one of several inputs and route it to an output
B) To convert an n-bit binary input into one of 2^n unique output lines
C) To store data temporarily during computation
D) To perform arithmetic operations on binary numbers
Correct Answer: To convert an n-bit binary input into one of 2^n unique output lines
Rationale: A decoder takes an n-bit binary input and activates exactly one of its 2^n output lines
based on the input value. It is the functional opposite of a multiplexer. It does not store data,
perform arithmetic, or select inputs.
3. Which of the following best describes the primary characteristic of a PROM
(Programmable Read-Only Memory)?
A) Data can be erased with ultraviolet light and reprogrammed
B) Both the inputs and outputs are fixed, and data can only be programmed once
C) It is a volatile memory that loses data when power is removed
D) It has a programmable AND array and a fixed OR array
Correct Answer: Both the inputs and outputs are fixed, and data can only be programmed once
Rationale: A PROM is a type of read-only memory that is programmed once by the user after
manufacturing. The inputs (address lines) and outputs (data lines) are fixed, and once
programmed, the data cannot be changed. It is non-volatile.
, 4. How many select lines are required for a 16-to-1 multiplexer?
A) 2
B) 3
C) 4
D) 5
Correct Answer: 4
Rationale: A multiplexer with 2^n data inputs requires n select lines. For 16 inputs, 2^4 = 16, so
4 select lines are needed.
5. What is the minimum number of 2:1 multiplexers required to build a 16:1 multiplexer?
A) 4
B) 8
C) 15
D) 16
Correct Answer: 15
Rationale: A 16:1 MUX requires 15 2:1 MUXes arranged as a tree: 8 in the first stage, 4 in the
second stage, 2 in the third stage, and 1 in the final stage. The total is 8 + 4 + 2 + 1 = 15.
6. What is the primary function of a look-up table (LUT) in an FPGA?
A) To implement combinational logic functions of its inputs
B) To store program code and constant data
C) To perform arithmetic operations such as addition and subtraction
D) To generate clock signals for the FPGA
Correct Answer: To implement combinational logic functions of its inputs
Rationale: In an FPGA, a LUT is a small memory that can implement any combinational logic
function of its inputs. It is the fundamental building block of FPGA logic. It does not store
program code, perform arithmetic, or generate clocks.
7. Which of the following is a characteristic of a programmable logic array (PLA)?
A) It has a fixed AND array and a programmable OR array
B) It has a programmable AND array and a programmable OR array
C) It has a programmable AND array and a fixed OR array
D) It has no programmable elements and is fixed at manufacture
Correct Answer: It has a programmable AND array and a programmable OR array
, Rationale: A PLA has both a programmable AND array and a programmable OR array, allowing it
to implement complex sum-of-products expressions. A PAL has a programmable AND array and
a fixed OR array.
8. How many output lines does a 3-to-8 decoder have?
A) 3
B) 6
C) 8
D) 16
Correct Answer: 8
Rationale: An n-to-2^n decoder has 2^n output lines. For a 3-to-8 decoder, n=3, so there are
2^3 = 8 output lines.
9. Which of the following can be used to implement an arbitrary Boolean function?
A) Decoder with OR gates
B) Multiplexer
C) PROM
D) All of the above
Correct Answer: All of the above
Rationale: Any Boolean function can be implemented using a decoder with OR gates (sum of
minterms), a multiplexer (MUX), or a PROM. NAND gates are also universal and can implement
any function.
10. What is the primary purpose of a tri-state buffer in a digital system?
A) To perform three-input logic operations
B) To allow an output to be in a high-impedance state, disconnecting it from a shared bus
C) To store three bits of data
D) To generate three-phase clock signals
Correct Answer: To allow an output to be in a high-impedance state, disconnecting it from a
shared bus
Rationale: A tri-state buffer has three output states: high (1), low (0), and high-impedance (Z).
The high-impedance state effectively disconnects the output from a shared bus, allowing
multiple devices to share the same bus.
11. What is the decimal equivalent of the unsigned binary number (1101)₂?
A) 11
B) 12
