# Multiple choice question for engineering

## Set 1

1. Controlled inverter is also known as
a) Controlled buffer
b) NOT gate
c) Both controlled buffer and NOT gate
d) None of the Mentioned

Answer: c [Reason:] Controlled inverter is also known as controlled buffer and NOT gate as well.

2. Why XOR gate is called an inverter?
a) Because of the same input
b) Because of the same output
c) It behaves like a NOT gate
d) None of the Mentioned

Answer: c [Reason:] The XOR (Exclusive Or) gate has a true output when the two inputs are different. When one input is true, the output is the inversion of the other. When one input is false, the output is the non-inversion of the other.

3. Controlled buffers can be useful
a) To control the circuit’s output into the bus
b) In comparison of component’s output with its input
c) In increasing the output from its low input
d) All of the Mentioned

Answer: a [Reason:] Controlled buffers can be useful when you have a wire (often called a bus) whose value should match the output of one of several components. By placing a controlled buffer between each component output and the bus, you can control whether that component’s output is fed onto the bus or not.

4. A logic circuit that provides a HIGH output for both inputs HIGH or both inputs LOW is
a) Ex-NOR gate
b) OR gate
c) Ex-OR gate
d) NAND gate

Answer: a [Reason:] EX-OR gate gives 1 if both inputs are different means 0 or 1 and gives 0 if both are same and EX-NOR is opposite of EX-OR gate, so it provides a HIGH output for both inputs HIGH or both inputs are LOW.

5. What is the first thing you will need if you are going to use a macro-function?
a) A complicated design project
b) An experienced design engineer
c) Good documentation
d) Experience in HDL

Answer: d [Reason:] Documentation is a set of documents provided on paper, or online, or on digital or analog media, such as audio tape or CDs. So, for the implementation of micro function good documentation is necessary.

b) Full adders can handle double-digit numbers
c) Full adders have a carry input capability
d) Half adders can handle only single-digit numbers

7. The binary subtraction of 0 – 0 = ?
a) Difference = 0, borrow = 0
b) Difference = 1, borrow = 0
c) Difference = 1, borrow = 1
d) Difference = 0, borrow = 1

Answer: a [Reason:] The binary subtraction of 0 – 0 = 0.

8. How many basic binary subtraction operations are possible?
a) 1
b) 4
c) 3
d) 2

Answer: b [Reason:] There are 4 binary subtraction operations (0-0, 1-0, 0-1, 1-1) are possible.

9. When performing subtraction by addition in the 2’s-complement system:
a) The minuend and the subtrahend are both changed to the 2’s-complement
b) The minuend is changed to 2’s-complement and the subtrahend is left in its original form
c) The minuend is left in its original form and the subtrahend is changed to its 2’s-complement
d) The minuend and subtrahend are both left in their original form

Answer: c [Reason:] When performing subtraction by addition in the 2’s-complement system, the minuend is left in its original form and the subtrahend is changed to its 2’s-complement.

10. What are the two types of basic adder circuits?
a) Sum and carry
c) Asynchronous and synchronous
d) One and two’s-complement

11. Which of the following is correct for full adders?
c) Full adders are limited to two inputs since there are only two binary digits
d) In a parallel full adder, the first stage may be a half adder

12. The selector inputs to an arithmetic/logic unit (ALU) determine the:
a) Selection of the IC
b) Arithmetic or logic function
c) Data word selection
d) Clock frequency to be used

Answer: b [Reason:] An ALU performs basic arithmetic and logic operations. Examples of arithmetic operations are addition, subtraction, multiplication, and division. Examples of logic operations are comparisons of values such as NOT, AND and OR.

## Set 2

1. The addition of binary numbers:
11011011010 + 010100101 = ?
a) 0111001000
b) 1100110110
c) 11101111111
d) 10011010011

2. Perform binary addition: 101101 + 011011 = ?
a) 011010
b) 1010100
c) 101110
d) 1001000

2. Perform binary subtraction: 101111 – 010101 = ?
a) 100100
b) 010101
c) 011010
d) 011001

3. The result obtained after (100101 – 011110) is
a) 000111
b) 111000
c) 010101
d) 101010

4. Multiply the binary number: 01001 × 01011 = ?
a) 001100011
b) 110011100
c) 010100110
d) 101010111

5. 100101 × 0110 = ?
a) 1011001111
b) 0100110011
c) 101111110
d) 0110100101

6. On multiplication of (10.10) and (01.01), we get
a) 101.0010
b) 0010.101
c) 011.0010
d) 110.0011

7. Divide the binary numbers: 111101 ÷ 1001 and find the remainder
a) 0010
b) 1010
c) 1100
d) 0011

9. Divide: 011010000 ÷ 0101 = ?
a) 10001
b) 10100
c) 11001
d) 01000

10. Subtract: 101101 – 001011 = ?
a) 100010
b) 010110
c) 110101
d) 101100

## Set 3

1. How many natural states will there be in a 4-bit ripple counter?
a) 4
b) 8
c) 16
d) 32

Answer: c [Reason:] 24 = 16 states.

2. A ripple counter’s speed is limited by the propagation delay of:
a) Each flip-flop
b) All flip-flops and gates
c) The flip-flops only with gates
d) Only circuit gates

Answer: a [Reason:] A ripple counter is something that is derived by other flip-flops. Its like a series of Flip Flops. Output of one FF becomes the input of the next. Because ripple counter is composed of FF only and no gates are there other than FF, so only propagation delay of FF will be taken into account.

3. One of the major drawbacks to the use of asynchronous counters is that:
a) Low-frequency applications are limited because of internal propagation delays
b) High-frequency applications are limited because of internal propagation delays
c) Asynchronous counters do not have major drawbacks and are suitable for use in high- and low-frequency counting applications
d) Asynchronous counters do not have propagation delays, which limits their use in high-frequency applications

Answer: b [Reason:] One of the major drawbacks to the use of asynchronous counters is that High-frequency applications are limited because of internal propagation delays.

4. Internal propagation delay of asynchronous counter is removed by
a) Ripple counter
b) Ring counter
c) Modulus counter
d) Synchronous counter

Answer: d [Reason:] Internal propagation delay of asynchronous counter is removed by synchronous counter because clock input is given to each flip-flop individually in synchronous counter.

5. What happens to the parallel output word in an asynchronous binary down counter whenever a clock pulse occurs?
a) The output increases by 1
b) The output decreases by 1
c) The output word increases by 2
d) The output word decreases by 2

Answer: a [Reason:] In an asynchronous counter, the output of 1st flip-flop is given to second flip-flop as clock input. So, in case of binary down counter the output word decreases by 1.

6. How many flip-flops are required to construct a decade counter?
a) 4
b) 8
c) 5
d) 10

Answer: a [Reason:] Number of flip-flop required is calculated by this formula: 2^(n-1)<=N<=2^n. 24=16and23=8, therefore, 4 flip flops needed.

7. The terminal count of a typical modulus-10 binary counter is
a) 0000
b) 1010
c) 1001
d) 1111

Answer: c [Reason:] Modulus-10 means count from 0 to 9. So, terminal count is 9 (1001).

8. How many different states does a 3-bit asynchronous counter have?
a) 2
b) 4
c) 8
d) 16

Answer: c [Reason:] 23=8, so 8 states a 3-bit asynchronous counter have.

9. A 5-bit asynchronous binary counter is made up of five flip-flops, each with a 12 ns propagation delay. The total propagation delay (tp(total)) is
a) 12 ms
b) 24 ns
c) 48 ns
d) 60 ns

Answer: d [Reason:] Each bit has propagation delay = 12ns. So, 5 bits = 12ns * 5 = 60ns.

10. An asynchronous 4-bit binary down counter changes from count 2 to count 3. How many transitional states are required?
a) 1
b) 2
c) 8
d) 15

Answer: d [Reason:] Transitional state is given by 24 – 1 = 15. So, total transitional states are 15.

11. A 4-bit ripple counter consists of flip-flops, which each have a propagation delay from clock to Q output of 15 ns. For the counter to recycle from 1111 to 0000, it takes a total of
a) 15 ns
b) 30 ns
c) 45 ns
d) 60 ns

Answer: d [Reason:] One bit change is 15 ns, so 4-bit change = 15 * 4 = 60.

a) 10
b) 20
c) 100
d) 1000

13. A ripple counter’s speed is limited by the propagation delay of:
a) Each flip-flop
b) All flip-flops and gates
c) The flip-flops only with gates
d) Only circuit gates

Answer: a [Reason:] A ripple counter’s speed is limited by the propagation delay of each flip-flop.

14. A 4-bit counter has a maximum modulus of
a) 3
b) 6
c) 8
d) 16

Answer: d [Reason:] 24 = 16.

15. A principle regarding most display decoders is that when the correct input is present, the related output will switch
a) HIGH
b) To high impedance
c) To an open
d) LOW

Answer: d [Reason:] A principle regarding most display decoders is that when the correct input is present, the related output will switch LOW.

## Set 4

1. Which of the following statements are true?
a) Asynchronous events does not occur at the same time
b) Asynchronous events are controlled by a clock
c) Synchronous events does not need a clock to control them
d) Only asynchronous events need a control clock

Answer: a [Reason:] Asynchronous events does not occur at the same time because of propagation delay.

2. A down counter using n-flip-flops count
a) Downward from a maximum count
b) Upward from a minimum count
c) Downward from a minimum to maximum count
d) None of the Mentioned

Answer: a [Reason:] As the name suggests down counter means counting occurs from a higher value to lower value (i.e. (2^n – 1) to 0).

3. UP Counter is
a) It counts in upward manner
b) It count in down ward manner
c) It counts in both the direction
d) None of the mentioned

Answer: a [Reason:] UP counter counts in upward manner from 0 to (2^n – 1).

4. DOWN counter is
a) It counts in upward manner
b) It count in downward manner
c) It counts in both the direction
d) None of the mentioned

Answer: b [Reason:] DOWN counter counts in downward manner from (2^n – 1) to 0.

5. How many different states does a 3-bit asynchronous down counter have?
a) 2
b) 4
c) 6
d) 8

Answer: d [Reason:] The state of a counter doesn’t change on changing the direction of count. So, it will have 2^3 = 8 states.

6. In a down counter, which flip-flop doesn’t toggle when the inverted output of the preceeding flip-flop goes from HIGH to LOW.
a) MSB flip-flop
b) LSB flip-flop
c) Master slave flip-flop
d) None of the Mentioned

Answer: b [Reason:] Since, the LSB flip-flop changes its state at each negative transition of clock. That is why LSB flip-flop doesn’t have toggle.

7. In a 3-bit asynchronous down counter, the initial content is
a) 000
b) 111
c) 010
d) 101

Answer: a [Reason:] Initially, all the flip-flops are RESET. So, the initial content is 000.

8. In a 3-bit asynchronous down counter, at the first negative transition of the clock, the counter content becomes
a) 000
b) 111
c) 101
d) 010

Answer: b [Reason:] Since, in the down counter, the counter content is decremented by 1 for every negative transition. Hence, in a 3-bit asynchronous down counter, at the first negative transition of the clock, the counter content becomes 111.

9. In a 3-bit asynchronous down counter, at the first negative transition of the clock, the counter content becomes
a) 000
b) 111
c) 101
d) 010

Answer: c [Reason:] Since, in the down counter, the counter content is decremented by 1 for every negative transition. Hence, in a 3-bit asynchronous down counter, at the first negative transition of the clock, the counter content becomes 101.

10. The hexadecimal equivalent of 15,536 is ________
a) 3CB0
b) 3C66
c) 63C0
d) 6300

Answer: a [Reason:] You just divide the number by 2 at the end and use LSB to MSB during arranging them in sequence. And make the pair of four bit from right to left.

11. In order to check the CLR function of a counter
a) Apply the active level to the CLR input and check all of the Q outputs to see if they are all in their reset state
b) Ground the CLR input and check to be sure that all of the Q outputs are LOW
c) Connect the CLR input to Vcc and check to see if all of the Q outputs are HIGH
d) Connect the CLR to its correct active level while clocking the counter; check to make sure that all of the Q outputs are toggling

Answer: a [Reason:] In order to check the CLR function of a counter, apply the active level to the CLR input and check all of the Q outputs to see if they are all in their reset state.

## Set 5

1. The decimal number system represent the decimal number in the form of
b) Binary coded
c) Octal
d) Decimal

Answer: b [Reason:] Binary-coded decimal (BCD) is a class of binary encodings of decimal numbers where each decimal digit is represented by a fixed number of bits, usually four or eight.

2. 2^9 input circuit will have total of
a) 32 entries
b) 128 entries
c) 256 entries
d) 512 entries

Answer: d [Reason:] 2^9 input circuit would have 512(2*2*2*2*2*2*2*2*2 = 512) entries.

3. BCD adder can be constructed with 3 IC packages each of
a) 2 bits
b) 3 bits
c) 4 bits
d) 5 bits

Answer: c [Reason:] BCD adder can be constructed with 3 IC packages. Each of 4-bit adders is an MSI(Medium scale Integration) function and 3 gates for the correction logic need one SSI package.

4. The output sum of two decimal digits can be represented in
a) Gray Code
b) Excess-3
c) BCD

Answer: c [Reason:] The output sum of two decimal digits can be represented in BCD(Binary-coded decimal).

5. The addition of two decimal digits in BCD can be done through

Answer: a [Reason:] The addition of two decimal digits in BCD can be done through BCD adder. Every input inserted, in addition by the user converted into binary and then proceed for the addition.

6. 3 bits full adder contains
a) 3 combinational inputs
b) 4 combinational inputs
c) 6 combinational inputs
d) 8 combinational inputs

7. The simplified expression of full adder carry is
a) c = xy+xz+yz
b) c = xy+xz
c) c = xy+yz
d) c = x+y+z

Answer: a [Reason:] The simplified expression of full adder carry is c = xy+xz+yz.

8. Complement of F’ gives back
a) F’
b) F
c) FF
d) undefined variable

Answer: b [Reason:] Complement means inversion. So, complement of F’ gives back F.

9. Decimal digit in BCD can be represented by
a) 1 input line
b) 2 input lines
c) 3 input lines
d) 4 input lines

Answer: d [Reason:] Decimal digit in BCD can be represented by 4 input lines. Since, it is constructed with 4-bits.

10. The number of logic gates and the way of their interconnections can be classified as
a) Logical network
b) System network
c) Circuit network
d) Gate network 