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# Combinational Logic Circuits Online Exam Quiz

Important questions about Combinational Logic Circuits. Combinational Logic Circuits MCQ questions with answers. Combinational Logic Circuits exam questions and answers for students and interviews.

Options

A : IF/THEN

B : IF/THEN/ELSE

C : CASE

D : ELSIF

### 2. The 7447A is a BCD-to-7-segment decoder with ripple blanking input and output functions. The purpose of these lines is to ________.

Options

A : turn off the display for any nonsignificant digit

B : turn off the display for any zero

C : turn off the display for leading or trailing zeros

D : test the display to assure all segments are operational

### 4. A circuit that can convert one of ten numerical keys pressed on a keyboard to BCD is a ________.

Options

A : priority encoder

B : decoder

C : multiplexer

D : demultiplexer

Options

A : BIT

B : BIT_VECTOR

C : STD_LOGIC

D : STD_VECTOR

Options

A : 01100

B : 10101

C : 11000

D : 00011

### 7. In an odd-parity system, the data that will produce a parity bit = 1 is ________.

Options

A : data = 1010011

B : data = 1111000

C : data = 1100000

D : All of the above

### 8. Parity generators and checkers use ________ gates.

Options

A : exclusive-AND

B : exclusive-OR/NOR

C : exclusive-OR

D : exclusive-NAND

### 9. When an open occurs on the input of a TTL device, the output will ________.

Options

A : go LOW, because there is no current in an open circuit

B : react as if the open input were a HIGH

C : go HIGH, since full voltage appears across an open

D : still be good, if only the good inputs are used

### 10. A half-adder does not have ________.

Options

A : carry in

B : carry out

C : two inputs

D : all of the above

### 1. Occasionally, a particular logic expression will be of no consequence in the operation of a circuit, such as in a BCD-to-decimal converter. These result in ________ terms in the K-map and can be treated as either ________ or ________, in order to ________ the resulting term.

Options

A : don't care, 1's, 0's, simplify

B : spurious, AND's, OR's, eliminate

C : duplicate, 1's, 0's, verify

D : spurious, 1's, 0's, simplify

### 4. Two 4-bit comparators are cascaded to form an 8-bit comparator. The cascading inputs of the most significant 4 bits should be connected ________.

Options

A : to the outputs from the least significant 4-bit comparator

B : to the cascading inputs of the least significant 4-bit comparator

C : A = B to a logic high, A < b and a > B to a logic low

D : ground

### 5. The AND-OR-INVERT gates are designed to simplify implementation of ________.

Options

A : POS logic

B : DeMorgan's theorem

C : NAND logic

D : SOP logic

Options

A : an AND

B : an OR

C : a NOR

D : a NAND

Options

A : maximum

B : minimum

C : median

D : Karnaugh

### 9. To subtract a signed number (the subtrahend) from another signed number (the minuend) in the 2's complement system, the minuend is ________.

Options

A : complemented only if it is positive

B : complemented only if it is negative

C : always complemented

D : never complemented

### 10. An 8-bit binary number is input to an odd parity generator. The parity bit will equal 1 only if ________.

Options

A : the number is odd

B : the number of 1s in the number is odd

C : the number is even

D : the number of 1s in the number is even

Options

A : 54

B : 2N

C : 74

D : TTL

Options

A : 1, 0, 0, 1

B : 0, 1, 0, 1

C : 1, 1, 1, 0

D : 1, 0, 0, 0

Options

A : XOR gate

B : XNOR gate

C : NAND gate

D : NOR gate

### 4. The ________ circuit produces a HIGH output whenever the two inputs are unequal.

Options

A : exclusive-AND

B : exclusive-NOR

C : exclusive-OR

D : inexclusive-OR