Number Systems & Codes MCQs

Practice Number Systems & Codes MCQs with four options, answers and explanations for focused Electronics & Telecommunication Engineering revision.

Question 1

Digital ElectronicsNumber Systems & Codes

In BCD, each decimal digit is normally represented by how many bits?

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Correct Answer: C. 4

Explanation: 8421 BCD represents each decimal digit independently using four bits.

Reference: 8421 BCD fundamentals

Question 2

Digital ElectronicsNumber Systems & Codes

The 1’s complement of binary 1010 is?

A0101
B1011
C0110
D1101

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Correct Answer: A. 0101

Explanation: The 1's complement is obtained by changing every 1 to 0 and every 0 to 1: 1010 becomes 0101.

Reference: Binary complement fundamentals

Question 3

Digital ElectronicsNumber Systems & Codes

The radix of the binary number system is?

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Correct Answer: A. 2

Explanation: Binary uses two symbols, 0 and 1, so its radix is 2.

Reference: Standard digital electronics fundamentals

Question 4

Digital ElectronicsNumber Systems & Codes

What is the decimal equivalent of binary 1011?

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Correct Answer: C. 11

Explanation: 1011₂ = 8 + 0 + 2 + 1 = 11₁₀.

Reference: Binary-to-decimal conversion

Question 5

Digital ElectronicsNumber Systems & Codes

What is the binary equivalent of decimal 15?

A1110
B1111
C1011
D1101

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Correct Answer: B. 1111

Explanation: 15 = 8 + 4 + 2 + 1, giving 1111₂.

Reference: Decimal-to-binary conversion

Question 6

Digital ElectronicsNumber Systems & Codes

The binary result of adding 1011 and 0101 is?

A10000
B01110
C11110
D10100

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Correct Answer: A. 10000

Explanation: Binary 1011 is 11 and 0101 is 5. Their sum is 16, which is binary 10000.

Reference: Standard digital electronics: binary arithmetic

Question 7

Digital ElectronicsNumber Systems & Codes

Using 8-bit two’s-complement representation, the binary code for decimal -5 is?

A00000101
B11111010
C11111011
D10000101

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Correct Answer: C. 11111011

Explanation: Start with +5 = 00000101, invert the bits to 11111010 and add 1, giving 11111011.

Reference: Standard digital electronics: two's complement

Question 8

Digital ElectronicsNumber Systems & Codes

In 8-bit two’s-complement arithmetic, the representable decimal range is?

A-127 to +127
B-128 to +127
C-128 to +128
D0 to 255

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Correct Answer: B. -128 to +127

Explanation: An n-bit two's-complement number ranges from -2^(n-1) through 2^(n-1)-1. For 8 bits this is -128 through +127.

Reference: Standard digital electronics: signed binary numbers

Question 9

Digital ElectronicsNumber Systems & Codes

The Gray-code equivalent of binary 1011 is?

A1110
B1010
C1101
D1001

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Correct Answer: A. 1110

Explanation: For binary-to-Gray conversion, the MSB is unchanged and each following Gray bit is the XOR of adjacent binary bits: 1, 1 XOR 0 = 1, 0 XOR 1 = 1, 1 XOR 1 = 0, giving 1110.

Reference: Standard digital electronics: Gray code conversion

Question 10

Digital ElectronicsNumber Systems & Codes

A key property of reflected Gray code is that adjacent code words normally differ in?

AAll bits
BExactly one bit
CExactly two bits
DNo bits

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Correct Answer: B. Exactly one bit

Explanation: Gray code is designed so consecutive code words differ by only one bit, reducing ambiguity during transitions.

Reference: Standard digital electronics: Gray code

Question 11

Digital ElectronicsNumber Systems & Codes

The Excess-3 code for decimal digit 6 is?

A0110
B1001
C1010
D1100

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Correct Answer: B. 1001

Explanation: Excess-3 represents a decimal digit by adding 3 and encoding the result in four-bit binary. For 6, 6+3=9, giving 1001.

Reference: Standard digital electronics: Excess-3 code

Question 12

Digital ElectronicsNumber Systems & Codes

Which useful property does the Excess-3 decimal code possess?

AIt is self-complementing
BIt uses only three bits per decimal digit
CIt is a weighted 8421 code
DAdjacent values always differ by one bit

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Correct Answer: A. It is self-complementing

Explanation: Excess-3 is a self-complementing code: complementing all four bits of a digit code gives the Excess-3 code for the 9's complement of that decimal digit.

Reference: Standard digital electronics: Excess-3 properties