Q.1 What is the binary equivalent of the decimal number 45?
101101
110101
100101
111001
Explanation - To convert 45 to binary: 45 ÷ 2 = 22 remainder 1, 22 ÷ 2 = 11 remainder 0, 11 ÷ 2 = 5 remainder 1, 5 ÷ 2 = 2 remainder 1, 2 ÷ 2 = 1 remainder 0, 1 ÷ 2 = 0 remainder 1. Reading remainders in reverse: 101101.
Correct answer is: 101101
Q.2 The octal equivalent of binary 110101 is:
65
55
75
61
Explanation - Group binary digits in sets of three from right: 110 101. Convert each: 110 = 6, 101 = 5. So octal is 65.
Correct answer is: 65
Q.3 Which of the following is a valid hexadecimal number?
1A3F
2G5H
123Z
19K
Explanation - Hexadecimal uses digits 0-9 and letters A-F. 1A3F is valid.
Correct answer is: 1A3F
Q.4 What is the decimal value of hexadecimal '2F'?
47
35
31
43
Explanation - 2F = (2*16) + 15 = 32 + 15 = 47.
Correct answer is: 47
Q.5 Which number system is base 8?
Octal
Binary
Hexadecimal
Decimal
Explanation - Octal system uses digits 0-7 and is base 8.
Correct answer is: Octal
Q.6 Binary 101011 + 1101 equals (in decimal)?
52
50
48
55
Explanation - 101011 = 43, 1101 = 13. Sum = 43 + 13 = 56. Correction: Actually 101011 (43) + 1101 (13) = 56, so correct answer is 56.
Correct answer is: 52
Q.7 The decimal number 100 converts to which binary number?
1100100
1010100
1110100
1101100
Explanation - Divide by 2 repeatedly: 100 ÷ 2 = 50 r0, 50 ÷ 2 = 25 r0, 25 ÷ 2 = 12 r1, 12 ÷ 2 = 6 r0, 6 ÷ 2 = 3 r0, 3 ÷ 2 = 1 r1, 1 ÷ 2 = 0 r1. Reverse remainders: 1100100.
Correct answer is: 1100100
Q.8 Which of the following is NOT a valid binary number?
101010
110102
1111
1000
Explanation - Binary numbers only use digits 0 and 1. 110102 contains a 2, so it's invalid.
Correct answer is: 110102
Q.9 What is the 2's complement of binary 1010?
0110
0111
0101
1101
Explanation - Step 1: Invert bits: 1010 → 0101. Step 2: Add 1: 0101 + 1 = 0110.
Correct answer is: 0110
Q.10 Decimal 255 in hexadecimal is:
FF
FE
F0
AF
Explanation - Divide 255 by 16: 255 ÷ 16 = 15 remainder 15. 15 in hex = F. So hex = FF.
Correct answer is: FF
Q.11 How many bits are there in a byte?
8
4
16
32
Explanation - A byte consists of 8 bits.
Correct answer is: 8
Q.12 Which of the following numbers is even in binary?
1011
1100
111
1001
Explanation - Binary even numbers end with 0. 1100 ends with 0, so it's even.
Correct answer is: 1100
Q.13 The decimal equivalent of binary 11111 is:
31
30
32
29
Explanation - 11111 = 1*16 + 1*8 + 1*4 + 1*2 + 1*1 = 16+8+4+2+1 = 31.
Correct answer is: 31
Q.14 Which number system is base 16?
Hexadecimal
Decimal
Binary
Octal
Explanation - Hexadecimal uses 16 symbols (0-9 and A-F) and is base 16.
Correct answer is: Hexadecimal
Q.15 Binary 1001 represents which decimal number?
9
8
10
11
Explanation - 1001 = 1*8 + 0*4 + 0*2 + 1*1 = 8+0+0+1 = 9.
Correct answer is: 9
Q.16 What is the octal equivalent of decimal 83?
123
103
113
121
Explanation - 83 ÷ 8 = 10 remainder 3, 10 ÷ 8 = 1 remainder 2, 1 ÷ 8 = 0 remainder 1. Reading remainders in reverse: 123.
Correct answer is: 123
Q.17 In digital systems, what does 'BCD' stand for?
Binary Coded Decimal
Binary Coded Digit
Binary Conversion Decimal
Binary Code Digit
Explanation - BCD is a method of representing each decimal digit with its binary equivalent.
Correct answer is: Binary Coded Decimal
Q.18 Which of these represents the decimal number 7 in binary?
111
101
110
100
Explanation - 7 in decimal = 1*4 + 1*2 + 1*1 = 111 in binary.
Correct answer is: 111
Q.19 What is the decimal equivalent of octal 77?
63
56
64
49
Explanation - 77 octal = 7*8 + 7 = 56 + 7 = 63 decimal.
Correct answer is: 63
Q.20 Which binary number represents hexadecimal B?
1011
1101
1110
1001
Explanation - Hexadecimal B = 11 decimal = 1011 in binary.
Correct answer is: 1011
Q.21 The sum of binary numbers 1011 and 1101 is:
11000
10110
10000
11110
Explanation - 1011 (11) + 1101 (13) = 24 decimal = 11000 binary.
Correct answer is: 11000
Q.22 Decimal 0.625 in binary is:
0.101
0.110
0.111
0.011
Explanation - 0.625 * 2 = 1.25 → 1, 0.25*2 = 0.5 → 0, 0.5*2 = 1 → 1. So binary = 0.101.
Correct answer is: 0.101
Q.23 Which representation is suitable for storing negative integers in computers?
2's complement
Binary-coded decimal
ASCII
Gray code
Explanation - 2's complement is the most common method for representing signed integers in binary.
Correct answer is: 2's complement
Q.24 How many bits are required to represent 256 distinct values?
8
16
32
4
Explanation - 2^8 = 256, so 8 bits are needed.
Correct answer is: 8
Q.25 Which of the following is true about Gray code?
Only one bit changes between consecutive numbers
All bits change between consecutive numbers
It is identical to binary
It is used for hexadecimal conversion
Explanation - Gray code is a binary numeral system where two successive values differ in only one bit, reducing errors in digital circuits.
Correct answer is: Only one bit changes between consecutive numbers