About this quiz
Binary, octal, decimal, hexadecimal and conversions.
This Lok Sewa practice set has 50 multiple-choice questions (Subject: Computer · For: Computer Operator · Level: Medium). Take the quiz above first; after that, use the study list below to revise every question with its correct answer and a short explanation.
Study list: all 50 questions with answers and explanations
Convert 13 (decimal) into binary.
- A) 1101 ✔
- B) 1100
- C) 10000
- D) 1111
Why: 13 = 8 + 4 + 1 = 1101 in binary.
Convert 25 (decimal) into binary.
- A) 11000
- B) 11001 ✔
- C) 11011
- D) 11100
Why: 25 = 16 + 8 + 1 = 11001 in binary.
Convert 37 (decimal) into binary.
- A) 100110
- B) 100010
- C) 100101 ✔
- D) 100011
Why: 37 = 32 + 4 + 1 = 100101 in binary.
Convert 50 (decimal) into binary.
- A) 110101
- B) 101111
- C) 110000
- D) 110010 ✔
Why: 50 = 32 + 16 + 2 = 110010 in binary.
Convert 64 (decimal) into binary.
- A) 1000000 ✔
- B) 1000001
- C) 111101
- D) 111111
Why: 64 is 2⁶, so it is 1 followed by six zeros: 1000000.
Convert 99 (decimal) into binary.
- A) 1100001
- B) 1100011 ✔
- C) 1100100
- D) 1100101
Why: 99 = 64 + 32 + 2 + 1 = 1100011 in binary.
Convert 45 (decimal) into binary.
- A) 101011
- B) 101111
- C) 101101 ✔
- D) 101010
Why: 45 = 32 + 8 + 4 + 1 = 101101 in binary.
Convert 18 (decimal) into binary.
- A) 10101
- B) 10000
- C) 1111
- D) 10010 ✔
Why: 18 = 16 + 2 = 10010 in binary.
Convert 1010₂ into decimal.
- A) 10 ✔
- B) 11
- C) 9
- D) 12
Why: 1010₂ = 8 + 0 + 2 + 0 = 10.
Convert 1111₂ into decimal.
- A) 16
- B) 15 ✔
- C) 14
- D) 17
Why: 1111₂ = 8 + 4 + 2 + 1 = 15.
Convert 10011₂ into decimal.
- A) 20
- B) 18
- C) 19 ✔
- D) 21
Why: 10011₂ = 16 + 2 + 1 = 19.
Convert 110110₂ into decimal.
- A) 55
- B) 53
- C) 56
- D) 54 ✔
Why: 110110₂ = 32 + 16 + 4 + 2 = 54.
Convert 100000₂ into decimal.
- A) 32 ✔
- B) 33
- C) 31
- D) 34
Why: 100000₂ = 2⁵ = 32.
Convert 111001₂ into decimal.
- A) 58
- B) 57 ✔
- C) 56
- D) 59
Why: 111001₂ = 32 + 16 + 8 + 1 = 57.
Convert 255 (decimal) into hexadecimal.
- A) 100
- B) 10F
- C) FF ✔
- D) FE
Why: 255 = 15 × 16 + 15, and 15 is F in hex, so 255 = FF.
Convert 26 (decimal) into hexadecimal.
- A) 1B
- B) 2A
- C) 19
- D) 1A ✔
Why: 26 = 1 × 16 + 10, and 10 is A, so 26 = 1A.
Convert 171 (decimal) into hexadecimal.
- A) AB ✔
- B) AC
- C) BB
- D) AA
Why: 171 = 10 × 16 + 11 = A and B, so 171 = AB.
Convert 100 (decimal) into hexadecimal.
- A) 65
- B) 64 ✔
- C) 74
- D) 63
Why: 100 = 6 × 16 + 4, so 100 = 64 in hex.
Convert 1F₁₆ into decimal.
- A) 32
- B) 21
- C) 31 ✔
- D) 47
Why: 1F₁₆ = 1 × 16 + 15 = 31.
Convert 2A₁₆ into decimal.
- A) 43
- B) 32
- C) 58
- D) 42 ✔
Why: 2A₁₆ = 2 × 16 + 10 = 42.
Convert FF₁₆ into decimal.
- A) 255 ✔
- B) 256
- C) 245
- D) 271
Why: FF₁₆ = 15 × 16 + 15 = 255.
Convert C8₁₆ into decimal.
- A) 201
- B) 200 ✔
- C) 190
- D) 216
Why: C8₁₆ = 12 × 16 + 8 = 200.
Convert 101110₂ into octal.
- A) 57
- B) 66
- C) 56 ✔
- D) 55
Why: Group binary in threes from the right: 101 110 = 5 6, so 56 in octal.
Convert 111011₂ into octal.
- A) 74
- B) 103
- C) 72
- D) 73 ✔
Why: 111 011 = 7 3, so 73 in octal.
Convert 100101₂ into octal.
- A) 45 ✔
- B) 46
- C) 55
- D) 44
Why: 100 101 = 4 5, so 45 in octal.
Convert 10101111₂ into hexadecimal.
- A) B0
- B) AF ✔
- C) BF
- D) AE
Why: Group in fours: 1010 1111 = A F, so AF in hex.
Convert 11110000₂ into hexadecimal.
- A) F1
- B) 100
- C) F0 ✔
- D) EF
Why: 1111 0000 = F 0, so F0 in hex.
Convert 00111100₂ into hexadecimal.
- A) 3D
- B) 4C
- C) 3B
- D) 3C ✔
Why: 0011 1100 = 3 C, so 3C in hex.
Add the binary numbers 1011 + 0110.
- A) 10001 ✔
- B) 10010
- C) 10000
- D) 1101
Why: 1011 (11) + 0110 (6) = 17 = 10001 in binary.
Add the binary numbers 1101 + 0111.
- A) 10101
- B) 10100 ✔
- C) 10011
- D) 1010
Why: 1101 (13) + 0111 (7) = 20 = 10100 in binary.
Add the binary numbers 1111 + 0001.
- A) 10001
- B) 1111
- C) 10000 ✔
- D) 1110
Why: 1111 (15) + 0001 (1) = 16 = 10000 in binary.
Convert 8 (decimal) into octal.
- A) 11
- B) 7
- C) 20
- D) 10 ✔
Why: 8 = 1 × 8 + 0, so 8 is 10 in octal.
Convert 20 (decimal) into octal.
- A) 24 ✔
- B) 25
- C) 23
- D) 34
Why: 20 = 2 × 8 + 4, so 20 is 24 in octal.
Convert 63 (decimal) into octal.
- A) 100
- B) 77 ✔
- C) 76
- D) 107
Why: 63 = 7 × 8 + 7, so 63 is 77 in octal.
Convert 100 (decimal) into octal.
- A) 145
- B) 143
- C) 144 ✔
- D) 154
Why: 100 = 1 × 64 + 4 × 8 + 4, so 100 is 144 in octal.
The base of the binary number system is:
- A) 8
- B) 10
- C) 16
- D) 2 ✔
Why: Binary uses two digits, 0 and 1, so its base is 2.
The base of the octal number system is:
- A) 8 ✔
- B) 2
- C) 10
- D) 16
Why: Octal uses eight digits, 0 to 7, so its base is 8.
The base of the hexadecimal number system is:
- A) 8
- B) 16 ✔
- C) 10
- D) 2
Why: Hexadecimal uses sixteen symbols, 0–9 and A–F, so its base is 16.
In hexadecimal, the letter F represents:
- A) 16
- B) 14
- C) 15 ✔
- D) 10
Why: In hexadecimal, F stands for 15.
In hexadecimal, the letter A represents:
- A) 11
- B) 1
- C) 16
- D) 10 ✔
Why: In hexadecimal, A stands for 10.
Which digit is NOT valid in octal?
- A) 8 ✔
- B) 7
- C) 0
- D) 5
Why: Octal digits are only 0 to 7, so 8 is not a valid octal digit.
Each hexadecimal digit represents how many bits?
- A) 3
- B) 4 ✔
- C) 8
- D) 2
Why: One hex digit covers 16 values = 2⁴, so it represents 4 bits.
Each octal digit represents how many bits?
- A) 4
- B) 2
- C) 3 ✔
- D) 8
Why: One octal digit covers 8 values = 2³, so it represents 3 bits.
1 + 1 in binary equals:
- A) 2
- B) 11
- C) 1
- D) 10 ✔
Why: 1 + 1 = 2, which is written 10 in binary (write 0, carry 1).
Standard ASCII uses how many bits per character?
- A) 7 ✔
- B) 8
- C) 16
- D) 4
Why: Standard ASCII uses 7 bits, giving 128 characters.
The code that can represent Devanagari and all world scripts is:
- A) ASCII
- B) Unicode ✔
- C) EBCDIC
- D) BCD
Why: Unicode can represent Devanagari and almost every world script, unlike ASCII.
The 1's complement of 1010 is:
- A) 1011
- B) 1001
- C) 0101 ✔
- D) 0110
Why: 1's complement flips every bit: 1010 becomes 0101.
The 2's complement of 0101 is:
- A) 1010
- B) 0110
- C) 1100
- D) 1011 ✔
Why: 2's complement = 1's complement + 1. 0101 → 1010 → 1011.
1 TB equals:
- A) 1024 GB ✔
- B) 1000 MB
- C) 1024 MB
- D) 100 GB
Why: 1 terabyte = 1024 gigabytes.
4 bits make one:
- A) Byte
- B) Nibble ✔
- C) Word
- D) Kilobyte
Why: 4 bits make one nibble. 8 bits make a byte.