WGU D684 INTRODUCTION TO COMPUTER
SCIENCE OBJECTIVE ASSESSMENT 2026 |
COMPLETE QUESTIONS BANK & VERIFIED
ANSWERS WITH RATIONALES | GUARANTEED
PASS
WGU D684 — INTRODUCTION TO COMPUTER SCIENCE
OBJECTIVE ASSESSMENT
COMPLETE QUESTION BANK & VERIFIED ANSWERS WITH RATIONALE |
GUARANTEED PASS
400 QUESTIONS | 12 TOPIC SECTIONS
SECTION 1: NUMBER SYSTEMS & BINARY (Q1–Q40)
Q1. What is the binary representation of the decimal number 13?
A. 1010 B. 1100 C. 1101 D. 1110 E. 1001
CORRECT ANSWER: C. 1101 RATIONALE: 13 = 8+4+1 = 2³+2²+2⁰ = 1101 in
binary.
Q2. What is the decimal equivalent of the binary number 10110?
A. 20 B. 21 C. 22 D. 23 E. 24
CORRECT ANSWER: C. 22 RATIONALE: 10110 = 16+4+2 = 22 in decimal.
Q3. How many unique values can be represented with 4 bits?
A. 4 B. 8 C. 12 D. 16 E. 32
CORRECT ANSWER: D. 16 RATIONALE: With n bits, you can represent 2ⁿ
values. 2⁴ = 16 unique values (0 through 15).
Q4. What is the hexadecimal representation of the decimal number 255?
A. EE B. FE C. FF D. F0 E. EF
, CORRECT ANSWER: C. FF RATIONALE: 255 = 15×16 + 15 = FF in
hexadecimal, where F represents 15.
Q5. What is the result of the binary addition 1011 + 0110?
A. 10001 B. 10010 C. 10011 D. 11001 E. 10100
CORRECT ANSWER: A. 10001 RATIONALE: 1011 (11) + 0110 (6) = 17 =
10001 in binary.
Q6. Which base is used in the hexadecimal number system?
A. 2 B. 8 C. 10 D. 16 E. 32
CORRECT ANSWER: D. 16 RATIONALE: Hexadecimal uses base 16, with
digits 0–9 and letters A–F representing values 10–15.
Q7. What is the octal representation of the decimal number 64?
A. 80 B. 100 C. 110 D. 120 E. 400
CORRECT ANSWER: B. 100 RATIONALE: 64 = 1×8² = 100 in octal.
Q8. What is the two's complement of the 8-bit binary number 00001010?
A. 11110101 B. 11110110 C. 11111010 D. 10001010 E. 01110110
CORRECT ANSWER: B. 11110110 RATIONALE: Invert all bits of 00001010 to
get 11110101, then add 1 to get 11110110.
Q9. What does the term "bit" stand for?
A. Binary Integer Transfer B. Binary Indexed Term C. Binary Digit D. Byte Integer Type
E. Basic Information Token
CORRECT ANSWER: C. Binary Digit RATIONALE: "Bit" is a portmanteau of
Binary Digit, the smallest unit of data in computing.
,Q10. How many bits are in one byte?
A. 4 B. 6 C. 8 D. 16 E. 32
CORRECT ANSWER: C. 8 RATIONALE: By standard definition, one byte
consists of 8 bits, allowing 256 unique values.
Q11. What is the decimal value of the hexadecimal number A3?
A. 153 B. 163 C. 143 D. 133 E. 173
CORRECT ANSWER: B. 163 RATIONALE: A3 = 10×16 + 3 = 160 + 3 = 163 in
decimal.
Q12. Which of the following is NOT a valid binary number?
A. 1010 B. 0001 C. 1102 D. 1111 E. 0000
CORRECT ANSWER: C. 1102 RATIONALE: Binary only uses digits 0 and 1.
The digit 2 in 1102 makes it invalid in base-2.
Q13. What is the result of binary multiplication 101 × 11?
A. 1101 B. 1110 C. 1111 D. 1010 E. 1001
CORRECT ANSWER: C. 1111 RATIONALE: 101 (5) × 11 (3) = 15 = 1111 in
binary.
Q14. What is the one's complement of 01001101?
A. 10110010 B. 10110011 C. 11001101 D. 01110010 E. 10010010
CORRECT ANSWER: A. 10110010 RATIONALE: One's complement simply
flips every bit: 01001101 becomes 10110010.
Q15. How many bytes are in 1 kilobyte (using binary convention)?
A. 100 B. 512 C. 1000 D. 1024 E. 2048
, CORRECT ANSWER: D. 1024 RATIONALE: In binary convention, 1 KB = 2¹⁰
= 1024 bytes. (SI convention uses 1000, but computing uses 1024.)
Q16. What is the binary equivalent of hexadecimal B?
A. 1010 B. 1011 C. 1100 D. 1101 E. 1001
CORRECT ANSWER: B. 1011 RATIONALE: Hexadecimal B = decimal 11 =
8+2+1 = 1011 in binary.
Q17. What is the decimal number 45 in binary?
A. 101011 B. 101101 C. 101100 D. 100110 E. 110101
CORRECT ANSWER: B. 101101 RATIONALE: 45 = 32+8+4+1 = 2⁵+2³+2²+2⁰
= 101101 in binary.
Q18. In two's complement, how is a negative number represented?
A. By setting the most significant bit to 1 only B. By inverting all bits C. By inverting all
bits and adding 1 D. By subtracting the value from 256 E. By prefixing the number with
a minus sign bit
CORRECT ANSWER: C. By inverting all bits and adding 1 RATIONALE:
Two's complement requires flipping all bits (one's complement) and then adding 1 to
represent negative numbers.
Q19. What is 0xFF in decimal?
A. 240 B. 250 C. 254 D. 255 E. 256
CORRECT ANSWER: D. 255 RATIONALE: FF = 15×16 + 15 = 255. It is also
the maximum value of an unsigned 8-bit integer.
Q20. What is the binary subtraction 1010 − 0011?
A. 0110 B. 0111 C. 1001 D. 0101 E. 1100
SCIENCE OBJECTIVE ASSESSMENT 2026 |
COMPLETE QUESTIONS BANK & VERIFIED
ANSWERS WITH RATIONALES | GUARANTEED
PASS
WGU D684 — INTRODUCTION TO COMPUTER SCIENCE
OBJECTIVE ASSESSMENT
COMPLETE QUESTION BANK & VERIFIED ANSWERS WITH RATIONALE |
GUARANTEED PASS
400 QUESTIONS | 12 TOPIC SECTIONS
SECTION 1: NUMBER SYSTEMS & BINARY (Q1–Q40)
Q1. What is the binary representation of the decimal number 13?
A. 1010 B. 1100 C. 1101 D. 1110 E. 1001
CORRECT ANSWER: C. 1101 RATIONALE: 13 = 8+4+1 = 2³+2²+2⁰ = 1101 in
binary.
Q2. What is the decimal equivalent of the binary number 10110?
A. 20 B. 21 C. 22 D. 23 E. 24
CORRECT ANSWER: C. 22 RATIONALE: 10110 = 16+4+2 = 22 in decimal.
Q3. How many unique values can be represented with 4 bits?
A. 4 B. 8 C. 12 D. 16 E. 32
CORRECT ANSWER: D. 16 RATIONALE: With n bits, you can represent 2ⁿ
values. 2⁴ = 16 unique values (0 through 15).
Q4. What is the hexadecimal representation of the decimal number 255?
A. EE B. FE C. FF D. F0 E. EF
, CORRECT ANSWER: C. FF RATIONALE: 255 = 15×16 + 15 = FF in
hexadecimal, where F represents 15.
Q5. What is the result of the binary addition 1011 + 0110?
A. 10001 B. 10010 C. 10011 D. 11001 E. 10100
CORRECT ANSWER: A. 10001 RATIONALE: 1011 (11) + 0110 (6) = 17 =
10001 in binary.
Q6. Which base is used in the hexadecimal number system?
A. 2 B. 8 C. 10 D. 16 E. 32
CORRECT ANSWER: D. 16 RATIONALE: Hexadecimal uses base 16, with
digits 0–9 and letters A–F representing values 10–15.
Q7. What is the octal representation of the decimal number 64?
A. 80 B. 100 C. 110 D. 120 E. 400
CORRECT ANSWER: B. 100 RATIONALE: 64 = 1×8² = 100 in octal.
Q8. What is the two's complement of the 8-bit binary number 00001010?
A. 11110101 B. 11110110 C. 11111010 D. 10001010 E. 01110110
CORRECT ANSWER: B. 11110110 RATIONALE: Invert all bits of 00001010 to
get 11110101, then add 1 to get 11110110.
Q9. What does the term "bit" stand for?
A. Binary Integer Transfer B. Binary Indexed Term C. Binary Digit D. Byte Integer Type
E. Basic Information Token
CORRECT ANSWER: C. Binary Digit RATIONALE: "Bit" is a portmanteau of
Binary Digit, the smallest unit of data in computing.
,Q10. How many bits are in one byte?
A. 4 B. 6 C. 8 D. 16 E. 32
CORRECT ANSWER: C. 8 RATIONALE: By standard definition, one byte
consists of 8 bits, allowing 256 unique values.
Q11. What is the decimal value of the hexadecimal number A3?
A. 153 B. 163 C. 143 D. 133 E. 173
CORRECT ANSWER: B. 163 RATIONALE: A3 = 10×16 + 3 = 160 + 3 = 163 in
decimal.
Q12. Which of the following is NOT a valid binary number?
A. 1010 B. 0001 C. 1102 D. 1111 E. 0000
CORRECT ANSWER: C. 1102 RATIONALE: Binary only uses digits 0 and 1.
The digit 2 in 1102 makes it invalid in base-2.
Q13. What is the result of binary multiplication 101 × 11?
A. 1101 B. 1110 C. 1111 D. 1010 E. 1001
CORRECT ANSWER: C. 1111 RATIONALE: 101 (5) × 11 (3) = 15 = 1111 in
binary.
Q14. What is the one's complement of 01001101?
A. 10110010 B. 10110011 C. 11001101 D. 01110010 E. 10010010
CORRECT ANSWER: A. 10110010 RATIONALE: One's complement simply
flips every bit: 01001101 becomes 10110010.
Q15. How many bytes are in 1 kilobyte (using binary convention)?
A. 100 B. 512 C. 1000 D. 1024 E. 2048
, CORRECT ANSWER: D. 1024 RATIONALE: In binary convention, 1 KB = 2¹⁰
= 1024 bytes. (SI convention uses 1000, but computing uses 1024.)
Q16. What is the binary equivalent of hexadecimal B?
A. 1010 B. 1011 C. 1100 D. 1101 E. 1001
CORRECT ANSWER: B. 1011 RATIONALE: Hexadecimal B = decimal 11 =
8+2+1 = 1011 in binary.
Q17. What is the decimal number 45 in binary?
A. 101011 B. 101101 C. 101100 D. 100110 E. 110101
CORRECT ANSWER: B. 101101 RATIONALE: 45 = 32+8+4+1 = 2⁵+2³+2²+2⁰
= 101101 in binary.
Q18. In two's complement, how is a negative number represented?
A. By setting the most significant bit to 1 only B. By inverting all bits C. By inverting all
bits and adding 1 D. By subtracting the value from 256 E. By prefixing the number with
a minus sign bit
CORRECT ANSWER: C. By inverting all bits and adding 1 RATIONALE:
Two's complement requires flipping all bits (one's complement) and then adding 1 to
represent negative numbers.
Q19. What is 0xFF in decimal?
A. 240 B. 250 C. 254 D. 255 E. 256
CORRECT ANSWER: D. 255 RATIONALE: FF = 15×16 + 15 = 255. It is also
the maximum value of an unsigned 8-bit integer.
Q20. What is the binary subtraction 1010 − 0011?
A. 0110 B. 0111 C. 1001 D. 0101 E. 1100
