WGU D684 INTRODUCTION TO COMPUTER SCIENCE –
OBJECTIVE ASSESSMENT (OA) – ACTUAL EXAM
Verified Solutions – Latest Updated Version – Pass
Guaranteed - A+ Graded
Part I: Foundations of Computing & Algorithms
Q1: A student is building a simple home computer and wants to understand what
happens when they press the power button. Which component is primarily responsible
for fetching instructions from memory, decoding them, and executing the operations?
A. The hard disk drive stores all programs permanently and runs them directly when
powered on.
B. The RAM holds the operating system and decides which program runs first at
startup.
C. The CPU fetches, decodes, and executes instructions in a continuous cycle.
[CORRECT]
D. The motherboard generates electrical signals that directly perform arithmetic without
needing other parts.
Correct Answer: C
Rationale: The best answer is C. The CPU—central processing unit—is literally built
around the fetch-decode-execute cycle. It pulls instructions from memory, figures out
what they mean, and then carries them out. The other parts play supporting roles, but
the CPU is the brain doing that core loop.
,Q2: Your friend asks why their 500 GB hard drive shows only about 465 GB of usable
space in the operating system. What is the most accurate explanation?
A. The drive manufacturer is using base-10 (1 GB = 1,000,000,000 bytes) while the OS
reports in base-2 (1 GiB = 1,073,741,824 bytes). [CORRECT]
B. The missing space is permanently reserved for the computer's BIOS firmware.
C. Hard drives always lose 10% of capacity due to magnetic field degradation over time.
D. The operating system rounds all storage numbers down to the nearest prime number
for security.
Correct Answer: A
Rationale: The best answer is A. This is a classic marketing-vs-technical measurement
mismatch. Drive makers advertise gigabytes in base-10, but Windows and most OSes
historically display gibibytes in base-2. That difference accounts for the "missing"
space—it's not actually lost, just labeled differently.
Q3: In binary, what decimal value does the 8-bit pattern 10110100 represent?
A. 178
B. 180 [CORRECT]
C. 182
D. 184
Correct Answer: B
,Rationale: The best answer is B. Working left to right: 128 + 32 + 16 + 4 = 180. The bits
in positions 7, 5, 4, and 2 are all set to 1, and adding those place values gives you 180.
It's a straightforward binary-to-decimal conversion.
Q4: A small program needs to store the letter 'M' in memory. Using standard ASCII
encoding, which 8-bit binary pattern would be written?
A. 01001101 [CORRECT]
B. 01101101
C. 01001100
D. 01101100
Correct Answer: A
Rationale: The best answer is A. In ASCII, uppercase 'M' is decimal 77. Breaking that
down: 64 + 8 + 4 + 1 = 77, which translates to binary 01001101. Lowercase 'm' would
be option B, so that's a common trap to watch for.
Q5: You're helping a classmate understand memory hierarchy. They want to know why
adding more RAM often makes a computer feel faster, even though the CPU speed
hasn't changed. What's the clearest explanation?
A. More RAM lets the CPU access data without waiting for slower disk storage as often.
[CORRECT]
B. RAM stores permanent files, so more RAM means more programs are saved forever.
C. Extra RAM increases the CPU's clock speed by reducing electrical resistance.
, D. The operating system converts unused RAM into additional CPU cores automatically.
Correct Answer: A
Rationale: The best answer is A. RAM is much faster than hard drives or SSDs. When
RAM fills up, the OS has to swap data to disk, which is slow. More RAM means less
swapping, so the CPU spends more time working and less time waiting. The CPU itself
isn't faster, but it's waiting less.
Q6: Which of the following best describes the role of an operating system?
A. It translates high-level programming languages into machine code for the CPU.
B. It manages hardware resources, provides user interfaces, and coordinates running
programs. [CORRECT]
C. It stores all user data permanently and prevents any program from ever crashing.
D. It replaces the need for physical memory by creating virtual files on the hard drive.
Correct Answer: B
Rationale: The best answer is B. The OS is essentially the traffic controller and middle
manager of the computer. It handles memory allocation, schedules CPU time for
different programs, manages file systems, and gives users a way to interact with the
machine. It doesn't write code or guarantee crash-proof operation.
Q7: A program needs to represent the color of a pixel using 24-bit RGB values. If the red
channel is 11111111, the green channel is 00000000, and the blue channel is
00000000, what color is displayed?
A. Pure green
B. Pure blue
OBJECTIVE ASSESSMENT (OA) – ACTUAL EXAM
Verified Solutions – Latest Updated Version – Pass
Guaranteed - A+ Graded
Part I: Foundations of Computing & Algorithms
Q1: A student is building a simple home computer and wants to understand what
happens when they press the power button. Which component is primarily responsible
for fetching instructions from memory, decoding them, and executing the operations?
A. The hard disk drive stores all programs permanently and runs them directly when
powered on.
B. The RAM holds the operating system and decides which program runs first at
startup.
C. The CPU fetches, decodes, and executes instructions in a continuous cycle.
[CORRECT]
D. The motherboard generates electrical signals that directly perform arithmetic without
needing other parts.
Correct Answer: C
Rationale: The best answer is C. The CPU—central processing unit—is literally built
around the fetch-decode-execute cycle. It pulls instructions from memory, figures out
what they mean, and then carries them out. The other parts play supporting roles, but
the CPU is the brain doing that core loop.
,Q2: Your friend asks why their 500 GB hard drive shows only about 465 GB of usable
space in the operating system. What is the most accurate explanation?
A. The drive manufacturer is using base-10 (1 GB = 1,000,000,000 bytes) while the OS
reports in base-2 (1 GiB = 1,073,741,824 bytes). [CORRECT]
B. The missing space is permanently reserved for the computer's BIOS firmware.
C. Hard drives always lose 10% of capacity due to magnetic field degradation over time.
D. The operating system rounds all storage numbers down to the nearest prime number
for security.
Correct Answer: A
Rationale: The best answer is A. This is a classic marketing-vs-technical measurement
mismatch. Drive makers advertise gigabytes in base-10, but Windows and most OSes
historically display gibibytes in base-2. That difference accounts for the "missing"
space—it's not actually lost, just labeled differently.
Q3: In binary, what decimal value does the 8-bit pattern 10110100 represent?
A. 178
B. 180 [CORRECT]
C. 182
D. 184
Correct Answer: B
,Rationale: The best answer is B. Working left to right: 128 + 32 + 16 + 4 = 180. The bits
in positions 7, 5, 4, and 2 are all set to 1, and adding those place values gives you 180.
It's a straightforward binary-to-decimal conversion.
Q4: A small program needs to store the letter 'M' in memory. Using standard ASCII
encoding, which 8-bit binary pattern would be written?
A. 01001101 [CORRECT]
B. 01101101
C. 01001100
D. 01101100
Correct Answer: A
Rationale: The best answer is A. In ASCII, uppercase 'M' is decimal 77. Breaking that
down: 64 + 8 + 4 + 1 = 77, which translates to binary 01001101. Lowercase 'm' would
be option B, so that's a common trap to watch for.
Q5: You're helping a classmate understand memory hierarchy. They want to know why
adding more RAM often makes a computer feel faster, even though the CPU speed
hasn't changed. What's the clearest explanation?
A. More RAM lets the CPU access data without waiting for slower disk storage as often.
[CORRECT]
B. RAM stores permanent files, so more RAM means more programs are saved forever.
C. Extra RAM increases the CPU's clock speed by reducing electrical resistance.
, D. The operating system converts unused RAM into additional CPU cores automatically.
Correct Answer: A
Rationale: The best answer is A. RAM is much faster than hard drives or SSDs. When
RAM fills up, the OS has to swap data to disk, which is slow. More RAM means less
swapping, so the CPU spends more time working and less time waiting. The CPU itself
isn't faster, but it's waiting less.
Q6: Which of the following best describes the role of an operating system?
A. It translates high-level programming languages into machine code for the CPU.
B. It manages hardware resources, provides user interfaces, and coordinates running
programs. [CORRECT]
C. It stores all user data permanently and prevents any program from ever crashing.
D. It replaces the need for physical memory by creating virtual files on the hard drive.
Correct Answer: B
Rationale: The best answer is B. The OS is essentially the traffic controller and middle
manager of the computer. It handles memory allocation, schedules CPU time for
different programs, manages file systems, and gives users a way to interact with the
machine. It doesn't write code or guarantee crash-proof operation.
Q7: A program needs to represent the color of a pixel using 24-bit RGB values. If the red
channel is 11111111, the green channel is 00000000, and the blue channel is
00000000, what color is displayed?
A. Pure green
B. Pure blue
