Practice gce model questions vol1 computer_studies 2023 Past Questions

Question 1 View Details

An 8‑bit computer system uses a power‑supply unit (PSU) that provides a $12\,\text{V}$ rail rated at $20\,\text{A}$ and a $5\,\text{V}$ rail rated at $10\,\text{A}$. The CPU consumes $65\,\text{W}$ and the GPU consumes $150\,\text{W}$, both drawn from the $12\,\text{V}$ rail. A hard‑disk drive draws $10\,\text{W}$ from the $5\,\text{V}$ rail. The total power drawn from the wall socket, measured by a watt‑meter, is $350\,\text{W}$. Assuming the remaining current on the $12\,\text{V}$ rail is used by cooling fans, determine the power consumed by the fans and then calculate the overall efficiency of the PSU, expressed as a percentage (rounded to one decimal place).

Correct A. 71.4

B. 73.5

C. 68.2

D. 66.7

Correct Answer: A

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Question 2 View Details

Consider the following Python function: ```python def count_abundant(nums): # remove duplicates uniq = list(set(nums)) def proper_divisor_sum(n): total = 0 for d in range(1, n): if n % d == 0: total += d return total count = 0 for x in uniq: if proper_divisor_sum(x) > x: count += 1 return count ``` If the list `data = [12, 18, 20, 28, 30, 42, 70, 84, 90, 100, 12, 30, 70]` is passed to `count_abundant`, what integer does the function return?

A. 8

B. 10

C. 7

Correct D. 9

Correct Answer: D

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Question 3 View Details

Given the following Python code: ```python total = 0 for i in range(1, 6): for j in range(i): if (i + j) % 3 == 0: total += i * j ``` What is the final value stored in `total` after the loops finish executing?

A. 28

B. 30

C. 40

Correct D. 35

Correct Answer: D

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Question 4 View Details

An information system uses a $(7,4)$ Hamming code with even parity to protect 4‑bit data blocks. The parity bits are placed at positions 1, 2 and 4 (counting from the left). The original 4‑bit data word is $1011$. After encoding, the transmitted 7‑bit code word is sent over a noisy channel and received as $0110111$. Assuming at most one bit error occurred, determine the corrected 4‑bit data word and give its decimal value.

A. 7

B. 13

Correct C. 11

D. 10

Correct Answer: C

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Question 5 View Details

Consider the following recursive sorting routine written in pseudocode: ``` procedure weirdSort(A, left, right) if left >= right then return mid ← floor((left + right) / 2) weirdSort(A, left, mid) weirdSort(A, mid + 1, right) for i ← left to right - 1 do if A[i] > A[i+1] then swap A[i] and A[i+1] ``` The routine is applied to an array $A$ containing $n$ distinct elements, where $n$ is a power of two. Let $C(n)$ denote the total number of comparisons performed by the `if` statement in the `for` loop over the entire execution of `weirdSort`. Derive a recurrence for $C(n)$ and compute $C(8)$.

Correct A. 17

B. 23

C. 19

D. 15

Correct Answer: A

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Question 6 View Details

A motherboard supports up to 4 RAM modules. Currently 2 modules of (2\,\text{GB}\) each are installed. The user wants a total of (12\,\text{GB}\) using only (4\,\text{GB}\) modules. What is the minimum number of additional modules required?

A. 3

Correct B. 2

C. 1

D. 4

Correct Answer: B

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Question 7 View Details

A text file contains 2500 characters. In UTF‑8 each character occupies on average 1.2 bytes. A compression program reduces the file size by 30 % and then adds a 128‑byte header. What is the final size of the compressed file in bytes?

Correct A. 2228

B. 2216

C. 2240

D. 2300

Correct Answer: A

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Question 8 View Details

The first commercially successful microprocessor was released in 1971 and the first personal computer with a graphical user interface appeared in 1984. How many years elapsed between these two milestones?

A. 15

B. 12

C. 14

Correct D. 13

Correct Answer: D

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Question 9 View Details

An organization is allocated the network 192.168.48.0/20. It needs subnets that can each support at least 500 usable host addresses. Determine the new subnet mask (in CIDR notation) and the maximum number of such subnets that can be created.

A. /25, 32 subnets

B. /24, 16 subnets

Correct C. /23, 8 subnets

D. /22, 4 subnets

Correct Answer: C

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Question 10 View Details

Consider the following HTML element and CSS rules (the external stylesheet is linked after the internal style block): HTML: <h1 id="title" class="header special" style="color: purple;">Welcome</h1> Internal CSS (in order): 1) h1 { color: black; } 2) .header { color: blue !important; } 3) #title { color: red; } 4) .special { color: green; } External CSS (appears after the internal block): 5) #title.special { color: orange !important; } Which colour will be rendered for the heading text?

A. blue

B. purple

C. green

Correct D. orange

Correct Answer: D

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Question 11 View Details

A program contains a nested loop where the outer loop variable i runs from 1 to n and the inner loop variable j runs from 1 to i. Each iteration of the inner loop executes a constant‑time operation that requires 5 CPU cycles. The processor runs at 2 GHz. The program must finish within 0.1 seconds. What is the greatest integer value of n that satisfies the time limit?

A. 8942

Correct B. 8943

C. 8945

D. 9021

Correct Answer: B

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Question 12 View Details

A source emits five symbols $A,B,C,D,E$ with frequencies 40, 25, 20, 10 and 5 respectively (total 100). Construct the optimal Huffman code for these symbols, then determine how many bits are required to encode a 200‑symbol message that follows the same frequency distribution.

Correct A. 420 bits

B. 400 bits

C. 415 bits

D. 430 bits

Correct Answer: A

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Question 13 View Details

An organisation evaluates three security threats. The risk score for a threat is calculated as $\text{Likelihood}\times\text{Impact}$ (both rated 1-5).\n\nThreats: T1 (L=4, I=3), T2 (L=2, I=5), T3 (L=5, I=2).\n\nThree possible controls are available, but only one can be afforded:\n- Control A: reduces T1 likelihood by 25% (cost $\$3000$).\n- Control B: reduces T2 impact by 40% (cost $\$2500$).\n- Control C: reduces T3 likelihood by 20% and impact by 20% (cost $\$4000$).\n\nWhich control gives the greatest reduction in the total risk score?

A. Control A

B. Control C

C. Control D

Correct D. Control B

Correct Answer: D

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Question 14 View Details

Relation R(A,B,C,D,E) has the functional dependencies: A→B, C→D, B→C, and A,E→D. Determine the highest normal form that R satisfies and give a lossless, dependency‑preserving decomposition of R into relations that are in Third Normal Form (3NF).

Correct A. Highest normal form: 1NF. 3NF decomposition: R1(A,B), R2(B,C), R3(C,D), R4(A,E).

B. Highest normal form: 2NF. 3NF decomposition: R1(A,B), R2(C,D), R3(A,E).

C. Highest normal form: 3NF. 3NF decomposition: R1(A,B), R2(B,C), R3(C,D), R4(A,E).

D. Highest normal form: 1NF. 3NF decomposition: R1(A,B), R2(C,D), R3(B,E).

Correct Answer: A

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Question 15 View Details

A company owns the network 192.168.0.0/24 and needs subnets for four departments requiring 50, 30, 20 and 10 hosts respectively. Using Variable Length Subnet Masking (VLSM), allocate the address space and state the network address (in CIDR notation) of the subnet assigned to the department that needs 20 hosts.

Correct A. 192.168.0.96/27

B. 192.168.0.128/27

C. 192.168.0.96/28

D. 192.168.0.64/27

Correct Answer: A

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Question 16 View Details

The following table shows the quarterly sales (in units) of three products. | Quarter | Product A | Product B | Product C | |---|---|---|---| | Q1 | 1200 | 800 | 600 | | Q2 | 1320 | 880 | 660 | | Q3 | 1386 | 924 | 693 | | Q4 | 1500 | 1000 | 750 | (a) Calculate the overall percentage increase in total sales from Q1 to Q4. (b) The company will award a bonus of ₦500 for each unit increase to the product that shows the greatest absolute increase in sales over the year. How much total bonus will be paid?

Correct A. 25% and ₦150,000

B. 20% and ₦120,000

C. 22% and ₦140,000

D. 30% and ₦180,000

Correct Answer: A

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Question 17 View Details

Consider the following HTML and CSS: HTML: ```html <div class="outer"> <div id="inner" class="box">Content</div> </div> ``` CSS: ```css .box { width: 200px; padding: 10px; border: 5px solid #000; box-sizing: content-box; } #inner { width: 180px; box-sizing: border-box; } .outer .box { padding: 15px; } div { margin: 20px; } ``` (a) Which rule determines the final width of the inner <div>? (b) Calculate the total horizontal space occupied by the inner <div> (including its margin, border and padding) as it will be rendered in the browser.

A. The div rule; total horizontal space = 240 px

B. The .box rule; total horizontal space = 210 px

C. The .outer .box rule; total horizontal space = 230 px

Correct D. The #inner rule; total horizontal space = 220 px

Correct Answer: D

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Question 18 View Details

A company evaluates three security threats using the formula: Risk Score = Probability × Impact (in ₦). The data are: | Threat | Probability | Impact (₦) | |---|---|---| | A | 0.20 | 500,000 | | B | 0.05 | 2,000,000 | | C | 0.10 | 800,000 | (a) Compute the risk score for each threat. (b) Only one threat can be mitigated due to budget limits. Assuming the company also considers the possible loss of life (Threat B could cause loss of life, the others would not), which threat should be prioritized for mitigation? Justify your choice using both the risk scores and the ethical factor.

A. Threat A should be mitigated because it has the highest risk score, even though it does not involve loss of life.

Correct B. Threat B should be mitigated because it has the highest (tied) risk score and also poses a possible loss‑of‑life, an ethical priority.

C. Threat B should be mitigated solely on the basis of its probability being the highest, ignoring the ethical consideration.

D. Threat C should be mitigated because its probability is the lowest, minimizing overall risk.

Correct Answer: B

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Question 19 View Details

The following Python function returns the sum of all numbers from 1 to *n* that are multiples of 3 or 5 but not both. ```python def f(n): total = 0 for i in range(1, n+1): if (i % 3 == 0) ^ (i % 5 == 0): # exclusive OR total += i return total ``` (a) What value does `f(20)` return? (b) Rewrite the function so that it computes the same result without using a loop, by applying arithmetic‑series formulas. (You need only give the new function body, not the full program.)

A. 78

B. 85

C. 90

Correct D. 83

Correct Answer: D

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Question 20 View Details

A histogram shows the distribution of test scores (out of 40) for a class of 30 students. The class intervals and their frequencies are: | Score interval | Frequency | |---|---| | 0 - 10 | 5 | | 10 - 20 | 12 | | 20 - 30 | 8 | | 30 - 40 | 5 | (a) Write the cumulative frequency for each interval. (b) Identify the median class. (c) Estimate the median score using linear interpolation within the median class. Give your answer to one decimal place.

A. 20.0

Correct B. 18.3

C. 16.7

D. 19.5

Correct Answer: B

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Question 21 View Details

In which year was the Intel 4004 microprocessor, the first commercially successful microprocessor, introduced?

A. 1969

Correct B. 1971

C. 1972

D. 1970

Correct Answer: B

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Question 22 View Details

A company requires passwords to be exactly eight characters long. Each password must contain at least one digit (0‑9) and at least one special character chosen from the set {!, @, #, $, %, ^, &, *, ?, /}. The remaining characters may be any of the 26 lowercase letters, the 10 digits, or the 10 special characters. How many different passwords satisfy the policy?

A. 46^8 - 36^8 + 26^8

B. 46^8 - 2*36^8 - 26^8

Correct C. 46^8 - 2*36^8 + 26^8

D. 45^8 - 2*35^8 + 26^8

Correct Answer: C

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Question 23 View Details

An organisation has the network address $192.168.0.0/24$. It needs to create sub‑nets that can each support at least 30 usable host addresses. What subnet mask should be used and how many such sub‑nets can be created?

A. Mask /27 (255.255.255.224); 4 sub‑nets

Correct B. Mask /27 (255.255.255.224); 8 sub‑nets

C. Mask /26 (255.255.255.192); 4 sub‑nets

D. Mask /28 (255.255.255.240); 16 sub‑nets

Correct Answer: B

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Question 24 View Details

A risk assessment identifies three potential threats to a company's data centre: - Threat A: probability $0.02$, financial impact $£200{,}000$ - Threat B: probability $0.05$, financial impact $£150{,}000$ - Threat C: probability $0.10$, financial impact $£80{,}000$ The company adopts a policy that any threat with an expected loss (probability × impact) of more than $£10{,}000$ must be mitigated. Which threats, if any, require mitigation and what is the highest expected loss?

A. Threat B exceeds £10,000; highest expected loss is Threat B with £7,500

Correct B. No threat exceeds £10,000; highest expected loss is Threat C with £8,000

C. Threat A exceeds £10,000; highest expected loss is Threat A with £40,000

D. Threat C exceeds £10,000; highest expected loss is Threat C with £8,000

Correct Answer: B

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Question 25 View Details

Consider a relation $R(A, B, C, D)$ with the following functional dependencies: $A \rightarrow B$, $B \rightarrow C$, $A \rightarrow D$. Determine the highest normal form that $R$ satisfies and provide a lossless‑join, dependency‑preserving decomposition of $R$ into relations that are in Boyce‑Codd Normal Form (BCNF).

A. 3NF; BCNF decomposition: R1(A, B) and R2(B, C, D)

Correct B. 2NF; BCNF decomposition: R1(B, C) and R2(A, B, D)

C. 2NF; BCNF decomposition: R1(A, C) and R2(A, B, D)

D. 2NF; BCNF decomposition: R1(B, D) and R2(A, B, C)

Correct Answer: B

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