Practice neco computer_studies 2020 Past Questions

Question 1 View Details

A Hamming(7,4) code is used for error detection. The received 7‑bit code is \(1011101\). Determine the position of the erroneous bit, give the corrected 7‑bit code, and state the original 4‑bit data block.

A. Error position: 7; Corrected code: 1011100; Original data: 1100

B. Error position: 5; Corrected code: 1011001; Original data: 1110

C. Error position: 3; Corrected code: 1001101; Original data: 1001

Correct D. Error position: 4; Corrected code: 1010101; Original data: 1101

Correct Answer: D

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Question 2 View Details

Consider the following CSS rules:\n```css\n#nav ul li a { color: blue; }\n.menu a { color: green !important; }\na { color: red; }\n```\nThe HTML element is \(<a id='home' class='menu' href='#'>Home</a>\) inside \(<li>\) inside \(<ul>\) inside \(<nav id='nav'>\). What is the final computed text colour of the link?

A. inherit

B. blue

C. red

Correct D. green

Correct Answer: D

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Question 3 View Details

A 150\,MB file is compressed to 60\% of its original size. The compressed data is sent over a network with a bandwidth of 12\,Mbps. Each packet can carry 1500\,bytes, of which 200\,bytes are header overhead. Assuming packets are filled to capacity with data payload, calculate the total transmission time in seconds, rounded to two decimal places.

Correct A. 72.60

B. 75.00

C. 69.23

D. 68.40

Correct Answer: A

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Question 4 View Details

Given the following pseudocode:\n```\nfor i = 1 to n\n for j = 1 to i\n if j mod 3 == 0\n for k = 1 to n\n print "*"\n```\nWhat is the time‑complexity of this algorithm in Big‑O notation?

A. O(n²)

B. O(n⁴)

Correct C. O(n³)

D. O(n log n)

Correct Answer: C

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Question 5 View Details

Who is commonly referred to as the "father of the computer", and what was his major contribution to computing history?

Correct A. Charles Babbage; he designed the Analytical Engine, the first concept of a programmable computer.

B. Alan Turing; he invented the first electronic computer, the ENIAC.

C. John von Neumann; he created the first mechanical calculator, the Difference Engine.

D. Ada Lovelace; she wrote the first computer program for the Analytical Engine.

Correct Answer: A

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Question 6 View Details

An organization requires that a password must be at least 8 characters long and may use uppercase letters (26), lowercase letters (26), digits (10) and 6 special symbols. An attacker can try \(10^{6}\) passwords per second. Determine the minimum password length that guarantees a brute‑force cracking time of more than one year, and state the approximate time (in years) for that length.

A. 9 characters; about 130 years

Correct B. 8 characters; about 14.5 years

C. 7 characters; about 0.9 years

D. 8 characters; about 2.3 years

Correct Answer: B

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Question 7 View Details

Name the computer that first implemented the stored‑program concept, completed in 1945.

A. ENIAC

Correct B. EDVAC

C. EDSAC

D. UNIVAC

Correct Answer: B

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Question 8 View Details

Consider a relation R(A,B,C,D,E) with functional dependencies: A\rightarrow B, BC\rightarrow D, D\rightarrow E, and A\rightarrow C. (a) Identify the highest normal form of R. (b) Decompose R into a set of relations that are in Boyce‑Codd Normal Form (BCNF). (c) State whether the decomposition is lossless‑join and whether it preserves all functional dependencies. List the resulting BCNF relations.

Correct A. Highest normal form: 2NF. BCNF relations: R1(B,C,D), R21(A,B), R221(A,C), R222(A,E). The decomposition is lossless‑join but not dependency‑preserving.

B. Highest normal form: 2NF. BCNF relations: R1(B,C,D), R21(A,B), R221(A,E), R222(A,C). The decomposition is not lossless‑join and not dependency‑preserving.

C. Highest normal form: 3NF. BCNF relations: R1(B,C,D), R21(A,B), R221(A,C), R222(A,E). The decomposition is lossless‑join and dependency‑preserving.

D. Highest normal form: 2NF. BCNF relations: R1(B,C,D), R21(A,B), R221(A,C). The decomposition is lossless‑join but not dependency‑preserving.

Correct Answer: A

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Question 9 View Details

An IPv4 network has address 192.168.48.0/20. The organization wants to create subnets that can each support at least 500 usable host addresses. Determine: (i) the subnet mask (in dotted‑decimal notation) to be used, (ii) the total number of subnets that can be created, and (iii) the network address of the first such subnet. Assume subnets are allocated sequentially from the start of the address space.

A. Subnet mask 255.255.252.0 (\/22); 4 subnets; first subnet network address 192.168.48.0

B. Subnet mask 255.255.254.0 (\/23); 8 subnets; first subnet network address 192.168.50.0

Correct C. Subnet mask 255.255.254.0 (/23); 8 subnets; first subnet network address 192.168.48.0

D. Subnet mask 255.255.254.0 (\/23); 16 subnets; first subnet network address 192.168.48.0

Correct Answer: C

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Question 10 View Details

Write a Python function `prime_digit_sum_square(nums)` that receives a list of integers `nums` and returns the sum of the squares of those numbers that satisfy both conditions: 1. The number itself is prime. 2. The sum of its decimal digits is also a prime number. Using the list `[13, 23, 29, 31, 41, 43, 59, 61, 73, 79]`, what value does the function return? (Do not include any input or output statements; only the function definition and the final returned value are required.)

A. 8092

B. 12102

Correct C. 8621

D. 4900

Correct Answer: C

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Question 11 View Details

Consider the following HTML element and CSS rules. HTML: ```html <div id="main" class="highlight" style="background: orange;">Content</div> ``` CSS: ```css #main { background: blue !important; } .highlight { background: yellow; } div { background: red; } ``` According to CSS cascade and specificity, what background colour will be displayed for the <div id="main"> element? Provide the colour name.

Correct A. blue

B. yellow

C. orange

D. red

Correct Answer: A

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Question 12 View Details

A relation R(A, B, C, D) has the following functional dependencies: \(A \rightarrow B\), \(B \rightarrow C\), and \(A \rightarrow D\). Assuming all attributes contain atomic values, determine the highest normal form (1NF, 2NF, 3NF, or BCNF) that R currently satisfies.

A. 1NF

B. 3NF

C. BCNF

Correct D. 2NF

Correct Answer: D

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Question 13 View Details

A data packet of 1500 bytes is transmitted from Host A to Host B through three identical routers. Each link between devices is 100 km long, the propagation speed on the links is \(2 \times 10^{8}\) m/s, and each link has a bandwidth of 10 Mbps. Each router introduces a processing delay of 2 ms and uses store‑and‑forward switching (the router must receive the entire packet before forwarding it). Calculate the total end‑to‑end delay (in milliseconds) from Host A to Host B.

A. 11.2

B. 13.6

C. 14.4

Correct D. 12.8

Correct Answer: D

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Question 14 View Details

In which year was the ENIAC computer completed and first put into operation?

A. 1944

B. 1946

Correct C. 1945

D. 1950

Correct Answer: C

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Question 15 View Details

The 8‑bit two's complement binary number \(10110110\) is stored in memory. a) Determine its decimal value. b) Add to it the 8‑bit two's complement binary number \(00101101\) using two's complement arithmetic. State the resulting decimal value and indicate whether an overflow occurred.

A. Decimal value = -75; after addition result = -30; overflow = No

B. Decimal value = -74; after addition result = -30; overflow = No

C. Decimal value = -74; after addition result = -29; overflow = Yes

Correct D. Decimal value = -74; after addition result = -29; overflow = No

Correct Answer: D

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Question 16 View Details

A simple selection sort algorithm makes \(\frac{n(n-1)}{2}\) comparisons to sort a list of \(n\) items. If the program reports that it performed 780 comparisons, determine the number of items \(n\). Then, assuming the list was initially in reverse order (worst case), each iteration swaps at most one element. Compute the total number of operations (comparisons plus swaps) required to sort the list.

A. 840

B. 818

C. 820

Correct D. 819

Correct Answer: D

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Question 17 View Details

The ENIAC computer was completed in \(1945\). The UNIVAC I was delivered three years later. In what year was the UNIVAC I delivered?

A. 1949

B. 1946

C. 1947

Correct D. 1948

Correct Answer: D

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Question 18 View Details

In a spreadsheet, column A contains quantities, column B unit prices, and column C calculates the total price for each item with the formula \(=A\_i*B\_i\). A discount of 10\% is applied to any item whose total price exceeds 5,000. Write the formula for column D that gives the final payable amount for each item after applying the discount. Then, using the following data rows, compute the overall amount payable for all three items:\n- Row 1: quantity 20, unit price 150\n- Row 2: quantity 35, unit price 80\n- Row 3: quantity 50, unit price 120

A. 11500

B. 11220

Correct C. 11200

D. 11800

Correct Answer: C

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Question 19 View Details

A sorted list containing 1,024 items is searched using binary search. Determine the maximum number of comparisons required in the worst case. Afterwards, the list size is increased to 1,500 items (still sorted). Determine the maximum number of comparisons required for the 1,500‑item list and state how many more comparisons this requires compared to the original list.

A. 12 comparisons, which is 2 more than the original 10 comparisons

Correct B. 11 comparisons, which is 1 more than the original 10 comparisons

C. 11 comparisons, which is 2 more than the original 9 comparisons

D. 10 comparisons, which is the same as the original 10 comparisons

Correct Answer: B

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Question 20 View Details

An organization implements two independent security controls, A and B. Control A fails with probability 0.02 and control B fails with probability 0.03. A breach occurs if both A and B fail simultaneously. Additionally, a third control C is activated only when either A or B fails (but not both), and C fails with probability 0.05. Assuming all failures are independent, calculate the overall probability that a breach occurs.

Correct A. 0.00304

B. 0.00204

C. 0.00344

D. 0.0034

Correct Answer: A

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Question 21 View Details

Consider the following Python program: ``` total = 0 for i in range(1, 7): for j in range(i, 9): if (i + j) % 3 == 0: total += i * j elif i == 4: total -= j print(total) ``` The condition checks whether \( (i + j) \bmod 3 = 0 \). What integer value is displayed when the program is executed?

Correct A. 170

B. 165

C. 190

D. 175

Correct Answer: A

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Question 22 View Details

A computer system uses a \(600\) W power‑supply unit (PSU) with an efficiency of \(85\)% . The components draw the following power: CPU \(95\) W, GPU \(150\) W, motherboard \(50\) W, and three hard‑disk drives each \(10\) W. Is the PSU adequate for this configuration? Answer "Yes" if it is sufficient, otherwise "No".

A. Negative

Correct B. Yes

C. No

D. Nope

Correct Answer: B

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Question 23 View Details

Arrange the following computer‑history milestones in chronological order from earliest to latest: (A) Introduction of the IBM PC, (B) Release of the first Apple Macintosh, (C) Invention of the Intel 4004 microprocessor, (D) Launch of Windows 95.

A. C, A, D, B

B. A, C, B, D

Correct C. C, A, B, D

D. C, B, A, D

Correct Answer: C

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Question 24 View Details

The following CSS and HTML are applied: ```html <div class="outer"> <div class="inner"></div> </div> ``` ```css .outer { width: 500px; /* content width */ padding: 20px; border: 5px solid #000; box-sizing: content-box; } .inner { width: 100%; padding: 10px; border: 2px solid #333; box-sizing: border-box; } ``` What is the computed content width (in pixels) of the inner `<div>` element?

A. 440

B. 410

Correct C. 426

D. 452

Correct Answer: C

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Question 25 View Details

The following Python function counts how many unordered pairs of numbers in a list have a sum divisible by 5: ```python def count_pairs(lst): count = 0 n = len(lst) for i in range(n): for j in range(i+1, n): if (lst[i] + lst[j]) % 5 == 0: count += 1 return count numbers = [12, 7, 3, 14, 8, 5] result = count_pairs(numbers) print(result) ``` What integer does the program print?

A. 6

B. 3

Correct C. 4

D. 5

Correct Answer: C

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