2023 Edexcel GCSE Computer Science (1CP2) 模擬試題連答案詳解

A temperature sensor outputs an 8-bit two's complement signed integer representation of temperature. The binary sequence read is 11101011. Calculate the decimal equivalent of this value. Show your working.

An audio enthusiast records a mono sound clip with a sample rate of 8,000 Hz and a bit depth of 16 bits. The clip is exactly 20 seconds long. Calculate the file size of the uncompressed audio in kilobytes (KB). Use 1 KB = 1,000 bytes. Show your working.

A network device transmits a file of size 15 Megabytes (MB) over a WAN connection with an upload speed of 40 Megabits per second (Mbps). Calculate the theoretical minimum time, in seconds, required to upload this file. Assume 1 Megabyte = 8 Megabits. Show your working.

A run-length encoding (RLE) system is used to compress a string of pixel colors. Decompress the RLE string 1W5K3W2B and state its original size in bytes, assuming each character in the decompressed output represents exactly 1 byte.

Consider the boolean expression: Q = (NOT A) AND (B OR C). Complete the evaluation of this expression for the state where A = 0, B = 1, and C = 0. Show your step-by-step logic evaluation.

A software developer is designing a system for a smart thermostat. They use abstraction to simplify the development process. Explain how the developer would apply abstraction to representing the concept of a 'heating schedule' containing times and target temperatures, and state why this benefits development.

A program uses an ascending bubble sort algorithm to sort the following array: [12, 7, 15, 3, 9]. Show the state of the array after the FIRST complete pass of the bubble sort algorithm has finished. Explain the steps of the comparisons during this first pass.

A database system holds an array of records representing student test submissions. Each record contains a student ID (stored as a 6-character ASCII string, where 1 character = 1 byte) and a score (stored as an 8-bit integer). Calculate the exact total memory required, in bytes, to store an array of exactly 50 of these records. Show your working.

Convert the negative denary number \(-35\) into an 8-bit Two's Complement binary integer. Show your working.

Complete the missing logic values for the logic expression \(Q = (\text{NOT } A) \text{ AND } (B \text{ OR } C)\) for the following two cases: Case 1: when \(A = 0, B = 1, C = 0\); Case 2: when \(A = 1, B = 1, C = 1\). State the output value of \(Q\) for each case.

Explain how a software engineer would apply the process of decomposition when designing a digital school registration system. Give two distinct examples of subsystems that would result from this.

A high-definition image file of size 15 Megabytes (MB) needs to be transmitted across a network with a stable transmission speed of 40 Megabits per second (Mbps). Calculate the theoretical minimum time required to transmit this file. Show your calculations.

A row of an image contains 120 consecutive White pixels, followed by 80 consecutive Black pixels, followed by 200 consecutive White pixels. Each raw pixel is stored using 1 byte of data. Run-Length Encoding (RLE) is used to compress this row, where each run is represented using 1 byte for the count and 1 byte for the pixel value. Calculate the storage space saved in bytes. Show your working.

In software development, programmers often use hexadecimal representation rather than binary. Explain two distinct benefits of using hexadecimal notation over binary for programmers, and state how many bits are represented by a single hexadecimal digit.

A school database has been compromised. The attacker manipulated an online login form by entering malicious database commands to bypass authentication. Identify the type of cyber security attack used, and explain how a database developer could prevent this specific vulnerability.

An algorithm uses a loop to search an array `scores` containing `[14, 25, 8, 19, 31]`. The variable `target` is set to `19`. The pseudocode is:
```text
index = 0
found = False
while index < length(scores) and found == False:
if scores[index] == target:
found = True
else:
index = index + 1
```
Determine the final values of the variables `index` and `found` after this algorithm completes execution, and state how many comparisons against the `target` were made.

An audio file is recorded with a sample rate of \(8\text{ kHz}\), a bit depth of \(16\text{ bits}\), and is monophonic (1 channel). The recording lasts for exactly \(10\text{ seconds}\). Calculate the file size of the uncompressed audio in kilobytes (KB). Assume \(1\text{ KB} = 1000\text{ bytes}\). Show your working.

Perform an arithmetic shift right by 2 places on the 8-bit two's complement signed binary integer \(11001000_{2}\). State the resulting binary number and its denary equivalent.

Complete the logic output \(Q\) for the expression \(Q = \text{NOT } (A \text{ AND } B) \text{ OR } C\) for the following three rows of a truth table: \
Row 1: \(A = 1, B = 1, C = 0\) \
Row 2: \(A = 0, B = 1, C = 0\) \
Row 3: \(A = 1, B = 0, C = 1\)

A software engineer is designing an app to track bus routes and arrival times. Explain how the engineer would apply abstraction to design the virtual map representation of the bus routes. Your answer should identify one detail that would be included and one detail that would be removed.

A client computer is downloading a web page asset of size \(400\text{ Kilobytes (KB)}\) over a network connection with a bandwidth of \(8\text{ Megabits per second (Mbps)}\). Calculate the theoretical minimum transmission time in seconds. Assume \(1\text{ KB} = 1000\text{ bytes}\) and \(1\text{ Mb} = 1,000,000\text{ bits}\). Show your working.

Complete the following hexadecimal subtraction: \(4\text{A}_{16} - 1\text{F}_{16}\). Show your working, and state both the hexadecimal result and its denary equivalent.

An automated greenhouse ventilation system uses three boolean inputs: High Humidity (H), High Temperature (T), and Manual Override (M). The ventilation fan (F) must turn on (F = 1) if Manual Override (M) is active, OR if both High Humidity (H) and High Temperature (T) are active.

(a) Describe the logic gate combination that represents this system, detailing the inputs to each gate and how they produce the output F. [3 marks]

(b) Complete the truth table for output F for all possible input combinations of H, T, and M. [4 marks]

(c) Explain how abstraction has been used by the designer when representing this physical greenhouse system as a digital logic model. [3 marks]

An algorithm calculates a shipping fee based on two inputs: Weight (W) in kilograms, and Distance (D) in kilometres.

The base delivery fee is £5.00.
- If Weight is greater than 10 kg, an extra charge of £4.00 is added.
- If Distance is greater than 50 km, an extra charge of £3.00 is added.
- If both of these extra charges are applied, a discount of £1.00 is subtracted from the total.

(a) Complete a trace table showing the intermediate conditions and final Delivery Cost for these three test inputs:
Case 1: W = 4, D = 30
Case 2: W = 12, D = 25
Case 3: W = 15, D = 80
[6 marks]

(b) Identify the standard geometric flowchart shape used to represent conditional decisions, and explain its logical function. [2 marks]

(c) State the programming construct used to execute different steps based on whether the Weight is greater than 10, and explain its purpose. [2 marks]

Analyse this faulty Python function, which is intended to validate a password. To be valid, a password must be at least 8 characters long, contain at least one digit, and contain at least one uppercase letter.

Line 1: def check_password(password)
Line 2: if len(password) < 8:
Line 3: return False
Line 4:
Line 5: has_digit = False
Line 6: has_upper = False
Line 7:
Line 8: for char in password:
Line 9: if char.isdigit():
Line 10: has_digit = True
Line 11: if char.isupper():
Line 12: has_upper = True
Line 13: else:
Line 14: has_upper = False
Line 15:
Line 16: if has_digit == True and has_upper = True:
Line 17: return True
Line 18: else:
Line 19: return False

(a) Identify two syntax errors in this code. For each error, state the line number and provide the corrected line of code. (2 marks)
(b) Describe the logical error in lines 11–14 and explain how to correct it. (2 marks)
(c) Write three lines of defensive programming code to insert at the very start of the function (between Line 1 and Line 2). This code must check if the type of the parameter "password" is a string. If it is not a string, the function must immediately return False. (3 marks)

Analyse this Python function, which is intended to calculate and return the average of all even numbers in a list of integers.

Line 1: def average_evens(numbers):
Line 2: total = 0
Line 3: count = 0
Line 4: for i in range(1, len(numbers)):
Line 5: if numbers[i] % 2 = 0:
Line 6: total = total + numbers[i]
Line 7: count == count + 1
Line 8:
Line 9: average = total / count
Line 10: return average

(a) Identify the two line numbers containing syntax errors and write the corrected lines of code. (2 marks)
(b) Identify the line number of the logical error that causes the function to skip checking the first number in the list. Write the corrected line of code. (2 marks)
(c) State the name of the runtime error that occurs when 'numbers' contains no even numbers. (1 mark)
(d) Write a selection code block (if-else statement) to replace Line 9 to safely handle the scenario where no even numbers are present (i.e., count is zero) and return 0.0. (3 marks)

Write a Python program that records and analyzes the performance of school athletes in a 100m sprint.

The program must:
1. Prompt the user to enter the number of athletes. This must be an integer between 1 and 20 inclusive. If the user enters an invalid number, the program must repeatedly prompt them until a valid number is entered.
2. For each athlete:
- Prompt for and input their name (which cannot be empty).
- Prompt for and input their sprint time in seconds (a float between 9.0 and 20.0 inclusive). The program must validate this time and repeatedly prompt if an invalid value is entered.
3. Calculate and print the average sprint time of all entered athletes to 2 decimal places.
4. Find and display the name and time of the fastest athlete (the one with the lowest time).

Write the complete Python code to solve this problem.

Write a Python function `find_seats(seating_chart, required_seats)` that searches a cinema seating plan for a group of adjacent free seats in a single row.

- `seating_chart` is a 2D list (grid) where each row represents a row of seats. Free seats are marked with `'O'` (capital letter O) and reserved seats are marked with `'X'`.
- `required_seats` is an integer representing the number of consecutive free seats the group needs.

The function must:
1. Iterate through each row of the seating chart (from index 0 upwards).
2. Within each row, search from left to right (from index 0 upwards) for a sequence of adjacent `'O'` seats of length equal to `required_seats`.
3. If a matching sequence is found, return a list containing two elements: `[row_index, start_column_index]` of the first matching group of seats found, and stop searching.
4. If no such group of adjacent seats is available anywhere in the theater, the function must return `None`.

Assume `required_seats` is always greater than 0. Do not use external libraries.

Write a Python function `rle_encode(message)` to compress an uppercase alphabetical string using a simple Run-Length Encoding (RLE) algorithm.

The function must:
1. Validate that the input string `message` is not empty and consists ONLY of uppercase letters (A-Z). If the string is empty or contains non-alphabetic or lowercase characters, return the string `'INVALID'`.
2. Count consecutive identical characters in the string.
3. Build and return a compressed string where each run of identical characters is replaced by the count followed by the character itself (e.g., `'AAABBC'` becomes `'3A2B1C'`).

Example inputs and expected outputs:
- `rle_encode('AAABBC')` -> `'3A2B1C'`
- `rle_encode('XYZ')` -> `'1X1Y1Z'`
- `rle_encode('A1B')` -> `'INVALID'`
- `rle_encode('')` -> `'INVALID'`
- `rle_encode('aBB')` -> `'INVALID'`

Write a Python function `calculate_invoice(order_items)` that calculates the total cost of an online order, applying specific rules for discounts and shipping.

The parameter `order_items` is a list of lists. Each inner list represents an item in the shopping cart and contains: `[item_name, unit_price, quantity]` (e.g., `['Laptop Stand', 24.99, 2]`).

The function must implement these rules:
1. Calculate the raw subtotal by summing the cost of all items (where cost of an item is `unit_price * quantity`).
2. Apply a 10% discount on the subtotal if the subtotal is strictly greater than £50.00. Otherwise, no discount is applied.
3. Calculate the shipping fee based on the discounted subtotal:
- If the discounted subtotal is £30.00 or more, shipping is free (£0.00).
- If the discounted subtotal is less than £30.00, add a flat shipping fee of £4.99.
4. Return a tuple containing four float values rounded to exactly 2 decimal places: `(subtotal, discount_amount, shipping_fee, final_total)`.

Do not use external libraries.