KS3 Edexcel Computer Science Unit Test Mock Paper Walkthrough | KS3 Edexcel 计算机单元测试模拟卷解析

📚 KS3 Edexcel Computer Science Unit Test Mock Paper Walkthrough | KS3 Edexcel 计算机单元测试模拟卷解析

Preparing for an end‑of‑unit test in Key Stage 3 computing can feel daunting, but working through a mock paper is one of the best ways to build confidence and spot gaps in your knowledge. This walkthrough takes you through a realistic KS3‑style assessment, unpacking each question with clear explanations. Each solution is paired with a matching Chinese translation so that bilingual learners can follow along seamlessly.

为 KS3 阶段的计算机单元测验做准备可能会让人感到畏惧，但通过模拟卷来练习是建立信心并发现知识漏洞的最佳方法之一。本解析将带你完成一套贴近真实 KS3 风格的评估卷，逐一详解每道题目。每段解析都配有对应的中文翻译，方便双语学习者同步理解。

---

1. Mock Paper Overview | 模拟卷概览

This mock paper is designed to reflect the breadth of a typical KS3 Edexcel‑aligned computing unit. It includes binary calculations, questions on the CPU cycle, input/output devices, programming concepts, flowchart interpretation, cybersecurity, and data representation. The paper mixes multiple‑choice, short‑answer, and debugging tasks to test both theory and practical understanding.

本模拟卷的设计覆盖了典型的 KS3 Edexcel 计算机单元的知识广度。题目包括二进制运算、CPU 周期问题、输入/输出设备、编程概念、流程图解读、网络安全以及数据表示。试卷混合了选择题、简答题和调试任务，以检测理论与实际应用两方面的理解。

---

2. Question 1: Binary to Denary Conversion | 二进制转十进制

Question: Convert the binary number 1011₂ into its denary equivalent. Show your working.

题目： 将二进制数 1011₂ 转换为十进制数。写出演算过程。

Solution: Place the binary digits under the place values 8, 4, 2, 1. 1×8 = 8, 0×4 = 0, 1×2 = 2, 1×1 = 1. Add them together: 8 + 0 + 2 + 1 = 11. So the answer is 11.

解析： 把二进制各位放在位值 8、4、2、1 下。1×8 = 8，0×4 = 0，1×2 = 2，1×1 = 1。全部相加：8 + 0 + 2 + 1 = 11。因此答案是 11。

---

3. Question 2: Denary to Binary Conversion | 十进制转二进制

Question: Convert the denary number 23 into an 8‑bit binary number.

题目： 将十进制数 23 转换为 8 位二进制数。

Solution: Find the largest power of 2 that fits: 16 (2⁴). Subtract: 23 − 16 = 7. Then 4 (2²) fits, leaving 3. Finally 2 (2¹) and 1 (2⁰) fit. Mark 1s for 16, 4, 2, 1, and 0s elsewhere: 00010111₂. As an 8‑bit number: 00010111.

解析： 找出所能容纳的 2 的最大幂：16 (2⁴)。相减：23 − 16 = 7。接下来是 4 (2²)，剩下 3。最后是 2 (2¹) 和 1 (2⁰)。在 16、4、2、1 位置记 1，其余记 0：00010111₂。作为 8 位二进制数：00010111。

---

4. Question 3: The Fetch–Decode–Execute Cycle | 取指–译码–执行周期

Question: Describe the three stages of the CPU’s instruction cycle in the correct order.

题目： 按正确顺序描述 CPU 指令周期的三个阶段。

Solution: The cycle is Fetch → Decode → Execute. In the fetch stage, the CPU retrieves an instruction from main memory (RAM). During decode, the control unit interprets what the instruction means. In execute, the arithmetic logic unit (ALU) or other components carry out the instruction. This cycle repeats billions of times per second.

解析： 周期顺序为 取指 → 译码 → 执行。在取指阶段，CPU 从主存（RAM）取出指令。在译码阶段，控制单元解读指令的含义。在执行阶段，算术逻辑单元（ALU）或其他部件执行指令。该周期每秒重复数十亿次。

---

5. Question 4: Input and Output Devices | 输入与输出设备

Question: Which of the following is an input device? (a) Monitor (b) Printer (c) Keyboard (d) Speaker

题目： 以下哪一项是输入设备？(a) 显示器 (b) 打印机 (c) 键盘 (d) 扬声器

Solution: The correct answer is (c) Keyboard. A keyboard sends data into the computer. Monitors, printers, and speakers are output devices because they present information to the user.

解析： 正确答案是 (c) 键盘。键盘将数据输入计算机。而显示器、打印机和扬声器是输出设备，因为它们向用户呈现信息。

---

6. Question 5: Programming Constructs – Sequence, Selection, Iteration | 程序结构——顺序、选择、迭代

Question: Look at this Scratch script: [move 10 steps] [if on edge, bounce] [say ‘Hello’]. Identify an example of sequence. Explain how you know.

题目： 观察以下 Scratch 脚本：[移动 10 步] [碰到边缘就反弹] [说 ‘Hello’]。指出其中一处顺序结构的例子，并说明判断依据。

Solution: The entire script demonstrates sequence because the blocks are executed one after another in a straight line from top to bottom. There is no condition or loop; the program simply follows the order of the blocks.

解析： 整个脚本展示了顺序结构，因为积木块自上而下按直线顺序逐一执行。没有条件判断或循环；程序只是按积木块排列的顺序依次执行。

---

7. Question 6: Flowchart Symbols | 流程图符号

Question: In a flowchart, what shape represents a decision? What goes inside it?

题目： 在流程图中，哪个形状表示判断？形状内应填入什么？

Solution: A decision is represented by a diamond shape. Inside the diamond, you write a question that can be answered with ‘Yes’ or ‘No’, such as ‘Is score > 50?’. The flow then branches accordingly.

解析： 判断用菱形表示。菱形内部需写出一个可以用“是”或“否”回答的问题，例如“分数 > 50？”。程序流程据此分支。

---

8. Question 7: Decomposition and Abstraction | 分解与抽象

Question: Explain the term ‘decomposition’ in computational thinking and give an example.

题目： 解释计算思维中的“分解”一词，并举例说明。

Solution: Decomposition means breaking a complex problem down into smaller, more manageable parts. For example, when designing a computer game, you could decompose it into graphics, gameplay, scoring, and controls. Each part can be solved independently, making the overall problem easier to tackle.

解析： 分解是指将一个复杂问题拆分成若干更小、更易于处理的部分。例如，在设计一款电脑游戏时，可以将其分解为图形、玩法、计分和操控等部分。每个部分可独立解决，从而使整个问题更容易应对。

---

9. Question 8: Cybersecurity – Recognising Phishing | 网络安全——识别网络钓鱼

Question: You receive an email claiming you have won a prize and asking you to click a link and enter your password. What type of cyber attack is this? What should you do?

题目： 你收到一封邮件，声称你中奖了，要求你点击链接并输入密码。这属于哪种网络攻击？你应该怎么做？

Solution: This is a phishing attack. The attacker is trying to trick you into revealing sensitive information. You should never click the link or provide personal details. Report the email as spam and delete it immediately.

解析： 这是一次钓鱼攻击。攻击者试图诱骗你泄露敏感信息。你绝不能点击链接或提供个人资料。应将此邮件报告为垃圾邮件并立即删除。

---

10. Question 9: Data Units and File Sizes | 数据单位与文件大小

Question: How many bits are there in 1 byte? How many bytes in a kilobyte (KB)?

题目： 1 字节（byte）等于多少位（bit）？1 千字节（KB）等于多少字节？

Solution: 1 byte = 8 bits. In most GCSE and KS3 contexts, 1 kilobyte = 1024 bytes (2¹⁰ bytes), though some manufacturers use 1000 bytes for simplicity. Always check which convention your exam expects, but typically computer science uses 1024.

解析： 1 字节 = 8 位。在 GCSE 和 KS3 的大多数情境下，1 千字节 = 1024 字节（2¹⁰ 字节），尽管有些制造商为方便使用 1000 字节。请注意考试所要求的约定，但计算机科学通常使用 1024。

---

11. Question 10: Scratch Debugging – Sprite Stuck | Scratch 调试——角色卡住

Question: A Scratch sprite is supposed to move right continuously when the program starts, but it only moves once. What is the likely bug, and how would you fix it?

题目： 一个 Scratch 角色应在程序启动后持续向右移动，但实际只移动了一次。可能的错误是什么？如何修复？

Solution: The script likely uses an ‘when green flag clicked’ block followed by a single ‘move 10 steps’ block, without a loop. To fix it, place the movement block inside a ‘forever’ loop or use a ‘repeat until’ block to make it run continuously while a condition is true.

解析： 该脚本很可能在“当绿旗被点击”后只接了一个“移动 10 步”积木，没有循环结构。修复方法是将移动积木放入“重复执行”或“等待直到”积木内，使其在条件为真时持续运行。

---

12. Final Tips for the Real Test | 正式测验终极提示

Read every question carefully, especially the command words like ‘describe’, ‘explain’, or ‘state’. For programming questions, always write code in a logical order and test it mentally if you can. Keep an eye on the marks allocated—a 3‑mark question often expects three distinct points. Lastly, practise binary conversions until they become second nature; they frequently appear in KS3 computer science assessments.

仔细阅读每一道题目，尤其要注意“描述”、“解释”、“陈述”等指令词。对于编程题，始终按逻辑顺序书写代码，并尽可能在脑中进行测试。留意题目分值——3 分的题目通常需要写出三个不同的要点。最后，反复练习二进制转换，直到熟能生巧；二进制题目在 KS3 计算机科学评估中十分常见。

Published by TutorHao | KS3 Computer Science Revision Series | aleveler.com

更多咨询请联系16621398022（同微信）