📚 Year 8 Edexcel Computer Science: Mock Unit Test Walkthrough | Year 8 Edexcel 计算机：单元测试模拟卷解析
Welcome to this detailed walkthrough of a Year 8 Edexcel Computer Science mock unit test. We will break down each question type, explain the correct answers, and reinforce key concepts to help you prepare for your real assessment. This mock test covers hardware, data representation, algorithms, programming basics, networks, and online safety – all essential topics for the Year 8 curriculum.
欢迎来到这份 Year 8 Edexcel 计算机科学单元测试模拟卷的详细解析。我们将逐一分解各类题型，解释正确答案，并巩固关键概念，帮助你为真正的评估做好准备。这份模拟卷涵盖了硬件、数据表示、算法、编程基础、网络和在线安全——所有 Year 8 课程的核心主题。
1. Computer Hardware Basics | 计算机硬件基础
Question 1 presented a list of devices: Scanner, Microphone, Monitor, Webcam, and asked which is an output device. The correct choice is Monitor, because output devices take information from the computer and present it to the user. A monitor displays visual output. The other three – Scanner, Microphone, and Webcam – are input devices; they send data into the computer.
第1题给出了一组设备：扫描仪、麦克风、显示器、网络摄像头，要求选出输出设备。正确答案是显示器，因为输出设备从计算机获取信息并呈现给用户。显示器展示视觉输出。其他三个——扫描仪、麦克风和网络摄像头——都是输入设备，它们将数据发送给计算机。
Question 2 asked which component stores the operating system when the power is off. The answer is the hard disk drive (HDD) or solid-state drive (SSD). These are non‑volatile secondary storage devices that retain data without electrical power. RAM, in contrast, is volatile and loses its contents when the computer is switched off. ROM holds firmware but not the full operating system.
第2题询问哪个组件在断电后存储操作系统。答案是硬盘驱动器或固态硬盘。这些是非易失性辅助存储设备，断电后依然能保留数据。相比之下，RAM 是易失性的，计算机关闭时会丢失内容。ROM 保存固件，但不是完整的操作系统。
An early foundational question: What does CPU stand for? CPU stands for Central Processing Unit. It is often called the brain of the computer because it executes program instructions and carries out arithmetic, logic, and control operations.
一个早期的基础题：CPU 代表什么？CPU 是中央处理单元。它常被称为计算机的大脑，因为它执行程序指令，进行算术、逻辑和控制操作。
2. Memory and Storage | 内存与存储
Question 3 tested your knowledge of acronyms: What does RAM stand for? RAM stands for Random Access Memory. It is used to hold data and instructions that the CPU needs right now. When you open an application, it loads from the hard drive into RAM so it can be accessed very quickly. RAM is volatile, meaning all its data is lost when the power is turned off.
第3题考查你知道术语缩写：RAM 代表什么？RAM 是随机存取存储器。它用于保存 CPU 当前需要的数据和指令。当你打开一个应用程序时，它会从硬盘加载到 RAM 中，以便快速访问。RAM 是易失性的，也就是说断电后所有数据都会丢失。
a storage capacity calculation: A USB stick has a capacity of 8 GB. How many bytes is this? y also accept the binary definition (1 GiB = 2³⁰ bytes), but for this level the decimal definition is standard.
第19题是一个存储容量计算：一个 U 盘容量为 8 GB，这是多少字节？在大多数存储场景中，1 GB 等于 10 亿字节（10⁹ 字节）。因此，8 GB = 8 × 1,000,000,000 = 80 亿字节。有些考试局可能也接受二进制定义（1 GiB = 2³⁰ 字节），但对于这个阶段，十进制定义是标准。
8 GB = 8 × 10⁹ bytes
8 GB = 8 × 10⁹ 字节
3. Data Representation – Binary | 数据表示 – 二进制
2³ (8), 2² (4), 2¹ (2), and 2⁰ (1). The binary digits 1 0 1 0 give us: one 8, zero 4s, one 2, zero 1s. Adding them up: 8 + 0 + 2 + 0 = 10.
第4题要求你将二进制数 1010 转换为十进制。每个二进制位代表 2 的幂。从右到左的位值是 2³(8)、2²(4)、2¹(2) 和 2⁰(1)。二进制数字 1 0 1 0 给出：一个8、零个4、一个2、零个1。把它们加起来：8 + 0 + 2 + 0 = 10。
1010₂ = (1 × 2³) + (0 × 2²) + (1 × 2¹) + (0 × 2⁰) = 8 + 0 + 2 + 0 = 10
1010₂ = (1 × 2³) + (0 × 2²) + (1 × 2¹) + (0 × 2⁰) = 8 + 0 + 2 + 0 = 10
Question 5 asked: What is the largest denary number that can be represented with 4 bits? l four bits should be 1: 1111₂. That is (1×8)+(1×4)+(1×2)+(1×1) = 15. So the answer is 15.
第5题问：用4个二进制位能表示的最大十进制数是多少？四个位每个都可以是1或0。要达到最大值，所有四个位都应为1：1111₂。计算为 (1×8)+(1×4)+(1×2)+(1×1) = 15。所以答案是 15。
1111₂ = 8 + 4 + 2 + 1 = 15
1111₂ = 8 + 4 + 2 + 1 = 15
4. Data Representation – Images | 数据表示 – 图像
Question 12 described a simple black‑and‑ r pixel is enough: 0 for white and 1 for black (or the other way around). The total number of bits needed is the number of pixels: 10 × 10 = 100 bits.
第12题描述了一幅简单的黑白图像，宽10像素、高10像素。每个像素可以是黑色或白色，因此只有两种颜色。有两种可能的颜色时，每个像素用一个比特就足够了：0表示白色，1表示黑色（或者反过来）。需要的总比特数等于像素数：10 × 10 = 100 比特。
ze would be 10 × 10 × 8 = 800 bits. This shows how colour depth directly affects file size – a concept often tested alongside resolution.
如果同样的图像使用每像素8位的颜色深度（允许256种不同颜色），文件大小将是 10 × 10 × 8 = 800 比特。这显示了颜色深度如何直接影响文件大小——这是一个经常与分辨率一起考查的概念。
Published by TutorHao | Year 8 Computer Science Revision Series | aleveler.com
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