📚 Year 7 SQA Computing: Unit Test Mock Paper Walkthrough | 七年级 SQA 计算机：单元测试模拟卷解析
Welcome to our detailed walkthrough of a typical Year 7 SQA Computing unit test. This mock paper is designed to help you check your understanding of key topics, from computer hardware to programming concepts and online safety. By reviewing each question, the model answer and the common mistakes behind it, you will feel far more confident before your real assessment.
欢迎参加七年级 SQA 计算机单元测试模拟卷的详细解析。这份模拟卷帮助你检验对计算机硬件、编程概念和网络安全等关键知识的掌握。通过回顾每道题目、标准答案以及背后的常见错误，你将在正式评估中更有信心。
Nothing in this walkthrough is a trick: every question maps directly onto a statement from the SQA Year 7 Computing course, and every answer can be justified in one sentence using the correct technical vocabulary.
本文没有任何“陷阱题”：每道题都直接对应 SQA 七年级计算机课程中的一条学习要求，每个答案都可以用一句话加正确的专业术语解释清楚。
1. Mock Paper Overview | 模拟卷概览
This mock paper contains ten multiple-choice and short-answer questions that reflect the SQA Year 7 Computing curriculum: a mixture of multiple-choice and short-answer items. Topics include input/output devices, data storage, binary numbers, Scratch programming, algorithms, debugging, programming constructs, file types and e-safety. Each question is worth one mark, so the paper totals 10 marks, and the total time allowed is 30 minutes.
这份模拟卷包含十道题，覆盖了 SQA 七年级计算机课程：选择题与简答题混合出现。主题包括输入/输出设备、数据存储、二进制数、Scratch 编程、算法、调试、程序结构、文件类型和网络安全。每题一分，全卷满分 10 分，总时长 30 分钟。
Multiple-choice questions test recognition, so you simply pick the best option. Short-answer questions test recall and explanation, so you must write the technical keyword the marker is looking for, such as 'input device' or 'iteration', rather than a vague description in everyday language.
选择题考查辨认能力，选出最佳选项即可；简答题考查回忆与解释能力，必须写出评分标准期待的专业词汇，例如 'input device'（输入设备）或 'iteration'（迭代/循环），而不是用日常语言含糊描述。
| Q | Topic | 主题 | Skill tested | 考查能力 |
| 1 | Input devices | 输入设备 | Recognise hardware | 辨认硬件 |
| 2 | Output devices | 输出设备 | Classify hardware | 硬件分类 |
| 3 | Data storage | 数据存储 | Units and conversion | 单位换算 |
| 4 | Binary numbers | 二进制数 | Number conversion | 进制转换 |
| 5 | Scratch | Scratch 编程 | Blocks and events | 积木与事件 |
| 6 | Algorithms | 算法 | Step-by-step logic | 分步逻辑 |
| 7 | Debugging | 调试 | Finding errors | 找出错误 |
| 8 | Programming constructs | 程序结构 | Sequence, selection, iteration | 顺序、选择、循环 |
| 9 | File types | 文件类型 | Extensions and formats | 扩展名与格式 |
| 10 | E-safety | 网络安全 | Safe online behaviour | 安全上网行为 |
Read the explanation for each answer carefully, especially the 'common error' tips, as they highlight where students often lose marks.
仔细阅读每题答案的解释，尤其是“常见错误”提示，这些地方往往是学生丢分的高发区。
2. Question 1: Identifying Input Devices | 第 1 题：识别输入设备
Question: Which of the following is an input device? (A) Monitor (B) Keyboard (C) Printer (D) Speakers. Answer: (B) Keyboard.
题目：下列哪一项是输入设备？(A) 显示器 (B) 键盘 (C) 打印机 (D) 音箱。答案：(B) 键盘。
An input device allows a user to send data or instructions into a computer system. The keyboard converts key presses into digital signals that the processor can read, so the direction of data flow is from the user into the computer.
输入设备允许用户把数据或指令送入计算机系统。键盘把按键动作转换为处理器可以读取的数字信号，因此数据流动的方向是从用户到计算机。
Other input devices you should be able to name include the mouse, trackpad, microphone, webcam, scanner, touchscreen, graphics tablet, game controller and sensors such as temperature or light sensors. Sensors are important because they collect data automatically without a human typing anything.
你还需要能说出其他输入设备：鼠标、触控板、麦克风、摄像头、扫描仪、触摸屏、数位板、游戏手柄，以及温度传感器、光传感器等传感设备。传感器很关键，因为它们无需人工输入就能自动采集数据。
Common error: choosing the touchscreen as 'not an input device'. A touchscreen is both an input and an output device, because it detects your touch and also displays an image. If a question asks for one answer, read the options again - the examiner normally includes only one device that is purely an input.
常见错误：认为触摸屏“不是输入设备”。触摸屏既是输入设备也是输出设备，因为它既能检测触摸，又能显示画面。如果题目要求选一个答案，请重新读选项——出题人通常只会放一个纯输入设备。
3. Question 2: Identifying Output Devices | 第 2 题：识别输出设备
Question: Which device below is used only for output? (A) Microphone (B) Scanner (C) Speaker (D) Webcam. Answer: (C) Speaker.
题目：下面哪一设备只用于输出？(A) 麦克风 (B) 扫描仪 (C) 音箱 (D) 摄像头。答案：(C) 音箱。
An output device presents data from the computer to the user. The speaker turns digital audio data into sound waves, so data flows out of the system. Other output devices include the monitor, projector, printer, 3D printer, plotter, headphones and haptic feedback devices in game controllers.
输出设备把计算机中的数据呈现给用户。音箱把数字音频数据转换成声波，因此数据从系统中流出。其他输出设备包括显示器、投影仪、打印机、3D 打印机、绘图仪、耳机，以及游戏手柄中的触觉反馈装置。
A quick way to answer these questions is to ask: does the data go in or come out? If you type on it, talk into it or point it at something to capture data, it is an input device. If it shows, prints, sounds or moves something, it is an output device.
快速判断方法是问自己：数据是进去还是出来？如果你在它上面打字、对着它说话，或者用它对准某个物体采集数据，它就是输入设备；如果它显示、打印、发声或产生运动，它就是输出设备。
Common error: assuming anything that plugs into a computer is an output device. A printer plugs in and prints, but a scanner plugs in and captures. Always check the direction of the data, not the cable.
常见错误：以为凡是插到电脑上的设备都是输出设备。打印机插上电脑后负责打印，扫描仪插上电脑后负责采集。判断依据永远是数据方向，而不是有没有插线。
4. Question 3: Data Storage and Units | 第 3 题：数据存储与单位
Question: How many bytes are there in 3 kilobytes (KB)? Answer: 3 072 bytes, because 1 KB = 1 024 bytes, and 3 × 1 024 = 3 072.
题目：3 千字节（KB）等于多少字节？答案：3 072 字节，因为 1 KB = 1 024 字节，3 × 1 024 = 3 072。
You must know the storage ladder and be able to move up and down it. A bit is a single binary digit, 0 or 1. Eight bits make one byte, which is enough to store one character such as the letter 'A'.
你必须掌握存储单位阶梯，并能上下换算。位（bit）是一个二进制数字，取值为 0 或 1。八位组成一个字节（byte），足以存储一个字符，比如字母 'A'。
8 bits = 1 byte → 1 024 bytes = 1 KB → 1 024 KB = 1 MB → 1 024 MB = 1 GB → 1 024 GB = 1 TB
n asks you to estimate whether a file fits on a device, convert everything to the same unit first, then compare.
注意乘数是 1 024 而不是 1 000，因为计算机以 2 的幂工作：1 024 = 2¹⁰。当题目要求你估算文件能否放进某个设备时，先把所有数据换算成同一单位，再进行比较。
Estimating file sizes is also examinable. A compressed photo is around 2-3 MB, a three-minute song is about 4-5 MB, and a minute of high-definition video can be over 20 MB. A 32 GB memory card therefore holds thousands of photos but only a few hours of video.
文件大小估算同样会考。一张压缩照片约 2-3 MB，一首三分钟的歌曲约 4-5 MB，而一分钟高清视频可能超过 20 MB。因此一张 32 GB 的存储卡能放几千张照片，却只能放几小时视频。
Common error: mixing up bits and bytes, or using 1 000 as the multiplier. If a question mentions 'megabits' (Mb) and the answer needs 'megabytes' (MB), divide by 8 first.
常见错误：把位和字节搞混，或者错用 1 000 作为乘数。如果题目提到兆位（Mb）而答案要求兆字节（MB），要先除以 8。
5. Question 4: Binary Numbers | 第 4 题：二进制数
Question: Convert the binary number 1011 0010₂ into denary (decimal). Answer: 178.
题目：把二进制数 1011 0010₂ 转换为十进制数。答案：178。
Write the place values above the eight bits, starting from the right: 128, 64, 32, 16, 8, 4, 2, 1. Then add the place values wherever there is a 1.
在这八位数字上方写下位权，从右往左依次是：128、64、32、16、8、4、2、1。然后把所有对应 1 的位权相加即可。
1011 0010₂ = 128 + 32 + 16 + 2 = 178
To go the other way, subtract the largest place value that fits and keep working downwards. For example, 178 ÷ 128 leaves 50, then 50 ÷ 32 leaves 18, 18 ÷ 16 leaves 2, and 2 ÷ 2 leaves 0, which gives 1011 0010 again.
反向转换时，先减去能容纳的最大位权，再继续往下做。例如 178 减去 128 余 50，50 减去 32 余 18，18 减去 16 余 2，2 减去 2 余 0，同样得到 1011 0010。
different values, from 0 to 255, which is why one byte can store a single character code.
计算机使用二进制，是因为电路只有两种可靠状态：通和断，分别用 1 和 0 表示。用 8 位可以存储 2⁸ = 256 个不同的值，从 0 到 255，这就是一个字节能存储一个字符编码的原因。
Common error: forgetting to include the leading zero when a question specifies a fixed-width answer. If the question says 'give your answer as 8 bits', then 0011 0010 is correct and 11 0010 will lose the mark.
常见错误：题目规定固定位数时忘记补前导零。如果题目要求“用 8 位给出答案”，那么 0011 0010 才正确，写成 11 0010 会失分。
6. Question 5: Scratch Programming Basics | 第 5 题：Scratch 编程基础
Question: In Scratch, which block starts a script when the green flag is clicked? Answer: The event block 'when green flag clicked'.
题目：在 Scratch 中，哪个积木块在点击绿旗时启动脚本？答案：事件类积木 'when green flag clicked'（当绿旗被点击）。
Scratch is a block-based programming language. Each block snaps together with others to form a script, and a script runs from the top block downwards. The stage is the area where the output is displayed, and sprites are the characters or objects that you program.
Scratch 是一种积木式编程语言。每块积木可以和其他积木拼接成脚本，脚本从最上面的积木块开始向下执行。舞台（stage）是显示结果的区域，角色（sprite）是你编程控制的人物或物体。
You should recognise the main block categories and what they do: motion blocks change position, direction and coordinates; looks blocks change costume, size and speech bubbles; sound blocks play audio; control blocks include repeat and forever loops; sensing blocks check conditions such as 'touching edge?'; variable blocks store values such as score or lives.
你应当认得主要积木类别及其作用：运动类改变位置、方向和坐标；外观类改变造型、大小和对话气泡；声音类播放音频；控制类包含重复和一直循环；侦测类判断条件，如“碰到边缘？”；变量类存储分数或生命值等数值。
A typical short-answer question asks you to describe what a script does. Answer in order: 'When the green flag is clicked, the sprite moves 10 steps, then turns 15 degrees, and repeats this 10 times, so it draws a shape with 10 sides.' Sequencing your answer in the same order as the blocks earns the mark.
典型简答题会要求你描述某段脚本的作用。请按执行顺序作答：“点击绿旗后，角色移动 10 步，然后右转 15 度，并重复 10 次，因此它画出一个十条边的图形。”答案顺序与积木顺序一致才能得分。
Common error: confusing the stage with a sprite, or writing 'the computer does the loop' instead of naming the blocks. Always name the block and say what it changes.
常见错误：把舞台和角色搞混，或者只写“电脑会循环”，而没有点出具体积木名称。永远要说出积木名称，并说明它改变了什么。
7. Question 6: Algorithms and Sequence | 第 6 题：算法与顺序
Question: Write an algorithm, in four steps, to find the largest of three numbers. Answer: (1) Input the three numbers. (2) Set the largest to the first number. (3) Compare each remaining number with the largest; if it is bigger, replace the largest. (4) Output the largest.
题目：用四个步骤写一个算法，找出三个数中的最大值。答案：(1) 输入三个数；(2) 把第一个数设为最大值；(3) 依次把其余的数与最大值比较，若更大则替换最大值；(4) 输出最大值。
An algorithm is a step-by-step set of instructions that solves a problem. A good algorithm must be clear and unambiguous, must have a finite number of steps, and must produce a result for any valid input.
算法是一组解决某个问题的分步指令。一个好的算法必须清晰无歧义、步骤数量有限，并且对所有合法输入都能得到结果。
Algorithms can be written as numbered steps, as pseudocode, or drawn as a flowchart. In a flowchart, an oval means start or stop, a parallelogram means input or output, a rectangle means a process such as a calculation, and a diamond means a decision with two possible exits.
算法可以写成编号步骤、伪代码，或画成流程图。流程图中，椭圆表示开始或
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