📚 Year 10 CIE Computer Science: Core Knowledge Recap | Year 10 CIE 计算机：核心知识点梳理
This article presents a structured revision of the core topics for Year 10 CIE Computer Science. Each section covers essential theory and practical understanding expected at this stage, from data representation and hardware to networking and programming fundamentals. The bilingual format is designed to help learners grasp concepts clearly in both English and Chinese.
本文对 Year 10 CIE 计算机课程的核心主题进行了系统梳理。每个部分涵盖了该阶段所需的基本理论与实践理解，从数据表示和硬件，到网络和编程基础。中英双语的格式旨在帮助学习者用两种语言清晰地掌握概念。
1. Number Systems: Binary, Denary and Hexadecimal | 数制：二进制、十进制与十六进制
Computers process data in binary form, using only 0s and 1s. Each binary digit (bit) is the smallest unit of data. Denary (base-10) is the system we use daily, and hexadecimal (base-16) provides a more compact way to represent binary values. Understanding how to convert between these three systems is fundamental.
计算机以二进制形式处理数据，只使用 0 和 1。每个二进制位（bit）是最小的数据单位。十进制（基数为 10）是我们日常使用的系统，而十六进制（基数为 16）提供了一种更紧凑的二进制值表示方法。理解如何在这三种数制之间进行转换是基础。
The place values in binary are powers of 2: … 128, 64, 32, 16, 8, 4, 2, 1. To convert a denary number to binary, subtract the largest possible power of 2 repeatedly. For hexadecimal, the digits 0–9 and letters A–F are used, where A = 10, B = 11, … F = 15. Each hex digit represents exactly four bits (a nibble).
二进制的位值是 2 的幂：……128、64、32、16、8、4、2、1。要将十进制数转换为二进制，请重复减去可能的最大 2 的幂。对于十六进制，使用数字 0–9 和字母 A–F，其中 A = 10，B = 11，……F = 15。每个十六进制数字恰好代表四个比特（一个半字节）。
Binary addition follows simple rules: 0+0=0, 0+1=1, 1+0=1, 1+1=0 carry 1, and 1+1+carry=1 carry 1. Overflow occurs when the result exceeds the allocated number of bits. Logical binary shifts multiply (left shift) or divide (right shift) by powers of 2.
二进制加法遵循简单规则：0+0=0、0+1=1、1+0=1、1+1=0 进位 1，以及 1+1+进位=1 进位 1。当结果超出分配的位数时，会发生溢出。逻辑移位通过左移（乘以 2 的幂）或右移（除以 2 的幂）实现乘除。
2. Data Storage Units and File Sizes | 数据存储单位与文件大小
A bit is a single binary value. Eight bits form a byte. Larger units follow powers of 2 and are often approximated for simplification: 1 kilobyte (KB) ≈ 1000 bytes, but precisely 1 KiB = 1024 bytes. CIE generally uses the approximation: kilo (10³), mega (10⁶), giga (10⁹), tera (10¹²).
一个比特是单个二进制值。八个比特组成一个字节。更大的单位遵循 2 的幂次，但为了简化通常近似表示：1 千字节（KB）≈ 1000 字节，但精确的 1 KiB = 1024 字节。CIE 通常使用近似值：千（10³）、兆（10⁶）、吉（10⁹）、太（10¹²）。
Common file size units: kilobyte (KB), megabyte (MB), gigabyte (GB), terabyte (TB). Learners should be able to estimate the size of different file types: a simple text file is a few KB, a high-resolution photo several MB, a HD video several GB. This helps in understanding storage requirements and data transfer times.
常见的文件大小单位有：千字节（KB）、兆字节（MB）、吉字节（GB）、太字节（TB）。学习者应能估算不同类型文件的大小：简单文本文件是几 KB，高分辨率照片是几 MB，高清视频是几 GB。这有助于理解存储需求和数据传输时间。
| Unit | Abbreviation | Approximate size (bytes) |
|---|---|---|
| kilobyte | KB | 10³ |
| megabyte | MB | 10⁶ |
| gigabyte | GB | 10⁹ |
| terabyte | TB | 10¹² |
3. Data Representation: Text, Sound and Images | 数据表示：文本、声音与图像
All data inside a computer is stored as binary numbers. Text is encoded using character sets like ASCII (7-bit, 128 characters) and Unicode (up to 32-bit, covering global scripts and symbols). ASCII is sufficient for English, but Unicode ensures universal compatibility.
计算机内部的所有数据都以二进制数存储。文本使用 ASCII（7 位，128 个字符）和 Unicode（最多 32 位，涵盖全球文字和符号）等字符集进行编码。ASCII 足以用于英语，但 Unicode 确保了通用兼容性。
Sound is analogue, so it must be converted to digital by sampling. The sample rate measures how many times per second the sound wave is measured; bit depth determines the number of bits for each sample. Higher sample rate and bit depth improve quality but increase file size. The formula for file size: sample rate × bit depth × duration (seconds) × channels. For example, 44 100 Hz × 16-bit × 60 s × 2 (stereo) ÷ 8 ≈ 10.6 MB.
声音是模拟信号，因此必须通过采样将其转换为数字信号。采样率衡量每秒测量声波的次数；位深度决定了每个样本的位数。更高的采样率和位深度可提高质量，但会增加文件大小。文件大小公式为：采样率 × 位深度 × 持续时间（秒）× 声道数。例如，44 100 Hz × 16 位 × 60 秒 × 2（立体声）÷ 8 ≈ 10.6 MB。
Images are represented as a grid of pixels. In a bitmap image, each pixel’s colour is stored as a binary number. The colour depth (bits per pixel) determines the number of available colours: 1 bit = 2 colours, 8 bits = 256 colours, 24 bits ≈ 16.7 million colours. Resolution is the total pixel count (width × height). Image file size = width × height × colour depth (in bits).
图像以像素网格表示。在位图图像中，每个像素的颜色存储为一个二进制数。颜色深度（每像素位数）决定了可用颜色的数量：1 位 = 2 种颜色，8 位 = 256 种颜色，24 位 ≈ 1670 万种颜色。分辨率是像素总数（宽度 × 高度）。图像文件大小 = 宽度 × 高度 × 颜色深度（以位为单位）。
4. Compression: Lossy and Lossless | 压缩：有损与无损
Compression reduces file size for storage and transmission. Lossless compression removes redundancy without losing data, so the original file can be perfectly reconstructed. Run-length encoding (RLE) replaces repeated bytes with a count and value; Huffman coding uses shorter codes for more frequent symbols.
压缩可减小文件大小，便于存储和传输。无损压缩在不丢失数据的情况下消除冗余，因此原始文件可以完美重建。游程编码（RLE）用计数和值替换重复的字节；哈夫曼编码为频率更高的符号使用更短的代码。
Lossy compression discards some data permanently, exploiting limitations of human perception. It is suitable for images (JPEG), sound (MP3) and video (MPEG). While quality is reduced, the reduction in file size is dramatic. Key is to know when each type is appropriate: text and programs require lossless; photographs tolerate lossy.
有损压缩会永久丢弃一些数据，利用了人类感知的局限性。它适用于图像（JPEG）、声音（MP3）和视频（MPEG）。虽然质量下降，但文件大小的减少是显著的。关键是要知道每种类型在何时适用：文本和程序需要无损；照片可以接受有损。
5. Computer Architecture: Von Neumann Model | 计算机体系结构：冯·诺依曼模型
The von Neumann architecture stores both program instructions and data in the same memory. Its core components are the control unit (CU), arithmetic logic unit (ALU), memory unit, and input/output devices. The CPU fetches, decodes and executes instructions in a cycle.
冯·诺依曼体系结构将程序指令和数据存储在同一个内存中。其核心部件包括控制单元（CU）、算术逻辑单元（ALU）、内存单元以及输入/输出设备。CPU 按周期执行取指、译码和执行操作。
Registers are small, high-speed storage locations inside the CPU. Key registers: Program Counter (PC) holds the address of the next instruction; Memory Address Register (MAR) holds the address being accessed; Memory Data Register (MDR) holds the data just read or to be written; Current Instruction Register (CIR) holds the instruction being decoded; Accumulator (ACC) stores results of ALU operations.
寄存器是 CPU 内部的小型高速存储位置。关键寄存器包括：程序计数器（PC）保存下一条指令的地址；内存地址寄存器（MAR）保存正在访问的地址；内存数据寄存器（MDR）保存刚读过或要写入的数据；当前指令寄存器（CIR）保存正在译码的指令；累加器（ACC）存储 ALU 运算的结果。
The fetch-decode-execute cycle works as follows: 1. PC’s address copied to MAR; 2. PC incremented; 3. Data from memory (via MAR) loaded into MDR; 4. MDR content copied to CIR; 5. CU decodes instruction; 6. Operand address placed in MAR; 7. Data fetched into MDR; 8. Execute using ALU, result in ACC. This simple model underpins all modern processors.
取指-译码-执行循环的工作方式如下：1. PC 的地址复制到 MAR；2. PC 递增；3. 从内存（通过 MAR）读取数据加载到 MDR；4. MDR 内容复制到 CIR；5. CU 对指令进行译码；6. 操作数地址放入 MAR；7. 数据取入 MDR；8. 使用 ALU 执行，结果存入 ACC。这个简单模型是所有现代处理器的基础。
6. Memory, Storage and I/O Devices | 内存、存储与输入/输出设备
Primary memory includes RAM (volatile, read-write, holds currently running programs and data) and ROM (non-volatile, read-only, stores BIOS/boot firmware). Secondary storage is non-volatile and retains data when power is off. Magnetic (HDD), solid-state (SSD) and optical (DVD) technologies each have advantages in speed, durability, cost and capacity.
主存储器包括 RAM（易失性、可读写、存放当前运行的程序和数据）和 ROM（非易失性、只读、存储 BIOS/引导固件）。辅助存储器是非易失性的，断电后仍能保留数据。磁存储（HDD）、固态存储（SSD）和光存储（DVD）技术在速度、耐用性、成本和容量上各有优势。
Input devices feed data into the computer: keyboard, mouse, scanner, microphone, sensor, touch screen. Output devices present results: monitor, printer, speaker, actuator. Some devices, like touch screens and external hard drives, serve both input and output functions. The choice of an I/O device depends on the application context—e.g., barcode scanners in retail, sensors in automated systems.
输入设备将数据送入计算机：键盘、鼠标、扫描仪、麦克风、传感器、触摸屏。输出设备呈现结果：显示器、打印机、扬声器、执行器。有些设备，如触摸屏和外置硬盘，兼具输入和输出功能。I/O 设备的选择取决于应用场景——例如，零售业中用条形码扫描器，自动化系统中用传感器。
7. Networks and the Internet | 网络与互联网
A network connects two or more computers to share resources. LANs (Local Area Networks) operate over a small geographic area, usually with high data rates and owned by one organisation. WANs (Wide Area Networks) connect LANs over large distances, using infrastructure like phone lines or satellites. The internet is a global WAN.
网络将两台或多台计算机连接起来以共享资源。局域网（LAN）在较小的地理区域内运行，通常具有高数据速率并由一个组织拥有。广域网（WAN）使用电话线或卫星等基础设施将局域网远距离连接起来。互联网是一个全球性的广域网。
Common network hardware includes: Network Interface Card (NIC) to connect a device to the network; switch to connect devices within a LAN and forward data intelligently; router to send data between different networks, often connecting LAN to the internet; modem to convert digital signals to analogue for transmission over telephone lines (and vice versa).
常见的网络硬件包括：网络接口卡（NIC），用于将设备连接到网络；交换机，在局域网内连接设备并智能转发数据；路由器，在不同网络之间发送数据，通常将局域网连接到互联网；调制解调器，用于将数字信号转换为模拟信号以便通过电话线传输，反之亦然。
Network protocols define rules for communication. TCP/IP is the fundamental suite: IP handles addressing and packet routing; TCP ensures reliable delivery and ordering. HTTP/HTTPS for web pages, FTP for file transfer, SMTP/POP3/IMAP for email. A MAC address is a unique hardware identifier; an IP address (IPv4 or IPv6) identifies a device on a network and can change.
网络协议定义了通信规则。TCP/IP 是基本的协议族：IP 处理寻址和数据包路由；TCP 确保可靠的传递和排序。HTTP/HTTPS 用于网页，FTP 用于文件传输，SMTP/POP3/IMAP 用于电子邮件。MAC 地址是唯一的硬件标识符；IP 地址（IPv4 或 IPv6）标识网络上的设备，并且可以更改。
8. Network Security Threats and Solutions | 网络安全威胁与解决方案
Malware includes viruses (attach to files, require user action), worms (self-replicate across networks), Trojan horses (disguise as legitimate software), and ransomware (encrypts files for ransom). Social engineering tricks users into revealing confidential information, for example through phishing emails that appear to be from trusted sources.
恶意软件包括病毒（附着在文件上，需要用户操作）、蠕虫（通过网络自我复制）、特洛伊木马（伪装成合法软件）和勒索软件（加密文件以索取赎金）。社会工程学诱骗用户泄露机密信息，例如通过看似来自可信来源的网络钓鱼电子邮件。
Brute-force attacks try all possible passwords; denial-of-service (DoS) attacks overwhelm systems with traffic; data interception (eavesdropping) reads data in transit if unencrypted. SQL injection inserts malicious code into database queries through unprotected user input fields.
暴力攻击尝试所有可能的密码；拒绝服务（DoS）攻击通过流量淹没系统；数据拦截（窃听）在传输中读取未加密的数据。SQL 注入通过未受保护的用户输入字段将恶意代码插入数据库查询。
Defence mechanisms include: antivirus and anti-malware software, firewalls that filter incoming/outgoing traffic, strong passwords and two-factor authentication, regular software updates, encryption (e.g., SSL/TLS for secure web traffic), and user education. Understanding these threats and countermeasures is essential for digital citizenship.
防御机制包括：防病毒和反恶意软件、过滤传入/传出流量的防火墙、强密码和双因素认证、定期软件更新、加密（例如用于安全网络流量的 SSL/TLS）以及用户教育。理解这些威胁和对策对于数字公民素养至关重要。
9. Software, Languages and Translators | 软件、语言与翻译器
System software manages hardware and provides a platform for application software. Examples: operating systems (Windows, Linux, iOS), compiler, interpreter, device drivers. Application software performs user-oriented tasks: word processors, browsers, games. Utility software aids in maintenance: disk defragmenter, backup, compression tools.
系统软件管理硬件并为应用软件提供平台。例如：操作系统（Windows、Linux、iOS）、编译器、解释器、设备驱动程序。应用软件执行面向用户的任务：文字处理、浏览器、游戏。实用软件辅助维护：磁盘碎片整理、备份、压缩工具。
Low-level languages include machine code (binary instructions specific to a processor) and assembly language (mnemonics like LDA, ADD). Assembly language must be translated by an assembler. High-level languages (Python, Java, C++) are portable and easier to read, but must be translated into machine code by a compiler or interpreter.
低级语言包括机器码（特定于处理器的二进制指令）和汇编语言（助记符，如 LDA、ADD）。汇编语言必须由汇编器翻译。高级语言（Python、Java、C++）具有可移植性且更易阅读，但必须由编译器或解释器翻译成机器码。
A compiler translates the entire source code into an executable file once; this file can run independently. An interpreter translates and executes line by line each time the program runs. Compilers produce faster execution but can be less convenient during development. Interpreters are easier for debugging but slower during run time. Hybrid approaches (e.g., Java’s bytecode + JVM) combine both benefits.
编译器一次性将整个源代码翻译成可执行文件；该文件可以独立运行。解释器在每次程序运行时逐行翻译和执行。编译器生成更快的执行速度，但在开发过程中可能不太方便。解释器更易于调试，但在运行时较慢。混合方法（例如 Java 的字节码 + JVM）结合了两者的优点。
10. Algorithms, Flowcharts and Pseudocode | 算法、流程图与伪代码
An algorithm is a step-by-step procedure to solve a problem. It must be precise, finite and effective. Algorithms can be expressed through flowcharts (visual, using standard symbols: oval for start/end, parallelogram for input/output, rectangle for process, diamond for decision) or pseudocode (structured English, similar to programming syntax).
算法是解决问题的分步过程。它必须精确、有限且有效。算法可以通过流程图（可视化，使用标准符号：椭圆表示开始/结束，平行四边形表示输入/输出，矩形表示处理过程，菱形表示判断）或伪代码（结构化英语，类似编程语法）来表达。
Basic programming constructs: sequence (instructions in order), selection (if-then-else, case), and iteration (loops – for, while, repeat-until). Understanding these structures is tested by writing, tracing and correcting algorithms. Trace tables track variable values step by step to verify logic.
基本编程结构：顺序（按顺序执行指令）、选择（if-then-else、case）和迭代（循环——for、while、repeat-until）。通过编写、跟踪和纠正算法来检验对这些结构的理解。跟踪表逐步跟踪变量值以验证逻辑。
Common algorithms for Year 10 include: linear search (check each item until found or end), binary search (on sorted array, repeatedly divide the search interval), bubble sort (compare adjacent elements and swap if out of order), and basic counting/totaling tasks. Efficiency consideration is introduced by counting the number of comparisons or loops.
Year 10 常见的算法包括：线性搜索（逐个检查项目直到找到或结束）、二分搜索（在排序数组中反复将搜索区间减半）、冒泡排序（比较相邻元素，如果顺序错误则交换）以及基本的计数/求和任务。通过计算比较次数或循环次数来介绍效率的概念。
11. Testing, Validation and Verification | 测试、验证与确认
Testing ensures a program works correctly. Normal data (expected, within range), boundary data (at the limits of acceptable), and invalid data (outside the range) must all be tested. A test plan outlines inputs, expected outputs and actual results.
测试确保程序正确工作。正常数据（预期范围内）、边界数据（处于可接受范围的极限）和无效数据（范围之外）都必须进行测试。测试计划概述了输入、预期输出和实际结果。
Validation checks if data is sensible and reasonable: range check, length check, type check, presence check, format check. Verification ensures that data has been entered or copied correctly: double entry (type twice) and visual check (compare on screen with original). These prevent many logic and runtime errors.
验证检查数据是否合理和恰当：范围检查、长度检查、类型检查、存在性检查、格式检查。确认确保数据已被正确输入或复制：双重输入（两次输入）和目视检查（在屏幕上与原件比较）。这些可以防止许多逻辑和运行时错误。
Common error types: syntax errors (grammar mistakes in code, detected by translator), logic errors (the program runs but gives wrong results due to flawed algorithm), and runtime errors (occur during execution, e.g., division by zero). Debugging techniques include stepping through code, using print statements and examining trace tables.
常见的错误类型：语法错误（代码中的语法错误，由翻译器检测）、逻辑错误（程序运行但因算法缺陷而给出错误结果）和运行时错误（在执行期间发生，例如除以零）。调试技术包括逐步执行代码、使用打印语句和检查跟踪表。
12. Ethical, Legal and Environmental Issues | 伦理、法律与环境问题
Technology brings responsibilities. Plagiarism is using someone else’s work without permission. Copyright law protects original works; software piracy is illegal. The Data Protection Act governs the collection and use of personal data. Computer misuse laws criminalise hacking and unauthorized access.
技术带来了责任。抄袭是未经许可使用他人的作品。版权法保护原创作品；软件盗版是非法的。数据保护法规范了个人数据的收集和使用。计算机滥用法将黑客攻击和未经授权的访问定为犯罪。
Ethical concerns include: censorship on the internet, surveillance, the digital divide (inequality in access), and the impact of automation on employment. Environmental concerns include the energy consumption of data centres, e-waste from discarded devices, and the carbon footprint of manufacturing. Responsible computing means considering sustainability and social consequences.
伦理问题包括：互联网审查、监控、数字鸿沟（访问机会不平等）以及自动化对就业的影响。环境问题包括数据中心的能源消耗、废弃设备产生的电子垃圾以及制造业的碳足迹。负责任的计算机使用意味着要考虑可持续性和社会后果。
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