📚 Year 12 SQA Computing: Core Concepts Revision | 核心知识点梳理
Preparing for the SQA Year 12 (Higher) Computing Science exam can be challenging, but a clear review of the core knowledge areas makes revision much more effective. This article outlines the essential topics—from computer systems and data representation to networking, cybersecurity, software development, databases, web technologies, and wider legal and ethical issues—helping you consolidate your understanding and tackle exam questions with confidence.
准备SQA Year 12 (Higher) 计算机科学考试可能充满挑战，但清晰地梳理核心知识领域能让复习更高效。本文概述了从计算机系统、数据表示到网络、网络安全、软件开发、数据库、网页技术以及更广泛的法律与伦理问题等基本主题，帮助你巩固理解，自信应对考题。
1. Computer Systems & Architecture | 计算机系统与体系结构
The von Neumann architecture underpins most modern computers, featuring a central processing unit (CPU), memory, input/output mechanisms, and the stored program concept. The CPU itself consists of the Arithmetic Logic Unit (ALU) for calculations, the Control Unit (CU) that directs operations, and a set of registers such as the Program Counter (PC), Memory Address Register (MAR), and Memory Data Register (MDR). Computer performance is influenced by clock speed, number of cores, and cache memory.
冯·诺依曼架构是现代计算机的基础，它包括中央处理器(CPU)、内存、输入/输出机制和存储程序概念。CPU由算术逻辑单元(ALU)进行计算，控制单元(CU)指挥操作，以及一组寄存器如程序计数器(PC)、内存地址寄存器(MAR)和内存数据寄存器(MDR)组成。计算机性能受时钟速度、核心数量和高速缓存的影响。
The system bus is a set of parallel wires connecting the CPU to memory and I/O devices. It typically comprises the address bus (carrying memory addresses), the data bus (carrying actual data), and the control bus (carrying timing and control signals). The width of the address bus determines the maximum addressable memory, e.g. a 32-bit address bus can directly address 232 memory locations.
系统总线是一组连接CPU与内存和I/O设备的并行导线。它通常包括地址总线（传输内存地址）、数据总线（传输数据）和控制总线（传输时序与控制信号）。地址总线的宽度决定了最大可寻址内存，例如32位地址总线可直接寻址232个内存位置。
Memory hierarchy includes registers (fastest, inside CPU), cache (SRAM), main memory (DRAM), and secondary storage (hard disk, SSD). Cache memory uses principles of temporal and spatial locality to speed up data access. Input/output is managed through interfaces and controllers, often using USB, HDMI, or PCIe standards.
内存层次结构包括寄存器（最快，在CPU内部）、高速缓存 (SRAM)、主存 (DRAM) 和辅助存储器（硬盘、固态硬盘）。缓存利用时间局部性和空间局部性原理来加速数据访问。输入/输出通过接口和控制器管理，通常采用 USB、HDMI 或 PCIe 标准。
2. Data Representation & Storage | 数据表示与存储
Computers use binary (base-2) to represent all data. Integer representation can be unsigned or signed using two's complement. In an 8-bit two's complement system, the range is -128 to 127. Floating-point numbers are stored using a mantissa and exponent, allowing representation of real numbers with varying precision; the IEEE 754 standard is widely used to define single and double precision formats.
计算机使用二进制（基数为2）表示所有数据。整数可以用无符号方式或二进制补码表示。在8位二进制补码系统中，范围是 -128 至 127。浮点数使用尾数和指数存储，可表示不同精度的实数；IEEE 754 标准被广泛用于定义单精度和双精度格式。
Text is encoded using character sets: ASCII uses 7 bits for 128 characters, while Unicode (UTF-8, UTF-16) supports a vast range of characters from many languages. Graphics can be represented as bit-mapped (a grid of pixels with a specific colour depth) or vector (stored as mathematical descriptions of lines, curves, and fills). Sound is sampled and stored digitally; sample rate (e.g. 44.1 kHz) and bit depth (e.g. 16 bits) determine audio quality and file size.
文本通过字符集编码：ASCII使用7位表示128个字符，而Unicode（UTF-8、UTF-16）支持多种语言的广泛字符。图形可表示为位图（像素网格及颜色深度）或矢量图（以线条、曲线和填充的数学描述存储）。声音经过采样后数字化存储；采样率（如44.1 kHz）和位深度（如16位）决定音频质量和文件大小。
Common storage units: bit, byte (B), kilobyte (KB ≈ 103 or 210 bytes), megabyte (MB), gigabyte (GB), terabyte (TB). Storage technologies include magnetic (HDD), solid-state (SSD), and optical (CD, DVD). Understanding how convert between units and calculate file sizes is crucial for the exam.
常见存储单位：位(bit)、字节(B)、千字节 (KB ≈ 103 或 210 字节)、兆字节(MB)、吉字节(GB)、太字节(TB)。存储技术包括磁性存储器 (HDD)、固态存储器 (SSD) 和光学存储器（CD、DVD）。理解单位换算与文件大小计算对考试至关重要。
3. Networking Fundamentals | 网络基础
A network is a group of interconnected devices that share resources and communicate. Local Area Networks (LANs) cover a small geographic area and often use Ethernet and Wi-Fi, while Wide Area Networks (WANs) span larger distances and may connect multiple LANs. The client-server model (central servers provide services) and peer-to-peer (P2P) model (devices act as both client and server) define common architectures.
网络是一组共享资源和进行通信的互连设备。局域网(LAN)覆盖较小的地理区域，通常使用以太网和Wi-Fi，而广域网(WAN)跨越较大距离，可连接多个局域网。客户端-服务器模型（中央服务器提供服务）和对等网络(P2P)模型（设备同时充当客户端与服务器）定义了常见的架构。
Network topologies such as star (each node connects to a central switch), mesh (each node connects to several others), and bus (a single backbone cable) affect reliability and scalability. Protocols like TCP/IP control data packet transmission. The OSI model consists of seven layers (Physical, Data Link, Network, Transport, Session, Presentation, Application), while the simplified TCP/IP model uses four layers (Application, Transport, Internet, Network Access).
网络拓扑如星型（每个节点连接到中央交换机）、网状（每个节点连接到多个其他节点）和总线型（单根主干电缆）影响可靠性与可扩展性。TCP/IP等协议控制数据包传输。OSI模型包含七层（物理层、数据链路层、网络层、传输层、会话层、表示层、应用层），而简化的TCP/IP模型使用四层（应用层、传输层、互联网层、网络接入层）。
4. Cybersecurity & Encryption | 网络安全与加密
Cybersecurity threats include malware (viruses, worms, trojans, ransomware), phishing, denial-of-service (DoS) attacks, and SQL injection. Defensive measures consist of firewalls, antivirus software, strong password policies, two-factor authentication, and staff training. Encryption transforms readable plaintext into ciphertext using a key; symmetric encryption uses the same key for both encryption and decryption, while asymmetric (public-key) encryption uses a pair of mathematically related keys – a public key to encrypt and a private key to decrypt.
网络安全威胁包括恶意软件（病毒、蠕虫、木马、勒索软件）、网络钓鱼、拒绝服务(DoS)攻击和SQL注入。防御措施包括防火墙、防病毒软件、强密码策略、双因素身份认证和员工培训。加密使用密钥将可读明文转换为密文；对称加密使用同一密钥进行加密和解密，而非对称（公钥）加密则使用一对数学相关密钥——公钥用于加密，私钥用于解密。
Simple ciphers like the Caesar cipher (a shift cipher) demonstrate substitution techniques, but modern encryption relies on complex algorithms such as AES (symmetric) and RSA (asymmetric). Legal frameworks, including the Computer Misuse Act and the Data Protection Act / GDPR, set out principles for handling personal data and criminalise unauthorised access.
简单密码如凯撒密码（移位密码）演示了替换技术，但现代加密依赖于AES（对称）和RSA（非对称）等复杂算法。法律框架，包括《计算机滥用法》和《数据保护法》/GDPR，规定了处理个人数据的原则，并将未经授权的访问定为犯罪。
5. Software Development Process | 软件开发流程
The software development life cycle (
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