A-Level WJEC Computer Science: Mind Map Quick Revision | WJEC A-Level 计算机科学：思维导图速记

📚 A-Level WJEC Computer Science: Mind Map Quick Revision | WJEC A-Level 计算机科学：思维导图速记

Mind maps offer a powerful, visual way to organise and recall the broad WJEC A-Level Computer Science specification. This article presents a structured, bilingual quick-revision guide that breaks down the core units into hierarchical concept clusters, helping you memorise key facts, relationships, and definitions efficiently.

思维导图为组织与回忆广阔的 WJEC A-Level 计算机科学课程提供了一种强大的可视化方法。本文呈现一份结构化的中英双语快速复习指南，将核心单元分解为层级化的概念集群，帮助你高效记忆关键事实、关联与定义。

1. Fundamentals of Computer Systems | 计算机系统基础

The study of computer systems begins with the architecture and organisation of hardware and software that enable computation. Understanding the roles of major components provides the foundation for all further topics.

计算机系统研究从实现计算的硬件与软件的体系结构与组织开始。理解主要组件的角色为所有后续主题奠定基础。

• Hardware Components
  • CPU: ALU, Control Unit, Registers (PC, MAR, MDR, CIR, ACC) | 中央处理器：ALU、控制单元、寄存器（PC、MAR、MDR、CIR、ACC）
  • Memory: RAM (volatile), ROM (non-volatile), Cache (levels) | 内存：RAM（易失）、ROM（非易失）、缓存（等级）
  • Buses: Data, Address, Control | 总线：数据、地址、控制
  • I/O Devices: Input (keyboard, sensors), Output (monitor, actuators) | I/O 设备：输入（键盘、传感器）、输出（显示器、执行器）
• Fetch-Decode-Execute Cycle
  • Fetch: PC -> MAR, address sent via address bus, instruction copied to MDR, then to CIR | 取指令：PC → MAR，地址通过地址总线发送，指令复制到 MDR，然后到 CIR
  • Decode: Control Unit interprets instruction in CIR | 译码：控制单元解释 CIR 中的指令
  • Execute: ALU performs operation, result stored in ACC or memory | 执行：ALU 执行操作，结果存于 ACC 或内存
• Types of Software
  • System Software: OS, compilers, interpreters, assemblers, utilities | 系统软件：操作系统、编译器、解释器、汇编器、实用工具
  • Application Software: word processors, spreadsheets, databases, bespoke vs off-the-shelf | 应用软件：文字处理、电子表格、数据库、定制 vs 成品

Key Link: The stored-program concept (Von Neumann architecture) means instructions and data share the same memory. | 关键联系：存储程序概念（冯·诺依曼体系结构）意味着指令与数据共享同一内存。

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2. Data Representation | 数据表示

Computers store everything as binary patterns. This section covers number systems, character sets, and units of storage, which underpin fields from graphics to compression.

计算机以二进制模式存储一切。本节涵盖数制、字符集与存储单位，这些构成了从图形到压缩等领域的基础。

• Number Systems
  • Denary (base 10), Binary (base 2), Hexadecimal (base 16) | 十进制、二进制、十六进制
  • Conversions: denary <-> binary, binary <-> hex, hex <-> denary | 转换：十进制 ↔ 二进制，二进制 ↔ 十六进制，十六进制 ↔ 十进制
• Binary Arithmetic
  • Addition, overflow errors | 二进制加法，溢出错误
  • Signed integers: Sign-and-magnitude, Two's complement (most common) | 有符号整数：符号-幅值、补码（最常用）
  • Two's complement: flip bits +1 to negate; range for n bits: -2ⁿ⁻¹ to 2ⁿ⁻¹ - 1 | 补码：反转各位 +1 得到相反数；n 位范围：-2ⁿ⁻¹ 到 2ⁿ⁻¹ - 1
• Character Encoding
  • 7-bit ASCII, Extended ASCII (8-bit) | 7位ASCII、扩展ASCII
  • Unicode (UTF-8, UTF-16) for global character set | Unicode 用于全球字符集
• Units & Images
  • Bit, nibble (4), byte (8 B), KB (10³ B), KiB (2¹⁰ B), MB, MiB, GB, GiB, TB, TiB | 位、半字节、字节、千字节、千比字节、兆字节、兆比字节等
  • Bitmap vs Vector graphics; colour depth, resolution, metadata, file size calculation | 位图与矢量图形；颜色深度、分辨率、元数据、文件大小计算

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3. Networks and Communication | 网络与通信

Networking knowledge includes topologies, protocols, and the Internet structure. This is crucial for understanding how data travels globally and securely.

网络知识包括拓扑、协议与互联网结构。这对理解数据如何全球安全传输至关重要。

• Network Types & Topologies
  • LAN (Local Area Network), WAN (Wide Area Network), PAN | LAN、WAN、PAN
  • Star, Bus, Mesh, Ring topologies; advantages/disadvantages | 星型、总线、网状、环型拓扑及其优缺点
• Protocols & Layers (TCP/IP Model)
  • Application: HTTP, HTTPS, FTP, SMTP, POP3, IMAP | 应用层：HTTP, HTTPS, FTP, SMTP, POP3, IMAP
  • Transport: TCP (reliable), UDP (fast) | 传输层：TCP（可靠）、UDP（快速）
  • Internet: IP addressing (IPv4, IPv6), routing | 网络层：IP 地址（IPv4、IPv6）、路由
  • Link: Ethernet, Wi-Fi (IEEE 802.11) | 链路层：以太网、Wi-Fi
• IP Addressing & DNS
  • Public vs private IPs; subnet mask; DHCP | 公网与私有 IP；子网掩码；DHCP
  • DNS: Domain Name System translates domain names to IPs | DNS：域名系统将域名转换为 IP 地址
• Network Security
  • Threats: malware, phishing, DoS, MitM, SQL injection | 威胁：恶意软件、钓鱼、DoS、中间人攻击、SQL 注入
  • Measures: Firewall, encryption (symmetric, asymmetric), digital certificates, penetration testing | 措施：防火墙、加密（对称、非对称）、数字证书、渗透测试

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4. Data Structures and Algorithms | 数据结构与算法

Efficient data handling relies on choosing the right structure and applying standard algorithms. This unit covers abstract data types, searching, sorting, and computational thinking.

高效的数据处理依赖于选择正确的结构并应用标准算法。本单元涵盖抽象数据类型、搜索、排序与计算思维。

• Arrays, Records, Lists & Files
  • 1D/2D arrays, index-based access | 一维/二维数组，基于索引的访问
  • Records (structs), linked lists (singly, doubly, circular) | 记录（结构体）、链表（单链、双链、循环）
  • Serial vs sequential files, file handling: open, read, write, close | 串行与顺序文件，文件操作：打开、读取、写入、关闭
• Abstract Data Types (ADTs)
  • Stack (LIFO): push, pop, isEmpty, isFull; uses in recursion, undo | 栈（LIFO）：push、pop、isEmpty、isFull；用于递归、撤销
  • Queue (FIFO): enqueue, dequeue; linear, circular, priority queues | 队列（FIFO）：enqueue、dequeue；线性、循环、优先级队列
  • Tree: binary search tree, traversal (pre-order, in-order, post-order) | 树：二叉搜索树，遍历（先序、中序、后序）
  • Hash table: hashing function, collisions, collision resolution | 哈希表：哈希函数、冲突、冲突解决
• Searching & Sorting
  • Linear search O(n), Binary search O(log n) (requires sorted data) | 线性搜索 O(n)，二分搜索 O(log n)（需排序数据）
  • Bubble sort O(n²), Insertion sort O(n²), Merge sort O(n log n), Quick sort O(n log n) average | 冒泡排序、插入排序、归并排序、快速排序平均时间复杂度
  • Algorithm efficiency: Big-O notation | 算法效率：大 O 表示法
• Graph Traversal
  • Breadth-first (BFS) using queue, Depth-first (DFS) using stack | 广度优先（BFS）用队列，深度优先（DFS）用栈
  • Shortest path: Dijkstra's algorithm, A* heuristic | 最短路径：Dijkstra 算法、A* 启发式

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5. Programming Paradigms and Translation | 编程范式与翻译

Understanding how high-level code becomes machine instructions is essential. This includes paradigms and the compilation/interpretation process.

理解高级代码如何成为机器指令至关重要。这包括范式与编译/解释过程。

• Low-Level Languages
  • Machine code: binary, hardware-specific | 机器码：二进制，与硬件相关
  • Assembly language: mnemonics (e.g., LDA, STA, ADD, SUB, BRA), labels, addressing modes (immediate, direct, indirect) | 汇编语言：助记符（如 LDA, STA, ADD, SUB, BRA）、标签、寻址模式（立即、直接、间接）
• High-Level Paradigms
  • Procedural: step-by-step instructions, functions/procedures | 过程式：逐步指令、函数/过程
  • Object-Oriented: classes, objects, inheritance, encapsulation, polymorphism | 面向对象：类、对象、继承、封装、多态
  • Functional: pure functions, recursion, higher-order functions (map, filter, reduce) | 函数式：纯函数、递归、高阶函数
  • Declarative: SQL, logic programming (Prolog) - describe what, not how | 声明式：SQL、逻辑编程（Prolog）——描述做什么，而非如何做
• Translators
  • Assembler: assembly -> machine code | 汇编器：汇编 → 机器码
  • Compiler: high-level -> machine code (entire file), creates executable | 编译器：高级语言 → 机器码（整个文件），创建可执行文件
  • Interpreter: translates and executes line-by-line, no executable | 解释器：逐行翻译执行，无可执行文件
  • Intermediate code, virtual machines (e.g., Java bytecode, JVM) | 中间代码、虚拟机（如 Java 字节码、JVM）

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6. Software Development Lifecycle | 软件开发生命周期

Structured development processes ensure robust, maintainable software. The lifecycle models and documentation are key exam topics.

结构化的开发过程确保软件的健壮性与可维护性。生命周期模型与文档是考试关键主题。

• Phases
  • Analysis: feasibility study, requirements specification | 分析：可行性研究、需求规格说明
  • Design: algorithms (flowcharts, pseudocode), data structures, UI design | 设计：算法（流程图、伪代码）、数据结构、用户界面设计
  • Implementation: coding, choice of language/tools | 实施：编码，语言/工具选择
  • Testing: black-box, white-box, alpha, beta, unit, integration, system, acceptance | 测试：黑盒、白盒、α测试、β测试、单元、集成、系统、验收
  • Maintenance: corrective, adaptive, perfective | 维护：校正性、适应性、完善性
• Models
  • Waterfall: linear, sequential, hard to revisit phases | 瀑布：线性顺序，难以回溯
  • Agile: iterative, incremental, Scrum, sprints, user stories | 敏捷：迭代增量，Scrum、冲刺、用户故事
  • Spiral: risk-driven, prototyping | 螺旋：风险驱动、原型开发
• Documentation
  • User documentation: installation guide, user manual | 用户文档：安装指南、用户手册
  • Technical documentation: commented code, system architecture, maintenance guide | 技术文档：注释代码、系统架构、维护指南

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7. Databases and SQL | 数据库与 SQL

Data persistence and retrieval are fundamental skills. This includes relational database theory, normalisation, and coding SQL queries.

数据持久化与检索是基础技能。包括关系数据库理论、规范化与编写 SQL 查询。

• Relational Databases
  • Entity, Attribute, Primary Key, Foreign Key, Composite Key | 实体、属性、主键、外键、复合键
  • Entity-Relationship (ER) diagrams: entities, relationships (1:1, 1:M, M:M) | ER 图：实体、联系（1:1、1:M、M:M）
• Normalisation (to 3NF)
  • 1NF: atomic values, no repeating groups, identify primary key | 1NF：原子值，无重复组，标识主键
  • 2NF: 1NF + all non-key attributes fully functionally dependent on PK | 2NF：1NF + 所有非键属性完全函数依赖于主键
  • 3NF: 2NF + no transitive dependencies | 3NF：2NF + 无传递依赖
• Structured Query Language (SQL)
  • DDL: CREATE TABLE, ALTER TABLE, DROP TABLE | DDL：CREATE TABLE, ALTER TABLE, DROP TABLE
  • DML: SELECT ... FROM ... WHERE ... ORDER BY ... GROUP BY ... HAVING; JOIN (INNER, LEFT, RIGHT); INSERT, UPDATE, DELETE | DML：SELECT ... FROM ... WHERE ... ORDER BY ... GROUP BY ... HAVING；JOIN（INNER, LEFT, RIGHT）；INSERT、UPDATE、DELETE
  • Aggregate functions: COUNT, SUM, AVG, MIN, MAX | 聚合函数：COUNT、SUM、AVG、MIN、MAX
• ACID & Transaction Management
  • Atomicity, Consistency, Isolation, Durability; record locking, deadlock | 原子性、一致性、隔离性、持久性；记录锁定、死锁

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8. Logic, Boolean Algebra and Circuits | 逻辑、布尔代数与电路

The hardware foundations of computing rely on logic gates and Boolean simplification. This unit connects truth tables with digital circuit design.

计算的硬件基础依赖于逻辑门与布尔化简。本单元将真值表与数字电路设计联系起来。

• Logic Gates & Truth Tables
  • NOT, AND, OR, NAND, NOR, XOR | 非门、与门、或门、与非门、或非门、异或门
  • Construct truth tables for given expressions; draw circuits from expressions and vice versa | 为给定表达式构建真值表；由表达式画电路图，反之亦然
• Boolean Identities & Simplification
  • Associative, Commutative, Distributive, Absorption, De Morgan's Laws | 结合律、交换律、分配律、吸收律、德·摩根定律
  • Simplifying expressions using algebraic manipulation or Karnaugh maps (K-maps) up to 4 variables | 使用代数操作或卡诺图（至多 4 变量）化简表达式
• Adders & Flip-Flops
  • Half Adder: S = A XOR B, C = A AND B | 半加器：S = A ⊕ B, C = A · B
  • Full Adder: uses carry-in, creates carry-out | 全加器：使用进位输入，生成进位输出
  • D-type flip-flop: stores one bit, used in registers; clock, data input, Q/Q' outputs | D 型触发器：存储一位，用于寄存器；时钟、数据输入、Q/Q' 输出

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9. Computational Mathematics & Big Data | 计算数学与大数据

Problem-solving with graphs, matrices, and big data analytics appears in contemporary specifications. This blend of discrete maths and data science is tested regularly.

用图、矩阵与大数据分析解决问题出现在当代大纲中。这种离散数学与数据科学的结合经常被考查。

• Graph & Network Concepts
  • Nodes, edges, weighted/unweighted, directed/undirected; adjacency matrix/list | 节点、边、加权/未加权、有向/无向；邻接矩阵/邻接表
  • Tree properties: n nodes => n-1 edges, no cycles | 树的性质：n 个节点 ⇒ n-1 条边，无环
• Matrices in Computing
  • Addition, multiplication, transpose; representing images, transformations | 加法、乘法、转置；表示图像、变换
• Big Data (Volume, Velocity, Variety, Veracity)
  • Distributed storage (HDFS), processing (MapReduce) | 分布式存储 (HDFS)、处理 (MapReduce)
  • Data mining, pattern recognition, machine learning basics | 数据挖掘、模式识别、机器学习基础

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10. Legal, Moral, Ethical and Environmental Issues | 法律、道德、伦理与环境问题

Modern computing carries societal impacts. WJEC expects candidates to discuss legislation, ethical dilemmas, and sustainability in technology.

现代计算带来社会影响。WJEC 期望考生讨论立法、伦理困境与技术中的可持续发展。

• UK Legislation
  • Data Protection Act 2018 (GDPR): principles, rights of data subjects | 2018 年数据保护法（GDPR）：原则、数据主体权利
  • Computer Misuse Act 1990: unauthorised access, modification, intent | 1990 年计算机滥用法：未经授权访问、修改、意图
  • Copyright, Designs and Patents Act 1988: intellectual property in software | 1988 年版权、外观设计和专利法：软件知识产权
  • Regulation of Investigatory Powers Act 2000 (RIPA): surveillance, interception | 2000 年调查权管理法：监视、截取
• Ethical & Moral Issues
  • Censorship, freedom of speech vs harmful content | 审查、言论自由与有害内容
  • AI bias, algorithmic fairness, deepfakes, privacy | AI 偏见、算法公平、深度伪造、隐私
  • Digital divide: access, skills gaps | 数字鸿沟：接入、技能差距
• Environmental Impact
  • E-waste disposal, rare earth metals | 电子废物处理、稀土金属
  • Energy consumption of data centres, cloud computing | 数据中心能耗、云计算
  • Green computing: virtualisation, power management, recyclable hardware | 绿色计算：虚拟化、电源管理、可回收硬件

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11. Systems Analysis and Design | 系统分析与设计

Building effective information systems requires thorough analysis and modelling. This topic includes feasibility, data flow modelling, and user interface design principles.

构建有效的信息系统需要充分的分析与建模。本主题包括可行性、数据流建模与用户界面设计原则。

• Feasibility Study
  • Economic (cost-benefit, ROI), Technical, Legal, Operational, Schedule feasibility | 经济（成本效益、ROI）、技术、法律、操作、进度可行性
• Modelling Techniques
  • Data Flow Diagrams (DFD): external entities, processes, data stores, data flows; Level 0, Level 1 | 数据流图：外部实体、处理、数据存储、数据流；0 级、1 级
  • State Transition Diagrams: states, events, transitions | 状态转换图：状态、事件、转换
  • Entity-Relationship Diagrams: already covered, expanded with cardinality | ER 图：已覆盖，扩展基数表示
• HCI / UI Design
  • Consistency, feedback, shortcuts, error prevention, Nielsen's heuristics | 一致性、反馈、快捷方式、错误预防、Nielsen 启发式
  • Accessibility: screen readers, colour contrast, alternative text | 可访问性：屏幕阅读器、颜色对比度、替代文本

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12. Emerging Technologies and Recap | 新兴技术总复习

Stay aware of innovations like quantum computing, IoT, and blockchain. This final section also provides the big-picture revision checklist for the WJEC A-Level exam.

关注量子计算、物联网与区块链等创新。最后一节同时提供 WJEC A-Level 考试的大图景复习清单。

• Emerging Trends
  • Quantum computing: qubits, superposition, entanglement; impact on encryption | 量子计算：量子比特、叠加、纠缠；对加密的影响
  • Internet of Things (IoT): sensors, actuators, edge computing, security challenges | 物联网：传感器、执行器、边缘计算、安全挑战
  • Blockchain: distributed ledger, consensus mechanisms, smart contracts | 区块链：分布式账本、共识机制、智能合约
• Rapid Revision Mind Map Tips
  • Draw links between units: e.g., stack usage in recursion and expression evaluation; DBMS and SQL for big data; network security vs Computer Misuse Act | 画出单元之间的联系：例如，递归与表达式求值中栈的使用；大数据中的 DBMS 与 SQL；网络安全 vs 计算机滥用法
  • Practise past papers: apply algorithms (tracing), SQL queries, Boolean simplification, normalisation steps | 练习历年真题：应用算法（追踪）、SQL 查询、布尔化简、规范化步骤
  • Create your own visual maps using colour-coded branches for each unit; test recall by reproducing from memory | 使用颜色编码的分支为自己的单元绘制视觉导图；通过默画测试记忆

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