📚 Year 13 WJEC Computer Science: Vocabulary and Terminology Memorisation Guide | Year 13 WJEC 计算机：词汇术语速记指南
Mastering the extensive terminology of the WJEC Year 13 Computer Science specification is one of the biggest hurdles before the final exam. This guide breaks down the high-frequency keywords across every major topic area and provides quick mnemonics, visual hooks, and comparison tables to help you lock them into long-term memory, ensuring you can recall precise definitions under timed conditions.
掌握 WJEC Year 13 计算机科学考纲中庞大的术语体系，是考前冲刺最难的一关。本文整理了各知识模块的高频词汇，搭配速记口诀、形象联想和对比表格，帮助你将精确的定义植入长期记忆，在限时笔试中快速提取。
1. Data Structures: Stacks, Queues and Lists | 数据结构：栈、队列和链表
Stack – A Last-In-First-Out (LIFO) abstract data type. Memorisation tip: Picture a stack of plates in a cafeteria; you can only add (push) or remove (pop) from the top. The acronym FILO (First In Last Out) is equivalent.
栈 – 后进先出 (LIFO) 的抽象数据类型。记忆窍门：想象食堂里的一摞盘子，你只能从顶部放入 (push) 或取出 (pop)。记住“先进后出”也可以，缩写 FILO 等价于 LIFO。
Queue – A First-In-First-Out (FIFO) structure. Visualise a real queue at a bus stop: the first person to join is the first to board. Operations: enqueue (add to rear) and dequeue (remove from front).
队列 – 先进先出 (FIFO) 的结构。想象真实的排队：先来的人先上车。操作为入队 (enqueue) 和出队 (dequeue)，元素从尾部加入，从头部移除。
Linked List – A dynamic collection of nodes, each containing data and a pointer to the next node. Memorisation: “a chain of carriages linked by a coupling”. Efficient insertion/deletion, but no random access. Remember sequential access.
链表 – 节点的动态集合，每个节点包含数据与指向下一个节点的指针。用“一列由车钩连接的车厢”来联想。插入和删除高效，但不能随机访问，记住是顺序存取。
Array vs Linked List – Arrays offer O(1) random access but fixed size; linked lists allow O(1) insertion at head but require O(n) access by index.
数组 vs 链表 – 数组提供 O(1) 随机访问但大小固定；链表头部插入 O(1)，但按索引访问需 O(n)。
2. Trees and Graphs: Branches and Networks | 树与图：分支与网络
Binary Search Tree (BST) – For each node, left subtree values < node < right subtree values. Memory phrase: Left is lesser, Right is greater. Searching is O(log n) if balanced; skewed tree becomes O(n) – like a linked list.
二叉搜索树 – 对任意节点，左子树所有值 < 节点值 < 右子树所有值。口诀：“左小右大”。平衡时查找 O(log n)，若退化成斜树则变为 O(n)，等价于链表。
Graph – Set of vertices connected by edges. Can be directed (edges have direction) or undirected. Quick formula: complete graph Kₙ has n(n−1)/2 edges. Memorise adjacency matrix vs adjacency list representation.
图 – 由顶点和边组成的集合。可分为有向图和无向图。速记公式：完全图 Kₙ 的边数为 n(n−1)/2。务必熟记邻接矩阵与邻接表两种存储方式的差异。
Traversal – Depth-first (DFS) uses a stack (LIFO); breadth-first (BFS) uses a queue (FIFO). Associate DFS with going deep down one branch, BFS with exploring level by level. The stack-queue duality is the key.
遍历 – 深度优先 (DFS) 用栈 (LIFO)；广度优先 (BFS) 用队列 (FIFO)。联想 DFS 沿一条分支深入，BFS 逐层探索。栈与队列的对偶性就是核心记忆点。
3. Algorithm Complexity and Big O Notation | 算法复杂度与 Big O 记法
Big O – on hierarchy from best to worst: O(1) → O(log n) → O(n) → O(n log n) → O(n²) → O(2ⁿ) → O(n!).
Big O – 表示当输入规模 n 增大时，时间或内存的上界。按优劣顺序记忆常见复杂度：O(1) → O(log n) → O(n) → O(n log n) → O(n²) → O(2ⁿ) → O(n!)。
Linear Search – O(n); Binary Search – O(log n) assuming sorted data. Quick recall: cutting the search space in half each time gives logarithmic time.
线性搜索 – O(n)；二分查找 – O(log n)，前提是数据已排序。每次将查找范围减半，所以得对数时间。
| Algorithm | Best Case | Average | Worst Case |
|---|---|---|---|
| Bubble Sort | O(n) | O(n²) | O(n²) |
| Merge Sort | O(n log n) | O(n log n) | O(n log n) |
| Quick Sort | O(n log n) | O(n log n) | O(n²) |
For sorting stability, remember: Merge keeps order, Quick can change it. Stable sorts preserve the relative order of equal elements.
排序的稳定性记法：归并保序，快速易变。稳定排序保持相等元素的相对顺序。
4. Object-Oriented Programming: The Four Pillars | 面向对象编程：四大支柱
Think of the acronym A PIE: Abstraction, Polymorphism, Inheritance, Encapsulation. This covers the essential OOP concepts required by WJEC.
记住首字母缩写 A PIE（英语“一块馅饼”）：抽象 (Abstraction)、多态 (Polymorphism)、继承 (Inheritance)、封装 (Encapsulation)，涵盖 WJEC 面向对象编程的要点。
Encapsulation – Wrapping data (attributes) and methods into a single unit, restricting direct access. Use private fields with public getters/setters. Mnemonic: “a capsule protecting its contents”.
封装 – 将数据（属性）与方法打包在一起，限制直接访问。用 private 字段配合公共 getter/setter。联想“胶囊保护内含物”。
Inheritance – A subclass inherits properties and behaviours from a superclass. Keyword extends in Java/C#. “Child inherits parent’s traits.”
继承 – 子类从父类继承属性和方法。Java/C# 中用 extends 关键字，犹如“孩子继承父母的性状”。
Polymorphism – “Many forms”. Method overriding allows a subclass to provide a specific implementation of a method defined in the superclass. Compile-time (overloading) vs runtime (overriding) polymorphism.
多态 – “多种形态”。方法重写允许子类给出父类方法的特化实现。区分编译时多态（重载）和运行时多态（重写）。
Abstraction – Hiding complex implementation details; exposing only essential features. Achieved through abstract classes and interfaces.
抽象 – 隐藏复杂的实现细节，只暴露必要功能。通过抽象类和接口实现。
5. Database Design and Normalisation | 数据库设计与规范化
Primary Key – A unique identifier for each tuple in a relation. Foreign Key – An attribute that creates a link between two tables by referencing a primary key. Remember: “Foreign key is a guest in another table”.
主键 – 关系中每条元组的唯一标识。外键 – 通过引用另一表的主键来建立表间联系的属性。记法：“外键是另一个表里的客人”。
Normalisation – Process to reduce data redundancy and anomalies. Main forms: 1NF (atomic values, no repeating groups), 2NF (1NF + all non-key attributes fully dependent on the whole primary key), 3NF (2NF + no transitive dependencies). Chant: “No repeats, fully depend, no transit”.
规范化 – 减少数据冗余和异常的过程。主要范式：1NF（值为原子，无重复组）、2NF（1NF + 所有非键属性完全依赖于整个主键）、3NF（2NF + 无传递依赖）。口诀：“无重复、全依赖、消传递”。
Entity-Relationship Diagram – Visual tool showing entities as rectangles, attributes as ovals, and relationships with cardinalities (1:1, 1:M, M:N). The linking of M:N relationships requires a bridge (associative) entity.
实体关系图 – 矩形表实体，椭圆表属性，连线标出关系的基数（1:1, 1:M, M:N）。M:N 关系必须通过桥接实体（关联实体）解析。
6. SQL: Data Definition and Manipulation | SQL：数据定义与操作
SQL is split into DDL (Data Definition Language) – CREATE, ALTER, DROP – and DML (Data Manipulation Language) – SELECT, INSERT, UPDATE, DELETE. Mnemonic: “DDL builds the house; DML moves the furniture.”
SQL 分为 DDL（数据定义语言）—— CREATE, ALTER, DROP，以及 DML（数据操作语言）—— SELECT, INSERT, UPDATE, DELETE。口诀：“DDL 建房，DML 搬家具”。
Joins – INNER JOIN returns rows with matches in both tables; LEFT JOIN returns all rows from the left table plus matched rows from the right; RIGHT JOIN is the mirror. Visualise Venn diagrams to distinguish them.
联接 (Join) – INNER JOIN 返回两表匹配的行；LEFT JOIN 返回左表全部行加上右表匹配行；RIGHT JOIN 相反。用韦恩图想象可快速区分。
Aggregate Functions – COUNT, SUM, AVG, MIN, MAX. Used with GROUP BY and HAVING for filtering groups. Remember: WHERE filters rows before aggregation, HAVING filters after.
聚合函数 – COUNT, SUM, AVG, MIN, MAX。常配合 GROUP BY 和 HAVING 对分组过滤。记住：WHERE 在聚合前过滤行，HAVING 在聚合后过滤组。
7. Networking Protocols and Models | 网络协议与模型
TCP/IP Stack – From bottom to top: Link, Internet, Transport, Application. Quick mnemonic: “Larry Is Taking Applications”. The OSI model adds more abstraction: Physical, Data Link, Network, Transport, Session, Presentation, Application – “Please Do Not Throw Sausage Pizza Away”.
TCP/IP 协议栈 – 自下而上：链路层、网络层、传输层、应用层。英文口诀 “Larry Is Taking Applications”。OSI 模型则更精细：物理层、数据链路层、网络层、传输层、会话层、表示层、应用层——英文可用 “Please Do Not Throw Sausage Pizza Away” 记忆。
Protocol Acronyms: HTTP (Hypertext Transfer), HTTPS (secure), FTP (File Transfer), SMTP (Simple Mail Transfer), POP3/IMAP (retrieve mail). DNS resolves domain names to IP addresses. All are application-layer protocols.
协议速记：HTTP 超文本传输，HTTPS 安全版，FTP 文件传输，SMTP 简单邮件传输，POP3/IMAP 取信。DNS 将域名解析为 IP 地址，这些均属应用层协议。
Packet Switching – Data is broken into packets, each finding its own route. Key terms: payload, header, checksum. Compare with circuit switching.
分组交换 – 数据被拆成包，各自寻路。关键术语：载荷、报头、校验和。与电路交换对比记忆。
8. Operating Systems and Virtual Machines | 操作系统与虚拟机
Virtual Machine (VM) – Software emulation of a physical computer, enabling multiple OS instances on one hardware. The hypervisor manages VMs. Think of VMs as “apartments sharing a building”.
虚拟机 – 物理计算机的软件仿真，让一台硬件上运行多个操作系统实例。管理程序 (hypervisor) 掌管虚拟机。可以把虚拟机想象成“共用一栋大楼的公寓”。
Memory Management – Paging divides physical memory into fixed-size page frames; segmentation uses variable-sized logical segments. Virtual memory uses disk as an extension of RAM. The key risk: thrashing (excessive swapping).
内存管理 – 分页将物理内存分为固定大小的页框；分段则使用可变大小的逻辑段。虚拟内存将磁盘作为 RAM 的扩展。关键风险：抖动 (thrashing)，即过度换页。
Scheduling – Algorithms: FCFS, SJF, Round Robin, Priority-based. Round Robin uses a time quantum; remember the circular queue analogy.
调度 – 算法：先来先服务、最短作业优先、时间片轮转、优先级调度。轮转法采用时间片，可类比循环队列。
9. Program Translation: Compilers, Interpreters, Assemblers | 程序翻译：编译器、解释器、汇编器
Compiler – ntifiers), syntax analysis (parse tree), semantic analysis, code generation, optimisation.
编译器 – 将高级语言源码一次性翻译为机器码，生成可执行文件。阶段：词法分析（生成记号）、语法分析（生成分析树）、语义分析、代码生成与优化。
Interpreter – Translates and executes line-by-line; no separate executable. Slower at runtime but easier for debugging. Hybrids use bytecode (e.g., Java: compile to bytecode, JVM interprets).
解释器 – 逐行翻译并执行，不生成本地可执行文件。运行时较慢但便于调试。混合型如 Java，先编译为字节码，再由 JVM 解释执行。
Assembler – Converts assembly language mnemonics (MOV, ADD) to machine code. One assembly instruction usually maps to one machine instruction. Remember: Assembler is for low-level symbolic representation.
汇编器 – 将汇编助记符 (MOV, ADD) 转为机器码。通常一条汇编指令对应一条机器指令。记忆：汇编器处理底层符号表示。
10. Computation Theory: Automata and Formal Languages | 计算理论：自动机与形式语言
Finite State Machine (FSM) – A model of computation with a finite number of states, transitions, and inputs (no memory beyond the state itself). Two types: Mealy (output depends on state and input) and Moore (output depends only on state). Mnemonic: “Mealy mines extra input output”.
有限状态机 – 状态数有限的计算模型，仅有状态、转换和输入，无额外内存。分两类：Mealy 机（输出依赖状态和输入）和 Moore 机（输出仅依赖状态）。英文联想：Mealy 多了一点点输入来生成输出。
Regular Expression – Patterns defining regular languages. Operators: * (zero or more), + (one or more), ? (zero or one), | (alternation). Recognised by FSMs. Cannot count – e.g., cannot match balanced parentheses.
正则表达式 – 定义正则语言的模式。运算符：*（零或多）、+（一或多）、?（零或一）、|（或）。能被有限状态机识别。致命弱点：不能计数，例如无法匹配成对的括号。
Turing Machine – A theoretical model with an infinite tape, a head that reads/writes, and a finite state control. It underpins the notion of computability. The Halting Problem proves some problems are undecidable.
图灵机 – 具有无限纸带、读写头和有限状态控制器的理论模型，奠定了可计算性概念。停机问题证明存在不可判定的问题。
11. Cryptography and Security | 加密与安全
Symmetric Encryption – Same key for encryption and decryption (e.g., Caesar, AES). Think of a single shared key between two parties. Challenge: secure key exchange. Asymmetric – uses a public/private key pair; computationally heavier but solves key distribution.
对称加密 – 加密与解密使用同一密钥（如凯撒密码、AES）。想象双方共有一把钥匙。挑战在于密钥的安全交换。非对称加密 – 使用公钥/私钥对，计算代价更高，但解决了密钥分发问题。
Hashing – One-way function producing a fixed-size digest; cannot be reversed. Used for password storage and integrity checks. Common algorithms: SHA-256, MD5 (now broken). Mnemonic: “Hash is a digital fingerprint, not encryption.”
哈希 – 单向函数，生成固定长度的摘要，不可逆。用于存储密码和完整性校验。常见算法：SHA-256，MD5（已不安全）。记法：“哈希是数字指纹，不是加密。”
Digital Signature – Encrypting a hash with sender’s private key to verify authenticity and integrity. Provides non-repudiation. Think: “sign a document with a digital pen only you hold”.
数字签名 – 发件人用自己的私钥加密哈希值，以验证真实性和完整性，提供不可否认性。联想“用只有你拥有的数字笔签署文件”。
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