📚 AQA A-Level Computer Science Year 12: Glossary & Key Terms Quick Reference | AQA A-Level 计算机 Year 12：词汇术语速记指南
Mastering the terminology of AQA A-Level Computer Science is half the battle won. This guide breaks down the most important Year 12 technical terms into clear definitions, paired with memory hooks and links to exam context, so you can recall them under pressure and use them precisely in written answers.
攻克 AQA A-Level 计算机科学的术语是成功的一半。本指南将 Year 12 最重要的技术词汇一一拆解，给出清晰定义，并搭配记忆线索和考试情境链接，让你在压力下也能准确回忆，并在笔答中精准使用。
1. Fundamental Programming Concepts | 基础编程概念
Variable: A named storage location in memory whose value can change during program execution. Think of it as a labelled box – you can swap the contents.
变量：内存中一个命名的存储位置，其值在程序执行过程中可以改变。把它想象成一个贴了标签的盒子——里面的东西可以换。
Constant: A named value that cannot be modified once assigned. Use 'final' or 'const' keywords. Memory trick: constants are like permanent marker – once written, it stays.
常量：一个命名值，一旦赋值就不能再修改。使用 'final' 或 'const' 关键字。记忆技巧：常量就像油性记号笔——写下去就擦不掉了。
Data type: A classification specifying the kind of data a variable can hold (e.g. integer, real/float, Boolean, character, string). AQA commonly asks about integer, real, Boolean, char and string, plus records and arrays.
数据类型：一种分类，指明变量可以存放的数据种类（如整型、实型/浮点型、布尔型、字符型、字符串）。AQA 常考 integer, real, Boolean, char, string，以及记录和数组。
Sequence, selection, iteration: The three structuring principles of structured programming. Sequence – execute in order; selection – IF/ELSE; iteration – loops (FOR, WHILE, REPEAT). Mnemonic: 'SSI' – Simple Simon Is.
顺序、选择、迭代：结构化程序设计的三个基本结构。顺序——依次执行；选择——IF/ELSE；迭代——循环（FOR, WHILE, REPEAT）。助记：'SSI'——顺序、选择、迭代。
Identifier: The name given to a variable, constant, subroutine or other program element. It must follow rules: start with a letter, no spaces. Think 'ID badge' for every element.
标识符：赋予变量、常量、子程序或其他程序元素的名字。必须遵循规则：以字母开头，不含空格。可想象为每个元素的'工牌'。
2. Subroutines, Parameters and Scope | 子程序、参数与作用域
Subroutine: pecific task. Two types: procedures (do something) and functions (return a value). Recall: 'Procedure = Perform, Function = Formula'.
子程序：一个命名代码块，执行特定任务。有两种：过程（执行动作）和函数（返回值）。记忆：'Procedure = Process, Function = Formula'。
Parameter: A variable defined in the subroutine header that receives a value when called. Actual parameter is the value passed; formal parameter is the placeholder. Analogy: a socket (formal) that accepts a plug (actual).
参数：在子程序头部定义的变量，用于接收调用时传递的值。实际参数是传递的值，形式参数是占位符。类比：插座（形式）接受插头（实际）。
Return value: The value that a function sends back to the calling code. A function must always return a value; a procedure never does. Link the 'fun' in function to 'funnel' – something flows back.
返回值：函数返回给调用代码的值。函数必须有返回值，过程则从不返回值。把 function 里的 'fun' 联想成 'funnel'（漏斗）——有东西流回来。
Local variable: Declared inside a subroutine, visible only there. Memory aid: 'local' = 'locked in a room'.
Global variable: Declared at the top level, accessible everywhere. Use sparingly – they can cause side effects.
局部变量：在子程序内部声明，仅在那里可见。记忆：'local' = 'locked in a room'。 全局变量：在顶层声明，到处可访问。慎用——容易引发副作用。
3. Data Structures | 数据结构
Array: A contiguous set of elements of the same data type, accessed by index. Think of a row of lockers numbered 0,1,2… AQA expects 1D and 2D arrays.
数组：一组连续存放、相同数据类型的元素，通过索引访问。想象一排编号为 0,1,2... 的储物柜。AQA 要求掌握一维和二维数组。
Record: A data structure that groups related fields of potentially different types. Like a paper form: name (string), age (integer), grade (char). Mnemonic: a record keeps 'fields' of information.
记录：一种数据结构，将可能不同类型的相关字段组合在一起。就像一张表格：姓名（字符串）、年龄（整数）、等级（字符）。助记：记录保存信息'字段'。
List / Linked list: An ordered collection of elements where each node contains data and a pointer to the next node. Dynamic size; insertion/deletion efficient. Pointer: think 'train car with a hook to the next'.
列表 / 链表：一个有序元素集合，每个节点包含数据和指向下一个节点的指针。大小动态；插入/删除高效。指针：想象'带挂钩连到下一节的车厢'。
Stack: Last-In-First-Out (LIFO) structure. Operations: push, pop, peek. Used for call stack or undo. Memory hook: a stack of plates – you take the top one.
堆栈：后进先出（LIFO）结构。操作：压入、弹出、查看。用于调用栈或撤销功能。记忆钩子：一摞盘子——你总是拿最上面的。
Queue: First-In-First-Out (FIFO). Operations: enqueue, dequeue. Analogy: a queue at a bus stop – first person gets on first. Often implemented as a circular queue with front and rear pointers.
队列：先进先出（FIFO）。操作：入队、出队。类比：公交车站排队——先来先上。常用循环队列实现，有队首和队尾指针。
4. Searching and Sorting Algorithms | 查找与排序算法
Linear search: Check each element in turn until the target is found or the list ends. O(n). Good for unsorted lists. Simple but slow for large n. Think 'reader scanning each line'.
线性查找：依次检查每个元素，直到找到目标或列表结束。时间复杂度 O(n)。适用于未排序列表。简单但 n 大时慢。想象'读者逐行扫描'。
Binary search: Repeatedly divide a sorted list in half, comparing the middle value. O(log n). Requires sorted data. Mnemonic: 'bi' means two – split into two.
二分查找：反复将有序列表分成两半，比较中间值。时间复杂度 O(log n)。要求数据有序。助记：'bi' 表示二——一分为二。
Bubble sort: Compare adjacent pairs and swap if out of order; repeat passes until no swaps. O(n²). Name comes from the way large elements 'bubble up' to the end. Visualise fizzy bubbles rising.
冒泡排序：比较相邻对，若逆序则交换；重复多趟直到无交换。O(n²)。名字来源于大元素'冒泡'到末尾。想象汽水泡泡上升。
Merge sort: A divide-and-conquer algorithm: split list into halves recursively, then merge sorted halves. O(n log n). Stable sort. Remember: 'merge' like merging two lanes of traffic.
归并排序：分治算法：递归地将列表分成两半，再合并已排序的两半。O(n log n)。稳定排序。记住：'merge' 像合并两条车道的车流。
5. Algorithm Complexity and Big O | 算法复杂度与大O符号
Time complexity: A measure of how the running time grows with input size n. Expressed with Big O notation. O(1) – constant; O(log n) – logarithmic; O(n) – linear; O(n²) – quadratic; O(2ⁿ) – exponential.
时间复杂度：衡量运行时间随输入规模 n 增长的度量。用大O符号表示。O(1)——常数；O(log n)——对数；O(n)——线性；O(n²)——平方；O(2ⁿ)——指数。
Big O notation: An upper bound on the growth rate of an algorithm's resource usage. Ignore constants and lower-order terms. Think 'O' as 'Order of magnitude'. For exam answers: tie back to the dominant operation.
大O符号：算法资源使用增长率的上界。忽略常数和低阶项。把 'O' 看作 'Order of magnitude'（数量级）。考试答题时：要联系主导操作。
Space complexity: The amount of memory an algorithm needs, also expressed in Big O. Includes the space for inputs, outputs and auxiliary data structures. Example: merge sort requires O(n) additional space.
空间复杂度：算法所需的内存量，也用大O表示。包括输入、输出和辅助数据结构占用的空间。例如归并排序需要 O(n) 额外空间。
6. Computer Systems and Architecture | 计算机系统与体系结构
Processor / CPU: The central processing unit. Contains the control unit (CU) which decodes instructions, and the arithmetic logic unit (ALU) which performs calculations. Clock speed measured in GHz.
处理器 / CPU：中央处理单元。包含控制单元 (CU) 解码指令，以及算术逻辑单元 (ALU) 执行计算。时钟频率以 GHz 为单位。
Von Neumann architecture: A stored-program concept where instructions and data share the same memory and bus. Key feature: single memory for both. Contrast with Harvard architecture (separate memories).
冯·诺依曼体系结构：存储程序概念，指令和数据共享同一内存和总线。关键特征：单一内存供两者共用。与哈佛体系结构（分开的内存）形成对比。
Registers: Tiny, fast storage locations inside the CPU. Crucial ones for AQA: PC (Program Counter), MAR (Memory Address Register), MDR (Memory Data Register), CIR (Current Instruction Register), ACC (Accumulator). Mnemonic for fetch-decode-execute: 'Police Car Moves Mysteriously Close Around'.
寄存器：CPU 内部微小、快速的存储位置。AQA 重点：PC（程序计数器）、MAR（存储器地址寄存器）、MDR（存储器数据寄存器）、CIR（当前指令寄存器）、ACC（累加器）。取指-解码-执行周期助记：'Police Car Moves Mysteriously Close Around'。
Fetch-Decode-Execute cycle: , decodes it (CU interprets), and executes it (ALU performs). PC increments automatically.
取指-解码-执行周期：CPU 重复从内存取指令（PC→MAR，内存→MDR→CIR），解码（CU 解释），执行（ALU 执行）的过程。PC 自动递增。
7. Memory and Storage | 内存与存储
RAM: Random Access Memory – volatile, fast, used for currently running programs and data. Loses content when power off. Think 'temporary desk space'.
RAM：随机存取存储器——易失性、速度快，用于存放正在运行的程序和数据。断电丢失。想象'临时桌面空间'。
ROM: Read-Only Memory – non-volatile, stores firmware/bootstrap. Cannot be changed easily. Contains the BIOS/UEFI. Analogy: a factory-installed manual.
ROM：只读存储器——非易失性，存储固件/引导程序。不易更改。包含BIOS/UEFI。类比：出厂自带的手册。
Cache memory: Small, very fast memory close to the CPU, storing frequently used data. Levels L1 (fastest, smallest), L2, L3. Key word: 'cache' as in 'stash'.
高速缓存：靠近 CPU 的小容量、超高速内存，存储常用数据。分级 L1（最快最小）、L2、L3。关键词：'cache' 音似 'cash'，就是'私藏'。
Virtual memory: A technique that uses disk space as an extension of RAM when RAM is full. Programs see a continuous address space. Drawback: disk thrashing may occur – much slower.
虚拟内存：当 RAM 满时用磁盘空间扩展 RAM 的技术。程序看到连续的地址空间。缺点：可能出现磁盘抖动——速度慢得多。
8. Systems Software and Translators | 系统软件与翻译器
Operating system (OS): Software that manages hardware resources, provides user interface, memory management, process scheduling, file management and security. Examples: Windows, Linux. Think 'air traffic controller' of the computer.
操作系统 (OS)：管理硬件资源、提供用户界面、内存管理、进程调度、文件管理和安全的软件。示例：Windows, Linux。想象计算机的'空中交通管制员'。
Compiler: Translates high-level source code into machine code all at once, producing an executable file. Fast execution, but slower compilation. Used for languages like C, C++.
编译器：一次性将高级源代码翻译成机器码，生成可执行文件。执行快，编译慢。用于 C、C++ 等语言。
Interpreter: Translates and executes source code line by line. No standalone executable produced. Good for debugging, but slower execution. Example: Python interpreter.
解释器：逐行翻译并执行源代码。不产生独立可执行文件。调试友好，但执行较慢。例如 Python 解释器。
Assembler: hine code. One-to-one mapping typically. Link: assembly → assembler like builder → builds.
汇编器：将汇编语言（助记符如 ADD, SUB）翻译成机器码。通常是一对一映射。联想：assembly → assembler 就像组装工人。
9. Networking and the Internet | 网络与互联网
Protocol: A set of rules governing data communication. Key ones: TCP/IP (transmission & routing), HTTP/HTTPS (web), FTP (file transfer), SMTP (send email), POP3/IMAP (receive email). Mnemonic: 'The Fast Postal Service' – TCP, FTP, POP, SMTP.
协议：一套管理数据通信的规则。关键协议：TCP/IP（传输与路由）、HTTP/HTTPS（网页）、FTP（文件传输）、SMTP（发送邮件）、POP3/IMAP（接收邮件）。助记：'The Fast Postal Service' – TCP, FTP, POP, SMTP。
TCP/IP stack: Four layers: Application, Transport, Internet, Link. Data is encapsulated with headers at each layer. Remember: 'All Tigers In London' (Application, Transport, Internet, Link).
TCP/IP 协议栈：四层：应用层、传输层、互联网层、链路层。每层数据封装头信息。记忆：'All Tigers In London'。
IP address: A unique numerical address identifying a device on a network. IPv4: 32-bit, e.g. 192.168.1.1. IPv6: 128-bit, written in hexadecimal blocks. Subnet mask distinguishes network and host portions.
IP 地址：唯一标识网络上设备的数字地址。IPv4：32位，如 192.168.1.1。IPv6：128位，十六进制分块表示。子网掩码区分网络和主机部分。
DNS: Domain Name System – translates human-friendly names (www.example.com) to IP addresses. Like a phonebook for the internet. AQA may ask about the DNS resolution process.
DNS：域名系统——将人类易读的名字 (www.example.com) 转换成 IP 地址。类似互联网的电话本。AQA 可能考 DNS 解析过程。
10. Cybersecurity Fundamentals | 网络安全基础
Encryption: The process of converting plaintext into ciphertext using an algorithm and a key. Two types: symmetric (same key for encrypt and decrypt) and asymmetric (public and private key pair).
加密：使用算法和密钥将明文转换为密文的过程。有两种：对称加密（加解密用同一密钥）和非对称加密（公钥和私钥对）。
Firewall: A barrier that monitors and filters incoming/outgoing network traffic based on security rules. Can be hardware or software. Think 'customs checkpoint'.
防火墙：一种监控并根据安全规则过滤进出流量的屏障。可以是硬件或软件。想象'海关检查站'。
Digital signature: A method to verify the authenticity and integrity of a message. The sender encrypts a hash of the message with their private key; receiver decrypts with sender's public key and compares hashes. Non-repudiation is achieved.
数字签名：验证消息真实性和完整性的方法。发送者用私钥加密消息摘要；接收者用发送者公钥解密并比对摘要。实现不可否认性。
Malware: Malicious software: virus (needs host), worm (self-replicating), Trojan horse (disguised), ransomware, spyware. Remember: 'Virus attaches, Worm travels, Trojan tricks'.
恶意软件：病毒（需要宿主）、蠕虫（自我复制）、特洛伊木马（伪装）、勒索软件、间谍软件。记忆：'病毒依附，蠕虫穿行，木马欺骗'。
11. Databases and SQL | 数据库与 SQL
Relational database: Data organised in tables (relations) linked by keys. Each table represents an entity; columns are attributes; rows are tuples/records. Entity relationship diagrams (ERD) model the structure.
关系型数据库：以表（关系）组织数据，通过键连接。每个表代表实体；列是属性；行是元组/记录。实体关系图 (ERD) 对结构建模。
Primary key: A unique identifier for each record in a table. Often an ID number. Underlined in schema. Foreign key: a field in one table that links to the primary key of another – enforces referential integrity.
主键：表中每条记录的唯一标识符。常为 ID 号。模式中用下划线标出。外键：一个表中的字段，链接到另一个表的主键——实现引用完整性。
Normalisation: The process of organising data to reduce redundancy. 1NF: atomic values, no repeating groups. 2NF: 1NF + no partial dependencies. 3NF: 2NF + no transitive dependencies. Mnemonic: 'No Repeating, No Partial, No Transitive'.
规范化：组织数据以减少冗余的过程。1NF：原子值，无重复组。2NF：1NF + 无部分依赖。3NF：2NF + 无传递依赖。助记：'无重复、无部分、无传递'。
SQL queries: Structured Query Language commands: SELECT ... FROM ... WHERE ... ORDER BY ... Use JOINS (INNER, LEFT, RIGHT) to combine tables. DDL (Data Definition Language) creates/alters tables; DML (Data Manipulation Language) inserts, updates, deletes data.
SQL 查询：结构化查询语言命令：SELECT ... FROM ... WHERE ... ORDER BY ... 使用 JOIN (INNER, LEFT, RIGHT) 合并表。DDL（数据定义语言）创建/修改表；DML（数据操纵语言）插入、更新、删除数据。
12. Theory of Computation and Functional Programming | 计算理论与函数式编程
Finite State Machine (FSM): An abstract model with a finite number of states, inputs, and transitions. Used in pattern recognition, vending machines. AQA expects you to draw state transition diagrams and tables. Deterministic FSM: each input causes single transition.
有限状态机 (FSM)：一种抽象模型，具有有限数量的状态、输入和转换。用于模式识别、自动售货机。AQA 要求绘制状态转换图和表。确定性 FSM：每个输入导致单一转换。
Regular expression: A notation for describing sets of strings. Symbols: * (zero or more), + (one or more), ? (zero or one), | (or), ( ) for grouping. E.g., a(b|c)*d. Used in pattern matching and lexical analysis.
正则表达式：一种描述字符串集合的表示法。符号：*（零或多个）、+（一个或多个）、?（零或一个）、|（或）、( ) 分组。例如 a(b|c)*d。用于模式匹配和词法分析。
Turing machine: A hypothetical model of computation with an infinite tape, a head that reads/writes, and a set of states. It can simulate any algorithm. The Halting Problem proves that some problems are undecidable.
图灵机：一个假想的计算模型，包含无限长纸带、读写头和一组状态。它能模拟任何算法。停机问题证明有些问题不可判定。
Functional programming basics: Emphasises evaluation of mathematical functions, avoids mutable state. First-class functions: functions can be passed as arguments. Higher-order functions: take functions as input or return them. Map, filter, reduce/fold are common.
函数式编程基础：强调数学函数求值，避免可变状态。一等函数：函数可以作为参数传递。高阶函数：接受函数作为输入或返回函数。常见的有 map, filter, reduce/fold。
Map, filter, reduce: Map applies a function to each list element. Filter selects elements meeting a condition. Reduce (fold) combines elements using a function to produce a single value. Think 'three musketeers of functional programming'.
Map, filter, reduce：Map 对列表每个元素应用一个函数。Filter 选择满足条件的元素。Reduce (fold) 使用函数将元素合并为单个值。想象'函数式编程三剑客'。
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