📚 Year 12 Edexcel Computer Science: Glossary & Rapid Memorisation Guide | Edexcel 12年级计算机：词汇术语速记指南
Mastering the precise terminology of Computer Science is not only essential for achieving top marks in the Edexcel Year 12 exams but also for building a solid foundation for advanced topics. This guide organises key terms by topic, providing clear definitions, context, and bilingual explanations to help you rapidly internalise the language of computing.
掌握计算机科学精确的术语不仅在 Edexcel 12 年级考试中取得高分至关重要，而且为深入学习高级主题打下坚实基础。本指南按主题整理关键术语，提供清晰的定义、语境和双语解释，帮助你快速内化计算机的语言。
1. Programming Fundamentals | 编程基础
A variable is a named storage location in memory that holds a value which can change during program execution.
变量是内存中的一个命名存储位置，其中保存的值在程序执行过程中可以改变。
A constant is similar but its value is set once and cannot be altered, enforced by the keyword const in many languages.
常量类似，但其值设定后不可改变，在许多语言中通过关键字 const 强制实现。
Data type defines the kind of data a variable can hold, such as integer, real/float, Boolean, character, and string. Choosing the correct type affects memory usage and the operations that can be performed.
数据类型定义了变量可以保存的数据种类，例如整型、实型/浮点型、布尔型、字符型和字符串型。选择正确的类型会影响内存用量和可执行的操作。
Assignment is the process of giving a value to a variable using the = operator. Iteration (loops) repeats a block of code: definite iteration uses FOR loops with a known number of repetitions, while indefinite iteration uses WHILE loops based on a condition.
赋值是使用 = 运算符将值赋予变量的过程。迭代（循环）重复执行代码块：计数控制迭代使用 FOR 循环，重复次数已知；条件控制迭代使用 WHILE 循环，基于条件。
Selection uses IF...ELSE or SWITCH/CASE to control the flow of execution based on Boolean conditions.
选择结构使用 IF...ELSE 或 SWITCH/CASE 基于布尔条件控制程序执行流。
2. Data Structures | 数据结构
An array is a static, indexed collection of elements of the same data type, stored contiguously in memory. A list (in Python) is dynamic and can hold mixed types.
数组是一种静态、带索引的同类型元素集合，在内存中连续存储。列表（Python 中）则是动态的，可包含混合类型。
A 2D array can be visualised as a table with rows and columns. A record is a data structure that groups related fields of possibly different types, like a row in a database.
二维数组可看作具有行和列的表。记录是一种将可能不同类型的相关字段组合在一起的数据结构，如同数据库中的一行。
Stack (LIFO – Last In, First Out) and queue (FIFO – First In, First Out) are abstract data types used in backtracking, function calls, and scheduling. A graph consists of vertices (nodes) and edges; a tree is a connected, acyclic graph used in binary search and file systems.
栈（LIFO – 后进先出）和队列（FIFO – 先进先出）是在回溯、函数调用和调度中使用的抽象数据类型。图由顶点（节点）和边构成；树是一种连通无环图，用于二分搜索和文件系统。
3. Algorithms & Computational Thinking | 算法与计算思维
Decomposition means breaking a complex problem into smaller, manageable parts. Abstraction involves focusing on essential details while ignoring irrelevant complexity.
分解指将复杂问题分解为更小、可管理的部分。抽象涉及关注重要细节而忽略无关的复杂性。
Algorithmic thinking is the ability to design step-by-step solutions. A pseudocode is a human-readable, language-independent representation of an algorithm. Flowchart symbols include oval for start/end, parallelogram for input/output, rectangle for process, and diamond for decision.
算法思维是设计逐步解决方案的能力。伪代码是一种人类可读、独立于语言的算法表示形式。流程图符号包括椭圆形表示开始/结束，平行四边形表示输入/输出，矩形表示处理，菱形表示判断。
Key algorithms include binary search (O(log n)), which repeatedly divides a sorted list, and linear search (O(n)). Sorting algorithms like bubble sort (O(n²)) repeatedly swap adjacent elements, while merge sort (O(n log n)) uses divide-and-conquer.
关键算法包括二分查找（O(log n)），它重复划分有序列表；以及线性查找（O(n)）。排序算法如冒泡排序（O(n²)）重复交换相邻元素，而归并排序（O(n log n)）使用分治策略。
Big-O notation describes the worst-case time/space complexity of an algorithm in terms of input size n.
大 O 表示法以输入规模 n 表示算法的最坏情况时间/空间复杂度。
4. Programming Techniques | 编程技巧
A subroutine is a named block of code that performs a specific task. A function returns a value, while a procedure does not. Using parameters allows passing data into subroutines; passing by value copies the data, passing by reference allows the original variable to be modified.
子程序是一个执行特定任务的命名代码块。函数会返回一个值，而过程不会。使用参数可以向子程序传递数据；按值传递复制数据，按引用传递允许修改原始变量。
Scope refers to the visibility of a variable: local variables exist only within the subroutine they are declared in, while global variables are accessible throughout the program. Excessive use of global variables can lead to side effects and difficult debugging.
作用域指变量的可见性：局部变量仅在声明它的子程序内存在，而全局变量在整个程序都可访问。过度使用全局变量可能导致副作用和调试困难。
Recursion is when a subroutine calls itself, requiring a base case to prevent infinite execution. Compare with iteration which uses loops.
递归指子程序调用自身，需要基本情况以防止无限执行。与使用循环的迭代对比。
5. Data Representation | 数据表示
Computers use binary (base 2): bit (b) is a single 0 or 1, a nibble is 4 bits, a byte (B) is 8 bits. To convert positive denary to binary, repeatedly divide by 2 and read remainders.
计算机使用二进制：位（bit）是单个 0 或 1，半字节（nibble）是 4 位，字节（byte）是 8 位。将正十进制转为二进制，反复除以 2 并读取余数。
Hexadecimal (base 16) uses digits 0-9 and letters A-F, representing every nibble with one symbol, making binary more readable. Two's complement is the method to represent negative integers: invert all bits and add 1. The most significant bit indicates sign.
十六进制使用数字 0-9 和字母 A-F，每半字节用一个符号表示，使二进制更易读。二进制补码是表示负整数的方法：将所有位取反后加 1。最高位指示符号。
Floating point representation stores real numbers as mantissa × 2exponent, trading range for precision. Normalisation ensures numbers are stored in a standard form for maximum precision.
浮点数表示将实数存储为尾数 × 2指数，在范围和精度之间权衡。规格化确保数字以标准形式存储以最大化精度。
Character sets: ASCII uses 7 bits (128 characters), extended ASCII 8 bits. Unicode uses up to 32 bits to support global scripts and emojis. Bitmap image is a grid of pixels with colour depth (bits per pixel) and resolution (pixels per inch). Sound is sampled at a rate (Hz) with bit depth determining dynamic range.
字符集：ASCII 使用 7 位（128 个字符），扩展 ASCII 使用 8 位。Unicode 最多使用 32 位以支持全球文字和表情符号。位图图像是由像素网格组成，涉及颜色深度（每像素位数）和分辨率（每英寸像素数）。声音通过采样率（Hz）数字化，位深度决定动态范围。
6. Computer Systems & Architecture | 计算机系统与体系结构
The Von Neumann architecture stores data and instructions in the same memory, fetched and executed in a cycle. The CPU consists of Control Unit (CU), Arithmetic Logic Unit (ALU), and registers: PC (Program Counter), MAR (Memory Address Register), MDR (Memory Data Register), CIR (Current Instruction Register), and ACC (Accumulator).
冯·诺依曼体系结构将数据和指令存储在同一内存中，以循环方式取指和执行。CPU 包含控制单元（CU）、算术逻辑单元（ALU）以及寄存器：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）和ACC（累加器）。
The Fetch-Decode-Execute (FDE) cycle: fetch address from PC to MAR, read instruction to MDR, copy to CIR, decode, execute, repeat. Clock speed (Hz), number of cores, and cache size affect performance.
取指-译码-执行（FDE）周期：从 PC 取地址到 MAR，读指令到 MDR，复制到 CIR，译码，执行，重复。时钟速度（Hz）、核心数量和高速缓存大小影响性能。
RAM (Random Access Memory) is volatile main memory. ROM (Read Only Memory) is non-volatile, storing firmware like BIOS. Virtual memory uses secondary storage as if it were RAM when physical RAM is full.
RAM（随机存取存储器）是易失性主存。ROM（只读存储器）是非易失性的，存储固件如 BIOS。虚拟内存在物理 RAM 满时将辅助存储器当作 RAM 使用。
7. Systems Software & OS | 系统软件与操作系统
The operating system (OS) manages hardware, provides a user interface, memory management (paging, segmentation), processor scheduling (round robin, priority), file management, and I/O control. Interrupts are signals from hardware or software that cause the CPU to pause the current task and run an interrupt service routine (ISR).
操作系统管理硬件，提供用户界面、内存管理（分页、分段）、处理器调度（轮转、优先级）、文件管理和 I/O 控制。中断是来自硬件或软件的信号，使 CPU 暂停当前任务并运行中断服务程序（ISR）。
Utility software: antivirus, defragmentation, backup, compression. Application software performs user-oriented tasks. A virtual machine emulates a computer system, allowing multiple OS to run on one physical machine.
实用软件：防病毒、碎片整理、备份、压缩。应用软件执行面向用户的任务。虚拟机模拟计算机系统，允许在一台物理机上运行多个操作系统。
Open source software allows access to the source code for modification; proprietary (closed source) does not. Translators: compiler translates entire high-level code to machine code before execution; interpreter translates line-by-line at runtime; assembler converts assembly language.
开源软件允许访问源代码进行修改；专有（闭源）则不允许。翻译器：编译器在执行前将整个高级代码翻译为机器码；解释器在运行时逐行翻译；汇编器转换汇编语言。
8. Networks & Communication | 网络与通信
A LAN (Local Area Network) covers a small geographic area; a WAN (Wide Area Network) spans large distances. The Internet is a global network of networks using TCP/IP protocols.
LAN（局域网）覆盖小范围地理区域；WAN（广域网）跨越远距离。因特网是一个使用 TCP/IP 协议的全球性网络之网络。
Network topologies: star (all devices connect to a central switch, easy to manage but single point of failure), mesh (devices interconnect, robust but expensive), bus (single backbone cable, low cost but collisions).
网络拓扑：星型（所有设备连到中心交换机，易管理但单点故障），网状（设备互连，高鲁棒但昂贵），总线型（单一主干电缆，成本低但易冲突）。
Protocols are agreed rules for communication: TCP ensures reliable delivery, IP handles addressing and routing, HTTP/HTTPS for web, FTP for file transfer, SMTP for sending email, POP3/IMAP for receiving. The TCP/IP stack has four layers: Application, Transport, Internet, Network Access.
协议是通信的约定规则：TCP 确保可靠交付，IP 处理寻址与路由，HTTP/HTTPS 用于网页，FTP 用于文件传输，SMTP 发送邮件，POP3/IMAP 接收邮件。TCP/IP 协议栈有四层：应用层、传输层、网际层、网络接入层。
Packet switching breaks data into packets, each routed independently, reassembled at destination. CSMA/CA (WiFi) avoids collisions by sensing and waiting. IP address (IPv4: 32 bits, IPv6: 128 bits) and MAC address (48 bits, hardcoded to NIC) are identifiers.
分组交换将数据分成数据包，每个包独立路由，在目的地重组。CSMA/CA（WiFi）通过侦听和等待避免冲突。IP 地址（IPv4：32 位，IPv6：128 位）和MAC 地址（48 位，固化在网卡中）是标识符。
9. Databases & SQL | 数据库与 SQL
A relational database organises data into tables (relations) with rows (records) and columns (fields/attributes). Each table has a primary key uniquely identifying each record. A foreign key links tables by referencing a primary key in another table.
关系数据库将数据组织成表（关系），包含行（记录）和列（字段/属性）。每个表有一个主键唯一标识每条记录。外键通过引用另一张表的主键来链接表。
Normalisation is the process of structuring data to reduce redundancy: 1NF (atomic values), 2NF (no partial dependencies), 3NF (no transitive dependencies).
规范化是为减少冗余而结构化数据的过程：1NF（原子值）、2NF（无部分依赖）、3NF（无传递依赖）。
SQL (Structured Query Language) commands: SELECT, FROM, WHERE, JOIN (INNER, LEFT, RIGHT), INSERT, UPDATE, DELETE. Example: SELECT name, grade FROM Students WHERE grade > 7 ORDER BY name ASC;
SQL（结构化查询语言）命令：SELECT、FROM、WHERE、JOIN（INNER、LEFT、RIGHT）、INSERT、UPDATE、DELETE。例如：SELECT name, grade FROM Students WHERE grade > 7 ORDER BY name ASC;
DBMS (Database Management System) is software managing databases; examples MySQL, PostgreSQL. Data dictionary stores metadata about tables, fields, and constraints.
DBMS（数据库管理系统）是管理数据库的软件；例如 MySQL、PostgreSQL。数据字典存储关于表、字段和约束的元数据。
10. Cybersecurity & Threats | 网络安全与威胁
Malware: virus (replicates by attaching to files), worm (self-replicates across networks), trojan (disguised as legitimate software), ransomware (encrypts data for ransom), spyware (secretly monitors).
恶意软件：病毒（通过附加文件复制）、蠕虫（通过网络自我复制）、木马（伪装成合法软件）、勒索软件（加密数据索要赎金）、间谍软件（秘密监视）。
Phishing uses fraudulent emails to trick users into revealing sensitive info. DoS/DDoS attacks overwhelm a server with traffic. Brute-force attack systematically tries all passwords. SQL injection inserts malicious SQL into input fields.
钓鱼使用欺诈电子邮件诱骗用户泄露敏感信息。DoS/DDoS 攻击利用流量淹没服务器。暴力攻击系统地尝试所有密码。SQL 注入将恶意 SQL 插入输入字段。
Encryption: symmetric (same key for encrypt/decrypt, e.g. AES), asymmetric (public/private key pair, e.g. RSA). Firewalls filter traffic based on rules. Digital signature verifies authenticity using hashing and encryption.
加密：对称加密（同一个密钥加解密，如 AES），非对称加密（公钥/私钥对，如 RSA）。防火墙基于规则过滤流量。数字签名使用哈希和加密验证真伪。
11. Ethical, Legal & Environmental Issues | 伦理、法律与环境问题
Data Protection Act principles: data must be processed lawfully, fairly, for specified purposes, accurate, not kept longer than necessary, and secure. Computer Misuse Act criminalises unauthorised access and modification.
数据保护法原则：数据必须合法、公平地处理，用于特定目的，准确，不保留超过必要时间，并保证安全。计算机滥用法将未授权访问和修改定为犯罪。
Copyright, Designs and Patents Act covers software and digital content. Creative Commons licenses allow flexible sharing. Digital divide is the gap between those with and without access to technology.
版权、设计和专利法涵盖软件和数字内容。知识共享许可允许灵活共享。数字鸿沟指有无技术访问的人群之间的差距。
Environmental considerations: e-waste, energy consumption of data centers, and the role of technology in smart grids and remote work.
环境考虑：电子垃圾、数据中心的能源消耗，以及技术智能电网和远程办公的作用。
12. Emerging Trends & Recap Techniques | 新兴趋势与回顾技巧
Artificial Intelligence (AI) simulates human intelligence; machine learning enables systems to learn from data without explicit programming. Big Data refers to datasets too large for traditional processing, characterised by volume, velocity, variety.
人工智能（AI）模拟人类智能；机器学习使系统无需显式编程即可从数据中学习。大数据指传统处理无法处理的数据集，特征是数量大、速度快、种类多。
Memorisation tips: create flashcards with term on one side and definition plus example on the other. Use mnemonics (e.g., "F-D-E Cycle: Fetch-Decode-Execute" = pile of plates). Regularly practise past paper questions focusing on command words like 'Define', 'Explain', 'Compare'.
记忆技巧：制作抽认卡，一面是术语，另一面是定义和示例。使用助记符（例如 "F-D-E 周期：取指-译码-执行"）。将新术语与现实世界类比（栈 = 一叠盘子）。定期练习历年真题，重点关注“定义”、“解释”、“比较”等指令词。
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