📚 AS CCEA Computer Science: Glossary Quick-Memory Guide | AS CCEA 计算机：词汇术语速记指南
Mastering technical vocabulary is the first step to tackling AS CCEA Computer Science with confidence. This guide uses mnemonics, root-word clues, and simple analogies to help you lock in key terms, making revision faster and more effective.
掌握专业术语是自信应对 AS CCEA 计算机科学考试的第一步。本指南使用助记法、词根线索和简单的类比，帮助你牢牢记住关键术语，让复习更高效。
1. Data Representation | 数据表示
The term bit (binary digit) is the smallest unit of data. Picture a light switch: 1 is on, 0 is off. Every digital file is ultimately a long sequence of these switches.
比特（bit） 即二进制位，是最小的数据单位。想象一个电灯开关：1 是开，0 是关。每个数字文件最终都是由这样一长串开关状态组成的。
Byte – a group of 8 bits. Mnemonic: ‘by eight’ sounds like ‘byte’. One byte typically stores one character, such as ‘A’ in ASCII.
字节（Byte） – 由 8 个比特组成的单位。记忆技巧：“by eight” 的发音与 “byte” 相似。一个字节通常存储一个字符，例如 ASCII 码中的 ‘A’。
Overflow occurs when the result of an arithmetic operation is too large for the available number of bits. Think of a car’s odometer rolling over from 9999 to 0000 – the extra digit is lost.
溢出（Overflow） 发生在运算结果太大而可用位数无法表示时。就像汽车里程表从 9999 跳到 0000——多余的数字丢失了。
Two’s complement is a method to represent negative integers in binary. To find the negative of a number, flip all bits and add 1. Visual aid: flip the bits like inverting a pancake, then add a little sugar (1).
补码（Two’s complement） 是一种用二进制表示负整数的方法。求一个数的负数时，将所有位取反再加 1。形象化：把位取反就像把煎饼翻面，然后撒上一点糖（加1）。
Unicode extends ASCII to represent characters from many languages and symbols. Remember: ‘Uni-‘ means one – one system to unify all world writing systems.
Unicode 是对 ASCII 的扩展，能表示许多语言和符号的字符。记住：“Uni-” 表示“一”——一个统一全世界书写系统的编码方案。
Hexadecimal uses base 16, with digits 0-9 and A-F. One hex digit perfectly represents 4 bits (a nibble). Think of hex as a ‘shortcut’ for writing long binary – colour codes in web design use hex.
十六进制（Hexadecimal） 使用基数为 16，数字包括 0-9 和 A-F。一位十六进制恰好表示 4 个比特（半字节）。把十六进制看作书写长二进制数的“捷径”——网页设计中的颜色代码就采用十六进制。
2. Programming Constructs | 编程结构
Sequence means executing instructions one after another, in the order they are written. Kitchen analogy: follow a recipe step by step without skipping.
顺序（Sequence） 指按照书写顺序一条接一条地执行指令。厨房类比：像照着食谱一步步操作，不跳跃。
Selection uses conditions to choose between different paths. Think of a road fork where an IF statement decides ‘if rainy, take the left path; else go right’.
选择（Selection） 使用条件在不同路径之间进行抉择。想象一个岔路口，IF 语句决定“如果下雨就走左边，否则走右边”。
Iteration (looping) repeats a block of code. Two main types: definite (FOR loop, known number of repetitions) and indefinite (WHILE loop, until a condition changes). Like a gym exercise: ‘do 10 push-ups’ vs ‘keep going until the timer rings’.
迭代（Iteration） 即循环，重复执行一段代码。主要有两种：确定循环（FOR 循环，次数已知）和不确定循环（WHILE 循环，直到条件改变）。就像健身：“做 10 个俯卧撑”对比“一直做到铃响”。
Pseudocode is a plain-language outline of an algorithm that ignores language-specific syntax. It is the ‘sketch’ of your program, using keywords like IF, WHILE, OUTPUT.
伪代码（Pseudocode） 是用接近自然语言的方式描述算法，忽略具体编程语言语法。它是程序的“草图”，使用 IF、WHILE、OUTPUT 等关键词。
Variable is a named storage location whose value can change during execution. Compare it to a whiteboard: you can write a number, erase it, and write a new one.
变量（Variable） 是一个有名称的存储位置，其值在程序运行期间可以改变。就像一块白板：你可以写一个数字，擦掉后再写一个新的。
Constant is similar to a variable, but its value stays fixed throughout the program. Think of the mathematical constant π – always 3.14.
常量（Constant） 类似于变量，但其值在程序运行过程中保持不变。想想数学常数 π——总是 3.14。
3. Data Structures | 数据结构
Array is a collection of elements of the same data type, stored in contiguous memory. Visualise a row of lockers numbered 0, 1, 2… Each locker holds exactly one item of the same kind.
数组（Array） 是一组相同数据类型的元素的集合，存储在连续的内存空间中。想象一排编号为 0、1、2……的储物柜，每个柜子只放一种同类物品。
Record (or structure) groups related fields of possibly different data types. A student record might contain name (string), age (integer), and grade (character). Like a paper form with boxes for different information.
记录（Record） （或结构体）将可能属于不同数据类型的相关字段组合在一起。一个学生记录可能包含姓名（字符串）、年龄（整数）和成绩（字符），就像一张有各个信息栏的纸质表格。
Stack follows Last In, First Out (LIFO). Imagine a stack of plates: you take the topmost plate first. Operations: PUSH (add) and POP (remove).
栈（Stack） 遵循后进先出（LIFO）原则。想象一摞盘子：你首先取走最上面的那个。操作：PUSH（放入）和 POP（取出）。
Queue follows First In, First Out (FIFO), like people lining up at a bus stop. Operations: ENQUEUE (join the back) and DEQUEUE (leave from the front).
队列（Queue） 遵循先进先出（FIFO）原则，就像人们在公交站排队。操作：ENQUEUE（入队，在队尾加入）和 DEQUEUE（出队，从队首离开）。
Graph consists of vertices (nodes) connected by edges. Use it to model networks, maps, and social relationships. Think of a tube map: stations are vertices, railway lines are edges.
图（Graph） 由顶点（节点）和连接它们的边组成。它常用于建模网络、地图以及社交关系。想想地铁线路图：车站是顶点，轨道路线是边。
4. Algorithms | 算法
Decomposition breaks a complex problem into smaller, manageable sub-problems. It is ‘divide and conquer’ – tackling an essay by planning separate paragraphs.
分解（Decomposition） 将一个复杂问题拆分成更小、更易管理的子问题。这是“分而治之”的策略——就像写论文时先规划好单独的段落。
Abstraction focuses on the essential features while ignoring irrelevant detail. When using a sat nav, you see the route and key junctions, not every lamppost.
抽象（Abstraction） 专注于本质特征，忽略无关细节。使用卫星导航时，你看到的是路线和关键路口，而不是沿途的每一个灯柱。
Linear search checks each element one by one until the target is found. It works on unsorted data but is slow for large lists – like searching for your keys room by room without any clue.
线性搜索（Linear search） 逐个检查每个元素直到找到目标。它适用于未排序的数据，但在大规模列表中速度很慢——就像你毫无头绪地挨个房间找钥匙。
Binary search requires sorted data and repeatedly divides the search interval in half. Think of the ‘guess the number’ game where you ask ‘is it higher or lower?’ after each mid-point guess.
二分搜索（Binary search） 要求数据已排序，并重复将搜索区间一分为二。想想“猜数字”游戏，你每次猜测中间值后问“大了还是小了？”。
Bubble sort repeatedly swaps adjacent out-of-order elements. The largest elements ‘bubble’ to the end on each pass. Memory aid: bubbles rise to the top.
冒泡排序（Bubble sort） 反复交换相邻的乱序元素。每一趟中，最大的元素会“冒泡”到最后面的位置。记忆提示：气泡会升到最上面。
Insertion sort builds the sorted list one element at a time by inserting each new item into its correct position. Like arranging a hand of playing cards as you pick them up one by one.
插入排序（Insertion sort） 通过逐个将新元素插入到已排序部分的正确位置来构建有序列表。就像玩扑克牌时，一边抓牌一边在手中整理顺序。
5. Computer Architecture | 计算机体系结构
Central Processing Unit (CPU) is the brain of the computer. It has three main parts: Control Unit (CU), Arithmetic Logic Unit (ALU), and registers. The CU fetches and decodes; the ALU executes arithmetic and logic.
中央处理器（CPU） 是计算机的大脑，主要由控制单元（CU）、算术逻辑单元（ALU）和寄存器组成。控制单元负责取指与译码，算术逻辑单元负责执行算术和逻辑运算。
Fetch-Decode-Execute cycle is the heartbeat of the CPU. The processor fetches an instruction from memory, decodes what it means, executes it, and then repeats. Think of a chef: read recipe line (fetch), understand it (decode), cook the step (execute).
取指-译码-执行周期 是 CPU 的心跳。处理器从内存取出指令，译码理解其含义，执行指令，然后不断重复。想象一位厨师：看食谱一行（取指），理解它（译码），完成该步骤（执行）。
Program Counter (PC) holds the address of the next instruction to be fetched. It acts like a finger moving along a list of instructions.
程序计数器（PC） 存放下一条待取指令的地址，就像一根手指沿着指令列表移动。
Memory Address Register (MAR) stores the address of the memory location being read from or written to. Think of it as writing the envelope address before sending a letter.
内存地址寄存器（MAR） 存储要读取或写入的内存位置的地址。就像在寄信前写好信封上的地址。
Memory Data Register (MDR) temporarily holds the data that has been read from or is about to be written to memory. It is the actual ‘letter’ inside the envelope.
内存数据寄存器（MDR） 暂时存放从内存中读出的数据或即将写入内存的数据。它就是信封里那封实际的“信”。
Cache memory is very fast, small memory located close to the CPU, storing frequently accessed data. It saves the CPU from repeatedly walking all the way to the slow main memory (RAM).
高速缓存（Cache） 是靠近 CPU 的极快的小容量存储器，存放常用数据。它使 CPU 不必每次都长途跋涉去访问较慢的主存（RAM）。
6. Networks | 网络
LAN (Local Area Network) covers a small geographical area, like a school or office building. Equipment is usually owned by the organisation.
局域网（LAN） 覆盖较小的地理范围，如一所学校或办公楼。设备通常由组织自行拥有。
WAN (Wide Area Network) spans large distances and often uses leased telecommunications lines. The internet is the largest WAN.
广域网（WAN） 跨越长距离，常租用电信线路。互联网是最大的广域网。
TCP/IP is a protocol stack that governs data transmission on the internet. TCP manages the reliable splitting and reassembly of data; IP handles addressing and routing. Analogy: TCP is the courier that guarantees delivery, IP is the postal address system.
TCP/IP 是管理互联网数据传输的协议栈。 TCP 负责可靠地拆分与重组数据，IP 处理寻址与路由。类比：TCP 好比确保包裹送达的快递员，IP 则是邮政地址系统。
MAC address is a unique hardware identifier burned into a network interface card (NIC). It works at the data link layer and looks like this: 00:1A:2B:3C:4D:5E. Think of it as a device’s permanent ID card.
MAC 地址 是烧录在网卡中的唯一硬件标识符，工作于数据链路层，形式如 00:1A:2B:3C:4D:5E。可把其看作设备的永久身份证。
Client-server model: a powerful server provides services (web pages, files) and multiple clients request them. The server is like a restaurant kitchen; clients are the tables sending orders.
客户端-服务器模型：一台功能强大的服务器提供服务（网页、文件等），多个客户端发出请求。服务器好比餐厅厨房，客户端则是下单的餐桌。
Cloud computing delivers computing services—storage, software, processing—over the internet on a pay-as-you-go basis. Instead of owning your own power station, you plug into the electricity grid.
云计算（Cloud computing） 通过互联网按需提供存储、软件、处理能力等计算服务，按使用量付费。你不必自建发电站，而是接入电网用电。
7. Databases | 数据库
Relational database stores data in tables that are linked by relationships. These tables reduce redundancy and improve data integrity.
关系型数据库 将数据存储在通过关系相互关联的表中。这类表能减少冗余并增强数据完整性。
Primary key is a field that uniquely identifies each record in a table, like a student ID number. No two records can have the same primary key value.
主键（Primary key） 是表中能唯一标识每条记录的字段，如同学生学号。表中不允许两条记录拥有相同的主键值。
Foreign key is a field in one table that refers to the primary key of another table. It creates the link between tables – like the ‘department ID’ column in an employee table that points to the department table.
外键（Foreign key） 是某个表中引用另一张表主键的字段，它在表之间建立联系——就像员工表中“部门编号”一列指向部门表。
SQL (Structured Query Language) is used to manage relational databases. Keywords SELECT, FROM, WHERE help retrieve data. ‘SELECT name FROM students WHERE grade=’A” means ‘give me the names of all students with an A’.
SQL（结构化查询语言） 用于管理关系数据库。关键字 SELECT、FROM、WHERE 用来检索数据。比如 “SELECT name FROM students WHERE grade=’A’” 意思是“给我所有成绩为 A 的学生姓名”。
Data redundancy means unnecessary repetition of data. If the same customer address appears in ten different files, that is redundancy – it wastes space and can lead to inconsistency.
数据冗余（Data redundancy） 指不必要的数据重复。如果同一个客户地址出现在十个不同的文件中，这便是冗余——浪费空间并可能引发不一致。
Normalisation is the process of organising data to reduce redundancy by splitting tables. The goal is to have each piece of information stored only once.
规范化（Normalisation） 是通过拆分表来减少冗余的数据组织过程，目标是要让每项信息只保存一次。
8. Software Development Life Cycle | 软件开发生命周期
Waterfall model is a linear sequential approach: analysis → design → implementation → testing → evaluation → maintenance. Each stage must be completed before the next begins, like a real waterfall flowing downwards.
瀑布模型 是一种线性顺序方法：分析 → 设计 → 实现 → 测试 → 评估 → 维护。每个阶段必须完成后才能进入下一阶段，就像真正的瀑布只向下流。
Prototyping involves building an early sample or mock-up of the system to gather user feedback. It helps clarify requirements before full-scale development.
原型法（Prototyping） 指先构建系统的早期样品或模型以收集用户反馈，有助于在全面开发前澄清需求。
Agile development focuses on iterative progress through small, cross-functional teams. Work is done in short cycles (sprints) and changes are welcomed even late in development.
敏捷开发（Agile development） 注重通过跨职能小团队以迭代方式推进工作。工作以短周期（冲刺）进行，即使在开发后期也欢迎需求变动。
Acceptance testing is performed by the end user to check whether the system meets their original requirements. This is the final ‘sign-off’ before the system goes live.
验收测试（Acceptance testing） 由最终用户执行，检查系统是否满足最初的需求，是系统上线前的最终“签字认可”。
Syntax error is a mistake in the grammar of the programming language, such as a missing semicolon. The compiler or interpreter will immediately flag it.
语法错误（Syntax error） 是编程语言语法层面的错误，比如漏掉了分号。编译器或解释器会立刻指出。
Logic error is when the program runs but produces incorrect results because the underlying algorithm is flawed. Like a supermarket checkout that calculates total price as 10 + 20 = 200 due to a wrong operator.
逻辑错误（Logic error） 指程序能运行，但因底层算法错误而产生不正确的结果。就像超市收银机因运算符错误将 10+20 算成了 200。
9. Ethics and Legal Frameworks | 伦理与法律框架
Data Protection Act governs how personal data should be processed. It sets out principles like data must be used fairly, lawfully, and kept secure. Think of it as a rulebook protecting people’s privacy.
数据保护法案（Data Protection Act） 规范个人数据处理方式，确立了公平使用、合法且安全保存等原则。把它看作保护个人隐私的规则手册。
Computer Misuse Act makes unauthorised access to computer systems and data a criminal offence. This includes hacking and spreading malware. The three levels: unauthorised access, unauthorised access with intent to commit crime, and unauthorised modification of data.
计算机滥用法案（Computer Misuse Act） 将未经授权访问计算机系统及数据定为刑事犯罪，包括黑客攻击和传播恶意软件。三个层级：未经授权的访问、有犯罪意图的未经授权访问、以及未经授权修改数据。
Copyright protects original works—software, music, text—from being copied without permission. When you buy software, you typically purchase a licence to use it, not ownership of the code.
版权（Copyright） 保护原创作品——软件、音乐、文本——免遭未经许可的复制。购买软件时，你通常获得的是使用许可，而非代码的所有权。
Plagiarism is the unethical act of presenting someone else’s work or ideas as your own. In computing, copying code without attribution falls under this.
抄袭（Plagiarism） 是一种不道德的行为，将他人成果或想法当作自己的呈现。在计算机领域，未经注明引用就复制代码即属抄袭。
Censorship on the internet involves controlling or suppressing what people can access or publish. It raises ethical debates between protecting citizens and restricting free speech.
网络审查（Censorship） 指控制或压制人们访问与发布内容的行为，引发了在保护公民与限制言论自由之间的伦理争论。
10. Boolean Algebra and Logic | 布尔代数与逻辑
AND gate outputs 1 only if both inputs are 1. Think of a double lock: you need both keys to open the door.
与门（AND gate） 仅在两个输入全为 1 时输出 1。想象双锁门：你需要两把钥匙才能开门。
OR gate outputs 1 if at least one input is 1. Like a hallway with two light switches – either switch can turn the light on.
或门（OR gate） 只要至少有一个输入为 1，输出就为 1。就像走廊里的两个开关——任意一个都能开灯。
NOT gate inverts the input: 1 becomes 0, 0 becomes 1. It is a ‘contrarian’ gate that always says the opposite.
非门（NOT gate） 反转输入：1 变 0，0 变 1。它像一个“唱反调”的门，永远说相反的话。
XOR gate (exclusive OR) gives 1 if the inputs are different. It is the ‘odd one out’ detector – useful for parity checks.
异或门（XOR gate） （异或门）在输入不同时输出 1。它是“找不同”探测器——常用于奇偶校验。
Truth table lists all possible input combinations and the resulting output. It is the ultimate proof of a logic circuit’s behaviour.
真值表（Truth table） 列出所有可能的输入组合及其对应的输出，是验证逻辑电路行为的终极工具。
De Morgan’s Laws provide shortcuts for simplifying Boolean expressions:
NOT (A AND B) = (NOT A) OR (NOT B)
NOT (A OR B) = (NOT A) AND (NOT B).
Memory aid: break the bar and change the sign.
德摩根定律（De Morgan’s Laws） 提供了简化布尔表达式的捷径：
NOT (A AND B) = (NOT A) OR (NOT B)
NOT (A OR B) = (NOT A) AND (NOT B)。
记忆口诀：拆断长杠，符号变样。
11. System Software and Translators | 系统软件和翻译器
Operating System (OS) manages hardware, provides a user interface, and handles multitasking, memory, and peripheral management. It is the ‘manager’ sitting between applications and bare metal.
操作系统（Operating System） 管理硬件，提供用户界面，并处理多任务、内存和外设管理。它是坐镇应用程序和裸机之间的“经理”。
Utility software performs maintenance tasks—antivirus, backup, disk defragmentation. These are the ‘handymen’ that keep the system healthy.
实用软件（Utility software） 执行维护任务——防病毒、备份、磁盘碎片整理。它们是保持系统健康的“修理工”。
Compiler translates the entire high-level source code into machine code in one go, producing an executable file. Like translating a whole book into another language before anyone reads it.
编译器（Compiler） 一次性将整个高级语言源代码翻译成机器码并生成可执行文件。好比先把整本书翻译成另一种语言，再让人阅读。
Interpreter translates and executes source code line by line, without creating a standalone executable. It’s like a live translator at a conference – immediate but no written record.
解释器（Interpreter） 逐行翻译并执行源代码，不生成独立可执行文件。就像会议中的同声传译——即时但没有书面记录。
Assembler translates assembly language mnemonics (like MOV, ADD) into machine code. Assembly is a low-level language with a near one-to-one mapping to machine code.
汇编器（Assembler） 将汇编语言助记符（如 MOV、ADD）翻译成机器码。汇编语言是一种与机器码近乎一一对应的低级语言。
12. Quick Revision Mnemonics and Tips | 快速复习助记符号与技巧
For the fetch cycle registers: PC points to the next instruction, MAR holds the address to access, MDR holds the data, CIR (Current Instruction Register) stores the instruction being executed. Acronym: Please Make Me Coffee (PC, MAR, MDR, CIR).
取指周期寄存器速记：PC 指向下一条指令，MAR 保存要访问的地址，MDR 保存数据，CIR（当前指令寄存器）存储正在执行的指令。首字母缩略词：请给我冲咖啡（PC, MAR, MDR, CIR）。
OSI model layers top-down: All People Seem To Need Data Processing (Application, Presentation, Session, Transport, Network, Data link, Physical). Although AS may not require all seven, this mnemonic supports deeper understanding.
OSI 模型从上往下：所有人似乎都需要数据处理（应用层、表示层、会话层、传输层、网络层、数据链路层、物理层）。虽然 AS 可能不要求全部七层，但该助记符有助于加深理解。
Sorting algorithms complexity in a nutshell: Bubble and Insertion sorts are O(n²) in worst case – slow for big data. Binary search is O(log n) – much faster. Use the ‘logarithmic’ term as a reminder that the data size is halved repeatedly.
排序算法复杂度速记：冒泡排序和插入排序在最差情况下是 O(n²) —— 大数据量时很慢。二分搜索是 O(log n) —— 快得多。用“对数”一词提醒自己，数据规模会反复减半。
In databases, remember ACID for transaction properties: Atomicity, Consistency, Isolation, Durability. A solid database transaction is like an unbreakable sealed unit.
在数据库中，用 ACID 记住事务属性：原子性（Atomicity）、一致性（Consistency）、隔离性（Isolation）、持久性（Durability）。一次可靠的数据库事务就像一个不可分割的密封单元。
To distinguish
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