📚 Year 10 Cambridge Computer Science: Key Terms & Memory Aids | 剑桥IGCSE计算机科学核心术语速记指南
Mastering the vocabulary of Cambridge IGCSE Computer Science is half the battle. This guide walks you through the most essential terms, grouped by topic, with memory hooks and straightforward explanations. Each English explanation is immediately followed by its Chinese counterpart so you can absorb both languages seamlessly.
攻克剑桥 IGCSE 计算机科学的词汇就赢了一半。这份指南按主题梳理最核心的术语，配有助记口诀和直白解释，每条英文说明后紧跟中文对照，让你能够顺畅地同步吸收双语表述。
1. Number Systems | 数制基础
Binary (Base-2): A number system using only 0s and 1s, because computers rely on two-state logic (on/off). Memory hook: 'Bi' means two; binary has two digits.
二进制（基数为2）：仅使用0和1的数制，因为计算机依赖两态逻辑（开/关）。记忆口诀：“二”就是两个数字。
Denary / Decimal (Base-10): The everyday number system with digits 0–9. Think of 'deci' meaning ten — humans have ten fingers.
十进制（基数为10）：日常使用的0–9的数制。联想“deci”代表十——人类有十根手指。
Hexadecimal (Base-16): Uses 0–9 and A– t represents four binary bits (a nibble). Memory aid: Hex gives a compact way to write long binary strings; MAC addresses and colours (#FF00AA) use it.
十六进制（基数为16）：使用0–9和A–F（A=10，B=11 … F=15）。每个十六进制数位代表四个二进制位（半字节）。助记：十六进制是长二进制串的缩写写法；MAC地址和颜色代码（#FF00AA）都用它。
Conversion tip: Binary to hexadecimal — split the binary into groups of four bits from the right, then convert each group.
转换技巧：二进制转十六进制——从右向左每四位一组，然后逐组转换。
2. Data Units | 数据单位
Bit: The smallest unit of data, a single 0 or 1. Visualise a light switch: off or on.
位（bit）：数据的最小单位，单个0或1。想象灯泡开关：关或开。
Nibble: 4 bits. Half a byte. Sometimes used in hexadecimal shorthand.
半字节（nibble）：4个位。字节的一半。有时用于十六进制简写。
Byte: 8 bits. The basic building block for storing a character (like 'A' in ASCII).
字节（byte）：8个位。存储一个字符（如ASCII中的‘A’）的基本构件。
Kilobyte (KB), Megabyte (MB), Gigabyte (GB), Terabyte (TB) on powers of 2. Technically 1 KB = 1024 bytes, 1 MB = 1024 KB, and so on. Simple mnemonic: 'King Penguins Make Good Tea' — Kilo, Mega, Giga, Tera. In exams, you may also be told to use 1000 for simplicity.
千字节（KB）、兆字节（MB）、吉字节（GB）、太字节（TB）：基于2的幂次的单位。严格来说1 KB = 1024字节，1 MB = 1024 KB，以此类推。简易口诀：“King Penguins Make Good Tea”——Kilo、Mega、Giga、Tera。考试中可能也允许按1000近似计算。
3. Data Compression | 数据压缩
Lossy compression: Permanently removes some data to reduce file size. Used for JPEG images, MP3 audio. The quality degrades slightly, but the file becomes much smaller. Think: 'Lossy loses data forever'.
有损压缩：永久删除部分数据以减小文件体积，用于JPEG图片、MP3音频。画质音质略有下降，但文件显著变小。联想：“Lossy”就是丢失（lose）了数据。
Lossless compression: Reduces file size without losing any original data; the original can be perfectly reconstructed. Used for PNG images, ZIP files. Memory aid: 'Lossless keeps everything – nothing is lost'.
无损压缩：在不丢失任何原始数据的情况下减小文件体积；原始文件可完美还原。用于PNG图片、ZIP文件。口诀：“Lossless”保留了全部，零丢失。
| Lossy (有损) | Lossless (无损) |
| Some data discarded (部分数据丢弃) | All data kept, only redundancy removed (保留全部数据，仅消除冗余) |
| Smaller file but quality trade-off (文件更小但质量牺牲) | Moderate file size reduction (文件适度缩小) |
| Cannot retrieve original (无法还原原始文件) | Original fully restorable (原始文件可完全恢复) |
4. Representing Text & Sound | 文本与声音的表示
Character set: A defined list of characters recognised by computer hardware and software. Examples: ASCII, Unicode.
字符集：计算机硬件和软件识别的字符定义列表。例如：ASCII、Unicode。
ASCII esent 128 or 256 characters. Suitable for English but limited for other languages. Recall: 'A' = 65, 'a' = 97.
ASCII码：美国信息交换标准代码。每个字符用7或8位表示，可表示128或256个字符。适合英文，但对其他语言支持有限。记忆：‘A’=65，‘a’=97。
Unicode supporting multiple languages and emojis. Can use up to 32 bits per character. Why needed? To represent Chinese, Arabic, etc. Think 'Universal code' = Unicode.
Unicode：更庞大的字符集，支持多种语言和表情符号。每个字符最多可用32位。为何需要？为了表示中文、阿拉伯文等。联想“Universal code”（通用代码）即Unicode。
Sampling (sound) sample rate → better quality, larger file. Memory hook: like taking snapshots of a signal.
采样（声音）：以固定间隔测量声波振幅。采样率即每秒测量次数（Hz）。采样率越高→质量越好，文件越大。助记：如同对信号拍照。
Sampling resolution (bit depth) mber of bits used to record each sample. More bits → finer amplitude detail → larger file.
采样分辨率（位深度）：记录每个样本所用的位数。位数越多→振幅细节越精细→文件越大。
5. CPU Architecture | 中央处理器架构
CPU (Central Processing Unit): The 'brain' of the computer, executing instructions. Major components: ALU, CU, registers.
CPU（中央处理器）：计算机的“大脑”，负责执行指令。主要部件：ALU、CU、寄存器。
ALU (Arithmetic Logic Unit) +, −, ×, ÷) and logic (AND, OR, NOT) operations. Think: ALU = calculator + decision maker.
ALU（算术逻辑单元）：执行算术（+、−、×、÷）和逻辑（AND、OR、NOT）运算。联想：ALU = 计算器 + 决策器。
CU (Control Unit): Directs the flow of data and instructions; decodes instructions and sends control signals. Memory aid: CU is the 'conductor' of the orchestra.
CU（控制单元）：指挥数据与指令的流动；解码指令并发送控制信号。助记：CU就像乐团的“指挥”。
Registers: Tiny, super-fast memory locations inside the CPU. Key ones: PC (Program Counter) holds address of next instruction; MAR (Memory Address Register) holds address of data/instruction to be fetched or written; MDR (Memory Data Register) holds the actual data or instruction; CIR (Current Instruction Register) stores the instruction currently being executed; Accumulator holds intermediate arithmetic/logic results.
寄存器：CPU内部极小的超高速存储器。关键寄存器：PC（程序计数器）存放下一条指令的地址；MAR（存储器地址寄存器）存放待读取或写入数据的地址；MDR（存储器数据寄存器）存放实际数据或指令；CIR（当前指令寄存器）存储正在执行的指令；累加器暂存算术/逻辑中间结果。
Mnemonics for registers: 'MAR the Address', 'MDR the Data'. Picture a post office: MAR is the house number, MDR is the letter.
寄存器口诀：“MAR管地址”，“MDR管数据”。想象邮局：MAR是门牌号，MDR是信件。
6. The Fetch-Decode-Execute Cycle | 取指-译码-执行周期
Fetch: The address from PC is copied to MAR; the instruction at that address is fetched from RAM into MDR, then moved to CIR. PC is incremented to point to the next instruction.
取指：PC中的地址被复制到MAR；RAM中该地址的指令被取到MDR，然后移入CIR。PC自动递增，指向下一条指令。
Decode: The CU decodes the instruction in the CIR — works out what operation to perform and what data is needed.
译码：控制单元解码CIR中的指令——确定需要执行什么操作以及需要哪些数据。
Execute: The ALU performs the required operation; data may be read from memory or written back. The result might be stored in the accumulator or RAM.
执行：ALU完成所需运算；可能从内存读取数据或写回。结果可能存入累加器或RAM。
Cycle loop → Decode → Execute → (repeat). Understanding this is key to explaining how the CPU works.
周期循环：每秒重复数十亿次。顺序：取指→译码→执行→（重复）。理解这一过程是解释CPU工作原理的关键。
7. Memory & Storage | 存储器与存储设备
Primary memory: RAM and ROM — directly accessible by the CPU.
主存：RAM和ROM——CPU可直接访问。
RAM (Random Access Memory) latile (loses data when power off). Stores currently running programs and data. Why called 'random access'? Any memory cell can be accessed directly in any order. More RAM = more multitasking.
RAM（随机存取存储器）：易失性（断电丢失数据）。存储正在运行的程序和数据。为何叫“随机存取”？任何存储单元都可按任意顺序直接访问。RAM越大，多任务处理能力越强。
ROM (Read Only Memory): Non-volatile, stores firmware/BIOS — instructions to boot the computer. It is read-only under normal operation. Think of it as a permanent recipe book for startup.
ROM（只读存储器）：非易失性，存储固件/BIOS——开机引导指令。正常工作时只能读取，不可写入。把它看作一本永久的开机菜谱。
Secondary storage: Long-term storage, not directly accessed by CPU. Types: magnetic (HDD), optical (CD/DVD/Blu-ray), solid state (SSD, USB flash).
辅助存储：长期存储，CPU不直接访问。类型：磁性（机械硬盘）、光学（CD/DVD/蓝光）、固态（固态硬盘、U盘）。
Magnetic: Uses spinning platters and read/write heads. Large capacity, cheap, but slower and fragile. Optical: Lasers read pits and lands on a reflective disc. Portable but lower capacity. Solid state: No moving parts, uses flash memory. Fast, durable, but more expensive per GB.
磁性：使用旋转盘片和读写磁头。容量大、便宜，但较慢且怕震动。光学：激光读取光盘上的凹坑与平面。便携但容量较低。固态：无移动部件，使用闪存。速度快、耐用，但每GB成本更高。
8. Networks & Topologies | 网络与拓扑结构
LAN (Local Area Network): Covers a small geographical area, e.g., school or office. Hardware is usually owned by the organisation. Fast data transfer.
LAN（局域网）：覆盖较小地理范围，如学校或办公室。硬件通常由组织内部拥有。数据传输速度快。
WAN (Wide Area Network): Connects LANs across large distances; the internet is the largest WAN. Uses external communication infrastructure (fibre, satellites).
WAN（广域网）：远距离连接各个局域网；互联网是最大的广域网。使用外部通信基础设施（光纤、卫星）。
Client-server model: A central server provides services/resources (files, web pages, email) and clients request them. Centralised management, easier backups.
客户机-服务器模型：中央服务器提供服务/资源（文件、网页、电子邮件），客户机发出请求。管理集中，备份便捷。
Peer-to-peer (P2P) model: All computers act as both client and server, sharing resources directly. No central server; often used for file sharing and collaboration. Advantage: easy to set up, no single point of failure. Disadvantage: harder to manage security.
对等（P2P）模型：所有计算机同时充当客户机和服务器，直接共享资源。无中央服务器；常用于文件共享和协作。优点：安装简单，无单点故障。缺点：安全管理较难。
Network topologies: Common ones — Star (all devices connect to a central switch; if one cable fails, others work), Mesh (every device connected to many others, robust but expensive).
网络拓扑：常见有——星型（所有设备连至中央交换机；一根线缆故障不影响其他设备），网状（每个设备与多个设备互联，健壮但昂贵）。
9. Internet Protocols & Addressing | 互联网协议与寻址
Protocol: A set of rules governing how data is transmitted and received. Without protocols, devices would not understand each other.
协议：一组管理数据发送和接收的规则。没有协议，设备将无法互相理解。
IP address (Internet Protocol address): A unique logical address for a device on a network, e.g., 192.168.1.1 (IPv4). Can be dynamic or static. Think: postal address for your computer.
IP地址：网络中设备的唯一逻辑地址，如192.168.1.1（IPv4）。可动态或静态。联想：计算机的邮政地址。
MAC address (Media Access Control): A hard-coded physical address assigned to a network interface card, e.g., 00-1A-2B-3C-4D-5E. Unchangeable and unique to each device. Think: device's fingerprint.
MAC地址：网卡出厂时硬编码的物理地址，如00-1A-2B-3C-4D-5E。不可更改且每台设备唯一。联想：设备的指纹。
HTTP & HTTPS: Hypertext Transfer Protocol (Secure). Used to transfer web pages. HTTPS adds encryption via SSL/TLS for security (padlock symbol).
HTTP与HTTPS：超文本传输协议（安全版）。用于传输网页。HTTPS通过SSL/TLS增加加密（显示挂锁图标）。
FTP (File Transfer Protocol): Used for transferring files between a client and a server. Often used to upload website files.
FTP（文件传输协议）：用于客户机与服务器间传输文件。常用于上传网站文件。
TCP/IP stack: Transmission Control Protocol / Internet Protocol. TCP breaks data into packets and reassembles them, ensuring reliable delivery. IP handles addressing and routing the packets.
TCP/IP协议栈：传输控制协议/互联网协议。TCP将数据拆包并重组，保证可靠传输；IP负责寻址和路由数据包。
DNS (Domain Name System): Translates human-friendly domain names (like aleveler.com) into IP addresses. Memory hook: 'DNS is the phonebook of the internet'.
DNS（域名系统）：将人类易记的域名（如 aleveler.com）转换为IP地址。口诀：“DNS是互联网的电话簿”。
10. Security Threats & Protection | 安全威胁与防护
Malware: Malicious software designed to damage, disrupt or gain unauthorised access. Includes viruses, worms, trojans, spyware. Virus attaches to files, worm self-replicates, trojan disguises as legitimate software.
恶意软件：旨在破坏、干扰或未经授权访问的恶意软件，包括病毒、蠕虫、木马、间谍软件。病毒依附文件，蠕虫自我复制，木马伪装成合法软件。
Phishing: Fraudulent emails or websites that trick users into revealing sensitive information (passwords, bank details). The bait looks real. Tip: always check URL and sender.
钓鱼攻击：欺诈性邮件或网站，诱骗用户泄露敏感信息（密码、银行资料）。诱饵看起来逼真。提示：务必核实网址和发件人。
Social engineering: Manipulating people into breaking security procedures, e.g., pretending to be IT support. Humans are often the weakest link.
社会工程学：通过人际操控绕过安全规程，例如冒充IT支持人员。人往往是最薄弱的环节。
Encryption: Scrambling data into an unreadable form; only those with the key can decrypt it. Symmetric encryption uses the same key for encryption and decryption (like a shared secret). Asymmetric encryption uses a public key to encrypt and a private key to decrypt (like a locked mailbox: anyone can drop a letter, only owner opens).
加密：将数据扰乱成不可读形式；只有持有密钥者才能解密。对称加密使用同一密钥加密解密（如共享秘密）。非对称加密用公钥加密、私钥解密（如同邮箱：任何人都可投信，仅主人能开箱）。
Firewall: Monitors and controls incoming/outgoing network traffic based on predetermined security rules. Think of it as a security guard checking IDs.
防火墙：根据预设规则监控和控制进出网络流量。想象成门卫检查身份证。
Proxy server: Acts as an intermediary for requests from clients seeking resources from other servers. Can filter traffic, cache web pages, and hide IP addresses.
代理服务器：作为客户端向其他服务器请求资源的中介。可过滤流量、缓存网页并隐藏IP地址。
11. Algorithms & Programming Constructs | 算法与编程结构
Algorithm: A step-by-step procedure for solving a problem. Not code — a logical plan. Can be expressed in pseudocode or flowcharts.
算法：解决问题的分步操作过程。不是代码，而是逻辑方案。可用伪代码或流程图表达。
Sequence: Instructions executed in order, one after another. The default flow of control.
顺序：指令逐条按序执行。默认的控制流。
Selection: Decision-making using IF, ELSE, CASE statements. The program chooses between different paths based on a condition (true/false).
选择：使用IF、ELSE、CASE语句进行决策。程序根据条件（真/假）选择不同路径。
Iteration (Loop): Repeating a block of code. Count-controlled (FOR loop — know the number of repeats), condition-controlled (WHILE or REPEAT...UNTIL loops — repeat while/until condition is true).
迭代（循环）：重复执行一段代码。计数控制（FOR循环——知晓重复次数），条件控制（WHILE或REPEAT...UNTIL循环——当/直到条件为真时重复）。
Variable & Constant e.g., PI = 3.14). Use constants to make code more readable and prevent accidental changes.
变量与常量：变量是命名的存储位置，其值在运行时可改变。常量整个程序过程中值固定（如 PI=3.14）。使用常量可提高可读性，避免意外修改。
Data types: Integer (whole numbers), Real/Float (decimal numbers), Boolean (TRUE/FALSE), Char (single character), String (text). Important for correct operations and memory allocation.
数据类型：整数（整型）、实数/浮点数（小数）、布尔值（TRUE/FALSE）、字符（单个字符）、字符串（文本）。对运算正确性和内存分配至关重要。
12. Pseudocode, Flowcharts & Testing | 伪代码、流程图与测试
Pseudocode: A simplified, language-agnostic way to describe an algorithm. Uses keywords like INPUT, OUTPUT, IF...THEN...ENDIF, FOR...NEXT, WHILE...ENDWHILE. It is not real code, but easy to translate into any programming language.
伪代码：一种简化、不依赖具体语言的算法描述方式。使用 INPUT, OUTPUT, IF...THEN...ENDIF, FOR...NEXT, WHILE...ENDWHILE 等关键字。不是真实代码，但易转写成任何编程语言。
Flowchart symbols: Oval (Terminator — Start/Stop), Rectangle (Process — assignment or calculation), Parallelogram (Input/Output), Diamond (Decision — yes/no), Arrow (Flow line). Drawing correctly is often examined.
流程图符号：椭圆（起止符——开始/结束），矩形（处理——赋值或计算），平行四边形（输入/输出），菱形（判断——是/否），箭头（流程线）。正确绘制常为考点。
Trace table: A tool to test an algorithm by manually tracking variable values step by step. Each column is a variable, each row shows values after an instruction. Helps spot logical errors.
跟踪表：通过手动逐步追踪变量值来测试算法的工具。每列一个变量，每行展示执行某指令后的值。有助于发现逻辑错误。
Types of testing: Syntax error — grammar of language broken (e.g., missing colon). Logic error — program runs but produces wrong output (e.g., using < instead of >). Runtime error — crashes during execution (division by zero). Use normal, extreme, and erroneous test data.
测试类型：语法错误——违反语言文法（如缺少冒号）。逻辑错误——程序能运行但输出错误（如用<代替>）。运行时错误——执行中崩溃（除以零）。使用正常、边界、异常数据测试。
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