📚 AS OCR Computer: Terminology Quick Memorisation Guide | AS OCR 计算机：词汇术语速记指南
Building a solid vocabulary is essential for mastering AS-level Computer Science. This guide pairs key technical terms with clear definitions, helping you memorise and apply the terminology required for OCR H046 exams.
扎实的术语积累是掌握 AS 计算机科学的关键。本指南将核心专业术语与清晰定义配对，帮助你记忆并灵活运用 OCR H046 考试所需的词汇。
1. Bits, Bytes and Binary | 比特、字节与二进制
Bit: A bit (binary digit) is the smallest unit of data in a computer, represented by a single 0 or 1. All digital information is built from bits.
比特 (位): 比特是计算机中最小的数据单位，由一个 0 或 1 表示，所有数字信息均由比特构成。
Byte: A byte is a group of 8 bits. It serves as the basic addressable unit of storage and can represent 256 different values (0–255).
字节: 一个字节由 8 个比特组成，是基本的可寻址存储单元，能表示 256 种不同的值（0 到 255）。
Nibble (or Nybble): A nibble consists of 4 bits, half of a byte. It is useful when working with hexadecimal representation because one nibble converts directly to one hex digit.
半字节: 一个半字节由 4 个比特构成，即半个字节，便于与十六进制相互转换，因为一个半字节恰好对应一位十六进制数字。
Most Significant Bit (MSB) and Least Significant Bit (LSB): The MSB is the leftmost bit in a binary number, having the highest place value, while the LSB is the rightmost bit, with the smallest value (1).
最高有效位 (MSB) 与最低有效位 (LSB): MSB 是二进制数中最左边的位，具有最高的位权；LSB 则是最右边的位，位权最小（1）。
2. Number Bases and Storage Units | 数制与存储单位
Denary (decimal): The base‑10 number system we use every day, using digits 0–9. All computing arithmetic may be tested alongside conversions to binary and hex.
十进制: 我们日常使用的基数为 10 的数字系统，使用数字 0 到 9。考试中常要求将其与二进制、十六进制相互转换。
Binary (base‑2): A number system using only 0 and 1, fundamental to digital circuits. For example, 1011₂ = 1×2³ + 0×2² + 1×2¹ + 1×2⁰ = 11₁₀.
二进制 (基数为 2): 只使用 0 和 1 的数字系统，是数字电路的基础。例如 1011₂ = 1×2³ + 0×2² + 1×2¹ + 1×2⁰ = 11₁₀。
Hexadecimal (base‑16): A compact base‑16 system using symbols 0–9 and A–F (A=10, B=11, C=12, D=13, E=14, F=15). It is widely used to represent memory addresses and colour codes. 1F₁₆ = 31₁₀.
十六进制 (基数为 16): 一种紧凑的基数为 16 的系统，使用符号 0–9 和 A–F（A=10, B=11, C=12, D=13, E=14, F=15），常用于表示内存地址和颜色代码。1F₁₆ = 31₁₀。
Binary prefix units: Data quantities use binary prefixes: kibibyte (KiB) = 2¹⁰ bytes, mebibyte (MiB) = 2²⁰ bytes, etc. However, many systems still label them as kilobyte (KB) meaning 10³ bytes; the OCR specification recognises this distinction.
二进制前缀单位: 数据量使用二进制前缀：1 KiB = 2¹⁰ 字节，1 MiB = 2²⁰ 字节。但许多系统仍标记为 KB 代表 10³ 字节；OCR 规范要求注意这一区别。
3. Character Encoding | 字符编码
Character set: A defined collection of characters, each assigned a unique binary code. A computer uses a character set to convert letters, digits and symbols into binary and back.
字符集: 一个定义好的字符集合，每个字符分配唯一的二进制码。计算机利用字符集将字母、数字和符号与二进制进行相互转换。
ASCII (American Standard Code for Information Interchange): A 7‑bit character set that can represent 128 characters, including English letters, digits, and control codes. Extended ASCII uses the 8th bit for an extra 128 characters.
ASCII (美国信息交换标准代码): 一种 7 位字符集，可表示 128 个字符，包括英文字母、数字和控制码。扩展 ASCII 利用第 8 位再表示 128 个字符。
Unicode: A universal character encoding standard designed to represent text from all writing systems. UTF‑8 is a variable‑length encoding that is backwards‑compatible with ASCII and can represent over a million code points.
Unicode: 一种通用字符编码标准，旨在涵盖世界上所有的书写系统。UTF‑8 是可变长编码，与 ASCII 向下兼容，可表示超过一百万个码点。
4. CPU and the Fetch‑Decode‑Execute Cycle | 中央处理器与取指‑译码‑执行周期
Central Processing Unit (CPU): The brain of the computer that carries out instructions. It contains the Arithmetic Logic Unit (ALU), Control Unit (CU) and registers.
中央处理器 (CPU): 计算机的“大脑”，负责执行指令。它包含算术逻辑单元 (ALU)、控制单元 (CU) 和多个寄存器。
Arithmetic Logic Unit (ALU): Performs arithmetic operations (addition, subtraction) and logical operations (AND, OR, NOT). All calculations and comparisons happen here.
算术逻辑单元 (ALU): 执行算术运算（如加、减）和逻辑运算（AND, OR, NOT），所有计算与比较均在此发生。
Control Unit (CU): Directs the operation of the CPU. It decodes instructions and sends control signals to coordinate data movement between registers, ALU and memory.
控制单元 (CU): 指挥 CPU 的操作，负责译码指令并发送控制信号，以协调寄存器、ALU 与内存之间的数据流动。
Key registers: The Program Counter (PC) holds the address of the next instruction. The Memory Address Register (MAR) holds the address to be read/written. The Memory Data Register (MDR) holds the actual data. The Current Instruction Register (CIR) stores the instruction being executed. The Accumulator (ACC) temporarily holds results from the ALU.
关键寄存器: 程序计数器 (PC) 存放下一条指令的地址；内存地址寄存器 (MAR) 存放待读取/写入的地址；内存数据寄存器 (MDR) 存放实际数据；指令寄存器 (CIR) 存放正在执行的指令；累加器 (ACC) 暂存 ALU 的计算结果。
Fetch‑Decode‑Execute (FDE) cycle: The sequence of steps the CPU follows continuously: fetch the next instruction from memory, decode it to determine what needs to be done, then execute it using appropriate components.
取指‑译码‑执行 (FDE) 周期: CPU 不断重复的步骤：从内存中取出下一条指令，译码以确定要做什么，然后使用相应部件执行。
5. Primary and Secondary Storage | 主存与辅存
Random Access Memory (RAM): Volatile, fast memory that stores the operating system, applications and data currently in use. Its contents are lost when power is turned off.
随机存取存储器 (RAM): 易失性高速内存，存储当前正在使用的操作系统、应用程序和数据；断电后内容消失。
Read Only Memory (ROM): Non‑volatile memory that retains its contents without power. It typically stores firmware, such as the BIOS or bootloader, and cannot be altered by ordinary users.
只读存储器 (ROM): 非易失性存储器，断电后仍能保留数据，通常存储固件（如 BIOS 或启动程序），普通用户无法随意修改。
Virtual memory: A technique that uses a portion of secondary storage (e.g., hard disk) as if it were main memory. When RAM is full, the OS swaps pages of data between RAM and disk, enabling larger programs to run, though at slower speed.
虚拟内存: 一种利用部分辅存（如硬盘）模拟主存的技术。当 RAM 不足时，操作系统在 RAM 与磁盘之间换入换出数据页，从而支持运行更大的程序，但速度会变慢。
Secondary storage: Non‑volatile devices used for long‑term storage. Examples include magnetic hard disk drives (HDD), solid‑state drives (SSD), optical discs (CD, DVD) and flash drives. HDDs use spinning platters, while SSDs use NAND flash memory with no moving parts.
辅助存储: 用于长期保存数据的非易失性设备，例如磁盘硬盘 (HDD)、固态硬盘 (SSD)、光盘和闪存盘。HDD 依靠旋转盘片，SSD 则使用无机械部件的闪存芯片。
6. Systems Software and Operating Systems | 系统软件与操作系统
Systems software: Software designed to operate and control the hardware, and to provide a platform for running application software. It includes the operating system, device drivers and utility programs.
系统软件: 用于操作和控制硬件，并为运行应用软件提供平台的软件，包括操作系统、设备驱动程序以及实用工具程序。
Operating system (OS): A key piece of systems software that manages the computer’s resources. Its main functions are: memory management, processor scheduling, file management, managing input/output devices, and providing a user interface (GUI or CLI).
操作系统 (OS): 管理计算机资源的核心系统软件，主要功能包括：内存管理、处理器调度、文件管理、管理输入/输出设备以及提供用户接口 (GUI 或 CLI)。
Device driver: A specialised program that allows the operating system to communicate with a specific hardware device, e.g., a printer or graphics card. Each device requires its own driver.
设备驱动程序: 一种专用程序，使操作系统能够与特定硬件设备（如打印机或显卡）通信，每个设备都需要各自的驱动程序。
Utility software: Programs designed to help maintain or optimise the computer, such as antivirus, backup utilities, disk defragmenters and compression tools. They run alongside the OS but are not part of the kernel.
实用工具软件: 用于维护或优化计算机的程序，例如防病毒软件、备份工具、磁盘碎片整理程序和压缩工具，它们与 OS 一起运行，但不属于内核。
Virtual machine: An emulation of a computer system that runs an OS and applications as if it were a separate physical machine. It provides an isolated environment, useful for testing and running older software.
虚拟机: 一种计算机系统的仿真，可以像独立物理机一样运行操作系统和应用程序，提供隔离环境，常用于测试或运行旧版软件。
7. Networks and the Internet | 网络与互联网
Local Area Network (LAN): A network confined to a small geographical area, such as a school or office building. LANs use dedicated hardware like switches and Ethernet cables or Wi‑Fi.
局域网 (LAN): 只覆盖较小地理范围的网络，如学校或办公楼，通常使用交换机、以太网电缆或 Wi‑Fi 等专用硬件。
Wide Area Network (WAN): A network that spans large distances, connecting multiple LANs. The Internet is the largest WAN. WANs often rely on third‑party communication links such as leased lines or satellite.
广域网 (WAN): 跨越远距离的网络，连接多个 LAN；互联网是最大的 WAN。WAN 通常依赖专线或卫星等第三方通信链路。
Client‑server model: A network architecture where clients (e.g., browsers) request services and servers (e.g., web servers) provide them. Servers are often powerful machines hosting shared resources.
客户‑服务器模型: 一种网络架构，客户端（如浏览器）请求服务，服务器（如 Web 服务器）提供响应；服务器通常是承载共享资源的高性能计算机。
Peer‑to‑peer (P2P) model: All devices (peers) share resources and services directly, without a central server. Each peer acts as both client and server. Commonly used for file sharing.
点对点 (P2P) 模型: 所有设备（对等点）直接共享资源和服务，无需中央服务器；每个对等点同时充当客户端和服务器，常用于文件共享。
Protocol: A set of rules governing data communication. Examples include TCP/IP (transmission control), HTTP/HTTPS (web), FTP (file transfer), and SMTP/POP3/IMAP (email). Protocols ensure different systems can communicate reliably.
协议: 一组管理数据通信的规则。例：TCP/IP（传输控制）、HTTP/HTTPS（网页）、FTP（文件传输）、SMTP/POP3/IMAP（电子邮件），协议确保不同系统能可靠通信。
Packet switching: Data is split into small packets, each carrying the destination address. Packets travel independently through different routes and are reassembled at the destination. Routers forward packets based on the most efficient path.
分组交换: 数据被拆分成小数据包，每个包含目的地址；数据包独立经不同路径传输，到达后重组，路由器根据最优路径转发数据包。
8. Network Security | 网络安全
Encryption: The process of scrambling plaintext into ciphertext using an algorithm and a key, so that only authorised parties with the correct key can read it. It ensures confidentiality of data in transit or at rest.
加密: 使用算法和密钥将明文打乱成密文的过程，只有拥有正确密钥的授权方才能解密，从而保证传输或存储中数据的机密性。
Symmetric encryption: The same key is used for both encryption and decryption. It is fast and efficient but requires a secure way to share the key beforehand.
对称加密: 加密和解密使用相同密钥，速度快、效率高，但需要事先通过安全途径共享密钥。
Asymmetric encryption: Uses a pair of keys: a public key (shared with everyone) and a private key (kept secret). Data encrypted with the public key can only be decrypted with the private key. This solves the key‑distribution problem.
非对称加密: 使用一对密钥：公钥（公开）和私钥（保密）；用公钥加密的数据只能用私钥解密，解决了密钥分发难题。
Firewall: A hardware or software system that monitors incoming and outgoing network traffic based on predetermined security rules. It acts as a barrier between a trusted internal network and untrusted external networks.
防火墙: 一种监控进出网络流量并依据预设安全规则进行过滤的硬件或软件系统，作为可信内部网络与不可信外部网络之间的屏障。
Malware: Malicious software designed to damage or gain unauthorised access. Types include viruses, worms, trojans, ransomware and spyware. Anti‑malware software must be updated regularly.
恶意软件: 旨在破坏或非法访问的恶意软件，类型包括病毒、蠕虫、木马、勒索软件和间谍软件；需定期更新反恶意软件才能防御。
Phishing: A social engineering attack where an attacker sends deceptive emails or messages pretending to be a trustworthy entity, tricking victims into revealing sensitive information such as passwords.
网络钓鱼: 一种社会工程攻击，攻击者发送伪装成可信实体的欺诈性邮件或消息，诱骗受害者泄露密码等敏感信息。
9. Computational Thinking and Algorithms | 计算思维与算法
Computational thinking: A problem‑solving approach that involves abstraction, decomposition, pattern recognition and algorithmic thinking. It is a core skill for developing solutions that a computer can execute.
计算思维: 一种涉及抽象、分解、模式识别和算法思维的问题解决方法，是开发计算机可执行方案的核心技能。
Abstraction: The process of removing unnecessary details and focusing only on the important aspects of a problem. For example, a map omits minor details but shows roads and landmarks.
抽象: 去除不必要的细节，只关注问题的重要方面，例如地图省略次要信息而只显示道路和地标。
Decomposition: Breaking a complex problem into smaller, more manageable sub‑problems, each of which can be solved independently.
分解: 将复杂问题拆分为更小、更易于处理的子问题，每个子问题可独立求解。
Algorithm: A step‑by‑step sequence of instructions designed to solve a specific problem or perform a task. Algorithms must be precise, finite, and produce a result.
算法: 为解决特定问题或完成某项任务而设计的一步步指令序列，算法必须精确、有限，并能产生结果。
Pseudocode: A notation resembling a simplified programming language, used to express algorithms without worrying about strict
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