📚 AS WJEC Computer Science: Glossary Quick Revision Guide | AS WJEC 计算机：词汇术语速记指南
Mastering the precise vocabulary of computer science is half the battle in AS WJEC exams. This guide breaks down the essential terminology into logical clusters, giving you clear English definitions immediately followed by their Chinese equivalents, so you can build fluency in both languages while preparing for the assessment.
掌握计算机科学的精确词汇是AS WJEC考试成功的一半。这份指南将关键术语按逻辑分组，先给出清晰的英文定义，紧接着提供对应的中文解释，帮助你在备考过程中同时提升双语表达的流利度。
1. Data Representation and Units | 数据表示与单位
A bit is the smallest unit of data, representing a binary digit (0 or 1). A nibble consists of 4 bits, and a byte contains 8 bits, capable of representing 256 different values. Larger units follow powers of two: a kibibyte (KiB) is 210 bytes, a mebibyte (MiB) is 220 bytes, and so on. The term ‘word’ refers to the natural unit of data used by a particular processor design, often 16, 32 or 64 bits wide.
位（bit）是最小的数据单位，表示一个二进制数字（0或1）。半字节（nibble）由4位组成，字节（byte）包含8位，可以表示256种不同的值。更大的单位遵循2的幂次：1千比字节（KiB）等于210字节，1兆比字节（MiB）等于220字节，以此类推。“字”（word）指特定处理器设计所使用的自然数据单位，通常为16、32或64位宽。
Unsigned binary represents only non‑negative integers, whereas two’s complement encodes both positive and negative numbers by inverting bits and adding 1. Sign-and-magnitude uses the most significant bit for the sign, but two’s complement avoids a double zero and simplifies hardware.
无符号二进制只表示非负整数，而补码（two’s complement）通过反转位并加1来编码正数和负数。原码（sign‑and‑magnitude）用最高位表示符号，但补码避免了“负零”并简化了硬件电路。
| English Term | 中文术语 | Definition / 定义 |
|---|---|---|
| Overflow | 溢出 | When a calculation result exceeds the range that can be stored in the allocated bits. |
| Fixed point | 定点数 | A representation where the decimal point is in a fixed position; the binary point separates integer and fractional parts. |
| Floating point | 浮点数 | A number expressed as mantissa × baseexponent, allowing a wide dynamic range. |
| Normalisation | 规格化 | Adjusting a floating‑point number so the mantissa begins with 01 (for positive) or 10 (for negative) to maximise precision. |
2. Number Bases and Conversions | 数制与转换
The binary number system uses base 2, employing only digits 0 and 1. The denary (decimal) system is base 10, hexadecimal is base 16 (digits 0–9 and A–F). Converting from binary to hexadecimal involves grouping bits into nibbles, while converting from denary to binary uses repeated division by 2.
二进制数系统以2为基数，仅使用数字0和1。十进制（denary）系统基数为10，十六进制基数为16（数字0–9以及A–F）。二进制转十六进制时将比特分成每4位一组，十进制转二进制则使用反复除以2取余的方法。
Binary coded decimal (BCD) represents each denary digit by a 4‑bit binary pattern. Although inefficient in storage, BCD avoids rounding errors when representing decimal fractions, which is useful in financial applications.
BCD（二进制编码十进制）用4位二进制模式表示每一个十进制数字。虽然存储效率较低，但BCD在表示十进制小数时可以避免舍入误差，因此在金融应用中有用。
3. Character Encoding | 字符编码
ASCII uses 7 bits to encode 128 characters, including control codes, digits, uppercase and lowercase letters. Extended ASCII employs 8 bits to include additional symbols. Unicode provides a unique code point for every character across all writing systems; UTF‑8 is a variable‑length encoding that uses 1‑4 bytes per character, backward‑compatible with ASCII.
ASCII使用7位编码128个字符，包括控制码、数字、大小写字母。扩展ASCII使用8位以包含额外的符号。Unicode为所有书写系统中的每个字符提供唯一的码点；UTF‑8是一种变长编码，每个字符使用1至4字节，向后兼容ASCII。
4. Computer Architecture and the CPU | 计算机体系结构与中央处理器
The Von Neumann architecture stores both instructions and data in a single shared memory, using a system bus. In contrast, Harvard architecture uses separate memories for instructions and data, enabling parallel access. The fetch‑decode‑execute cycle describes how the processor retrieves an instruction, decodes it, and carries out the required operation. The program counter (PC) holds the address of the next instruction, while the current instruction register (CIR) holds the instruction being executed.
冯·诺伊曼架构将指令和数据存放在同一个共享内存中，通过系统总线访问。相比之下，哈佛架构为指令和数据分别设置存储器，允许并行访问。取指‑译码‑执行周期描述了处理器如何取出指令、译码并完成所要求的操作。程序计数器（PC）保存下一条指令的地址，当前指令寄存器（CIR）保存正在执行的指令。
The arithmetic logic unit (ALU) performs calculations and logical operations. The control unit (CU) directs the flow of data and controls the execution of instructions. Registers such as the accumulator (ACC) and memory address register (MAR) are high‑speed storage locations inside the CPU. The data bus carries data between processor and memory, while the address bus carries memory addresses.
算术逻辑单元（ALU）执行计算和逻辑运算。控制单元（CU）指挥数据流并控制指令的执行。累加器（ACC）和存储器地址寄存器（MAR）等寄存器是CPU内部的高速存储位置。数据总线在处理器与内存之间传送数据，地址总线则传送内存地址。
Factors affecting CPU performance include clock speed, the number of cores, cache size and architecture. Pipelining allows overlapping of instruction stages, increasing throughput.
影响CPU性能的因素包括时钟速度、核心数量、缓存大小和架构。流水线（pipelining）允许指令各阶段重叠，提高了吞吐量。
5. Memory and Storage Systems | 内存与存储系统
Primary memory (RAM and ROM) is directly accessible by the CPU. RAM (random access memory) is volatile, storing data and programs currently in use. ROM (read only memory) is non‑volatile and holds firmware such as the BIOS. Cache memory is a small, very fast memory located inside or close to the CPU, storing frequently accessed data to reduce average access time.
主存储器（RAM和ROM）可由CPU直接访问。RAM（随机存取存储器）是易失性的，存储当前使用的数据和程序。ROM（只读存储器）是非易失性的，保存固件如BIOS。缓存（cache）是位于CPU内部或附近的小容量超快速内存，存储频繁访问的数据以降低平均访问时间。
Secondary storage is non‑volatile and includes magnetic (hard disk drive), optical (CD, DVD) and solid‑state (SSD) technologies. Magnetic storage uses spinning platters and read/write heads; optical storage uses lasers to read pits and lands; solid‑state drives use NAND flash memory with no moving parts. Virtual memory uses part of the hard disk as an extension of RAM when physical RAM is full, managed through paging and the memory management unit (MMU).
辅助存储器是非易失性的，包括磁存储（硬盘驱动器）、光存储（CD、DVD）和固态存储（SSD）。磁存储使用旋转的盘片和读写头；光存储利用激光读取坑和岸；固态硬盘使用无移动部件的NAND闪存。虚拟内存在物理RAM满时使用硬盘的一部分作为RAM的扩展，通过分页和内存管理单元（MMU）来管理。
6. Logic Gates and Boolean Algebra | 逻辑门与布尔代数
Basic logic gates include AND, OR, NOT, NAND, NOR and XOR. NAND and NOR gates are functionally complete, meaning any Boolean function can be implemented using only one type of gate. Truth tables list all possible input combinations and corresponding outputs. Boolean algebra uses operators like conjunction (AND), disjunction (OR) and negation (NOT).
基本逻辑门包括与门、或门、非门、与非门、或非门和异或门。与非门和或非门具有功能完备性，意味着任何布尔函数都可以仅用一种类型的门来实现。真值表列出了所有可能的输入组合及对应的输出。布尔代数使用合取（与）、析取（或）和否定（非）等运算符。
The half adder adds two single bits and produces a sum (S) and a carry (C). The full adder accepts an additional carry‑in, enabling the construction of ripple‑carry adders. The D‑type flip‑flop is a sequential circuit that stores one bit of data, changing state only on the edge of a clock signal. It forms the basis for registers and memory cells.
半加器将两个单比特相加，产生和（S）与进位（C）。全加器接受一个额外的进位输入，从而可以构建行波进位加法器。D型触发器是一种时序电路，存储一位数据，仅在时钟信号边沿改变状态。它是寄存器和存储单元的基础。
De Morgan’s laws state that NOT (A AND B) equals (NOT A) OR (NOT B), and NOT (A OR B) equals (NOT A) AND (NOT B). Karnaugh maps simplify Boolean expressions by grouping adjacent cells.
德摩根定律指出：A与B的非等于非A或非B；A或B的非等于非A与非B。卡诺图通过将相邻单元分组来简化布尔表达式。
7. System Software and Operating Systems | 系统软件与操作系统
The operating system manages hardware resources, provides a user interface, and enables multitasking. Key functions include memory management, processor scheduling, file management, and handling input/output. Utility software performs maintenance tasks such as disk defragmentation, backup and virus scanning.
操作系统管理硬件资源、提供用户界面并支持多任务处理。主要功能包括内存管理、处理器调度、文件管理以及输入/输出处理。实用软件执行维护任务，如磁盘碎片整理、备份和病毒扫描。
Interrupts are signals that cause the CPU to suspend its current task and execute an interrupt service routine (ISR). Types include hardware interrupts (e.g., from I/O devices) and software interrupts. The interrupt vector table holds the addresses of ISRs. Scheduling algorithms like round‑robin, first‑come‑first‑served, and shortest job first determine which process runs next.
中断是导致CPU暂停当前任务并执行中断服务程序（ISR）的信号。类型包括硬件中断（例如来自I/O设备）和软件中断。中断向量表保存ISR的地址。调度算法如轮转法、先来先服务和最短作业优先法决定下一个运行的进程。
8. Networks and Communication | 网络与通信
A local area network (LAN) connects computers in a small geographical area, typically using Ethernet switches and twisted‑pair cables. A wide area network (WAN) spans large distances, often using public infrastructure. The Internet is a global WAN of interconnected networks using the TCP/IP protocol suite.
局域网（LAN）连接小地理范围内的计算机，通常使用以太网交换机和双绞线电缆。广域网（WAN）跨越远距离，常使用公共基础设施。互联网是使用TCP/IP协议套件的全球互联的广域网。
Protocols are rules governing data transmission. The TCP/IP stack includes the application layer (HTTP, FTP, SMTP), transport layer (TCP, UDP), internet layer (IP), and network interface layer. IP addresses uniquely identify devices; IPv4 uses 32‑bit addresses, while IPv6 uses 128‑bit addresses. DNS (Domain Name System) translates human‑readable domain names into IP addresses.
协议是管理数据传输的规则。TCP/IP协议栈包括应用层（HTTP、FTP、SMTP）、传输层（TCP、UDP）、网络层（IP）和网络接口层。IP地址唯一标识设备；IPv4使用32位地址，IPv6使用128位地址。DNS（域名系统）将人类可读的域名转换为IP地址。
Packet switching breaks data into packets that are routed independently across the network. Circuit switching establishes a dedicated path before communication. Network topologies include star (all nodes connected to a central switch), bus (a single backbone cable), and mesh (nodes interconnected with multiple paths).
分组交换将数据分割成数据包，在网络中独立路由。电路交换在通信前建立专用路径。网络拓扑包括星型（所有节点连接到中央交换机）、总线型（单一骨干电缆）和网状（节点之间多路径互连）。
9. Programming Concepts and Data Structures | 编程概念与数据结构
An algorithm is a step‑by‑step procedure to solve a problem. Pseudocode is a human‑readable description of an algorithm using structured English‑like syntax. Flowcharts use graphical symbols to represent the flow of control. Sequence, selection (if‑else), and iteration (for, while loops) are the three fundamental programming constructs.
算法是解决问题的分步过程。伪代码是一种使用结构化英文语法的人类可读算法描述。流程图使用图形符号表示控制流。顺序、选择（if‑else）和迭代（for、while循环）是三种基本编程结构。
A variable is a named storage location whose value can change during execution; a constant is fixed. Data types include integer, real, Boolean, character and string. Arrays store multiple items of the same type under one identifier, accessible by an index. Records (or structures) group related data of different types. Lists, stacks and queues are dynamic data structures. A stack follows Last‑In‑First‑Out (LIFO); a queue follows First‑In‑First‑Out (FIFO).
变量是命名的存储位置，其值可在执行期间改变；常量是固定的。数据类型包括整数、实数、布尔、字符和字符串。数组在一个标识符下存储多个相同类型的元素，可通过索引访问。记录（或结构体）将不同类型的相关数据组合在一起。列表、栈和队列是动态数据结构。栈遵循后进先出（LIFO）；队列遵循先进先出（FIFO）。
Subroutines include procedures (which perform actions) and functions (which return values). Parameters can be passed by value (a copy) or by reference (the original variable). Recursion occurs when a subroutine calls itself; it requires a base case to avoid infinite recursion.
子程序包括过程（执行动作）和函数（返回值）。参数可以按值传递（副本）或按引用传递（原始变量）。递归发生在子程序调用自身时；需要基准条件以避免无限递归。
10. Algorithms for Searching and Sorting | 查找与排序算法
Linear search examines each element sequentially until the target is found, with O(n) time complexity. Binary search works on sorted datasets by repeatedly dividing the search interval in half, giving O(log n) complexity. However, binary search requires random access and sorted data.
线性查找按顺序检查每个元素直到找到目标，时间复杂度为O(n)。二分查找在已排序数据集上通过反复将查找区间减半来工作，复杂度为O(log n)。但是，二分查找需要随机访问和已排序数据。
Bubble sort repeatedly swaps adjacent unordered elements, with average O(n2) time. Insertion sort builds the sorted list one element at a time by inserting each new element into its correct position. Merge sort recursively divides the list into halves, sorts them, and merges the sorted halves, achieving O(n log n) complexity. Quicksort selects a pivot and partitions the list, also averaging O(n log n), but worst‑case O(n2).
冒泡排序反复交换相邻的乱序元素，平均时间复杂度为O(n2)。插入排序每次将一个元素插入到已排序部分的正确位置。归并排序递归地将列表分成两半，分别排序后再合并，达到O(n log n)复杂度。快速排序选择一个基准值并分区，平均也是O(n log n)，但最坏情况为O(n2)。
11. Legal, Ethical and Environmental Issues | 法律、伦理与环境问题
The Data Protection Act regulates the collection and use of personal data, requiring that data be processed fairly and lawfully. The Computer Misuse Act makes unauthorised access to computer material, including hacking, a criminal offence. Copyright and intellectual property rights protect software, digital media and content. The Regulation of Investigatory Powers Act (RIPA) gives authorities powers to monitor communications under certain conditions.
数据保护法规范个人数据的收集和使用，要求数据处理必须公平和合法。计算机滥用法将未经授权访问计算机材料（包括黑客行为）定为刑事犯罪。版权和知识产权保护软件、数字媒体和内容。调查权规范法（RIPA）赋予当局在特定条件下监视通信的权力。
Environmental considerations include the energy consumption of data centres, e‑waste disposal, and the carbon footprint of manufacturing devices. Sustainable computing promotes efficient coding, virtualisation, and hardware recycling.
环境方面的考虑包括数据中心的能源消耗、电子废物处理以及制造设备的碳足迹。可持续计算提倡高效编程、虚拟化和硬件回收。
12. Software Development Life Cycle | 软件开发生命周期
The waterfall model follows a linear sequential flow: requirements analysis, design, implementation, testing, deployment and maintenance. Each phase must be completed before the next begins. The spiral model incorporates risk analysis and is iterative; prototyping involves building early versions to clarify requirements. Agile methodologies emphasise incremental delivery and collaboration.
瀑布模型遵循线性顺序流程：需求分析、设计、实现、测试、部署和维护。每个阶段必须在下一阶段开始之前完成。螺旋模型结合了风险分析且是迭代的；原型法通过构建早期版本来明晰需求。敏捷方法论强调增量交付与协作。
Testing strategies include white‑box testing (examining internal logic), black‑box testing (testing functionality without seeing code), alpha testing (in‑house) and beta testing (released to a limited audience). Acceptance testing verifies the software meets client requirements.
测试策略包括白盒测试（检查内部逻辑）、黑盒测试（不看代码测试功能）、α测试（内部测试）和β测试（面向有限用户发布）。验收测试验证软件是否满足客户需求。
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