📚 Year 12 AQA Computer Science: Key Terminology Quick-Reference | AQA计算机科学关键术语速记指南
Mastering the technical vocabulary is a critical step towards exam success in AQA A-Level Computer Science. This quick-reference guide presents essential concepts from the Year 12 specification, pairing clear English definitions with precise Chinese translations to support bilingual learning and retention. Each section groups related terms so you can build clusters of meaning, while worked examples and comparison tables reinforce application in context.
掌握技术词汇是 AQA A-Level 计算机科学考试成功的关键一步。这份速记指南覆盖了 12 年级考纲的核心概念，用清晰的英文定义搭配精确的中文翻译，帮助双轨学习与记忆。每一节将相关术语归类，方便建立语义集群，同时辅以实例和对比表格，强化在真实情境中的运用。
1. Computer System Fundamentals | 计算机系统基础
Central Processing Unit (CPU): The main component that executes instructions using the fetch‑decode‑execute cycle; it consists of the ALU, Control Unit, and registers.
中央处理器（CPU）： 通过取指‑译码‑执行周期执行指令的主要部件，由算术逻辑单元、控制单元和寄存器组成。
Arithmetic Logic Unit (ALU): Performs arithmetic calculations (e.g., addition, subtraction) and logical operations (AND, OR, NOT).
算术逻辑单元（ALU）： 执行算术运算（如加减）和逻辑操作（与、或、非）。
Control Unit (CU): Directs the flow of data inside the CPU and generates timing/control signals for the fetch‑decode‑execute cycle.
控制单元（CU）： 指挥 CPU 内部数据流动，为取指‑译码‑执行周期产生时序和控制信号。
Program Counter (PC): A register that holds the memory address of the next instruction to be fetched.
程序计数器（PC）： 保存下一条待取指令的内存地址的寄存器。
Memory Address Register (MAR): Holds the address of the memory location that the CPU needs to read from or write to.
内存地址寄存器（MAR）： 存放 CPU 需要读写的内存位置的地址。
Memory Data Register (MDR): Temporarily stores the data fetched from memory or the data to be written to memory.
内存数据寄存器（MDR）： 暂存从内存读出的数据或将要写入内存的数据。
Accumulator (ACC): Stores the intermediate results of arithmetic/logic operations inside the ALU.
累加器（ACC）： 在 ALU 内部存储算术/逻辑运算的中间结果。
Bus: A set of parallel wires that carry data, addresses, or control signals between components. Three main buses: data bus, address bus, control bus.
总线： 一组并行导线，在组件之间传输数据、地址或控制信号；主要有数据总线、地址总线和控制总线。
Von Neumann Architecture: A stored‑program concept where both instructions and data share the same memory and buses; used in most general‑purpose computers.
冯·诺依曼体系结构： 一种存储程序概念，指令和数据共享同一内存和总线；目前大多数通用计算机采用的结构。
Harvard Architecture: A design with separate memory and buses for instructions and data, allowing simultaneous access; often used in embedded systems.
哈佛体系结构： 指令和数据拥有独立的内存和总线，可以同时存取；常见于嵌入式系统。
2. Data Representation | 数据表示
Bit: The smallest unit of data, either 0 or 1.
位（比特）： 数据的最小单位，取值为 0 或 1。
Byte: A group of 8 bits, often used as the basic addressable unit of memory.
字节： 由 8 个位组成，常作为内存的基本寻址单元。
Binary (Base‑2): A number system using only digits 0 and 1; computers represent all data in binary.
二进制（基数为2）： 只使用数字 0 和 1 的计数系统；计算机内部所有数据均以二进制表示。
Hexadecimal (Base‑16): A compact number system using digits 0‑9 and letters A‑F; one hex digit represents 4 bits (a nibble).
十六进制（基数为16）： 使用数字 0‑9 和字母 A‑F 的紧凑记数法；一位十六进制数代表 4 个二进制位（半字节）。
Two’s Complement: A method for representing signed integers in binary, where the most significant bit indicates the sign (0 for positive, 1 for negative).
二进制补码： 用二进制表示有符号整数的方法，最高位为符号位（0 为正，1 为负）。
Floating‑Point Representation: rs with a mantissa (significant digits) and an exponent (scale factor), e.g., mantissa × 2exponent.
浮点表示： 利用尾数（有效数字）和阶码（缩放因子）存储实数，形如 尾数 × 2指数。
ASCII (American Standard Code for Information Interchange): A 7‑bit character set representing 128 characters, including letters, digits, and control codes.
ASCII（美国信息交换标准代码）： 7 位字符集，涵盖字母、数字和控制符共 128 个字符。
Unicode: A universal character encoding standard using between 8 and 32 bits per character to support global scripts and symbols.
Unicode： 通用字符编码标准，每字符使用 8 至 32 位，支持全球文字和符号。
Resolution: e, usually given as width × height (e.g., 1920×1080); higher resolution gives more detail.
分辨率： 数字图像中的像素数量，通常表示为宽度×高度（如 1920×1080）；分辨率越高，细节越丰富。
Colour Depth: The number of bits used to represent the colour of a single pixel; e.g., 8‑bit colour allows 256 colours, 24‑bit gives about 16.7 million.
颜色深度： 表示单个像素颜色所使用的位数；例如 8 位可显示 256 色，24 位约能呈现 1670 万色。
Sampling Rate (Sound): The number of samples taken per second when converting an analogue sound wave to digital; measured in Hz. Higher rates capture higher frequencies.
采样率（声音）： 模拟声波数字化时每秒采集的样本数，单位为 Hz；采样率越高，能捕获的频率越高。
Bit Depth (Sound): The number of bits per sample; greater bit depth allows finer amplitude differentiation and less quantisation noise.
位深度（声音）： 每个样本的位数；位深度越大，振幅区分越精细，量化噪声越小。
3. Computer Architecture & Hardware | 计算机体系结构与硬件
Clock Speed: The frequency at which the CPU’s internal clock pulses, measured in GHz; each pulse triggers a fetch‑decode‑execute cycle step. Higher clock speed generally means more instructions per second.
时钟速度： CPU 内部时钟振荡的频率，以 GHz 为单位；每个脉冲触发一步取指‑译码‑执行周期。时钟速度越高，通常每秒可执行更多指令。
Cache Memory: A small, high‑speed memory located close to the CPU that stores frequently accessed data and instructions, reducing the average memory access time.
高速缓存（Cache）： 位于 CPU 附近的小容量高速内存，存放常用数据和指令，以降低平均内存访问时间。
Pipelining: A technique that overlaps the fetch, decode, and execute stages of multiple instructions to improve CPU throughput.
流水线技术： 将多条指令的取指、译码、执行阶段重叠进行，以提高 CPU 吞吐量。
Register: A temporary storage location within the CPU that can hold a word of data. Examples: PC, MAR, MDR, ACC, CIR (Current Instruction Register).
寄存器： CPU 内部暂存一个字数据的存储位置，如 PC、MAR、MDR、ACC、CIR（当前指令寄存器）。
Logic Gate: An electronic circuit that performs a Boolean operation (AND, OR, NOT, XOR, NAND, NOR) on one or more inputs to produce a single output.
逻辑门： 对一个或多个输入进行布尔运算（与、或、非、异或、与非、或非）并产生单一输出的电子电路。
Truth Table: A table showing all possible input combinations and the corresponding output for a logic circuit or gate.
真值表： 列出逻辑电路或门所有可能的输入组合及其对应输出的表格。
Full Adder: A combinational circuit that adds three 1‑bit binary numbers (two operands and a carry‑in) to produce a sum and a carry‑out.
全加器： 实现三个一位二进制数（两个操作数和一个进位输入）相加，生成和与进位输出的组合逻辑电路。
Secondary Storage: Non‑volatile storage used to keep data and programs permanently, e.g., HDD, SSD, optical discs.
辅助存储器： 用于永久保存数据和程序的非易失性存储器，如 HDD、SSD、光盘。
4. Programming Basics | 编程基础
Variable: A named storage location in memory whose value can change during program execution; each variable has a data type and an identifier.
变量： 内存中具有名称、值可变的存储位置；每个变量有数据类型和标识符。
Constant: A named memory location whose value cannot be modified after initialisation; it makes code easier to read and maintain.
常量： 一旦初始化后值不可更改的命名内存位置；有助于提高代码的可读性和可维护性。
Data Type: A classification that specifies the kind of data a variable can hold, such as integer, real (float), Boolean, character, or string.
数据类型： 规定变量可以存储的数据类型的分类，如整型、实型（浮点型）、布尔型、字符型和字符串。
Sequence: The execution of statements in the order they are written; the most fundamental control structure.
顺序结构： 按代码书写顺序逐条执行语句；是最基本的控制结构。
Selection: A control structure that allows a program to choose between alternative paths of execution, using constructs like IF‑THEN‑ELSE or CASE.
选择结构： 程序可以根据条件选择不同执行路径的控制结构，如 IF‑THEN‑ELSE 或 CASE 语句。
Iteration (Loop): A control structure that repeats a block of code while a condition is true (WHILE) or for a specified number of times (FOR).
迭代（循环）： 当条件为真（WHILE）或按指定次数（FOR）反复执行一段代码的控制结构。
Array: A collection of elements of the same data type stored in contiguous memory locations, accessed by an index.
数组： 存储于连续内存区域、数据类型相同的一组元素，通过下标访问。
Procedure: A named block of code that performs a specific task but does not return a value; it may have parameters.
过程： 执行特定任务但不返回值的命名代码块，可带有参数。
Function: A named block of code that performs a task and returns a single value; used in expressions.
函数： 执行任务并返回一个值的命名代码块，可用于表达式。
Parameter Passing: The mechanism for supplying input values to a subroutine. Pass by value copies the data; pass by reference provides the memory address of the argument.
参数传递： 向子程序提供输入值的机制。按值传递复制数据，按引用传递提供实参的内存地址。
Local Variable: A variable declared inside a subroutine, only accessible within that subroutine.
局部变量： 在子程序内部声明、仅在该子程序内可访问的变量。
Global Variable: A variable declared outside all subroutines, accessible from any part of the program; over‑use can make debugging harder.
全局变量： 在所有子程序外部声明、程序的任何部分都能访问的变量；过度使用会增加调试难度。
5. Data Structures | 数据结构
Tuple: An ordered, immutable collection of items, which can be of different data types; elements are accessed by position.
元组： 有序且不可变的数据项集合，项的数据类型可以不同；通过位置访问元素。
Record: A composite data type that groups related fields of different types under a single identifier; often used to represent a row in a database.
记录： 将不同类型、互相关联的字段组合在一起的自定义数据类型；常用来表示数据库中的一行。
Linked List: A dynamic data structure consisting of nodes, each containing data and a pointer to the next node; efficient insertions/deletions compared to arrays, but no random access.
链表： 由节点组成的动态数据结构，每个节点包含数据和指向下一节点的指针；相比数组，插入与删除更高效，但无法随机访问。
Stack (LIFO): A Last‑In‑First‑Out abstract data type; elements are added (push) and removed (pop) only from the top. Used in subroutine calls, undo operations.
栈（后进先出）： 后进先出的抽象数据类型；只能在栈顶添加（push）和移除（pop）元素，常用于子程序调用、撤销操作。
Queue (FIFO): A First‑In‑First‑Out abstract data type; elements are added at the rear (enqueue) and removed from the front (dequeue). Used in buffering and scheduling.
队列（先进先出）： 先进先出的抽象数据类型；在队尾添加（enqueue）元素，在队首移除（dequeue）元素，常用于缓冲和调度。
Hash Table: A data structure that maps keys to values using a hash function; collisions are handled by techniques like separate chaining or open addressing.
哈希表： 通过哈希函数将键映射到值的数据结构；冲突通过链表分离法或开放定址法处理。
Binary Search Tree (BST): A rooted binary tree where the left subtree contains values less than the node, and the right subtree contains values greater; allows efficient searching, insertion, and deletion (average O(log n)).
二叉搜索树 (BST)： 每个节点左子树的值小于该节点，右子树的值大于该节点的二叉树；搜索、插入和删除的平均时间复杂度为 O(log n)。
Graph: A collection of vertices (nodes) connected by edges; can be directed or undirected, weighted or unweighted. Used to model networks, maps, etc.
图： 由顶点（节点）和边组成的集合；可有无向图、有向图、加权图等，用于建模网络、地图等。
6. Algorithms & Complexity | 算法与复杂度
Algorithm: A step‑by‑step procedure for solving a problem; must be finite, unambiguous, and effective.
算法： 解决特定问题的步骤序列，必须具有有限性、确定性和有效性。
Big O Notation: A mathematical notation describing the upper bound of an algorithm’s running time or space requirements as the input size grows, expressed as O(f(n)).
大 O 表示法： 描述随着输入规模增大，算法运行时间或空间需求的上界的数学记法，表示为 O(f(n))。
Linear Search: Sequentially checks each element of a list until the target is found; worst‑/average case O(n).
线性搜索： 逐个检查列表元素直到找到目标；最坏/平均情况为 O(n)。
Binary Search: Repeatedly divides a sorted list in half, comparing the middle element with the target; worst case O(log n).
二分搜索： 将有序列表反复对半分，比较中间元素与目标；最坏情况 O(log n)。
Bubble Sort: Compares adjacent elements and swaps them if they are in the wrong order; repeats passes until no swaps occur. Average O(n²).
冒泡排序： 比较相邻元素，若顺序错误则交换；反复遍历直到无交换发生，平均时间复杂度 O(n²)。
Merge Sort: A divide‑and‑conquer algorithm that splits the list into halves, recursively sorts them, and merges the sorted halves; guaranteed O(n log n).
归并排序： 分治算法，将列表不断分成两半，递归排序后再合并有序子列表；时间复杂度恒为 O(n log n)。
Comparison of Common Sorting Algorithms (Time Complexity)
| Algorithm | Best Case | Average Case | Worst Case |
|---|---|---|---|
| Bubble Sort | O(n) | O(n²) | O(n²) |
| Insertion Sort | O(n) | O(n²) | O(n²) |
| Merge Sort | O(n log n) | O(n log n) | O(n log n) |
| Quick Sort | O(n log n) | O(n log n) | O(n²) |
7. Networking Fundamentals | 网络基础
LAN (Local Area Network): A network covering a small geographical area, such as a building; usually owned and managed by a single organisation.
局域网 (LAN)： 覆盖较小地理范围（如一座建筑）的网络，通常由单一组织拥有和管理。
WAN (Wide Area Network): A network that spans a large area, connecting multiple LANs; the internet is the largest WAN.
广域网 (WAN)： 跨越大范围地域、连接多个局域网的大型网络；互联网是最大的广域网。
Star Topology: All devices connect to a central switch or hub; failure in one cable does not affect others, but the central device is a single point of failure.
星型拓扑： 所有设备连接到中央交换机或集线器；单根电缆故障不影响其他设备，但中央设备是单一故障点。
Bus Topology: All devices share a single backbone cable; cheap but a break in the backbone disables the whole segment.
总线拓扑： 所有设备共用一条主干电缆；成本低，但主干断裂会导致整个网段瘫痪。
Protocol: A set of rules governing data communication, e.g., HTTP, TCP/IP, SMTP. Protocols define message format, timing, sequencing, and error handling.
协议： 管理数据通信的一组规则，如 HTTP、TCP/IP、SMTP，规定了消息格式、时序、顺序和差错处理。
TCP/IP Stack (4 layers): Application, Transport (TCP/UDP), Internet (IP), Link (hardware). Each layer provides services to the layer above.
TCP/IP 协议栈（4 层）： 应用层、传输层（TCP/UDP）、网际层（IP）、链路层（硬件），每层为上层提供服务。
IP Address: A logical address assigned to a device
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