📚 Mind Map Quick Memorization for A-Level Edexcel Computer Science | A-Level Edexcel 计算机：思维导图速记
This mind-map-style guide condenses the entire Edexcel A-Level Computer Science specification into interconnected, high-yield nodes. Follow the branches to link concepts, memorise key terms, and visualise how each topic fits together for rapid revision and deeper understanding.
这份思维导图式指南将Edexcel A-Level 计算机科学全部考纲浓缩为相互关联的高频节点。顺着分支把概念串联起来，记忆关键词汇，可视化每个主题之间的关联，帮助你快速复习、深化理解。
1. System Architecture & Memory | 系统架构与存储
Start at the heart of the machine: the Von Neumann architecture. CPU contains Control Unit, ALU, and registers. The fetch‑decode‑execute cycle uses Program Counter (PC), Memory Address Register (MAR), Memory Data Register (MDR), and Accumulator (ACC). The data bus, address bus, and control bus connect everything.
从机器核心出发：冯·诺依曼体系结构。CPU 包含控制器、ALU 和寄存器。取指‑解码‑执行循环使用程序计数器 (PC)、内存地址寄存器 (MAR)、内存数据寄存器 (MDR) 和累加器 (ACC)。数据总线、地址总线和控制总线连接所有部件。
- Primary storage: RAM (volatile, fast) and ROM (non‑volatile, holds bootloader).
- 主存：RAM（易失，快速）和 ROM（非易失，存放引导程序）。
- Secondary storage: magnetic (HDD), optical (CD/DVD), solid‑state (SSD). Trade‑off speed vs capacity vs cost.
- 辅助存储：磁存储 (HDD)、光存储 (CD/DVD)、固态存储 (SSD)。速度、容量、成本之间的权衡。
- Virtual memory: uses part of the hard disk as an extension of RAM when RAM is full. Page swapping may cause disk thrashing.
- 虚拟内存：当 RAM 满时，借用硬盘空间作为 RAM 扩展。页面交换可能导致磁盘颠簸。
2. Data Representation | 数据表示
All data boils down to binary. Unsigned binary, two's complement for negative integers, and floating‑point (mantissa × 2exponent) store real numbers. Normalisation ensures maximum precision. Character sets: ASCII (7/8‑bit), Unicode (UTF‑8 variable length). Sound is sampled (sample rate, bit depth, Nyquist theorem). Images use pixels with colour depth and resolution; vector graphics store drawing instructions.
一切数据归根到底都是二进制。无符号二进制、补码表示负数、浮点数（尾数 × 2指数）存储实数。规格化保证最大精度。字符集：ASCII（7/8 位）、Unicode（UTF‑8 变长）。声音采样（采样率、位深度、奈奎斯特定理）。图像用像素（颜色深度和分辨率）；矢量图存储绘图指令。
- tion, logical shifts (left = multiply by 2, right = divide by 2), arithmetic shift for two's complement.
- 二进制运算：加法、逻辑移位（左移 = 乘以 2，右移 = 除以 2）、补码的算术移位。
- Hexadecimal: compact format, base‑16. One hex digit = 4 bits.
- 十六进制：紧凑格式，基数为 16。一个十六进制位 = 4 个二进制位。
- Compression: lossless (Huffman coding, run‑length encoding) vs lossy (JPEG, MP3).
- 压缩：无损（霍夫曼编码、游程编码）对比有损（JPEG、MP3）。
3. Computer Networks | 计算机网络
Networks connect nodes via NICs and transmission media (copper, fibre, wireless). Topologies: star, mesh, bus, with switches acting as intelligent central devices in a star. The TCP/IP stack has four layers: Application, Transport, Internet, Network Access. IP addresses (IPv4 32‑bit, IPv6 128‑bit) and MAC addresses identify devices. DNS translates domain names to IP.
网络通过网卡和传输介质（铜线、光纤、无线）连接节点。拓扑结构：星型、网状、总线型，交换机作为星型结构中的智能中心设备。TCP/IP 协议栈分四层：应用层、传输层、网际层、网络接入层。IP 地址（IPv4 32 位，IPv6 128 位）和 MAC 地址标识设备。DNS 将域名转换为 IP。
- Protocols: HTTP/HTTPS (web), FTP (file), SMTP/POP3/IMAP (email), SSL/TLS (security).
- 协议：HTTP/HTTPS（网页）、FTP（文件）、SMTP/POP3/IMAP（电子邮件）、SSL/TLS（安全）。
- Packet switching: data split into packets, routed independently. Routers use routing tables.
- 分组交换：数据拆分成数据包，独立路由。路由器使用路由表。
- The Internet: worldwide network of networks. WWW is a service on the Internet.
- 互联网：全球网络的网络。万维网是互联网上的一项服务。
4. Cybersecurity | 网络安全
Threats: malware (virus, worm, Trojan), social engineering (phishing, pretexting), brute‑force attacks, DoS/DDoS. Defences: firewalls (packet filtering, stateful inspection), encryption (symmetric key, public key with RSA), penetration testing. Authentication methods: passwords, biometrics, two‑factor authentication. Network policies: acceptable use, backup, disaster recovery.
威胁：恶意软件（病毒、蠕虫、木马）、社会工程学（网络钓鱼、借口）、暴力攻击、DoS/DDoS。防御：防火墙（包过滤、状态检测）、加密（对称密钥、RSA 公钥）、渗透测试。身份认证方法：密码、生物识别、双因素认证。网络策略：可接受使用、备份、灾难恢复。
- Encryption: symmetric uses one key; asymmetric uses public‑private key pair. CA issues digital certificates.
- 加密：对称加密使用同一密钥；非对称加密使用公钥‑私钥对。CA 颁发数字证书。
- SQL injection: bad input can alter SQL queries. Mitigation: parameterised queries, input validation.
- SQL 注入：恶意输入可改变 SQL 查询。缓解措施：参数化查询、输入验证。
5. Databases | 数据库
Relational databases organise data into tables (relations) with rows (records/tuples) and columns (attributes/fields). Primary key uniquely identifies a row; foreign key links two tables. SQL: DDL (CREATE, ALTER) and DML (SELECT, INSERT, UPDATE, DELETE). Normalisation reduces redundancy: 1NF, 2NF, 3NF create a set of linked tables without update anomalies.
关系型数据库将数据组织为表（关系），含行（记录/元组）和列（属性/字段）。主键唯一标识一行；外键连接两张表。SQL：DDL（CREATE, ALTER）和 DML（SELECT, INSERT, UPDATE, DELETE）。规范化减少冗余：1NF、2NF、3NF 创建一组无更新异常的关联表。
- Transactions: ACID properties – Atomicity, Consistency, Isolation, Durability.
- 事务：ACID 特性 – 原子性、一致性、隔离性、持久性。
- Indexes: speed up searches; B‑tree common. DBMS manages concurrency and security.
- 索引：加速搜索；常用 B‑树。数据库管理系统 (DBMS) 管理并发和安全。
6. Data Structures & Algorithms | 数据结构与算法
Arrays (static/fixed size) and records (heterogeneous fields). Stacks (LIFO, push & pop) used for subroutine calls, recursion. Queues (FIFO, enqueue & dequeue) for buffering. Circular queues prevent overflow. Linked lists: singly, doubly; dynamic size, nodes store data and pointer. Trees: binary search tree for fast search, insert, delete; depth‑first and breadth‑first traversal.
数组（静态/固定大小）和记录（异构字段）。栈（LIFO，push & pop）用于子程序调用、递归。队列（FIFO，入队 & 出队）用于缓冲。循环队列防止溢出。链表：单向、双向；动态大小，节点存储数据和指针。树：二叉搜索树实现快速搜索、插入、删除；深度优先和广度优先遍历。
- Hashing: maps key→index. Collision resolution: chaining, linear probing.
- 哈希：键映射到索引。冲突解决：链地址法、线性探测法。
- Algorithms: linear search, binary search. Sorting: bubble, insertion, quick, merge. Big‑O notation: O(1), O(log n), O(n), O(n²).
- 算法：线性搜索、二分搜索。排序：冒泡、插入、快速、归并。大 O 记号：O(1), O(log n), O(n), O(n²)。
7. Programming: Paradigms, Constructs & Techniques | 编程：范型、结构与技术
Paradigms: procedural (sequence, selection, iteration), object‑oriented (classes, objects, encapsulation, inheritance, polymorphism), declarative (logic, functional). Low‑level: machine code, assembly language (mnemonics like LDA, STA, JMP). High‑level languages: compiler translates whole program, interpreter runs line‑by‑line. Bytecode (e.g., Java) provides portability.
编程范型：过程式（顺序、选择、循环）、面向对象（类、对象、封装、继承、多态）、声明式（逻辑式、函数式）。低级语言：机器码、汇编语言（助记符如 LDA、STA、JMP）。高级语言：编译器翻译整个程序，解释器逐行执行。字节码（如 Java）提供了可移植性。
- Data types: integer, float, boolean, char, string. Operators: arithmetic, relational (==, !=, >), logical (AND, OR, NOT).
- 数据类型：整型、浮点型、布尔型、字符、字符串。运算符：算数、关系（==, !=, >）、逻辑（AND, OR, NOT）。
- Subroutines: functions return a value, procedures do not. Parameters: passed by value or by reference. Recursion needs a base case.
- 子程序：函数返回值，过程不返回值。参数：按值传递或按引用传递。递归需要基例。
- IDEs: editor, debugger, compiler/interpreter, breakpoints, trace, variable watch.
- 集成开发环境：编辑器、调试器、编译器/解释器、断点、追踪、变量监视。
8. Software Engineering & System Development | 软件工程与系统开发
Development lifecycles: waterfall (linear, rigid), agile (iterative, sprints), spiral (risk‑driven), extreme programming (pair programming, test‑first). Analysis: feasibility study, requirements specification (functional, non‑functional). Design: modular decomposition, data flow, UML diagrams (class, sequence). Implementation: coding standards, version control, alpha/beta testing. Testing: unit, integration, system, acceptance. White‑box vs black‑box testing. Orthogonality of test data: normal, boundary, erroneous.
开发生命周期：瀑布模型（线性、刚性）、敏捷（迭代、冲刺）、螺旋模型（风险驱动）、极限编程（结对编程、测试先行）。分析：可行性研究、需求规格说明（功能性、非功能性）。设计：模块分解、数据流、UML 图（类图、时序图）。实现：编码规范、版本控制、alpha/beta 测试。测试：单元、集成、系统、验收。白盒测试与黑盒测试。测试数据正交性：正常、边界、错误数据。
- Maintenance: corrective, adaptive, perfective. Big-O applies to algorithmic efficiency as well.
- 维护：纠正性、适应性、完善性。大 O 符号同样适用于算法效率。
9. Boolean Algebra & Digital Logic | 布尔代数与数字逻辑
Logic gates: AND (∧), OR (∨), NOT (¬), NAND, NOR, XOR. Truth tables define all input‑ lement, De Morgan’s theorems. Karnaugh maps (up to 4 variables) simplify expressions. Half‑adder (sum = A XOR B, carry = A AND B); full adder includes carry‑in. Flip‑flops store one bit: D‑type flip‑flop (rising edge‑triggered), SR flip‑flop. Combining flip‑flops builds registers and counters.
逻辑门：与门 (∧)、或门 (∨)、非门 (¬)、与非门、或非门、异或门。真值表定义所有输入输出组合。布尔定律：交换律、结合律、分配律、同一律、互补律、德·摩根定理。卡诺图（最多 4 变量）化简表达式。半加器（和 = A XOR B，进位 = A AND B）；全加器包含进位输入。触发器存储 1 位：D型触发器（上升沿触发）、SR触发器。触发器组合构成寄存器和计数器。
| Gate | Symbol | Boolean Expression |
|---|---|---|
| AND | ∧ | X = A . B |
| OR | ∨ | X = A + B |
| NOT | ¬ | X = ¬A |
AND → A · B OR → A + B NOT → Ā
10. Computational Thinking & Problem Solving | 计算思维与问题求解
Four cornerstones: decomposition (break down), pattern recognition, abstraction (focus on essentials), algorithm design. Standard algorithms: bubble sort (compare adjacent), merge sort (divide & conquer). Search: binary search on sorted array. Thinking procedurally: stepwise refinement (top‑down design). Finite state machines (FSM): states, transitions, inputs, outputs. State transition diagrams model behaviour. The Turing machine underpins computability.
四大基石：分解（拆解）、模式识别、抽象（抓住本质）、算法设计。标准算法：冒泡排序（比较相邻元素）、归并排序（分治法）。搜索：有序数组上的二分搜索。过程化思维：逐步细化（自顶向下设计）。有限状态机 (FSM)：状态、转换、输入、输出。状态转换图建模行为。图灵机奠定了可计算性基础。
- Problem solving: define input‑process‑output, test with trace tables, handle extreme cases.
- 问题解决：定义输入‑处理‑输出，用跟踪表测试，处理极端情况。
11. Legal, Ethical & Environmental Issues | 法律、道德与环境议题
Legislation: Data Protection Act (DPA 2018 / GDPR) – 6 principles for processing personal data; Computer Misuse Act – unauthorised access and modification; Copyright, Designs and Patents Act – protects software IP; Freedom of Information Act. Ethics: privacy, digital divide, AI bias, net neutrality. Environmental: energy consumption of data centres, e‑waste, sustainable programming (efficiency reduces power).
立法：数据保护法（DPA 2018 / GDPR）– 处理个人数据的 6 项原则；计算机滥用法 – 未经授权的访问和修改；版权、设计和专利法 – 保护软件知识产权；信息自由法。伦理：隐私、数字鸿沟、AI 偏见、网络中立。环境：数据中心能耗、电子废弃物、可持续编程（高效能降低功耗）。
- Impacts: automation jobs, loss, but new roles created. Digital skills gap. Ethical hacking requires permission.
- 影响：自动化导致岗位流失，但也创造新角色。数字技能差距。道德黑客需要获得授权。
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