📚 GCSE Computer Science: Mind Map Quick Revision | GCSE 计算机：思维导图速记
A mind map is a powerful tool for quick revision – it helps you organise key concepts visually, link ideas, and recall information faster. This GCSE Computer Science mind map covers the core topics, presenting each branch in bite-sized English and Chinese explanations. Use it to strengthen your memory and boost exam confidence.
思维导图是快速复习的利器——它能帮你将关键概念可视化、连接思路、更快回忆信息。这份GCSE计算机科学思维导图覆盖了核心专题，每个分支都配以简短的英文与中文解释。用它来强化记忆，提升考试自信。
1. Data Representation | 数据表示
All data in a computer is stored as binary (base-2), using only 0 and 1. A single binary digit is a bit; 8 bits make a byte. Larger units: kilobyte (KB ≈ 1,024 bytes), megabyte (MB), gigabyte (GB), terabyte (TB).
计算机中所有数据都以二进制（基2）形式存储，只使用0和1。一个二进制位叫1比特；8比特为1字节。更大的单位：千字节（KB ≈ 1,024字节）、兆字节（MB）、吉字节（GB）、太字节（TB）。
To convert denary (base-10) to binary, repeatedly divide by 2 and record remainders. Binary addition follows rules like 1+1=10 (carry 1). Hexadecimal (base-16) uses 0–9 and A–F; each hex digit represents exactly 4 bits, e.g., A2₁₆ = 1010 0010₂.
把十进制（基10）转换成二进制时，反复除以2并记录余数。二进制加法遵循1+1=10（进位1）等规则。十六进制（基16）使用0–9和A–F；每个十六进制位恰好代表4个比特，例如A2₁₆ = 1010 0010₂。
Text is encoded with character sets: ASCII uses 7 bits (128 characters); Unicode (e.g., UTF-8) can encode over a million characters, using 1–4 bytes per symbol. Images are grids of pixels: file size (bytes) = (width × height × colour depth in bits) ÷ 8.
文字通过字符集编码：ASCII用7比特（128个字符）；Unicode（如UTF-8）可编码上百万个字符，每个符号占1～4字节。图像是像素网格：文件大小（字节）=（宽×高×颜色深度（位））÷ 8。
Sound is converted to digital by sampling. File size = sample rate (Hz) × bit depth × duration (s) × number of channels. Lossy compression (JPEG, MP3) removes some data to shrink files; lossless compression (PNG, ZIP) preserves all original data.
声音通过采样转为数字信号。文件大小 = 采样率（Hz）× 位深度 × 时长（秒）× 声道数。有损压缩（JPEG、MP3）丢弃部分数据来缩小文件；无损压缩（PNG、ZIP）保留所有原始数据。
2. Computer Systems | 计算机系统
The CPU (Central Processing Unit) follows the von Neumann architecture. Key components: Control Unit (CU), Arithmetic Logic Unit (ALU), registers such as Program Counter (PC), Memory Address Register (MAR) and Memory Data Register (MDR).
中央处理器 (CPU) 遵循冯·诺依曼架构。关键部件：控制单元 (CU)、算术逻辑单元 (ALU)、程序计数器 (PC)、内存地址寄存器 (MAR) 和内存数据寄存器 (MDR) 等寄存器。
The fetch-decode-execute cycle repeats: fetch instruction from RAM (address in PC → MAR, then data to MDR), decode in CU, execute (ALU performs operation), then repeat. Performance is affected by clock speed (GHz), number of cores, and cache size.
取指-解码-执行周期不断循环：从内存取指令（PC 给出地址 → MAR，数据到 MDR），在 CU 中解码，执行（ALU 运算），然后重复。性能受时钟速度（GHz）、核心数量和缓存大小影响。
Primary memory includes volatile RAM (holds running programs and data) and non‑volatile ROM (stores boot‑up firmware). Virtual memory uses part of the hard disk as extra RAM when main memory is full, but it is slower.
主存包括易失性的 RAM（存放正在运行的程序和数据）和非易失性的 ROM（存放引导固件）。当内存不足时，虚拟内存将硬盘的一部分当作额外 RAM 使用，但速度较慢。
Secondary storage: magnetic hard disks (HDD – large, cheap but fragile), optical discs (CD/DVD – portable), and solid‑state drives (SSD – fast, durable, no moving parts). Cloud storage stores data on remote servers accessed via the internet.
辅助存储：磁硬盘（HDD – 容量大、便宜但易碎），光盘（CD/DVD – 便携），固态硬盘（SSD – 速度快、耐用、无活动部件）。云存储将数据保存在远程服务器上，通过网络访问。
3. System Software & Operating Systems | 系统软件与操作系统
The operating system (OS) provides a user interface (GUI/CLI), manages multitasking, memory (allocating RAM to processes), peripherals (via drivers), file systems, and security (user accounts, permissions).
操作系统 (OS) 提供用户界面（图形化/命令行）、管理多任务、内存（为进程分配RAM）、外设（通过驱动程序）、文件系统以及安全（用户账户、权限）。
Utility software maintains the system: disk defragmentation rearranges fragmented files on HDDs for faster access; backup utilities create copies; encryption tools protect data; compression tools reduce file sizes.
实用软件维护系统：磁盘碎片整理重新排列 HDD 上的碎片文件加快读取速度；备份工具创建副本；加密工具保护数据；压缩工具减小文件大小。
Open source software allows users to view and modify source code (e.g., Linux). Proprietary software keeps source code secret and requires a license (e.g., Windows, Microsoft Office).
开源软件允许用户查看和修改源代码（如 Linux）。专属软件源代码保密，需要许可证（如 Windows、Microsoft Office）。
4. Networks | 网络基础
A network is two or more computers connected to share resources. LAN (Local Area Network) covers a small area; WAN (Wide Area Network) connects LANs over large distances, often using leased lines or the internet.
网络是两台或多台计算机连接以共享资源。局域网 (LAN) 覆盖小范围；广域网 (WAN) 将局域网远距离连接起来，通常使用专线或互联网。
Common topologies: star (each device connects to a central switch; failure of one cable doesn’t affect others), bus (backbone cable; easy to set up but collision prone), ring (data travels in one direction).
常见拓扑：星型（每台设备连接中央交换机，单线故障不影响其他节点），总线型（骨干线缆，易搭建但易碰撞），环型（数据单向传输）。
Protocols define rules for communication. The TCP/IP model has four layers: Application (HTTP, FTP, SMTP), Transport (TCP, UDP), Internet (IP), Network Access (Ethernet, Wi‑Fi). MAC addresses identify NICs; IP addresses identify devices on a network. DNS translates domain names to IPs.
协议定义通信规则。TCP/IP 模型有4层：应用层（HTTP、FTP、SMTP）、传输层（TCP、UDP）、网络层（IP）、网络接入层（以太网、Wi‑Fi）。MAC 地址标识网卡；IP 地址标识网络上的设备。DNS 将域名转换为 IP 地址。
Hardware: routers forward data between networks, switches connect devices within a LAN, wireless access points (WAP) enable Wi‑Fi, NICs (Network Interface Cards) provide physical connection.
硬件：路由器在网络间转发数据，交换机连接局域网内设备，无线接入点 (WAP) 提供 Wi‑Fi，网卡 (NIC) 提供物理连接。
5. Cyber Security | 网络安全
Malware includes viruses (attach to files, spread by user action), worms (self‑replicate across networks), Trojans (disguised as legitimate software), ransomware (encrypts files for ransom), and spyware (steals data).
恶意软件包括病毒（附着于文件，通过用户操作传播）、蠕虫（在网络中自我复制）、特洛伊木马（伪装成合法软件）、勒索软件（加密文件索要赎金）和间谍软件（窃取数据）。
Social engineering attacks: phishing (fake emails trick users into revealing credentials), shoulder surfing, blagging. Denial of Service (DoS) floods a server with traffic. SQL injection inserts malicious code into database queries. Brute‑force attacks try many passwords.
社会工程攻击：网络钓鱼（虚假邮件骗取凭证）、肩窥、冒名欺诈。拒绝服务攻击 (DoS) 用流量淹没服务器。SQL 注入将恶意代码插入数据库查询。暴力攻击大量试猜密码。
Defences: firewalls filter network traffic, anti‑malware software detects and removes threats, encryption (e.g., AES, TLS) scrambles data, two‑factor authentication adds an extra verification step, physical security prevents direct access.
防御：防火墙过滤网络流量，反恶意软件检测并清除威胁，加密（如 AES、TLS）打乱数据，双因素认证增加验证步骤，物理安全阻止直接接触。
Penetration testing (ethical hacking) simulates attacks to find vulnerabilities. User access levels restrict data access to authorised personnel only. Secure passwords (long, mixed characters) and regular updates are essential.
渗透测试（道德黑客）模拟攻击以发现漏洞。用户权限级别限制只有授权人员能访问数据。安全密码（长、混合字符）和定期更新至关重要。
6. Databases | 数据库基础
A relational database stores data in tables made of rows (records) and columns (fields). Each field has a data type (text, integer, date, etc.). A primary key uniquely identifies each record. Foreign keys link tables together.
关系型数据库将数据存储在表中，表由行（记录）和列（字段）组成。每个字段有数据类型（文本、整数、日期等）。主键唯一标识每条记录。外键将表关联起来。
SQL (Structured Query Language) is used to manage data. Basic query: SELECT field1, field2 FROM table WHERE condition ORDER BY field ASC/DESC; The WHERE clause filters records; ORDER BY sorts results.
SQL（结构化查询语言）用于管理数据。基本查询：SELECT field1, field2 FROM table WHERE condition ORDER BY field ASC/DESC; WHERE 子句过滤记录；ORDER BY 对结果排序。
Databases reduce data redundancy (duplicate data) and improve data integrity (accuracy and consistency). They allow multiple users to access data simultaneously with proper locks and security.
数据库减少数据冗余（重复数据），提高数据完整性（准确性与一致性）。它们允许多用户通过适当的锁和安全机制同时访问数据。
7. Programming Fundamentals | 编程基础
Variables store data that can change; constants store fixed values. Data types: integer (whole number), real/float (decimal), Boolean (true/false), character, string, and arrays (collections of same data type).
变量存储可变化的数据；常量存储固定值。数据类型：整数、实数/浮点、布尔值（真/假）、字符、字符串以及数组（相同数据类型的集合）。
Assignment uses = (or ← in pseudocode). Arithmetic operators: +, –, *, /, MOD (remainder), DIV (integer division). Comparison operators: ==, !=, >, <, >=, <=. Logical operators: AND, OR, NOT.
赋值使用 =（伪代码中有时为 ←）。算术运算符：+、–、*、/、MOD（取余）、DIV（整除）。比较运算符：==、!=、>、<、>=、<=。逻辑运算符：AND、OR、NOT。
Control structures: sequence (line by line), selection (if, else if, else), iteration (for loop when count is known, while loop when unknown). Nested structures combine them. Subroutines: procedures (perform actions) and functions (return values).
控制结构：顺序（逐行执行）、选择（if, else if, else）、循环（已知次数用 for 循环，未知次数用 while 循环）。嵌套结构将它们组合起来。子程序：过程（执行操作）和函数（返回值）。
Arrays store multiple items under one name. 1D arrays are like a list; 2D arrays are like a table. Indexing usually starts at 0. Pseudocode often uses array[0], array[1] and LEN() to find length.
数组用一个名称存储多个项目。一维数组像列表；二维数组像表格。索引通常从0开始。伪代码常使用 array[0], array[1] 和 LEN() 获取长度。
8. Algorithms: Searching & Sorting | 算法：搜索与排序
Linear search checks each element sequentially until the target is found or the list ends. It works on unsorted data, but is slow for large datasets: worst‑case O(n).
线性搜索逐个检查元素，直到找到目标或列表结束。它适用于未排序数据，但大数据集下速度慢：最坏情况 O(n)。
Binary search repeatedly divides a sorted list in half, comparing the middle element with the target. It discards half the data each time, giving O(log n) efficiency, but the list must be sorted first.
二分搜索反复将有序列表对半分，比较中间元素与目标值。每次舍弃一半数据，效率为 O(log n)，但列表必须先排序。
Bubble sort repeatedly passes through the list, comparing adjacent items and swapping them if they are in the wrong order. Larger elements “bubble” to the end. It is simple but slow: O(n²) average.
冒泡排序反复遍历列表，比较相邻元素并在顺序错误时交换。较大元素逐渐“冒泡”到末端。算法简单但速度较慢：平均 O(n²)。
Merge sort uses a divide‑and‑conquer approach: split the list into sublists until each has one item, then repeatedly merge sublists to produce new sorted sublists. Its average complexity is O(n log n), much faster on large data.
归并排序采用分治法：将列表拆分成只有一个元素的子列表，然后不断合并子列表形成新的有序子列表。平均复杂度 O(n log n)，在大数据集上快得多。
9. Computational Thinking | 计算思维
Computational thinking has four pillars: decomposition (break a problem into smaller parts), pattern recognition (identify similarities), abstraction (focus on essential details, ignore irrelevant ones), and algorithm design (create step‑by‑step solutions).
计算思维有四大支柱：分解（将问题拆成小部分）、模式识别（找出相似性）、抽象（关注关键细节，忽略无关的）和算法设计（制定逐步解决方案）。
Flowcharts use standard symbols: oval (start/stop), parallelogram (input/output), rectangle (process), diamond (decision), arrows (flow direction). They help visualise algorithms clearly.
流程图使用标准符号：椭圆形（开始/结束），平行四边形（输入/输出），矩形（处理），菱形（判断），箭头（流向）。它们能清晰地将算法可视化。
Tracing an algorithm means stepping through code or pseudocode with sample data to check variables and logic. It is crucial for testing and debugging. A trace table records variable values line by line.
跟踪算法是指用样本数据逐步运行代码或伪代码，检查变量和逻辑。这对测试和调试至关重要。跟踪表逐行记录变量值。
10. Legal, Ethical & Environmental Issues | 法律、伦理与环境问题
The Data Protection Act / GDPR sets principles for handling personal data: it must be processed fairly, used only for stated purposes, kept accurate and secure, and not kept longer than necessary. Subjects have rights to access their data.
数据保护法 / GDPR 为处理个人数据制定了原则：数据必须公平处理，仅用于明确目的，保持准确和安全，保存时间不超过必要期限。数据主体有权访问自己的数据。
The Computer Misuse Act makes unauthorised access, modification, or disruption of computer systems illegal. Hacking, spreading malware, and denial‑of‑service attacks fall under this law.
计算机滥用法将未经授权的访问、修改或干扰计算机系统定为非法。黑客攻击、传播恶意软件和拒绝服务攻击都属于该法律范畴。
Copyright and patent laws protect intellectual property. Software piracy (illegal copying), using unlicensed media, and plagiarism are unethical and illegal. Creators can use open‑source licenses to grant permissions.
版权与专利法保护知识产权。软件盗版（非法复制）、使用未授权媒体以及剽窃都是不道德且违法的。创作者可以使用开源许可证授予权限。
Ethical concerns include bias in AI algorithms, privacy implications of facial recognition, the digital divide (unequal access to technology), and environmental impact: e‑waste, energy consumption of data centres, and mining of rare materials.
伦理问题包括人工智能算法中的偏见、人脸识别引发的隐私问题、数字鸿沟（技术获取不平等），以及环境影响：电子废弃物、数据中心的能源消耗和稀有材料开采。
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