📚 GCSE Edexcel Computer Science: Mind Map Quick Revision | GCSE Edexcel 计算机科学：思维导图速记
This article transforms the entire GCSE Edexcel Computer Science syllabus into a set of visual mind maps, helping you memorise key concepts quickly. Each branch of the map is explained in bite‑sized bilingual paragraphs, so you can lock the knowledge into long‑term memory with ease.
本文把整个 GCSE Edexcel 计算机科学考纲转化为一系列视觉思维导图，帮你快速记住核心概念。导图的每个分支都用一小段双语解释，让你轻松将知识塞进长期记忆。
1. Computational Thinking | 计算思维
Decomposition is the process of breaking a complex problem down into smaller, manageable parts that are easier to solve individually.
分解是将一个复杂问题拆解成更小、更容易单独处理的部分的方法。
Abstraction means removing unnecessary detail so you can focus on the elements that actually matter for solving the problem.
抽象意味着去除不必要的细节，把注意力集中在解决问题真正需要的关键元素上。
Algorithmic thinking is the ability to design step‑by‑step instructions that, when followed, always lead to the correct solution.
算法思维是指设计出一套分步指令的能力，只要按指令执行，就一定能得出正确答案。
2. Data Representation | 数据表示
Binary is a base‑2 number system using only 0 and 1. All data inside a computer – numbers, text, images, sound – is stored as binary digits (bits).
二进制是只用 0 和 1 的逢二进一计数系统。计算机内部的所有数据——数字、文字、图像、声音——都以二进制位（比特）存储。
Denary, or decimal, is base‑10. To convert denary to binary, repeatedly divide by 2 and read the remainders upwards.
十进制就是逢十进一。把十进制转二进制的方法是连续除以 2，然后从下往上读取余数。
Hexadecimal (base‑16) uses digits 0‑9 and letters A‑F. Two hex digits can represent one byte, making binary much easier to read for humans.
十六进制使用数字 0‑9 和字母 A‑F。两个十六进制位正好可以表示一个字节，让人类读二进制时轻松很多。
Overflow occurs when the result of an addition is too large to fit into the fixed number of bits allocated.
当加法结果太大，无法放入规定位数的二进制数中时，就会发生溢出错误。
Character sets map letters and symbols to binary numbers. ASCII uses 7 bits (128 characters), while Unicode uses up to 32 bits to cover languages worldwide.
字符集把字母和符号映射成二进制数。ASCII 用 7 位比特表示 128 个字符，Unicode 则使用最多 32 位来涵盖世界各种语言。
Images are stored as grids of pixels. In a bitmap, each pixel is given a binary code for its colour; higher colour depth means more bits per pixel and more possible colours.
图像以像素网格的形式存储。在位图中，每个像素用一个二进制颜色码表示；颜色深度越高，每个像素使用的比特数越多，可显示的颜色也越多。
Sound is sampled thousands of times per second. Sample rate and bit depth determine the quality and file size; higher values give a more accurate digital recording.
声音以每秒数千次的频率采样。采样率和位深度决定了音质和文件大小；数值越高，数字录音就越精确。
3. Computer Systems & Hardware | 计算机系统与硬件
The CPU (Central Processing Unit) is the brain of the computer. It follows the fetch‑decode‑execute cycle, constantly pulling instructions from RAM and carrying them out.
CPU（中央处理器）是计算机的大脑。它按照取指－解码－执行周期不停地工作，从内存中取出指令并执行。
The CPU contains the ALU (arithmetic and logic unit), the CU (control unit), and registers such as the program counter, MAR, MDR, and accumulator.
CPU 内部有 ALU（算术逻辑单元）、CU（控制单元）以及各种寄存器，如程序计数器 PC、内存地址寄存器 MAR、内存数据寄存器 MDR 和累加器。
Clock speed, number of cores, and cache size all affect CPU performance. More cores allow true multitasking, and a larger cache reduces the time spent accessing slow main memory.
时钟频率、核心数量和缓存大小都会影响 CPU 性能。更多的核心可以实现真正的多任务处理，更大的缓存则减少了访问低速主存的时间。
Embedded systems are specialised computers built into larger devices, such as microwaves, cars, or fitness trackers. They usually run a limited, dedicated program and are highly reliable.
嵌入式系统是内置在更大设备里的专用计算机，例如微波炉、汽车或健身手环。它们通常运行单一、专用的程序，并且非常可靠。
Primary memory includes RAM (volatile, holds currently running programs) and ROM (non‑volatile, stores boot instructions like BIOS).
主存储器包括 RAM（易失性，存放正在运行的程序）和 ROM（非易失性，存储启动指令如 BIOS）。
Secondary storage devices – magnetic hard disks, solid‑state drives, and optical discs – keep data permanently. SSDs are faster and more durable than HDDs because they have no moving parts.
辅助存储设备——磁性硬盘、固态硬盘和光盘——可以永久保存数据。固态硬盘因为没有活动部件，比机械硬盘更快、更耐用。
4. Software & Operating Systems | 软件与操作系统
System software includes the operating system, utilities, and device drivers. It manages hardware and provides a platform for application software.
系统软件包括操作系统、工具软件和设备驱动程序。它负责管理硬件，并为应用软件提供运行平台。
The OS handles memory management, multitasking, file management, and user interface. It also oversees peripheral devices through drivers.
操作系统负责内存管理、多任务调度、文件管理以及用户界面。它还通过驱动程序控制外部设备。
Application software does specific jobs for the user, such as word processing, creating spreadsheets, or editing images. It relies on the OS to access hardware.
应用软件为用户完成特定任务，例如文字处理、制作电子表格或编辑图像。它依赖操作系统才能使用硬件资源。
5. Networks | 网络
A LAN (local area network) connects computers over a small geographical area, like a school or campus. A WAN (wide area network) connects LANs over cities or countries, often using rented fibre lines.
局域网覆盖较小的地理范围，例如一所学校或一个校园。广域网则把多个局域网跨城市或跨国连接起来，常常租用光纤线路。
Network topologies define how devices are physically or logically arranged. In a star network, all devices connect to a central switch; failure of one cable only affects a single device.
网络拓扑定义了设备的物理或逻辑布局。在星形网络中，所有设备都连接到一台中央交换机；一根线缆坏掉只会影响一台设备。
A mesh network provides multiple paths between nodes, making it highly resilient. The internet itself is a large‑scale partial mesh.
网状网络在节点之间提供多条路径，因此容错性极强。互联网本身就是一个大规模的部分网状结构。
Protocols are rules that govern data transmission. TCP/IP splits data into packets, routes them, and reassembles them. HTTP is for web pages, FTP for file transfer, and SMTP for email.
协议是管理数据传输的规则。TCP/IP 将数据分割成数据包、路由并重组。HTTP 用于网页，FTP 用于文件传输，SMTP 用于电子邮件。
The TCP/IP stack consists of four layers: application, transport, internet, and link. Each layer adds its own header, wrapping data like an envelope inside an envelope.
TCP/IP 协议栈由四层组成：应用层、传输层、互联网层和链路层。每一层都加上自己的头部信息，像信封套信封一样包裹数据。
6. Network Security | 网络安全
Malware is malicious software that includes viruses, worms, Trojan horses, spyware, and ransomware. A virus attaches itself to a legitimate file, whereas a worm spreads on its own.
恶意软件包括病毒、蠕虫、特洛伊木马、间谍软件和勒索软件。病毒会附着在合法文件上，而蠕虫能自行传播。
Social engineering tricks people into giving away sensitive information, for example through phishing emails that look like they come from a trusted bank.
社会工程学通过欺骗手段让人泄露敏感信息，例如发送看起来像来自可信用银行的钓鱼邮件。
Brute‑force attacks systematically try every possible password. Strong passwords, lock‑out policies, and two‑factor authentication help defeat them.
暴力攻击会系统地试遍所有可能的密码。强密码、账户锁定策略和双因素认证有助于抵御这类攻击。
Firewalls filter incoming and outgoing network traffic based on rules. Encryption, such as SSL/TLS, scrambles data so only the intended receiver can read it.
防火墙根据规则过滤进出网络的流量。加密技术（如 SSL/TLS）把数据扰乱，只有预期的接收者才能解读。
Penetration testing is a controlled attack on a system to find weaknesses. Security patches are then applied before real attackers can exploit them.
渗透测试是对系统进行受控攻击以发现弱点，之后在真正的攻击者利用它们之前打上安全补丁。
7. Algorithms | 算法
An algorithm is a precise sequence of steps that solves a problem. It must be unambiguous, have a clear start and end, and produce the correct output for any valid input.
算法是解决某个问题的精确步骤序列。它必须清晰无歧义，有明确的起点和终点，对任何合法输入都能给出正确输出。
Search algorithms locate data efficiently. Linear search checks every element one by one; binary search chops a sorted list in half each time, running in log₂n time.
搜索算法能高效地定位数据。线性搜索逐个检查每个元素；二分搜索每次把有序列表对半切开，时间复杂度为 log₂n。
Bubble sort repeatedly swaps adjacent items that are out of order. Merge sort divides the list into halves, sorts them recursively, and then merges sorted sub‑lists.
冒泡排序反复交换相邻的乱序项。归并排序先将列表分成两半，递归排序，再合并已排序的子列表。
Flowcharts use symbols to represent steps: an oval for start/end, a rectangle for a process, a diamond for a decision, and arrows for flow of control.
流程图用符号表示步骤：椭圆代表开始/结束，矩形代表处理过程，菱形代表判断，箭头表示控制流。
Pseudocode bridges human language and code. It uses structured English without worrying about syntax, allowing you to focus purely on logic.
伪代码是自然语言和代码之间的桥梁。它使用结构化的英语，不必拘泥于语法，让你完全聚焦于逻辑。
8. Programming Fundamentals | 编程基础
Variables are named memory locations that store values which can change during execution. Constants are values fixed at the start and never modified.
变量是命名的内存空间，存储的值可以在程序运行时改变。常量则是一开始就固定下来、永远不变的值。
Data types tell the computer how to interpret a value. Common types include integer, real (float), Boolean (true/false), character, and string.
数据类型告诉计算机如何解释一个值。常见类型有整型、实型（浮点）、布尔型（真/假）、字符和字符串。
Sequence, selection, and iteration are the three building blocks of structured programs. IF…ELSE handles decision, and FOR/WHILE loops handle repetition.
顺序、选择和迭代是结构化程序的三个基本构件。IF…ELSE 处理决策，FOR/WHILE 循环处理重复。
Arrays hold multiple values of the same type under one name. A one‑dimensional array is like a list; a two‑dimensional array is like a table with rows and columns.
数组用一个名字存放多个同类数值。一维数组像一个列表；二维数组则像一个有行和列的表格。
Subroutines are named blocks of code. Functions return a value; procedures do not. They promote reusability and make programs easier to debug.
子程序是有名字的代码块。函数会返回一个值，过程则不返回值。它们提升了重用性，也更容易调试程序。
9. Logic Gates | 逻辑门
Logic gates are the fundamental building blocks of digital circuits. Each gate performs a Boolean function on one or more binary inputs to give a single binary output.
逻辑门是数字电路的基本构建块。每个门对一个或多个二进制输入执行布尔运算，产生一个二进制输出。
The AND gate outputs 1 only if all inputs are 1. The OR gate outputs 1 if at least one input is 1. The NOT gate inverts its single input (0 becomes 1, 1 becomes 0).
与门在所有输入都为 1 时才输出 1。或门只要至少一个输入为 1 就输出 1。非门则将单一输入取反（0 变 1，1 变 0）。
| A | B | A ∧ B (AND) | A ∨ B (OR) | ¬A (NOT A) |
|---|---|---|---|---|
| 0 | 0 | 0 | 0 | 1 |
| 0 | 1 | 0 | 1 | 1 |
| 1 | 0 | 0 | 1 | 0 |
| 1 | 1 | 1 | 1 | 0 |
Truth tables list every possible input combination alongside the corresponding output, making it easy to verify a logic circuit’s behaviour.
真值表列出了所有可能的输入组合及其对应输出，可以方便地验证逻辑电路的行为。
Logic circuits are drawn using distinct symbols. Common gates are combined to build adders, flip‑flops, and the control unit of a CPU.
逻辑电路使用独特的符号绘制。常见逻辑门组合起来可以构建加法器、触发器和 CPU 控制单元。
10. Databases & Data Structures | 数据库与数据结构
A database is a structured collection of data. In a flat‑file database, all data sits in a single table, while a relational database splits data across linked tables to avoid duplication.
数据库是结构化的数据集合。在平面文件数据库中，所有数据放在一个表里；关系型数据库则把数据拆分到相互关联的表中，以避免重复。
Tables consist of records (rows) and fields (columns). Each field has a data type, such as text, number, date, or Boolean.
表由记录（行）和字段（列）组成。每个字段都有数据类型，例如文本、数字、日期或布尔类型。
Primary keys uniquely identify each record in a table. Foreign keys link tables together by referencing another table’s primary key.
主键唯一标识表中的每一条记录。外键通过引用另一张表的主键将表关联起来。
SQL is used to query relational databases. A SELECT statement retrieves data, and a WHERE clause filters it, e.g. ‘SELECT name FROM students WHERE grade > 7’.
SQL 用于查询关系型数据库。SELECT 语句检索数据，WHERE 子句进行过滤，例如 ‘SELECT name FROM students WHERE grade > 7’。
Data structures – such as arrays, lists, and records – organise data in memory. Choosing the right structure makes programs faster and memory efficient.
数据结构——如数组、列表和记录——在内存中组织数据。选择正确的数据结构能让程序运行更快且节省内存。
11. Ethical, Legal & Environmental Issues | 道德、法律与环境问题
The digital divide is the gap between those who have access to computers and the internet and those who do not. It affects education, job opportunities, and social inclusion.
数字鸿沟指能够使用计算机和互联网的人群与无法使用的人群之间的差距，它影响到教育、就业机会和社会包容度。
Copyright law protects the creator’s right to control how their work is used. Software piracy, downloading music without payment, and unlicensed image use all break copyright.
版权法保护创作者控制自己作品使用方式的权利。软件盗版、未付费下载音乐和未经授权使用图片都触犯了版权。
The Data Protection Act ensures organisations use personal data fairly, keep it secure, and don’t hold it longer than necessary. GDPR strengthens these rules across Europe.
数据保护法要求机构公平使用个人数据、妥善保管，并且保存时间不得超过必需期限。GDPR 在整个欧洲强化了这些规定。
Computer misuse laws make it illegal to access computers without permission, to hack with intent, or to spread malware. Offences carry serious penalties.
计算机滥用法认为未经允许访问他人计算机、恶意入侵或传播恶意软件都是违法的，违法者会受到严厉处罚。
E‑waste from discarded devices contains toxic materials. Recycling, designing longer‑lasting products, and cloud computing (which can reduce the number of physical devices) help lower environmental impact.
废弃设备产生的电子垃圾含有有毒物质。回收利用、设计更长寿命的产品以及云计算（可以减少物理设备数量）都有助于降低环境影响。
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