📚 GCSE CIE Computer Science: Mind Map Quick Revision | GCSE CIE 计算机：思维导图速记
This mind-map-style revision guide breaks down the entire CIE GCSE Computer Science syllabus into 12 core branches, each with concise bullet points to speed up recall. Perfect for last-minute revision, every key concept is paired with a Chinese explanation to reinforce understanding.
本文以思维导图的结构将 CIE GCSE 计算机科学考纲拆分为 12 个核心分支，每个分支用精简的要点帮助快速记忆。适合考前冲刺，每个关键概念都配有中文解释，加深理解。
1. Number Systems | 数制转换
Binary is a base-2 system using only digits 0 and 1, while denary is base-10. Hexadecimal (hex) is base-16, using 0–9 and A–F, often used for memory addresses and colour codes.
二进制是基数为 2 的数制，只用数字 0 和 1；十进制是基数为 10。十六进制为基 16，使用 0–9 和 A–F，常用于内存地址和颜色代码。
To convert binary to denary, add up place values wherever a 1 appears. For example, 1101₂ = 8 + 4 + 1 = 13₁₀. Hex to binary: each hex digit becomes a 4-bit nibble, e.g., A3₁₆ = 1010 0011₂.
二进制转十进制时，将出现 1 的位权值相加，如 1101₂ = 8 + 4 + 1 = 13₁₀。十六进制转二进制：每个十六进制位展开成 4 位二进制，例如 A3₁₆ = 1010 0011₂。
Hex is especially useful because it compactly represents large binary numbers, reducing human error when reading memory dumps or setting colour values like #FF00CC.
十六进制的优势在于能紧凑地表示长二进制数，在读取内存转储或设置像 #FF00CC 这样的颜色值时，能大大减少人为失误。
2. Binary Arithmetic & Overflow | 二进制运算与溢出
Binary addition follows simple rules: 0+0=0, 0+1=1, 1+0=1, 1+1=0 with a carry of 1. Multiple carries can ripple through higher bits.
二进制加法规则简单：0+0=0, 0+1=1, 1+0=1, 1+1=0 并向高位进 1。进位可逐位传递到更高位。
An overflow error occurs when the result of an 8-bit addition exceeds 255 (or the range for signed numbers). The carry bit is lost, producing an incorrect answer.
当 8 位加法结果超过 255（或超出带符号数范围）时，会发生溢出错误，进位丢失，导致结果错误。
Logical shifts move bits left or right, discarding the end bit and filling the empty position with 0. A left shift multiplies by 2ⁿ, while a right shift does integer division by 2ⁿ.
逻辑移位将位左移或右移，丢弃末端位，空位补 0。左移 n 位相当于乘以 2ⁿ，右移 n 位相当于整数除以 2ⁿ。
For negative numbers, two’s complement representation is used. To find -5 in 8-bit two’s complement, invert the bits of 5 (00000101 → 11111010) and add 1, giving 11111011.
负数使用二补码表示。求 -5 的 8 位二补码：将 5 (00000101) 逐位取反得 11111010，再加 1，结果为 11111011。
3. Data Storage & Units | 数据存储与单位
The smallest unit is a bit; 8 bits make a byte. Larger units follow powers of 2: 1 KiB = 1024 bytes, 1 MiB = 1024 KiB, 1 GiB = 1024 MiB, 1 TiB = 1024 GiB.
最小单位是位（bit），8 位组成 1 字节（byte）。更大单位按 2 的幂次递进：1 KiB = 1024 字节，1 MiB = 1024 KiB，1 GiB = 1024 MiB，1 TiB = 1024 GiB。
Decimal prefixes (KB, MB, GB) often used by storage manufacturers are based on powers of 10, making a 1 TB drive appear slightly smaller in KiB units.
存储厂商常使用基于 10 的幂次的十进制前缀（KB, MB, GB），导致 1 TB 硬盘在 KiB 单位下显示略小。
Compression reduces file size. Lossy compression (e.g., MP3, JPEG) permanently discards some data, while lossless compression (e.g., ZIP, PNG) preserves all original information.
压缩可减小文件体积。有损压缩（如 MP3、JPEG）永久丢弃部分数据；无损压缩（如 ZIP、PNG）保留全部原始信息。
4. Logic Gates & Circuits | 逻辑门与电路
Logic gates are the building blocks of digital circuits. The AND gate outputs 1 only when all inputs are 1; OR outputs 1 if at least one input is 1; NOT inverts the input.
逻辑门是数字电路的基石。与门（AND）仅在所有输入均为 1 时输出 1；或门（OR）至少一个输入为 1 时输出 1；非门（NOT）将输入取反。
NAND is the opposite of AND; NOR is the opposite of OR; XOR (exclusive OR) outputs 1 when an odd number of inputs are 1. Each has a specific symbol and truth table.
与非门（NAND）是 AND 的相反；或非门（NOR）是 OR 的相反；异或门（XOR）在输入中有奇数个 1 时输出 1。每种门都有对应的符号和真值表。
A truth table for AND: 0,0→0; 0,1→0; 1,0→0; 1,1→1. For XOR: 0,0→0; 0,1→1; 1,0→1; 1,1→0. Combining gates builds complex logic circuits.
AND 真值表：0,0→0; 0,1→0; 1,0→0; 1,1→1。XOR 真值表：0,0→0; 0,1→1; 1,0→1; 1,1→0。将多个门组合可以构建复杂逻辑电路。
Logic expressions can be written using notation: A AND B is A.B, OR is A+B, NOT is Ā. Circuits are drawn with standard ANSI or IEC symbols.
逻辑表达式可用符号表示：A AND B 写作 A.B，OR 写作 A+B，NOT 写作 Ā。电路图使用标准的 ANSI 或 IEC 符号绘制。
5. Computer Architecture | 计算机体系结构
The Von Neumann architecture stores both program instructions and data in the same memory, forming the basis of most modern CPUs.
冯·诺依曼体系结构将程序指令和数据存放在同一个内存中，是现代大多数 CPU 的基础。
Core CPU components: ALU performs arithmetic and logic, CU controls data flow and decodes instructions, and registers provide fast temporary storage.
CPU 核心部件：算术逻辑单元 (ALU) 执行算术与逻辑运算，控制单元 (CU) 控制数据流并译码指令，寄存器提供高速临时存储。
Key registers: PC holds the address of the next instruction; MAR holds the memory address to read/write; MDR holds the data; CIR holds the current instruction; ACC stores intermediate results.
关键寄存器：程序计数器 (PC) 存放下条指令地址；地址寄存器 (MAR) 存放读写地址；数据寄存器 (MDR) 存放数据；指令寄存器 (CIR) 存放当前指令；累加器 (ACC) 存中间结果。
The fetch-decode-execute cycle repeats: fetch instruction from memory address in PC, decode in CU, execute by ALU or other units, then update PC.
取指 – 译码 – 执行循环不断重复：根据 PC 从内存取指，CU 译码，ALU 等执行，然后更新 PC。
6. Memory & Storage | 内存与存储
Primary memory includes RAM (volatile, used for currently running programs and data) and ROM (non-volatile, stores boot-up firmware). Virtual memory uses hard disk space when RAM is full.
主存储器包括 RAM（易失，存放正在运行的程序和数据）和 ROM（非易失，存放启动固件）。当 RAM 满时，虚拟内存会借用硬盘空间。
Secondary storage is non-volatile: HDDs use magnetic platters, are cheap and high capacity but fragile; SSDs use flash memory, are faster, lighter, but costlier per GB.
辅助存储器是非易失的：机械硬盘 (HDD) 用磁碟，便宜容量大但易损；固态硬盘 (SSD) 用闪存，更快更轻，但每 GB 成本更高。
Optical discs (CD, DVD, Blu-ray) use laser; cloud storage offers remote servers accessed via the internet. Storage choice depends on capacity, speed, portability, durability and cost.
光盘 (CD、DVD、蓝光) 用激光读取；云存储通过互联网访问远程服务器。选择存储时需考虑容量、速度、便携性、耐用性和成本。
7. Networks & Topologies | 网络与拓扑
LAN covers a small geographical area, often within a building; WAN spans large distances, connecting LANs across cities or countries.
局域网 (LAN) 覆盖较小地理范围，通常在一栋建筑内；广域网 (WAN) 跨越远距离，连接不同城市的 LAN。
Client-server networks rely on a central server providing resources; peer-to-peer networks allow each device to share resources directly, without a central server.
客户 – 服务器网络依赖中央服务器提供资源；对等网络 (P2P) 允许每台设备直接共享资源，无需中央服务器。
Star topology connects all devices to a central switch, offering easy fault isolation; bus topology uses a single backbone cable, cheap but not scalable; mesh provides redundancy; ring is circular data flow.
星型拓扑将所有设备连接到中央交换机，故障隔离容易；总线拓扑使用单根主干电缆，便宜但不易扩展；网状提供冗余；环形拓扑是数据单向循环。
Network hardware: router forwards packets between networks, switch connects devices within a LAN, NIC provides physical connection, WAP enables wireless access.
网络硬件：路由器在网络间转发数据包，交换机连接 LAN 内设备，网卡 (NIC) 提供物理连接，无线接入点 (WAP) 实现无线连接。
Protocols are sets of rules: TCP/IP for internet transmission, HTTP/HTTPS for web, FTP for file transfer, SMTP for sending email, IMAP for receiving, Ethernet for wired LAN, Wi-Fi for wireless.
协议是规则集合：TCP/IP 用于互联网传输，HTTP/HTTPS 用于网页，FTP 传输文件，SMTP 发送邮件，IMAP 接收邮件，以太网用于有线 LAN，Wi-Fi 用于无线网络。
8. System Software | 系统软件
The operating system manages hardware resources, provides a user interface, handles file management, memory management, processor scheduling, and security such as user authentication.
操作系统管理硬件资源，提供用户界面，处理文件管理、内存管理、处理器调度，以及用户身份验证等安全功能。
Utility software performs maintenance tasks: antivirus detects and removes malware, disk defragmenter reorganises files for faster access, backup software creates copies of data, compression tools reduce file size.
实用工具软件执行维护任务：杀毒软件检测并删除恶意软件，磁盘碎片整理程序重组文件以加快访问，备份软件创建数据副本，压缩工具缩小文件体积。
Language translators convert high-level source code into machine code: a compiler translates the whole program at once, an interpreter translates line by line, an assembler translates assembly language to machine code.
语言翻译器将高级源代码转为机器码：编译器一次翻译整个程序，解释器逐行翻译，汇编器将汇编语言转为机器码。
9. Algorithms & Flowcharts | 算法与流程图
Algorithmic thinking involves abstraction (reducing complexity by hiding unnecessary details) and decomposition (breaking a problem into smaller sub-problems).
算法思维包括抽象（通过隐藏不必要的细节降低复杂度）和分解（将问题拆分为较小的子问题）。
Pseudocode is a text-based way to describe algorithms using structured English; flowcharts use symbols: oval for start/end, parallelogram for input/output, rectangle for process, diamond for decision, arrows for flow.
伪代码是一种用结构化英语描述算法的文本方式；流程图使用符号：椭圆为开始/结束，平行四边形为输入/输出，矩形为处理，菱形为判断，箭头为流向。
Standard searching algorithms: linear search checks each element in turn until found (works on unsorted list); binary search repeatedly divides a sorted list in half, much faster for large data sets.
标准搜索算法：线性搜索逐个检查元素直到找到（适用于未排序列表）；二分搜索反复将已排序列表一分为二，大数据集下速度快得多。
Sorting algorithms: bubble sort compares adjacent items and swaps if out of order, passes through the list repeatedly; insertion sort builds a sorted portion by taking one element at a time and inserting it correctly.
排序算法：冒泡排序比较相邻元素并交换错误顺序，多次遍历列表；插入排序逐个取出元素并插入已排序部分的正确位置。
10. Programming Concepts | 编程概念
Data types include integer, real/float, character, string, Boolean. Variables are named storage locations whose values can change; constants hold values that remain fixed.
数据类型包括整型、实型/浮点型、字符、字符串、布尔型。变量是可改变值的命名存储位置；常量存放固定不变的值。
Sequence, selection, and iteration are the three basic control structures. Selection uses IF…THEN…ELSE or CASE statements; iteration uses FOR loops (counted) or WHILE/REPEAT loops (conditional).
顺序、选择和迭代是三种基本控制结构。选择使用 IF…THEN…ELSE 或 CASE 语句；迭代使用 FOR 循环（计数）或 WHILE/REPEAT 循环（条件）。
String manipulation includes concatenation, substring extraction, length calculation, character position (e.g., LEFT, RIGHT, MID functions).
字符串操作包括连接、取子串、计算长度、字符位置（如 LEFT、RIGHT、MID 函数）。
Arrays store multiple values of the same type: a 1D array is a simple list; a 2D array is like a table with rows and columns. Index usually starts at 0.
数组存放同类型多个值：一维数组是简单列表；二维数组像行和列构成的表格。索引通常从 0 开始。
Procedures perform a task without returning a value; functions return a value. Parameters can be passed by value or by reference, enabling modular and reusable code.
过程执行任务但不返回值；函数返回一个值。参数可以按值或按引用传递，使代码模块化、可复用。
11. Databases & SQL | 数据库与 SQL
A relational database organises data into tables with rows (records) and columns (fields). Each table has a primary key that uniquely identifies each record.
关系型数据库将数据组织为表，由行（记录）和列（字段）组成。每个表都有一个唯一标识每条记录的主键。
A foreign key is a field in one table that refers to the primary key in another, establishing relationships between tables and reducing data redundancy.
外键是一个表中引用另一表主键的字段，用于建立表之间的关系并减少数据冗余。
SQL commands: SELECT retrieves specified fields, FROM identifies the table, WHERE filters records, ORDER BY sorts results, JOIN can combine related data from multiple tables.
SQL 命令：SELECT 检索指定字段，FROM 指定表，WHERE 筛选记录，ORDER BY 排序结果，JOIN 可组合多个表的相关数据。
Data validation checks input is sensible (e.g., range check, presence check, format check). Verification ensures data is entered correctly (e.g., double entry).
数据有效性验证检查输入是否合理（如范围检查、存在检查、格式检查）；数据验证确保输入正确（如双重录入）。
12. Cybersecurity | 网络安全
Malware includes viruses, worms, Trojans, spyware, adware; phishing tricks users into revealing personal details; brute-force attacks repeatedly guess passwords; DoS floods a server with traffic.
恶意软件包括病毒、蠕虫、木马、间谍软件、广告软件；网络钓鱼诱骗用户泄露个人信息；暴力攻击反复猜测密码；拒绝服务攻击 (DoS) 用流量淹没服务器。
SQL injection inserts malicious SQL code into input fields to manipulate the database. Social engineering exploits human psychology to gain confidential information.
SQL 注入将恶意 SQL 代码插入输入字段以操纵数据库。社会工程学利用人的心理获取机密信息。
Prevention methods: firewalls filter network traffic, encryption scrambles data (e.g., SSL/TLS), strong authentication (passwords, biometrics), regular penetration testing, anti-malware software and keeping systems updated.
防范措施：防火墙过滤网络流量，加密扰乱数据（如 SSL/TLS），强认证（密码、生物识别），定期渗透测试，防恶意软件并保持系统更新。
Ethical and legal considerations cover data protection acts, computer misuse acts, and the importance of respecting intellectual property and digital privacy.
伦理与法律考量包括数据保护法、计算机滥用法，以及尊重知识产权和数字隐私的重要性。
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