IGCSE OCR Computer Science: Mind Map Quick Revision | IGCSE OCR 计算机科学：思维导图速记

📚 IGCSE OCR Computer Science: Mind Map Quick Revision | IGCSE OCR 计算机科学：思维导图速记

This mind map style revision guide distills the entire IGCSE OCR Computer Science syllabus into key concepts and connections, helping you quickly review and memorise core topics for exams.

这份思维导图式复习指南将 IGCSE OCR 计算机科学整个教学大纲浓缩为关键概念和联系，帮助你快速回顾和记忆考试核心主题。

1. Computer Systems Architecture | 计算机系统架构

Central Processing Unit (CPU) includes the Control Unit (CU), Arithmetic Logic Unit (ALU), and special registers such as Program Counter (PC), Memory Address Register (MAR), Memory Data Register (MDR), and Accumulator.

中央处理器 (CPU) 包含控制单元 (CU)、算术逻辑单元 (ALU) 以及特殊寄存器，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。

The Von Neumann architecture stores both program instructions and data in the same main memory, with a single bus system.

冯·诺依曼架构 将程序指令和数据存储在同一个主存中，采用单一总线系统。

The fetch-decode-execute cycle repeats indefinitely: the CPU fetches an instruction from memory, decodes it, and then executes it.

取指—译码—执行周期 无限循环：CPU 从内存中取出一条指令，译码后执行。

Performance factors include clock speed (more cycles per second), cache size (faster access to frequently used data), and number of cores (parallel processing).

性能因素 包括时钟速度（每秒更多周期）、缓存大小（更快访问常用数据）和核心数量（并行处理）。

Embedded systems are dedicated computers within larger devices (e.g., microwave ovens, washing machines), optimised for a limited set of functions.

嵌入式系统 是大型设备内部的专用计算机（如微波炉、洗衣机），为有限功能进行了优化。

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2. Memory and Storage | 内存与存储

Primary memory: RAM is volatile and holds currently running programs and data; ROM is non-volatile and stores the boot program (BIOS).

主存储器：RAM 是易失性的，存放当前运行的程序和数据；ROM 是非易失性的，存储启动程序 (BIOS)。

Virtual memory uses a portion of the hard disk/SSD as an extension of RAM when physical RAM is full, causing slower performance due to disk access times.

虚拟内存 在物理 RAM 满时使用硬盘/SSD 的一部分作为 RAM 的扩展，由于磁盘访问时间导致性能变慢。

Secondary storage types: magnetic (HDD – high capacity, low cost, mechanical parts), solid state (SSD – faster, more durable, more expensive per GB), and optical (CD/DVD/Blu-ray – portable, low capacity).

辅助存储器 类型：磁介质 (HDD – 容量大、成本低、有机械部件)，固态 (SSD – 更快、更耐用、每 GB 更贵)，以及光介质 (CD/DVD/Blu-ray – 便携、容量低)。

(MB) → gigabyte (GB) → terabyte (TB). All conversions are powers of 2 (1 KB = 1024 bytes).

数据容量单位：位 → 半字节 (4 位) → 字节 (8 位) → 千字节 (KB) → 兆字节 (MB) → 吉字节 (GB) → 太字节 (TB)。所有转换都是以 2 为底的幂 (1 KB = 1024 字节)。

le size, e.g., image size = width × height × colour depth in bits, plus metadata overhead.

计算文件大小，例如，图像大小 = 宽度 × 高度 × 颜色深度（以位为单位），加上元数据开销。

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3. Networks | 网络

LAN covers a small geographical area (e.g., a school) and connects computers using private cabling or Wi-Fi. WAN spans large distances (e.g., the Internet) and uses public infrastructure and leased lines.

LAN 覆盖小地理范围（如学校），使用专用布线或 Wi-Fi 连接计算机。WAN 跨越远距离（如互联网），使用公共基础设施和专线。

Network performance is affected by bandwidth (bits per second), number of users, transmission media (fibre optic > copper > wireless), error rate, and latency.

网络性能 受带宽（每秒位数）、用户数量、传输介质（光纤 > 铜线 > 无线）、误码率和延迟的影响。

Key hardware: router sends packets between networks; switch connects devices within a LAN and sends data only to the intended recipient; NIC provides a physical connection to the network.

关键硬件：路由器 在网络之间发送数据包；交换机 连接 LAN 内的设备并仅将数据发送给目标接收方；网卡 (NIC) 提供与网络的物理连接。

Star topology: all devices connect to a central switch; if one cable fails, only that device is affected. Mesh topology: each device is connected to many others, offering excellent redundancy but high cabling cost.

星型拓扑：所有设备连接到中央交换机；若某条线缆故障，仅该设备受影响。网状拓扑：每台设备与多台设备相连，提供出色的冗余但布线成本很高。

Common protocols: TCP/IP (Internet communication), HTTP/HTTPS (web browsing), FTP (file transfer), SMTP/IMAP (email), and Wi-Fi (wireless). The TCP/IP 4-layer model: Application, Transport, Internet, Network Access.

常见协议：TCP/IP（互联网通信）、HTTP/HTTPS（网页浏览）、FTP（文件传输）、SMTP/IMAP（电子邮件）和 Wi-Fi（无线）。TCP/IP 四层模型：应用层、传输层、互联网层、网络接入层。

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4. Cybersecurity | 网络安全

Malware includes viruses (attach to files and replicate), worms (self-replicate over networks), trojans (disguised as legitimate software), spyware, and ransomware.

恶意软件 包括病毒（附加到文件并复制）、蠕虫（在网络上自我复制）、木马（伪装为合法软件）、间谍软件和勒索软件。

Social engineering manipulates people into revealing confidential information, e.g., phishing emails that appear to be from a trusted source.

社交工程 操纵人们泄露机密信息，例如看似来自可信来源的网络钓鱼邮件。

Denial of Service (DoS) attacks flood a server with traffic to prevent legitimate access. SQL injection exploits poorly validated input to run malicious database queries.

拒绝服务 (DoS) 攻击通过大量流量使服务器瘫痪，阻止合法访问。SQL 注入 利用验证不严的输入执行恶意数据库查询。

Prevention methods: firewalls monitor incoming and outgoing traffic; encryption scrambles data so only authorised parties can read it; penetration testing simulates attacks to find vulnerabilities; strong passwords and two-factor authentication.

预防方法：防火墙 监控进出流量；加密 扰乱数据，仅授权方可读取；渗透测试 模拟攻击以发现漏洞；强密码和双因素身份验证。

Data should be backed up regularly and stored off-site. Physical security measures include locks, biometric scanners, and CCTV.

数据应定期备份并异地存储。物理安全措施包括门锁、生物识别扫描器和闭路电视 (CCTV)。

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5. Systems Software | 系统软件

The operating system (OS) manages hardware, runs applications, and provides the user interface. Its key functions: memory management, multitasking, peripheral management (via drivers), and user management.

操作系统 (OS) 管理硬件、运行应用程序并提供用户界面。其主要功能包括：内存管理、多任务处理、外设管理（通过驱动程序）和用户管理。

Memory management: the OS allocates RAM to processes, frees it when done, and may use virtual memory. Multitasking allows multiple programs to appear to run simultaneously by rapidly switching processes.

内存管理：OS 为进程分配 RAM，结束后释放，并可能使用虚拟内存。多任务 通过快速切换进程，使多个程序看上去同时运行。

Utility software performs maintenance tasks: defragmentation reorganises files on a HDD for faster access; backup copies data to a second medium; compression reduces file sizes (lossy or lossless); encryption secures files.

实用工具软件 执行维护任务：碎片整理重新组织 HDD 上的文件以加快访问速度；备份将数据复制到第二个介质；压缩减少文件大小（有损或无损）；加密保护文件安全。

Embedded systems often have a real-time OS (RTOS) designed for reliability and rapid response, not general-purpose computing.

嵌入式系统通常使用实时操作系统 (RTOS)，专为可靠性和快速响应而设计，非通用计算。

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6. Ethical, Legal, Cultural and Environmental Impacts | 伦理、法律、文化和环境影响

The Data Protection Act 2018 (UK) governs how personal data is used, requiring data to be accurate, processed lawfully, and not kept longer than necessary.

《2018 年数据保护法》（英国）规范个人数据的使用，要求数据准确、合法处理且保留时间不超过必要。

The Computer Misuse Act 1990 makes unauthorised access to computer material (hacking), with intent to commit further offences, illegal. Unauthorised modification of data is also an offence.

《1990 年计算机滥用法》 将未经授权访问计算机材料（黑客攻击）并意图进一步犯罪定为非法。未经授权修改数据也属犯罪。

Copyright, Designs and Patents Act 1988 protects intellectual property including software, music, and digital content; it is illegal to distribute copyrighted material without permission.

《1988 年版权、设计与专利法》 保护包括软件、音乐和数字内容在内的知识产权；未经许可分发受版权保护的材料属违法行为。

Open source software is freely available with source code to modify and distribute, while proprietary software is owned by a company and the source code is kept secret.

开源 软件免费提供，可修改和分发源代码，而专有软件归公司所有，源代码保密。

Environmental impacts: manufacturing computers uses toxic chemicals and rare metals; e-waste should be recycled properly. Energy consumption of data centres is significant.

环境影响：制造计算机使用有毒化学物质和稀有金属；电子废物 应妥善回收。数据中心的能源消耗巨大。

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7. Algorithms | 算法

Computational thinking involves decomposition (breaking a problem down), abstraction (ignoring unnecessary details), and algorithmic thinking (designing step-by-step solutions).

计算思维 包括分解（拆分问题）、抽象（忽略不必要的细节）和算法思维（设计逐步解决方案）。

Linear search checks each element in turn; O(n) complexity. Binary search requires a sorted list, repeatedly dividing the search interval in half; O(log n).

线性搜索 逐一检查每个元素；复杂度 O(n)。二分搜索 需要已排序列表，反复将搜索区间减半；复杂度 O(log n)。

Sorting algorithms: bubble sort swaps adjacent items if in wrong order; merge sort divides the list into halves, sorts, then merges; insertion sort builds up a sorted portion by inserting each new item in the correct position.

排序算法：冒泡排序在顺序错误时交换相邻项；归并排序将列表分成两半排序后合并；插入排序通过将每个新项插入正确位置构建已排序部分。

Pseudocode uses plain English-like statements (INPUT, OUTPUT, IF…THEN…ELSE, WHILE…DO, FOR…TO…NEXT) to describe algorithms. Flowcharts use symbols: ovals for start/stop, parallelograms for input/output, rectangles for processes, diamonds for decisions.

伪代码 使用类似英语的语句（INPUT, OUTPUT, IF…THEN…ELSE, WHILE…DO, FOR…TO…NEXT）描述算法。流程图 使用符號：椭圆形表示开始/结束，平行四边形表示输入/输出，矩形表示处理，菱形表示判断。

Trace tables track variable values as a program is stepped through, useful for identifying logic errors.

跟踪表 在逐步执行程序时跟踪变量值，有助于识别逻辑错误。

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8. Programming Fundamentals | 编程基础

Core data types: integer, real (float), Boolean, character, and string. Variables hold values that can change; constants hold values fixed at compile time.

核心数据类型：整型、实型（浮点）、布尔型、字符型和字符串型。变量 存放可改变的值；常量 存放编译时固定的值。

Operators: arithmetic (+, -, *, /, MOD, DIV), comparison (==, !=, <, >, <=, >=), and logical (AND, OR, NOT).

运算符：算术 (+, -, *, /, MOD, DIV)，比较 (==, !=, <, >, <=, >=) 和逻辑 (AND, OR, NOT)。

Selection: IF…THEN…ELSE allows a program to choose between two branches; CASE/SWITCH handles multiple possible values cleanly.

选择：IF…THEN…ELSE 使程序可在两个分支间选择；CASE/SWITCH 可清晰地处理多个可能值。

Iteration: FOR loop (count-controlled), WHILE loop (condition at start), DO…UNTIL/REPEAT loop (condition at end, executes at least once).

迭代：FOR 循环（计数控制），WHILE 循环（条件在开头测试），DO…UNTIL/REPEAT 循环（条件在末尾测试，至少执行一次）。

String manipulation: length, substring, concatenation, character index access, converting case, etc.

字符串操作：长度、子串、连接、字符索引访问、大小写转换等。

Subprograms: procedures (perform actions but return no value) and functions (return a value). Parameters can be passed by value or by reference.

子程序：过程（执行操作但不返回值）和函数（返回一个值）。参数可以按值或按引用传递。

Arrays (lists) store multiple items of the same type under one identifier, accessed via index. 2D arrays are like tables.

数组（列表）将多个相同类型的项存储在一个标识符下，通过索引访问。二维数组类似表格。

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9. Producing Robust Programs | 设计健壮的程序

Defensive design anticipates misuse: input validation (range check, type check, presence check, format check) and authentication (password, biometrics) prevent invalid or malicious data.

防御性设计 预见到误用：输入验证（范围检查、类型检查、存在性检查、格式检查）和身份验证（密码、生物识别）防止无效或恶意数据。

Validation is an automatic check by the computer (e.g., age must be between 0 and 120). Verification is a human check (e.g., re-enter email address to catch typos).

验证 是计算机自动检查（例如，年龄必须在 0 到 120 之间）。校验 是人工检查（例如，重新输入电子邮件地址以发现拼写错误）。

Maintainability: use meaningful variable names, indentation, comments, and subprograms to make code easy to understand and update.

可维护性：使用有意义的变量名、缩进、注释和子程序，使代码易于理解和更新。

Types of testing: iterative (during development), final/terminal (after completion). Test data should include normal, boundary (edge) and erroneous data. A syntax error breaks grammar rules; a logic error produces wrong results.

测试类型：迭代测试（开发期间）、最终/终端测试（完成后）。测试数据 应包括正常、边界（边缘）和错误数据。语法错误违反语法规则；逻辑错误产生错误结果。

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10. Boolean Logic | 布尔逻辑

Logic gates are the building blocks of digital circuits. The three basic gates: NOT (inverts input, symbol ¬ or a triangle with a bubble), AND (outputs true when all inputs are true, symbol ∧), OR (outputs true when at least one input is true, symbol ∨).

逻辑门 是数字电路的构建模块。三个基本门：非门（反转输入，符号 ¬ 或带圆圈的三角形），与门（所有输入为真时输出真，符号 ∧），或门（至少一个输入为真时输出真，符号 ∨）。

Truth tables le list all possible input combinations and the corresponding output. For a two-input AND gate, output Q = A ∧ B is true only when A=1 and B=1.

真值表 列出所有可能的输入组合及相应输出。对于两输入与门，仅当 A=1 且 B=1 时，输出 Q = A ∧ B 为真。

Boolean expressions use variables and operators; they can be simplified using rules like De Morgan's laws: ¬(A ∨ B) = ¬A ∧ ¬B and ¬(A ∧ B) = ¬A ∨ ¬B.

布尔表达式 使用变量和运算符；可利用德摩根定律等规则化简：¬(A ∨ B) = ¬A ∧ ¬B 且 ¬(A ∧ B) = ¬A ∨ ¬B。

Logic circuits combine gates to perform more complex functions. The order of operations matters; brackets override precedence (NOT > AND > OR).

逻辑电路组合门以执行更复杂的功能。运算顺序很重要；括号可超越优先级（非 > 与 > 或）。

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11. Data Representation | 数据表示

Binary (base 2) uses 0 and 1. Denary is base 10. Hexadecimal 0-9 and letters A-F; it compactly represents long binary strings (one hex digit = 4 bits).

二进制（基数为 2）使用 0 和 1。十进制 是基数为 10。十六进制（基数为 16）使用数字 0-9 和字母 A-F；它能紧凑地表示长二进制字符串（一位十六进制 = 4 位）。

Conversions: denary to binary (repeated division by 2, note remainders); binary to hex (group bits into nibbles from right); hex to denary (multiply each digit by power of 16).

转换：十进制转二进制（反复除以 2，记录余数）；二进制转十六进制（从右起将位分组为半字节）；十六进制转十进制（每位数字乘以 16 的幂）。

Binary shifts: left shift multiplies by 2 for each shift; right shift divides by 2, discarding remainder. Overflow can occur if bits fall off the left end.

二进制移位：每次左移乘以 2；右移除以 2，舍去余数。如果位从左侧溢出，会发生溢出。

Characters are represented by numeric codes: 7-bit ASCII (128 characters) and Unicode (extended code for global scripts, e.g., UTF-8).

字符 用数字代码表示：7 位 ASCII（128 个字符）和 Unicode（用于全球文字的扩展编码，如 UTF-8）。

Images are stored as bitmap grids of pixels, each with a binary value based on colour depth (bits per pixel). Metadata stores width, height, colour palette.

图像 存储为像素的位图网格，每个像素根据颜色深度（每像素位数）具有二进制值。元数据存储宽度、高度和调色板。

Sound prove quality but increase file size. Sound file size = rate × depth × seconds × channels.

声音 以一定采样率（如 44.1 kHz）采样，每样本量化到位深度（如 16 位）。较高的采样率和位深度会提高质量但也增加文件大小。声音文件大小 = 采样率 × 位深度 × 秒数 × 声道数。

Compression: lossy (removes non-essential data permanently, e.g., JPEG, MP3) and lossless (reduces file size without losing data, e.g., ZIP, PNG). Run-length encoding (RLE) is a lossless method for images with repeated pixels.

压缩：有损压缩（永久移除非必要数据，如 JPEG、MP3）和无损压缩（减小文件大小而不丢失数据，如 ZIP、PNG）。行程编码 (RLE) 是一种针对重复像素图像的无损方法。

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