📚 IB Computer Science Final Revision Checklist | IB 计算机科学期末复习提纲
This checklist provides a concise summary of the key concepts, definitions, and models you must master for the IB Computer Science examination. Use it to guide your final review, ensuring you can explain each point clearly with relevant examples and pseudocode where needed.
本提纲简明总结了 IB 计算机科学考试中必须掌握的核心概念、定义和模型。用它来指导期末复习，确保能清晰解释每个要点，并在需要时辅以恰当的示例和伪代码。
1. System Fundamentals | 系统基础
A computer system consists of hardware, software, data, users, and processes working together in an organisational context. Stakeholders include end-users, developers, and managers who have different concerns.
计算机系统由硬件、软件、数据、用户和流程组成，在组织环境中协同工作。利益相关者包括最终用户、开发人员和管理者，他们关注的方面各不相同。
System planning involves feasibility studies (TELOS: Technical, Economic, Legal, Operational, Schedule). Changeover methods include direct cutover, parallel running, pilot conversion, and phased conversion – each with its own risk profile.
系统规划涉及可行性研究（TELOS：技术、经济、法律、运营、进度）。系统转换方法包括直接切换、并行运行、试点转换和分阶段转换，各有不同的风险特征。
Data loss can be prevented through regular backups (full, incremental, differential) and storage on-site/off-site. System security employs user authentication, access rights, encryption, and firewalls to protect data integrity and privacy.
通过定期备份（完全备份、增量备份、差异备份）和本地/异地存储可以防止数据丢失。系统安全采用用户认证、访问权限、加密和防火墙来保护数据完整性与隐私。
Ethical and social issues include the digital divide, intellectual property, online surveillance, and the environmental impact of e-waste. The design of user interfaces must consider accessibility, usability, and cultural factors.
伦理与社会问题包括数字鸿沟、知识产权、网络监控和电子垃圾对环境的影响。用户界面设计必须考虑可访问性、可用性和文化因素。
2. Computer Organization | 计算机组成
The von Neumann architecture contains a CPU (with ALU, CU, and registers such as MAR, MDR, PC, IR), memory, and I/O devices interconnected by data, address, and control buses.
冯·诺依曼架构包含 CPU（含 ALU、CU 以及 MAR、MDR、PC、IR 等寄存器）、存储器以及通过数据总线、地址总线和控制总线互联的 I/O 设备。
The machine instruction cycle follows Fetch-Decode-Execute. The PC holds the address of the next instruction; the instruction is fetched into the IR, decoded by the CU, and executed using the ALU.
机器指令周期遵循取指-译码-执行。PC 保存下一条指令的地址；指令被取入 IR，由 CU 译码后通过 ALU 执行。
Secondary storage devices are compared by speed, capacity, durability, and cost. HDD uses magnetic platters; SSD is based on NAND flash, offering faster access but higher cost per GB.
二级存储设备通过速度、容量、耐用性和成本进行比较。HDD 使用磁盘盘片；SSD 基于 NAND 闪存，访问速度更快但每 GB 成本更高。
Binary, hexadecimal, and two’s complement representation are fundamental. Floating-point numbers are stored as sign, mantissa, and exponent, e.g., ±M × 2E. The character sets ASCII and Unicode are used for text representation.
二进制、十六进制和补码表示是基础。浮点数存储为符号、尾数和阶码，如 ±M × 2E。字符集 ASCII 和 Unicode 用于文字表示。
Operating systems manage memory, processes, file systems, and I/O through paging, scheduling, and interrupt handling. Utility software includes antivirus, disk defragmenters, and backup tools.
操作系统通过分页、调度和中断处理来管理内存、进程、文件系统和 I/O。实用程序软件包括防病毒、磁盘碎片整理和备份工具。
3. Networks | 网络
Network types include LAN (small area, high speed), WAN (large geographical area), VPN (secure tunnel over public network), and PAN (personal devices). The client-server and peer-to-peer models define how resources are shared.
网络类型包括 LAN（小范围、高速）、WAN（广大地理区域）、VPN（公共网络上的安全隧道）和 PAN（个人设备）。客户端-服务器与对等模型定义了资源共享的方式。
The OSI model has seven layers (Physical, Data Link, Network, Transport, Session, Presentation, Application) while the TCP/IP model combines them into four. Protocols like HTTP, FTP, SMTP, and DNS operate at the Application layer.
OSI 模型有七层（物理层、数据链路层、网络层、传输层、会话层、表示层、应用层），而 TCP/IP 模型将其合并为四层。HTTP、FTP、SMTP 和 DNS 等协议工作在应用层。
Key network hardware includes routers (forward packets between networks), switches (connect devices within a LAN using MAC addresses), and modems (modulate/demodulate signals).
关键网络硬件包括路由器（在网络间转发数据包）、交换机（使用 MAC 地址连接 LAN 内设备）和调制解调器（调制/解调信号）。
Packet switching breaks data into packets routed independently; circuit switching establishes a dedicated path. Network security uses SSL/TLS, firewalls, and MAC address filtering to prevent unauthorized access.
分组交换将数据分成独立路由的数据包；电路交换建立专用路径。网络安全使用 SSL/TLS、防火墙和 MAC 地址过滤来防止未授权访问。
4. Computational Thinking & Programming | 计算思维与编程
Computational thinking involves decomposition, pattern recognition, abstraction, and algorithm design. Algorithms are expressed using pseudocode or flowcharts, following IB’s approved pseudocode conventions.
计算思维包括分解、模式识别、抽象和算法设计。算法使用伪代码或流程图表达，遵循 IB 认可的伪代码约定。
Basic data structures include arrays (static and dynamic), stacks (LIFO), queues (FIFO), and their operations such as push, pop, enqueue, and dequeue. Collections can be iterated with loops.
基本数据结构包括数组（静态和动态）、栈（LIFO）、队列（FIFO）以及它们的操作如 push、pop、enqueue 和 dequeue。集合可通过循环进行迭代。
Searching algorithms: linear search scans each element, taking O(n); binary search requires a sorted array and halves the search interval, O(log n). Sorting algorithms: bubble sort, selection sort, and insertion sort are O(n2) in the worst case.
搜索算法：线性搜索逐一扫描每个元素，时间复杂度 O(n)；二分搜索要求有序数组并通过折半查找，O(log n)。排序算法：冒泡排序、选择排序和插入排序最坏情况为 O(n2)。
Programming concepts: variables store data; conditionals (if-else) and loops (for, while) control program flow. Functions with parameters and return values promote modularity and reuse. Recursion is a function calling itself, requiring a base case.
编程概念：变量存储数据；条件语句 (if-else) 和循环 (for, while) 控制程序流程。带参数和返回值的函数促进模块化与复用。递归是函数自我调用，必须有基准情形。
5. Abstract Data Structures (HL) | 抽象数据结构（高级）
Linked lists are dynamic structures composed of nodes containing data and a pointer to the next node. Operations include insertion, deletion, and traversal. Doubly linked lists add a previous pointer for bidirectional movement.
链表是由节点组成的动态结构，每个节点包含数据和指向下一个节点的指针。操作包括插入、删除和遍历。双向链表增加前驱指针，支持双向移动。
Trees and binary trees store data hierarchically. Tree traversal algorithms: pre-order (root, left, right), in-order (left, root, right), post-order (left, right, root). Binary search trees enforce left < parent < right for efficient searching.
树和二叉树以分层方式存储数据。树的遍历算法：前序（根、左、右）、中序（左、根、右）、后序（左、右、根）。二叉搜索树强制左 < 父 < 右，以实现高效搜索。
Graphs can be represented using adjacency matrices or adjacency lists. Depth-first search (DFS) uses a stack, while breadth-first search (BFS) uses a queue to explore vertices.
图可以用邻接矩阵或邻接表表示。深度优先搜索（DFS）使用栈，广度优先搜索（BFS）使用队列来探索顶点。
Recursive thinking can solve problems like factorial, Fibonacci, and the Towers of Hanoi. The call stack manages recursive calls; each recursive step must move toward the base case to avoid stack overflow.
递归思维可解决阶乘、斐波那契数和汉诺塔等问题。调用栈管理递归调用；每次递归必须向基准情形推进以避免栈溢出。
6. Resource Management (HL) | 资源管理（高级）
Process scheduling algorithms include First-Come First-Served (FCFS), Shortest Job Next (SJN), Round Robin (RR), and Priority Scheduling. Performance is measured by throughput, turnaround time, and waiting time.
进程调度算法包括先来先服务 (FCFS)、最短作业优先 (SJN)、轮转调度 (RR) 和优先级调度。性能通过吞吐量、周转时间和等待时间衡量。
Deadlock occurs when processes hold resources and wait for each other indefinitely. Necessary conditions: mutual exclusion, hold and wait, no preemption, and circular wait. Prevention strategies break at least one condition.
死锁发生在进程持有资源并无限等待对方释放资源时。必要条件：互斥、占有且等待、不可抢占和循环等待。预防策略至少打破其中一个条件。
Memory management uses paging (dividing memory into fixed-size frames) and segmentation (variable-sized segments). Virtual memory allows execution of processes larger than physical RAM by swapping pages to disk.
内存管理使用分页（将内存划分为固定大小的帧）和分段（可变大小的段）。虚拟内存通过将页面交换到磁盘，允许执行大于物理 RAM 的进程。
Disk scheduling algorithms: FCFS, Shortest Seek Time First (SSTF), SCAN (elevator), and C-SCAN. The goal is to minimize seek time and improve I/O performance.
磁盘调度算法：FCFS、最短寻道时间优先 (SSTF)、SCAN（电梯算法）和 C-SCAN。目标是尽量减少寻道时间，提高 I/O 性能。
7. Control (HL) | 控制（高级）
A control system consists of a microcontroller or PLC, sensors (input), and actuators (output). Open-loop systems operate without feedback; closed-loop systems use feedback to adjust output for desired setpoint.
控制系统由微控制器或 PLC、传感器（输入）和执行器（输出）组成。开环系统无反馈运行；闭环系统利用反馈调整输出以达到设定的目标值。
Embedded systems are dedicated microprocessor-based systems within larger devices, often real-time. Examples: ABS in cars, medical devices, and smart appliances.
嵌入式系统是大型设备中专用的基于微处理器的系统，通常为实时系统。例如：汽车防抱死制动系统、医疗设备和智能家电。
The interrupt mechanism allows a processor to respond to external events without polling. When an interrupt occurs, the current context is saved, the ISR is executed, and context is restored. Polling checks a device repeatedly, which can waste CPU time.
中断机制允许处理器无需轮询即可响应外部事件。当中断发生时，当前上下文被保存，执行中断服务程序（ISR），然后恢复上下文。轮询则反复检查设备，可能浪费 CPU 时间。
Robotics combines sensors, control algorithms, and actuators to perform tasks. Degrees of freedom, end effectors, and feedback loops are essential concepts in robotic design.
机器人将传感器、控制算法和执行器结合起来完成任务。自由度、末端执行器和反馈回路是机器人设计中的基本概念。
8. Databases (Option) | 数据库（选修）
A relational database organises data into tables (relations) with rows (tuples) and columns (attributes). Keys: primary key uniquely identifies a record; foreign key creates relationships between tables.
关系数据库将数据组织成表（关系），包含行（元组）和列（属性）。键：主键唯一标识一条记录；外键在表之间建立关联。
Entity-Relationship Diagrams (ERD) model data using entities, attributes, and relationships (1:1, 1:M, M:N). Normalization up to 3NF removes redundancies and anomalies: 1NF (atomic values), 2NF (no partial dependencies), 3NF (no transitive dependencies).
实体关系图 (ERD) 使用实体、属性和联系（1:1、1:M、M:N）对数据建模。规范化至第三范式 (3NF) 消除冗余和异常：1NF（原子值）、2NF（无部分依赖）、3NF（无传递依赖）。
SQL commands: SELECT … FROM … WHERE … ORDER BY … GROUP BY … HAVING … JOIN types include INNER JOIN, LEFT JOIN, RIGHT JOIN. DDL for creating tables, DML for data manipulation.
SQL 命令：SELECT … FROM … WHERE … ORDER BY … GROUP BY … HAVING … 连接类型包括内连接（INNER JOIN）、左连接（LEFT JOIN）、右连接（RIGHT JOIN）。DDL 用于创建表，DML 用于数据操作。
Transaction processing ensures ACID properties: Atomicity, Consistency, Isolation, Durability. Locks and timestamps control concurrency to prevent lost updates and dirty reads.
事务处理确保 ACID 特性：原子性、一致性、隔离性和持久性。锁和时间戳控制并发，以防止丢失更新和脏读。
9. Modelling & Simulation (Option) | 建模与仿真（选修）
Models are simplified representations of real-world systems, and can be physical, mathematical, or computational. They allow experimentation without risk or high cost. A simulation runs the model over time to observe behaviour.
模型是现实系统的简化表示，可以是物理模型、数学模型或计算模型。模型允许无风险或低成本地进行实验。仿真是随时间运行模型以观察其行为。
The simulation process: problem definition, model design, implementation, verification (did we build the model right?) and validation (did we build the right model?). Outputs are analysed and compared with real data where possible.
仿真过程：问题定义、模型设计、实现、验证（我们是否正确地构建了模型？）和确认（我们是否构建了正确的模型？）。输出结果被分析并尽可能与实际数据比较。
Random numbers and Monte Carlo methods are used to model stochastic systems. Pseudorandom number generators produce sequences that pass statistical tests for randomness. Monte Carlo uses repeated random sampling to compute results.
随机数和蒙特卡洛方法用于对随机系统建模。伪随机数生成器产生通过随机性统计检验的序列。蒙特卡洛仿真使用反复随机抽样来计算结果。
Applications include climate modelling, traffic flow simulation, economic forecasting, and disease spread models. Visualisation tools (graphs, heat maps, animations) help communicate simulation outcomes.
应用包括气候建模、交通流仿真、经济预测和疾病传播模型。可视化工具（图形、热图、动画）有助于传达仿真结果。
10. Object-Oriented Programming | 面向对象编程
OOP is based on classes and objects. A class is a blueprint defining attributes (data) and methods (behaviour). An object is an instance of a class with its own state. Encapsulation bundles data and methods, restricting direct access from outside.
面向对象编程基于类和对象。类是定义属性（数据）和方法（行为）的蓝图。对象是类的一个实例，拥有自己的状态。封装将数据和方法捆绑在一起，限制外部直接访问。
Inheritance allows a subclass to reuse and extend the properties and methods of a superclass. Polymorphism means one interface, multiple implementations – often achieved through method overriding or interfaces.
继承允许子类重用和扩展超类的属性和方法。多态意味着一个接口，多种实现——通常通过方法重写或接口实现。
UML class diagrams show classes as boxes divided into name, attributes, and methods. Relationships include association, aggregation, composition, and inheritance with appropriate notation (e.g., open triangle for inheritance).
UML 类图将类表示为分为名称、属性和方法三部分的方框。关系包括关联、聚合、组合和继承，并配有相应符号（如继承用空心三角箭头表示）。
Constructors are special methods invoked when an object is created to initialise its state. Destructors clean up resources when an object is destroyed. Access modifiers (public, private, protected) control visibility of members.
构造器是创建对象时被调用的特殊方法，用于初始化对象状态。析构器在对象销毁时清理资源。访问修饰符（public、private、protected）控制成员的可见性。
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