📚 IB CIE Computer Science: End-of-Term Revision Guide | IB CIE 计算机：期末复习提纲
This revision guide covers the core topics of both the IB (SL/HL) and CIE (9618/9608) Computer Science syllabi, providing a structured overview to help you prepare for end-of-term examinations. Use it to review key concepts, definitions, and common problem-solving techniques.
本复习提纲涵盖IB (SL/HL) 与 CIE (9618/9608) 计算机科学课程的核心主题，以结构化概览助您备战期末考。可据此回顾关键概念、定义和常见解题技巧。
1. Computer Systems and Architecture | 计算机系统与体系结构
The Von Neumann architecture underpins most modern computers, featuring a single shared memory for both data and instructions. In contrast, Harvard architecture uses separate memory spaces, enabling simultaneous access in embedded systems.
冯·诺依曼架构是现代计算机的基础，数据和指令共用同一主存。与之不同，哈佛架构使用独立的存储空间，可在嵌入式系统中实现同时存取。
The central processing unit (CPU) consists of the control unit (CU), arithmetic logic unit (ALU), and a set of registers. Key registers include the program counter (PC), memory address register (MAR), memory data register (MDR), and accumulator (ACC). The fetch-decode-execute cycle is driven by the system clock and requires coordination with the system bus (address, data, control lines).
中央处理器 (CPU) 包括控制单元 (CU)、算术逻辑单元 (ALU) 和一组寄存器。关键寄存器有程序计数器 (PC)、内存地址寄存器 (MAR)、内存数据寄存器 (MDR) 和累加器 (ACC)。取指-译码-执行周期由系统时钟驱动，并需通过系统总线（地址、数据、控制线）协同工作。
he memory hierarchy (registers → cache → RAM → secondary storage) balances speed and cost.
高速缓存 (Cache) 是片上的高速 RAM，通过存放常用指令和数据来降低平均访存时间。存储层次（寄存器 → 缓存 → 内存 → 辅存）在速度和成本间取得平衡。
2. Data Representation | 数据表示
Computers store data in binary (base-2). Common representations include unsigned integers, signed integers using two's complement, and floating-point numbers (e.g., IEEE 754 single precision). Hexadecimal (base-16) is used as a shorthand for binary.
计算机以二进制储存数据。常见表示法包括无符号整数、用二进制补码表示的有符号整数，以及浮点数（如 IEEE 754 单精度）。十六进制常用作二进制的简写。
Two's complement allows subtraction to be performed by addition: flip all bits and add 1. For example, the 8-bit representation of -3 is 11111101₂. Overflow must be checked when the result exceeds the bit width.
二进制补码可使减法通过加法实现：所有位取反后加 1。例如 -3 的 8 位表示为 11111101₂。当结果超出位宽时需检查溢出。
Text is encoded using character sets such as ASCII (7-bit) and Unicode (e.g., UTF-8). Logic gates (AND, OR, NOT, XOR, NAND) form combinational circuits. Basic logic equations can be simplified using Boolean algebra or Karnaugh maps.
文本采用字符集编码，如 ASCII (7位) 和 Unicode (如 UTF-8)。逻辑门（与、或、非、异或、与非）构成组合电路。基本逻辑等式可用布尔代数或卡诺图化简。
| Gate | Symbol | Truth Table (A,B → Out) |
|---|---|---|
| AND | A · B | 0,0→0; 0,1→0; 1,0→0; 1,1→1 |
| OR | A + B | 0,0→0; 0,1→1; 1,0→1; 1,1→1 |
| NOT | ¬A | 0→1; 1→0 |
| XOR | A ⊕ B | 0,0→0; 0,1→1; 1,0→1; 1,1→0 |
3. Networks and Communication | 网络与通信
Network topologies include star, bus, ring, and mesh. The TCP/IP stack (Application, Transport, Internet, Network Access) dominates modern networking. Key protocols: HTTP/HTTPS, FTP, SMTP, POP3, TCP, UDP, IP, and ARP.
网络拓扑包括星形、总线、环形和网状。TCP/IP 协议栈（应用层、传输层、互联网层、网络接入层）主导现代网络。关键协议：HTTP/HTTPS、FTP、SMTP、POP3、TCP、UDP、IP 和 ARP。
IP addresses (IPv4: 32 bits; IPv6: 128 bits) identify devices. Subnet masks divide a network into smaller segments. DNS translates domain names to IP addresses. Routers, switches, and hubs function at different OSI layers.
IP 地址（IPv4：32位；IPv6：128位）用于标识设备。子网掩码可将网络划分为更小子网。DNS 将域名解析为 IP 地址。路由器、交换机和集线器工作在不同的 OSI 层次。
Circuit switching establishes a dedicated path (e.g., traditional telephone), while packet switching breaks data into packets and routes them independently (e.g., the Internet). Latency, bandwidth, and error rates are key performance metrics.
电路交换建立专用路径（如传统电话），而分组交换将数据分割成包并独立传输（如互联网）。延迟、带宽和错误率是关键性能指标。
4. Databases | 数据库
A relational database organizes data into tables (relations) with rows (tuples) and columns (attributes). Primary keys uniquely identify rows; foreign keys link tables. SQL (Structured Query Language) is used for data definition (DDL) and manipulation (DML).
关系数据库将数据组织为表（关系），表由行（元组）和列（属性）构成。主键唯一标识行；外键连接表。SQL（结构化查询语言）用于数据定义 (DDL) 和数据操纵 (DML)。
Normalization reduces data redundancy: 1NF eliminates repeating groups, 2NF removes partial dependencies, 3NF removes transitive dependencies. ACID properties (Atomicity, Consistency, Isolation, Durability) ensure reliable transactions.
规范化减少数据冗余：1NF 消除重复组，2NF 消除部分函数依赖，3NF 消除传递依赖。ACID 特性（原子性、一致性、隔离性、持久性）确保事务的可靠性。
Common SQL clauses: SELECT ... FROM ... WHERE ... ORDER BY ... GROUP BY ... HAVING ...; JOINs (INNER, LEFT, RIGHT) combine tables.
常用 SQL 子句：SELECT ... FROM ... WHERE ... ORDER BY ... GROUP BY ... HAVING ...；连接（INNER, LEFT, RIGHT）用于合并表。
5. Algorithms and Computational Thinking | 算法与计算思维
Algorithm efficiency is analysed using Big O notation: O(1) constant, O(log n) logarithmic, O(n) linear, O(n log n) linearithmic, O(n²) quadratic. Binary search is O(log n) on sorted arrays; linear search is O(n).
算法效率用大 O 标记分析：O(1) 常数级，O(log n) 对数级，O(n) 线性级，O(n log n) 线性对数级，O(n²) 平方级。二分查找在已排序数组上为 O(log n)；线性搜索为 O(n)。
Sorting algorithms: Bubble sort (O(n²)), insertion sort (O(n²)), merge sort (O(n log n)), quicksort (average O(n log n), worst O(n²)). Merge sort uses divide-and-conquer and is stable.
排序算法：冒泡排序 (O(n²))、插入排序 (O(n²))、归并排序 (O(n log n))、快速排序（平均 O(n log n)，最差 O(n²)）。归并排序采用分治法，且为稳定排序。
Recursion is a technique where a function calls itself with a base case to prevent infinite recursion. Examples: factorial, Fibonacci, tree traversals. Stacks are used implicitly in recursion.
递归指函数调用自身并通过基准情形防止无限递归。示例：阶乘、斐波那契数列、树遍历。递归隐式使用栈。
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