📚 Core Topics Revision for Year 10 CIE Computer Science | Year 10 CIE 计算机核心知识点梳理
This revision guide covers the essential topics for Year 10 students following the Cambridge IGCSE Computer Science syllabus (0478/0984). It explains key concepts in data representation, hardware, software, networks, security, algorithm design, programming, and databases, providing a bilingual reference for both English and Chinese learners.
本复习指南适用于学习剑桥 IGCSE 计算机科学（0478/0984）课程的 Year 10 学生，涵盖数据表示、硬件、软件、网络、安全、算法设计、编程和数据库等核心主题，为中英双语学习者提供对照参考。
1. Data Representation | 数据表示
Computers use binary (base‑2) to represent all types of data. A single binary digit is called a bit; 8 bits form a byte. Larger numbers can be expressed in denary (base‑10) and hexadecimal (base‑16).
计算机使用二进制（基数为 2）表示所有类型的数据。一个二进制位称为比特（bit），8 个比特构成一个字节（byte）。较大的数值可以用十进制（基数为 10）和十六进制（基数为 16）表示。
To convert a denary number to binary, repeatedly divide by 2 and record the remainders. For example, denary 13 in binary is 1101.
将十进制数转换为二进制，重复除以 2 并记录余数。例如，十进制 13 的二进制是 1101。
Hexadecimal uses digits 0‑9 and letters A‑F (A=10, B=11, … ore compact for representing long binary strings such as memory addresses or colour codes.
十六进制使用数字 0‑9 和字母 A‑F（A=10, B=11, … F=15）。每个十六进制位对应一个半字节（4 个比特），因而能更紧凑地表示长二进制串，如内存地址或颜色代码。
- Text is encoded using standards like ASCII and Unicode. ASCII uses 7 bits per character (extended: 8 bits); Unicode uses 1‑4 bytes per character to support global scripts.
- 文本使用 ASCII 和 Unicode 等标准编码。ASCII 每字符 7 比特（扩展版 8 比特）；Unicode 每字符使用 1‑4 字节以支持全球文字。
- Sound is sampled at regular intervals; the sample rate and bit depth determine the quality and file size. Higher values give more accurate representation but larger files.
- 声音通过等间隔采样进行数字化；采样率和位深度决定音质与文件大小。值越高，表示越精确，但文件越大。
- Images are represented as grids of pixels. In a bitmap, each pixel's colour is stored as a binary code (e.g., 24‑bit colour uses 8 bits each for red, green and blue).
- 图像表示为像素网格。在位图中，每个像素的颜色以二进制代码存储（例如 24 位颜色为红、绿、蓝各 8 位）。
Calculating file size: for a 10‑ e 44.1 kHz and bit depth 16 bits, file size = 44100 × 16 × 10 = 7 056 000 bits (≈ 882 KB).
计算文件大小：一段 10 秒单声道声音，采样率 44.1 kHz，位深度 16 位，文件大小 = 44100 × 16 × 10 = 7 056 000 比特（约 882 KB）。
2. Data Transmission | 数据传输
Data can be sent either serially (one bit at a time over a single wire) or in parallel (multiple bits simultaneously over several wires). Serial transmission is more reliable over long distances and is used in USB and Ethernet.
数据可以串行传输（一次一个比特通过单线）或并行传输（多比特同时通过多条线）。串行传输在长距离上更可靠，用于 USB 和以太网。
Simplex, half‑duplex, and full‑duplex describe the direction of communication: simplex is one‑way only (e.g., TV broadcast); half‑duplex allows both directions but only one at a time (walkie‑talkie); full‑duplex allows simultaneous two‑way transmission (telephone).
单工、半双工和全双工描述通信方向：单工仅为单向（如电视广播）；半双工允许双向但同一时间只能一个方向（对讲机）；全双工允许同时双向传输（电话）。
USB (Universal Serial Bus) is a standard for connecting peripherals. It supports hot‑swapping, provides power, and uses error‑checking for reliable data transfer.
USB（通用串行总线）是连接外设的标准，支持热插拔、提供电源，并使用差错校验确保可靠传输。
Error detection methods include parity checks, checksums, and echo checks. Parity can be even or odd; it cannot correct errors but detects single‑bit errors effectively.
差错检测方法包括奇偶校验、校验和和回显校验。奇偶校验分偶校验和奇校验；它不能纠正错误，但能有效检测单比特错误。
3. Hardware – Central Processing Unit (CPU) | 硬件——中央处理器
The CPU fetches, decodes, and executes instructions following the Von Neumann architecture. Its main components are the Control Unit (CU), Arithmetic Logic Unit (ALU), registers, and buses.
CPU 遵循冯·诺依曼架构，执行取指、译码、执行周期。其主要组成部分包括控制单元（CU）、算术逻辑单元（ALU）、寄存器和总线。
- CU: directs the operation of the processor, sending control signals.
- 控制单元：指挥处理器操作，发送控制信号。
- ALU: performs arithmetic (add, subtract) and logical (AND, OR, NOT) operations.
- 算术逻辑单元：执行算术（加、减）和逻辑（与、或、非）运算。
- Registers: fast, small‑capacity storage locations inside the CPU. Key registers include Program Counter (PC), Memory Address Register (MAR), Memory Data Register (MDR), Current Instruction Register (CIR), and Accumulator (ACC).
- 寄存器：CPU 内部的高速、小容量存储位置。关键寄存器包括程序计数器（PC）、内存地址寄存器（MAR）、内存数据寄存器（MDR）、当前指令寄存器（CIR）和累加器（ACC）。
- Buses: a group of parallel wires carrying data (data bus), addresses (address bus), and control signals (control bus).
- 总线：一组并行走线，传送数据（数据总线）、地址（地址总线）和控制信号（控制总线）。
The fetch‑decode‑execute cycle repeats continuously. Clock speed (measured in GHz) indicates how many cycles occur per second; a higher clock speed generally means faster processing.
取指—译码—执行周期不断重复。时钟速度（以 GHz 为单位）表示每秒发生的周期数；时钟速度越高通常意味着处理速度越快。
Cache memory is a very fast, small memory located close to the CPU that stores frequently used instructions and data to reduce access time.
高速缓存（cache）是一种非常快、容量小的存储器，靠近 CPU，存放常用指令和数据以减少访问时间。
4. Memory and Storage | 存储器与存储设备
Primary memory includes RAM (Random Access Memory) and ROM (Read Only Memory). RAM is volatile, used to hold currently running programs and data; ROM is non‑volatile, containing firmware or boot instructions.
主存储器包括 RAM（随机存取存储器）和 ROM（只读存储器）。RAM 是易失性的，用于保存正在运行的程序和数据；ROM 是非易失性的，包含固件或引导指令。
Secondary storage devices retain data permanently. Types: magnetic (HDD), optical (CD, DVD, Blu‑ray), and solid‑state (SSD, USB flash drive).
辅助存储设备永久保存数据，分为磁性存储（HDD）、光学存储（CD、DVD、蓝光）和固态存储（SSD、USB 闪存盘）。
Storage capacities are measured in bytes. Real‑life examples: a typical song is about 5 MB; a high‑definition movie can be 4 GB or more.
存储容量以字节为单位。实际示例：一首典型歌曲约 5 MB；一部高清电影可达 4 GB 或更高。
Virtual memory is a technique that uses part of the hard disk as if it were RAM, allowing the computer to run larger programs but at a slower speed.
虚拟内存是一种将部分硬盘当 RAM 使用的技术，允许计算机运行更大的程序，但速度较慢。
5. Software | 软件
Software is divided into system software and application software. System software includes operating systems, utilities, and device drivers; it manages hardware and provides a platform for applications.
软件分为系统软件和应用软件。系统软件包括操作系统、实用程序和设备驱动程序；它管理硬件并为应用程序提供平台。
Operating system functions: user interface (GUI/CLI), memory management, file management, peripheral management, process scheduling, and security.
操作系统的功能：用户界面（GUI/CLI）、内存管理、文件管理、外设管理、进程调度和安全管理。
Application software performs specific tasks for users, such as word processors, spreadsheets, web browsers, and database management systems.
应用软件执行面向用户的特定任务，如文字处理、电子表格、网页浏览器和数据库管理系统。
High‑level languages (e.g., Python, Java) are translated into machine code by compilers (translate whole program at once) or interpreters (translate line‑by‑line during execution). Assembly language uses mnemonics and is translated by an assembler.
高级语言（如 Python、Java）通过编译器（一次性翻译整个程序）或解释器（执行时逐行翻译）转换为机器码。汇编语言使用助记符，由汇编器翻译。
6. Networks and the Internet | 网络与互联网
A network connects computers to share resources. LAN (Local Area Network) covers a small geographical area; WAN (Wide Area Network) spans large distances, often using public infrastructure.
网络将计算机连接起来以共享资源。LAN（局域网）覆盖较小地理范围；WAN（广域网）跨越远距离，通常使用公共基础设施。
Network hardware: router (connects different networks, forwards data packets), switch (connects devices within a LAN, sends data to specific device), modem (converts digital ↔ analogue for transmission over telephone lines).
网络硬件：路由器（连接不同网络，转发数据包）、交换机（在局域网内连接设备，将数据发送到特定设备）、调制解调器（在电话线上进行数字 ↔ 模拟转换）。
Every device on a network has a MAC address (unique, hard‑coded in the NIC) and an IP address (logical, can change). IPv4 uses 32 bits (e.g., 192.168.1.1); IPv6 uses 128 bits to solve address exhaustion.
网络上的每个设备都有一个 MAC 地址（唯一，固化在网卡中）和 IP 地址（逻辑地址，可变）。IPv4 使用 32 位（如 192.168.1.1）；IPv6 使用 128 位以解决地址耗尽问题。
Protocols: HTTP/HTTPS (web), FTP (file transfer), SMTP/POP3/IMAP (email), TCP/IP (data transmission). TCP ensures reliable delivery; IP handles addressing and routing.
协议：HTTP/HTTPS（网页）、FTP（文件传输）、SMTP/POP3/IMAP（电子邮件）、TCP/IP（数据传输）。TCP 确保可靠交付；IP 处理寻址和路由。
7. Cyber Security | 网络安全
Threats to computer systems include malware (viruses, worms, Trojan horses, spyware, ransomware), phishing (fraudulent emails/websites), brute‑force attacks (trying all passwords), denial‑of‑service attacks (flooding a server), and SQL injection (malicious database queries).
计算机系统面临的威胁包括恶意软件（病毒、蠕虫、特洛伊木马、间谍软件、勒索软件）、网络钓鱼（欺诈性邮件/网站）、暴力破解（尝试所有密码）、拒绝服务攻击（淹没服务器）和 SQL 注入（恶意数据库查询）。
Prevention methods: use firewalls (filter incoming/outgoing traffic), anti‑virus software, strong passwords, two‑factor authentication, regular software updates, and user education.
防护措施：使用防火墙（过滤进出流量）、防病毒软件、高强度密码、双因素认证、定期软件更新和用户教育。
Encryption scrambles data so that only authorised parties with the key can read it. Symmetric encryption uses the same key for encryption and decryption; asymmetric encryption uses a public‑private key pair.
加密对数据进行乱序处理，只有持有密钥的授权方才能读取。对称加密使用相同密钥进行加密和解密；非对称加密使用公钥—私钥对。
8. Algorithm Design and Problem‑Solving | 算法设计与问题解决
An algorithm is a step‑by‑step procedure to solve a problem. It can be expressed using pseudocode, flowcharts, or programming code.
算法是解决问题的分步过程，可以用伪代码、流程图或程序代码表示。
Pseudocode uses English‑like statements and standard constructs: variables, input/output, selection (IF…THEN…ELSE), iteration (FOR, WHILE, REPEAT…UNTIL), and arrays.
伪代码使用类似英语的语句和标准结构：变量、输入/输出、选择（IF…THEN…ELSE）、循环（FOR、WHILE、REPEAT…UNTIL）和数组。
Flowcharts use symbols: oval for start/end, rectangle for process, diamond for decision. Arrows show the flow of control.
流程图使用符号：椭圆表示开始/结束，矩形表示处理，菱形表示判断。箭头表示控制流。
Testing: test data should include normal, boundary, and erroneous values. A trace table can be used to manually track variable values during dry‑run testing.
测试：测试数据应包括正常值、边界值和错误值。跟踪表可用于手动跟踪干运行测试中的变量值。
Standard searching algorithms: linear search (check each element in turn) and binary search (requires sorted list, repeatedly divide search interval). Standard sorting algorithms: bubble sort (compare and swap adjacent elements) and insertion sort (insert each element into its correct position).
标准搜索算法：线性搜索（依次检查每个元素）和二分搜索（要求列表已排序，重复将搜索区间减半）。标准排序算法：冒泡排序（比较并交换相邻元素）和插入排序（将每个元素插入到正确位置）。
9. Programming Concepts | 程序设计概念
Variables and constants hold data; they have a name, data type, and value. Data types include Integer, Real, Char, String, Boolean. Constants remain unchanged during program execution.
变量和常量存储数据；它们由名称、数据类型和值组成。数据类型包括整型、实型、字符型、字符串、布尔型。常量在程序执行期间保持不变。
Sequence, selection, and iteration are the three basic control structures. Selection uses IF, CASE statements. Iteration uses FOR (count‑controlled) or WHILE/REPEAT (condition‑controlled) loops.
顺序、选择和循环是三种基本控制结构。选择使用 IF、CASE 语句。循环使用 FOR（计数控制）或 WHILE/REPEAT（条件控制）循环。
Arrays are data structures that store multiple values of the same type under one name, accessed by indices (starting from 0 or 1 depending on language). Two‑dimensional arrays are like tables.
数组是存储多个相同类型值的数据结构，使用一个名称并通过索引访问（索引从 0 或 1 开始取决于语言）。二维数组类似表格。
Procedures and functions are reusable blocks of code. A function returns a value; a procedure does not. Parameters allow passing data into them.
过程和函数是可重用的代码块。函数返回一个值；过程不返回值。参数允许向它们传递数据。
Example pseudocode: IF age > 17 THEN OUTPUT "Adult" ELSE OUTPUT "Child".
伪代码示例：IF age > 17 THEN OUTPUT "Adult" ELSE OUTPUT "Child"。
10. Databases | 数据库
A database is an organised collection of data. Relational databases store data in tables (relations) with rows (records) and columns (fields).
数据库是有组织的数据集合。关系数据库将数据存储在表（关系）中，表由行（记录）和列（字段）构成。
Each table has a primary key – a field that uniquely identifies each record. A foreign key links to the primary key of another table to establish relationships.
每个表有一个主键——唯一标识每条记录的字段。外键链接到另一张表的主键，以建立关系。
SQL (Structured Query Language) is used to manage databases. Common commands: SELECT (retrieve data), INSERT INTO (add records), UPDATE (modify data), DELETE (remove records).
SQL（结构化查询语言）用于管理数据库。常用命令：SELECT（检索数据）、INSERT INTO（添加记录）、UPDATE（修改数据）、DELETE（删除记录）。
Example SQL query to select all students aged 16: SELECT * FROM Students WHERE Age = 16;
示例 SQL 查询，选择所有 16 岁学生：SELECT * FROM Students WHERE Age = 16;
Data validation ensures that data entered is sensible (range check, type check, presence check). Verification ensures data matches the original source (double entry, proofreading).
数据验证确保输入的数据是合理的（范围检查、类型检查、存在检查）。数据证实确保数据与原始来源一致（双重录入、校对）。
11. Ethics and Legal Issues | 伦理与法律问题
Computer systems bring ethical concerns: plagiarism (copying others' work without attribution), hacking (unauthorised access), and digital divide (inequality in access to technology).
计算机系统带来伦理问题：抄袭（未经注明复制他人作品）、黑客攻击（未授权访问）和数字鸿沟（技术获取不平等）。
Data protection laws (e.g., GDPR, DPA) require organisations to process personal data fairly, lawfully, and securely. Individuals have rights to access and correct their data.
数据保护法（如 GDPR、DPA）要求组织公平、合法、安全地处理个人数据。个人有权访问和更正自己的数据。
Computer Misuse Act criminalises unauthorised access, unauthorised modification, and related offences. Copyright law protects software, music, and other creative works.
《计算机滥用法》将未授权访问、未授权修改及相关行为定为犯罪。版权法保护软件、音乐和其他创作作品。
Artificial intelligence and automation raise questions about job displacement and algorithmic bias. Responsible computing stresses fairness, transparency, and accountability.
人工智能和自动化引发了关于岗位替代和算法偏见的质疑。负责任的计算机技术强调公平性、透明性和可问责性。
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