📚 Year 10 Cambridge Computer Science: Core Knowledge Review | 核心知识点梳理
This article provides a structured revision of the key topics from the Cambridge IGCSE / O Level Computer Science syllabus for Year 10 students. It brings together essential theory and programming concepts to support exam preparation and deep learning.
本文为 Year 10 学生系统梳理了剑桥 IGCSE / O Level 计算机科学课程的核心知识点，将理论与编程重点浓缩提炼，帮助巩固理解、高效备考。
1. Computer Systems Architecture | 计算机系统体系结构
The Von Neumann architecture describes a stored-program computer where data and instructions share the same memory. Its central processing unit (CPU) contains an Arithmetic Logic Unit (ALU), a Control Unit (CU), and a set of registers. The ALU performs arithmetic and logical operations; the CU decodes instructions and coordinates data movement; registers provide fast, temporary storage inside the CPU.
冯·诺依曼体系架构描述了一种存储程序计算机，数据和指令共享同一内存。中央处理器 (CPU) 内包含算术逻辑单元 (ALU)、控制单元 (CU) 和一组寄存器。ALU 执行算术与逻辑运算；CU 负责指令解码并协调数据流；寄存器则在 CPU 内部提供高速的临时存储。
The fetch-decode-execute cycle is the fundamental process that drives the CPU. In the fetch step, an instruction is retrieved from memory via the address bus and placed in the instruction register. The control unit then decodes the instruction, determines what operation is required, and signals the relevant components to execute it.
取指-译码-执行周期是驱动 CPU 工作的基本流程。取指阶段，指令通过地址总线从内存取出并放入指令寄存器；控制单元随后对指令译码，确定所需的操作，并指挥相关部件执行。
Key registers include the Program Counter (PC) that holds the address of the next instruction, the Memory Address Register (MAR) and Memory Data Register (MDR) that interface with memory, the Current Instruction Register (CIR) for the instruction being executed, and the Accumulator (ACC) for temporary calculation results.
重要的寄存器有：程序计数器 (PC) 存放下一条指令地址；内存地址寄存器 (MAR) 和内存数据寄存器 (MDR) 负责与内存交互；当前指令寄存器 (CIR) 存放正在执行的指令；累加器 (ACC) 暂存计算结果。
2. Data Representation | 数据表示
All data in a computer is represented in binary, using only the digits 0 and 1. A single binary digit is called a bit; 8 bits make a byte. A group of 4 bits is a nibble, which maps directly to one hexadecimal digit. Multiples of bytes are named kibibyte (KiB), mebibyte (MiB), gibibyte (GiB), corresponding to powers of 2, while decimal prefixes like kilobyte (KB) refer to powers of 10.
计算机中所有数据都用二进制表示，只使用 0 和 1 两个数字。一个二进制位称为比特 (bit)；8 个比特组成 1 字节 (byte)。4 比特组成的一个半字节 (nibble) 恰好对应一位十六进制数。字节的倍数有 kibi、mebi、gibi 等，以 2 的幂次计算，而十进制前缀 KB、MB 等则以 10 的幂次计算。
Hexadecimal (base-16) uses digits 0–9 and letters A–F. It is a compact way to represent binary values. For example, 8-bit binary 1010 1100 becomes AC in hex. Conversion between binary and hex is done by splitting the binary into nibbles and replacing each with the equivalent hex digit.
十六进制（基数 16）使用 0–9 和 A–F。它是表达二进制值的简洁方式，例如 8 位二进制 1010 1100 可表示为十六进制 AC。二进制与十六进制的转换方法是将二进制从右向左每 4 位分成一组，每组替换为对应的十六进制数字。
Text is encoded using character sets such as ASCII (7-bit, 128 characters) and Unicode (which can represent characters from all major writing systems). Images are represented as a grid of pixels; each pixel’s colour is stored as a binary code. The number of bits per pixel (colour depth) determines how many colours can be displayed. Sound is digitised through sampling: the analogue sound wave is measured at regular intervals, and each sample is stored as a binary number; higher sampling rate and higher bit depth give better quality but larger file sizes.
文本通过字符集编码，如 ASCII（7 位，128 个字符）和 Unicode（可表示几乎所有书写系统的字符）。图像用像素网格表示，每个像素的颜色存储为二进制码；每个像素的位数（颜色深度）决定了可显示的颜色数。声音通过采样数字化：以固定间隔测量模拟声波，每个采样值存为二进制数；采样率越高、位深度越高，音质越好，但文件也越大。
3. Logic Gates and Logic Circuits | 逻辑门与逻辑电路
Logic gates are the building blocks of digital circuits. The six fundamental gates are AND, OR, NOT, NAND, NOR and XOR. An AND gate outputs 1 only when all inputs are 1; an OR gate outputs 1 when at least one input is 1; a NOT gate (inverter) flips the input. NAND and NOR are the opposites of AND and OR respectively. XOR (exclusive OR) gives 1 when the inputs are different.
逻辑门是数字电路的基本构件。六种基本门为：与门 (AND)、或门 (OR)、非门 (NOT)、与非门 (NAND)、或非门 (NOR) 和异或门 (XOR)。与门仅在全部输入为 1 时输出 1；或门至少一个输入为 1 时输出 1；非门将输入取反；与非和或非分别是与和或的相反；异或门在输入不同时输出 1。
A truth table lists all possible input combinations and the corresponding output. For a two-input AND gate, output = A AND B. In Boolean algebra this is written as A · B. OR is A + B, and NOT A is written as ¬A or A’. These expressions can be used to design and simplify logic circuits.
真值表列出所有可能的输入组合及对应输出。两输入与门的输出等于 A AND B，布尔表达式写作 A · B；或门是 A + B；非 A 写作 ¬A 或 A’。利用这些表达式可以设计和化简逻辑电路。
Logic circuits are created by combining gates. A half-adder adds two bits and produces a sum and a carry; a full-adder extends this by also taking a carry-in. These combinational circuits form the basis of the ALU’s arithmetic operations.
将逻辑门组合即可构成逻辑电路。半加器可将两个比特相加，产生和与进位；全加器还额外接收一个输入进位。这些组合电路构成了 ALU 算术运算的基础。
4. Memory and Storage | 存储器与存储设备
Primary memory consists of RAM and ROM. RAM (Random Access Memory) is volatile, meaning it loses its contents when power is turned off. It holds the operating system, programs and data currently in use. ROM (Read-Only Memory) is non-volatile and stores firmware such as the BIOS, which is needed to boot the computer.
主存储器包括 RAM 和 ROM。RAM（随机存取存储器）是易失性的，断电后内容会丢失，它保存正在使用的操作系统、程序和文件。ROM（只读存储器）是非易失性的，存储固件如 BIOS，是启动计算机所必需的。
Virtual memory uses a portion of the hard disk or SSD as an extension of RAM when the physical memory is full. It allows larger programs to run but is slower than actual RAM. Secondary storage devices include hard disk drives (HDD), solid-state drives (SSD), optical discs (CD, DVD, Blu-ray) and USB flash drives. SSDs are faster and more durable than HDDs because they have no moving parts.
虚拟内存利用硬盘或固态硬盘的一部分空间来扩展 RAM。当物理内存用满时，它让更大的程序得以运行，但速度比真实 RAM 慢。二级存储设备包括机械硬盘 (HDD)、固态硬盘 (SSD)、光盘 (CD、DVD、蓝光) 以及 USB 闪存盘。SSD 因无机械部件，比 HDD 更快、更耐用。
5. Input and Output Devices | 输入与输出设备
Input devices feed data into a computer. Manual devices require human interaction: keyboard, mouse, touch screen, microphone, scanner, webcam, joystick. Automatic devices sense the environment: barcode reader, QR scanner, magnetic stripe reader, sensors (temperature, light, pressure, motion). Touch screens function as both input and output.
输入设备将数据送入计算机。手动设备需要人工操作，如键盘、鼠标、触摸屏、麦克风、扫描仪、摄像头、游戏杆。自动设备则感知环境，例如条形码阅读器、二维码扫描仪、磁条阅读器、传感器（温度、光、压力、运动）。触摸屏兼具输入与输出功能。
Output devices present processed data to the user. Common examples are monitors (LCD, LED), projectors, printers (inkjet, laser, 3D), speakers, and actuators such as motors or LEDs. A screen’s quality can be described by its resolution (number of pixels) and colour depth.
输出设备将处理过的数据呈现给用户。常见例子有显示器（液晶、LED）、投影仪、打印机（喷墨、激光、3D）、音箱以及执行器如电机或 LED 灯。屏幕质量可用分辨率（像素数量）和颜色深度来衡量。
6. Software | 软件
System software manages the hardware and provides a platform for other software. The operating system (OS) is the most important system software; its functions include managing the user interface, memory, multitasking, peripherals, and file systems, as well as providing security and a platform for applications. Utilities are also system software: antivirus, backup, disk defragmentation and compression tools.
系统软件管理硬件并为其他软件提供平台。操作系统是最重要的系统软件；其功能包括管理用户界面、内存、多任务处理、外设、文件系统，并提供安全机制和应用程序运行环境。实用程序也属于系统软件，如杀毒软件、备份工具、磁盘碎片整理和压缩工具。
Translators convert high-level source code into machine code. A compiler translates the entire program at once, creating an executable file. An interpreter translates and executes one line at a time. Assembly language is translated by an assembler. Application software lets users perform specific tasks: word processors, spreadsheets, databases, web browsers, games and multimedia editing tools.
翻译器将高级源代码转换成机器码。编译器一次性翻译整个程序，生成可执行文件；解释器则逐行翻译并执行。汇编语言由汇编器翻译。应用软件让用户完成特定任务，如文字处理、电子表格、数据库、网页浏览器、游戏和多媒体编辑工具。
7. Networks and the Internet | 网络与互联网
A network connects two or more computers to share resources. Networks are classified by geographical size: LAN (Local Area Network) covers a small area like a school or office; WAN (Wide Area Network) spans a city, country or the globe, such as the Internet. Network hardware includes routers (direct data packets between networks), switches (connect devices within a LAN), network interface cards (NICs), wireless access points, and transmission media (twisted-pair copper cables, fibre optics, radio waves).
网络连接两台或多台计算机以共享资源。按地理范围分类：局域网 (LAN) 覆盖小区域如学校或办公室；广域网 (WAN) 跨越城市、国家或全球，例如互联网。网络硬件包括路由器（网络间转发数据包）、交换机（局域网内连接设备）、网卡 (NIC)、无线接入点以及传输介质（双绞铜线、光纤、无线电波）。
The Internet relies on protocols – sets of rules governing data transmission. TCP/IP is the fundamental suite: TCP breaks data into packets and reassembles them, while IP addresses and routes packets. HTTP/HTTPS transfers web pages, FTP transfers files, SMTP sends emails, and POP3/IMAP retrieve emails. Every device on a network has a Media Access Control (MAC) address, a unique identifier assigned to the NIC, and an IP address that identifies it on the network.
互联网依赖协议（数据通信的规则集合）。TCP/IP 是基础协议族：TCP 将数据分片并重组，IP 负责寻址及路由。HTTP/HTTPS 传输网页，FTP 传输文件，SMTP 发送邮件，POP3/IMAP 接收邮件。网络中每台设备都有 MAC 地址（网卡固化唯一标识）和 IP 地址（在网络中标识设备）。
A Uniform Resource Locator (URL) is a web address composed of a protocol (https://), a domain name (www.example.com), and optionally a path to a specific page. The Domain Name System (DNS) translates human-readable domain names into IP addresses so that browsers can load websites. The client-server model underpins most Internet services: a client requests data, and a server provides it.
统一资源定位符 (URL) 是网页地址，由协议 (https://)、域名 (www.example.com) 以及可选的路径组成。域名系统 (DNS) 将人类可读的域名转换为 IP 地址，供浏览器加载网站。客户端-服务器模式是互联网服务的基础：客户端请求数据，服务器响应并提供。
8. Cyber Security and Data Ethics | 网络安全与数据伦理
Threats to computer systems include malware (viruses, worms, Trojan horses, ransomware, spyware), phishing (deceptive emails to steal credentials), brute-force attacks (guessing passwords), Denial of Service (DoS) attacks that overwhelm servers, and social engineering that tricks users into giving away information.
计算机系统面临的威胁包括：恶意软件（病毒、蠕虫、木马、勒索软件、间谍软件）、钓鱼邮件（欺骗性邮件窃取凭证）、暴力攻击（猜测密码）、拒绝服务攻击导致服务器瘫痪，以及通过社会工程学诱骗用户泄露信息。
Protection measures include installing a firewall that filters incoming and outgoing traffic, using anti-malware software, keeping systems updated, encrypting sensitive data, implementing strong password policies, and enabling two-factor authentication (2FA). Organisations also apply data backup strategies and access controls.
防护措施有：安装防火墙过滤进出流量，使用反恶意软件，保持系统更新，加密敏感数据，执行强密码策略并启用双因素认证 (2FA)。组织还会实施数据备份和访问控制策略。
Ethical and legal considerations cover data privacy (personal data must be collected and processed lawfully), intellectual property rights (respecting copyright and software licences), and acceptable use policies. Computer-related laws include data protection acts and computer misuse acts that criminalise hacking and unauthorised access.
道德与法律考量涵盖数据隐私（须合法收集和处理个人信息）、知识产权（尊重版权与软件许可）以及合理使用政策。计算机相关法律包括数据保护法和惩治黑客入侵与未经授权访问的计算机滥用法。
9. 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 in pseudocode (structured plain English) or as a flowchart. Standard flowchart symbols include ovals for start/end, rectangles for processes, diamonds for decisions, and parallelograms for input/output.
算法是解决问题的分步骤过程，可用伪代码（结构化的自然语言）或流程图表达。流程图的常用符号：椭圆表示开始/结束，矩形表示处理步骤，菱形表示判断，平行四边形表示输入/输出。
The three basic programming constructs are sequence (steps executed in order), selection (branching using IF…THEN…ELSE), and iteration (looping). Definite iteration uses FOR…TO…NEXT with a known number of repetitions; indefinite iteration uses WHILE…DO…ENDWHILE or REPEAT…UNTIL depending on a condition.
三种基本编程结构是：顺序（按次序执行步骤）、选择（用 IF…THEN…ELSE 分支）和迭代（循环）。确定次数的循环用 FOR…TO…NEXT；条件控制的循环用 WHILE…DO…ENDWHILE 或 REPEAT…UNTIL。
Well-designed algorithms are tested with normal, boundary and erroneous data. Trace tables help step through an algorithm manually to verify its logic. Common algorithms studied at Year 10 include linear search, binary search, bubble sort and counting/totalling operations.
良好的算法需要用正常、边界和异常数据来测试。跟踪表可以手动走查算法以验证逻辑。Year 10 需掌握的常见算法包括线性搜索、二分搜索、冒泡排序以及计数/累加操作。
10. Programming Concepts | 编程基础概念
High-level programming languages use variables to store data. Common data types are integer (whole numbers), real/float (decimal numbers), char (single character), string (text), and boolean (TRUE/FALSE). Variables must be declared before use, often with meaningful identifiers following naming conventions.
高级编程语言使用变量存储数据。常见数据类型有：整数、实数/浮点数、字符、字符串和布尔值 (TRUE/FALSE)。变量使用前须声明，并遵循命名习惯给出有意义的标识符。
Programming structures implement selection and iteration. An IF statement tests a condition and executes a block of code if true; an ELSE clause provides an alternative. FOR loops repeat a block a specific number of times; WHILE loops repeat while a condition is true. Nested structures allow complex logic.
编程结构实现选择和迭代。IF 语句检测条件，为真时执行一段代码；ELSE 子句提供备用分支。FOR 循环将一段代码重复指定的次数；WHILE 循环在条件为真时重复。嵌套结构可以实现复杂的逻辑。
Procedures and functions are named blocks of code that can be called repeatedly. A procedure performs a task; a function performs a task and returns a value. Parameters allow data to be passed in; parameters can be passed by value (a copy) or by reference (the actual variable). Local variables exist only inside the subroutine; global variables are accessible throughout the program.
过程和函数是可重复调用的命名代码块。过程执行任务；函数执行任务并返回一个值。参数用于传递数据，可传值（传递副本）或传引用（传递实际变量）。局部变量仅在子程序内有效，全局变量可在整个程序中访问。
Arrays store multiple values of the same data type under one identifier. A one-dimensional array is like a list; a two-dimensional array resembles a table with rows and columns. Elements are accessed by an index, typically starting from 0. Arrays are used for lists of marks, names, or grid-based data.
数组用同一个标识符存储多个同类型值。一维数组类似列表，二维数组类似表格，通过行和列索引访问元素。下标通常从 0 开始。数组可用于保存成绩列表、姓名清单或网格数据。
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