📚 Year 10 CAIE Computer Science: Core Concepts Review | Year 10 CAIE 计算机：核心知识点梳理
This article provides a structured overview of the core topics covered in Year 10 CAIE IGCSE Computer Science (0478). It is designed to help you consolidate key definitions, concepts, and processes that form the foundation of the syllabus. From how computers represent data to the design of algorithms and logic circuits, each section pairs concise English explanations with Chinese translations to support bilingual learning.
本文系统梳理了 Year 10 CAIE IGCSE 计算机科学（0478）的核心主题，旨在帮助你巩固构成课程基础的关键定义、概念和流程。从计算机如何表示数据，到算法与逻辑电路的设计，每个小节都以简洁的英文解释配中文翻译的形式呈现，以支持双语学习。
1. Data Representation | 数据表示
Computers use binary (base‑2) to represent all data. The smallest unit is a bit (0 or 1), and 8 bits make a byte. Numbers can be represented as unsigned binary, two's complement, or floating‑point. Characters are encoded using character sets such as ASCII (7‑bit) and Unicode.
计算机使用二进制（基数为2）表示所有数据。最小单位是比特（0或1），8个比特组成一个字节。数字可以用无符号二进制、二进制补码或浮点数表示。字符则使用如 ASCII（7位）和 Unicode 等字符集进行编码。
=1, and 1+1=0 carry 1. Overflow occurs when a result exceeds the available number of bits.
将十进制数转换为二进制，需反复除以2并记录余数。二进制加法规则为 0+0=0，0+1=1，1+0=1，1+1=0 进1。当运算结果超出可用位数时会发生溢出。
Hexadecimal (base‑ to 4 bits (nibble). Denary 26 becomes 1A in hex because 16+10 = 26, where A represents 10.
十六进制（基数为16）通常被用作二进制的简写表示。每个十六进制数字对应4个比特（半字节）。十进制26在十六进制中为 1A，因为 16+10=26，其中 A 表示 10。
Images can be stored as bitmaps or vector graphics. A bitmap image is a grid of pixels, each assigned a colour value. The colour depth (bits per pixel) determines the number of colours available. A colour depth of 24 bits allows over 16 million colours.
图像可以存储为位图或矢量图。位图图像是由像素组成的网格，每个像素分配一个颜色值。颜色深度（每像素比特数）决定了可用的颜色数量。24位颜色深度允许超过1600万种颜色。
Sound is captured by sampling the amplitude of a sound wave at regular intervals. The sample rate (measured in kHz) and bit depth (bits per sample) affect the quality and file size of a digital audio recording. High sample rates and larger bit depths produce better fidelity but require more storage.
声音通过对声波振幅进行固定间隔的采样来捕捉。采样率（以 kHz 为单位）和采样深度（每样本比特数）影响数字录音的质量和文件大小。高采样率和较大的采样深度能提供更好的保真度，但需要更多的存储空间。
Lossless compression reduces file size without losing any information, using techniques like run‑length encoding (RLE). Lossy compression permanently removes some data (e.g., MP3, JPEG), achieving much smaller files at the cost of quality.
无损压缩在不丢失任何信息的情况下减小文件大小，使用如游程编码（RLE）等技术。有损压缩则永久删除部分数据（如 MP3、JPEG），以牺牲质量为代价获得更小的文件。
File size (bits) = sample rate × bit depth × duration (seconds) × number of channels
文件大小（比特）= 采样率 × 采样深度 × 时长（秒）× 声道数
2. Computer Architecture | 计算机体系结构
The von Neumann architecture stores both program instructions and data in the same memory. It consists of a central processing unit (CPU), memory, input/output interfaces, and a system bus. The CPU contains the arithmetic logic unit (ALU), control unit (CU), and registers such as the program counter (PC), memory address register (MAR), memory data register (MDR), current instruction register (CIR), and accumulator (ACC).
冯·诺依曼架构将程序指令和数据存储在同一内存中。它由中央处理器（CPU）、存储器、输入/输出接口和系统总线组成。CPU 包含算术逻辑单元（ALU）、控制单元（CU）以及一些寄存器，如程序计数器（PC）、存储器地址寄存器（MAR）、存储器数据寄存器（MDR）、当前指令寄存器（CIR）和累加器（ACC）。
The fetch‑decode‑execute cycle is the process by which the CPU reads an instruction from memory, interprets it, and then carries out the required action. In the fetch stage, the PC supplies the address of the next instruction to the MAR; the instruction is then placed into the MDR and copied to the CIR.
取指‑译码‑执行周期是 CPU 从内存读取指令、解释指令并执行所需操作的过程。在取指阶段，PC 将下一条指令的地址送入 MAR；然后指令被放入 MDR，并复制到 CIR。
During the decode stage, the CU decodes the instruction in the CIR. In the execute stage, the ALU performs arithmetic or logic operations, and data may be moved between registers and memory. After execution, the PC is incremented to point to the next instruction.
在译码阶段，CU 对 CIR 中的指令进行译码。在执行阶段，ALU 执行算术或逻辑运算，数据可能在寄存器和内存之间移动。执行完毕后，PC 递增以指向下一条指令。
Factors affecting CPU performance include clock speed (measured in GHz), number of processor cores, and cache memory size. A higher clock speed means more cycles per second; multiple cores allow true parallel processing; larger cache reduces the time needed to access frequently used data.
影响 CPU 性能的因素包括时钟速度（以 GHz 为单位）、处理器核心数量和缓存大小。更高的时钟速度意味着每秒更多的周期；多个核心可实现真正的并行处理；更大的缓存可减少访问常用数据所需的时间。
Embedded systems are dedicated computer systems designed to perform a specific task within a larger device. Examples include microwave ovens, washing machine controllers, and car engine management systems. They often use microcontrollers that combine a CPU, memory, and I/O ports on a single chip.
嵌入式系统是为在较大设备中执行特定任务而设计的专用计算机系统。例如微波炉、洗衣机控制器和汽车发动机管理系统。它们通常使用微控制器，将 CPU、内存和 I/O 端口集成在单个芯片上。
3. Input and Output Devices | 输入输出设备
Input devices allow users to enter data or commands into a computer. Common examples include keyboards (text entry), mice (pointer control), touchscreens (direct interaction), microphones (audio input), scanners (digitising documents), and sensors (measuring physical quantities such as temperature, light, and motion).
输入设备允许用户将数据或命令输入计算机。常见例子包括键盘（文本输入）、鼠标（指针控制）、触摸屏（直接交互）、麦克风（音频输入）、扫描仪（文档数字化）以及传感器（测量温度、光线和运动等物理量）。
to a preset threshold and activates a heater if needed. This forms a feedback loop: input → process → output.
传感器广泛应用于自动控制系统中。温室中的温度传感器将读数发送给计算机，计算机将值与预设阈值进行比较，必要时启动加热器。这形成了一个反馈回路：输入 → 处理 → 输出。
Output devices display or present data from a computer. Monitors (LCD/LED) produce visual output; printers produce hard copies; speakers and headphones output sound; actuators (such as motors) convert signals into mechanical motion.
输出设备显示或呈现来自计算机的数据。显示器（LCD/LED）产生视觉输出；打印机产生硬拷贝；扬声器和耳机输出声音；执行器（如电机）将信号转换为机械运动。
Inkjet printers spray tiny droplets of ink onto paper and are suitable for high‑quality colour images. Laser printers use toner and a heated fuser, offering faster speeds and lower cost per page for high‑volume text printing.
喷墨打印机将微小的墨滴喷射到纸张上，适合高质量的彩色图像。激光打印机使用碳粉和加热定影器，对于大量文本打印，具有更快的速度和更低的单页成本。
4. Memory and Storage | 内存与存储
Primary memory is directly accessible by the CPU. RAM (Random Access Memory) is volatile, meaning it loses its contents when power is turned off. It holds the operating system, applications, and data currently in use. ROM (Read Only Memory) is non‑volatile and stores firmware such as the BIOS/bootloader.
主存储器可由 CPU 直接访问。RAM（随机存取存储器）是易失性的，意味着断电后会丢失内容。它保存当前在用的操作系统、应用程序和数据。ROM（只读存储器）是非易失性的，存储诸如 BIOS/引导加载程序等固件。
Secondary storage provides long‑term, non‑volatile data retention. Magnetic storage (e.g., HDD) uses spinning platters and read/write heads. Solid‑state storage (e.g., SSD, USB flash drive) uses NAND flash memory with no moving parts, making it faster and more durable but often more expensive per gigabyte.
辅助存储提供长期、非易失的数据保存。磁性存储（如 HDD）使用旋转盘片和读写磁头。固态存储（如 SSD、USB 闪存驱动器）使用无移动部件的 NAND 闪存，速度更快、更耐用，但每 GB 成本通常更高。
Optical storage includes CDs (∼700 MB), DVDs (4.7 GB single‑layer), and Blu‑ray discs (25 GB single‑layer). Data is read by a laser beam detecting pits and lands. These are mainly used for distributing media and software.
光学存储包括 CD（约700 MB）、DVD（单层4.7 GB）和蓝光光盘（单层25 GB）。数据通过激光束检测凹坑和平面来读取。这些主要用于分发媒体和软件。
Cloud storage stores data on remote servers accessed via the internet. Advantages include accessibility from any location, automatic backup, and easy collaboration. Disadvantages include reliance on an internet connection and potential security and privacy concerns.
云存储将数据存储于可通过互联网访问的远程服务器上。优点包括可从任何地点访问、自动备份和方便协作。缺点包括依赖互联网连接以及潜在的安全和隐私问题。
5. Networks and the Internet | 网络与互联网
A network connects two or more computing devices to share resources and communicate. LANs (Local Area Networks) cover a small geographical area, such as a school or building, and typically use Ethernet or Wi‑Fi. WANs (Wide Area Networks) span large distances, such as the internet, and often use leased telecommunications lines.
网络连接两个或多个计算设备以共享资源和进行通信。局域网（LAN）覆盖较小的地理区域，如学校或建筑物，通常使用以太网或 Wi‑Fi。广域网（WAN）跨越远距离，如互联网，通常使用租用的电信线路。
Network hardware includes routers, switches, hubs, and network interface cards (NICs). A router forwards data packets between networks using IP addresses. A switch connects devices in a LAN and forwards data only to the intended recipient port based on MAC addresses.
网络硬件包括路由器、交换机、集线器和网络接口卡（NIC）。路由器使用 IP 地址在网络之间转发数据包。交换机连接局域网内的设备，并根据 MAC 地址仅将数据转发到目标端口。
IP addresses uniquely identify devices on a network. IPv4 uses 32‑bit addresses written as four dotted decimal numbers (e.g., 192.168.1.1). IPv6 uses 128‑bit addresses to overcome IPv4 exhaustion. MAC addresses are 48‑bit unique identifiers assigned to NIC hardware, usually displayed as six pairs of hex digits.
IP 地址唯一标识网络上的设备。IPv4 使用32位地址，写为四个点分十进制数（如 192.168.1.1）。IPv6 使用128位地址以克服 IPv4 地址枯竭问题。MAC 地址是分配给 NIC 硬件的48位唯一标识符，通常显示为六对十六进制数字。
Protocols are agreed rules for communication. Key internet protocols include HTTP/HTTPS (web browsing), FTP (file transfer), SMTP (sending email), POP3/IMAP (receiving email), and TCP/IP, which divides data into packets and ensures reliable delivery.
协议是一致同意的通信规则。主要的互联网协议包括 HTTP/HTTPS（网页浏览）、FTP（文件传输）、SMTP（发送电子邮件）、POP3/IMAP（接收电子邮件）以及 TCP/IP，后者将数据分成数据包并确保可靠传递。
6. Cyber Security | 网络安全
Malware is malicious software designed to damage or gain unauthorised access to a system. Viruses attach themselves to legitimate files and spread when these files are executed. Worms self‑replicate over networks without user intervention. Trojan horses disguise themselves as useful software but carry a malicious payload.
恶意软件是旨在破坏或未经授权访问系统的恶意软件。病毒附着在合法文件上，并在这些文件被执行时传播。蠕虫无需用户干预即可通过网络自我复制。特洛伊木马伪装成有用的软件，但携带恶意负载。
Phishing involves sending fraudulent emails or messages that appear to be from reputable sources to trick recipients into revealing personal information like passwords and bank details. Spear‑phishing targets specific individuals or organisations with personalised messages.
网络钓鱼涉及发送看似来自信誉良好来源的欺诈性电子邮件或信息，诱骗收件人泄露密码和银行详细信息等个人信息。鱼叉式钓鱼则使用个性化信息针对特定的个人或组织。
Brute‑force attacks try every possible combination of characters to guess a password. Dictionary attacks use a list of common words and phrases. To protect against these, systems enforce strong password policies, account lockouts, and multi‑factor authentication.
暴力攻击尝试所有可能的字符组合来猜测密码。字典攻击使用常见单词和短语的列表。为了防范这些攻击，系统会强制执行强密码策略、账户锁定和多因素身份验证。
Denial of Service (DoS) attacks flood a server with traffic to overwhelm it and prevent legitimate users from accessing a service. A Distributed DoS (DDoS) uses many compromised computers (a botnet) to launch the attack simultaneously. Firewalls and intrusion detection systems can help mitigate such threats.
拒绝服务（DoS）攻击通过向服务器发送大量流量来淹没服务器，阻止合法用户访问服务。分布式拒绝服务（DDoS）攻击使用许多被入侵的计算机（僵尸网络）同时发起攻击。防火墙和入侵检测系统可以帮助减轻此类威胁。
7. Logic Gates | 逻辑门
Logic gates are the fundamental building blocks of digital circuits. They accept binary inputs and produce a single binary output based on a logical operation. The six basic gates are NOT, AND, OR, NAND, NOR, and XOR.
逻辑门是数字电路的基本构建模块。它们接收二进制输入，并根据逻辑运算产生一个二进制输出。六种基本门有 NOT、AND、OR、NAND、NOR 和 XOR。
- NOT gate: Output is the inverse of the input. A single input A gives output Q = NOT A.
- NOT 门：输出是输入的反相。单一输入 A 产生输出 Q = NOT A。
- AND gate: Output is 1 only if all inputs are 1. For two inputs A and B, Q = A AND B.
- AND 门：仅当所有输入均为1时，输出才为1。对于两个输入 A 和 B，Q = A AND B。
- OR gate: Output is 1 if at least one input is 1. Q = A OR B.
- OR 门：如果至少有一个输入为1，则输出为1。Q = A OR B。
- NAND gate: Output is 0 only if all inputs are 1 (AND followed by NOT). Q = A NAND B.
- NAND 门：仅当所有输入均为1时，输出为0（AND 后接 NOT）。Q = A NAND B。
- NOR gate: Output is 1 only if all inputs are 0 (OR followed by NOT). Q = A NOR B.
- NOR 门：仅当所有输入均为0时，输出为1（OR 后接 NOT）。Q = A NOR B。
- XOR gate: Output is 1 if the inputs are different. For two inputs, Q = A XOR B.
- XOR 门：当输入不同时输出为1。对于两个输入，Q = A XOR B。
be evaluated by first determining NOT C, then A AND B, and finally ORing the two results.
真值表列出所有可能的输入组合及相应的输出。逻辑表达式如 Q = (A AND B) OR (NOT C)，可以通过先确定 NOT C，然后计算 A AND B，最后将两个结果进行 OR 运算来求值。
Logic circuits combine multiple gates to perform more complex operations. Half‑adders and full‑adders for binary addition are classic examples. A half‑adder uses an XOR gate for the sum and an AND gate for the carry.
逻辑电路组合多个门来执行更复杂的操作。用于二进制加法的半加器和全加器是经典例子。半加器使用一个 XOR 门产生和，使用一个 AND 门产生进位。
8. Algorithms and Flowcharts | 算法与流程图
An algorithm is a step‑by‑step procedure to solve a problem. Algorithms can be expressed in pseudocode, flowcharts, or program code. They must be precise, unambiguous, and eventually terminate.
算法是解决问题的一步一步的过程。算法可以用伪代码、流程图或程序代码表达。它们必须精确、无歧义且最终能够终止。
The three basic control structures are sequence, selection, and iteration. Sequence means executing instructions one after the other. Selection (e.g., IF…THEN…ELSE) makes decisions based on a condition. Iteration repeats a block of code; it can be definite (FOR loop) or indefinite (WHILE or REPEAT…UNTIL loop).
三种基本控制结构是顺序、选择和迭代。顺序指一条接一条地执行指令。选择（如 IF…THEN…ELSE）根据条件做出决策。迭代重复执行一段代码；可分为确定循环（FOR 循环）或非确定循环（WHILE 或 REPEAT…UNTIL 循环）。
Flowcharts use standard symbols: an oval for start/stop, a rectangle for a process, a diamond for a decision, and a parallelogram for input/output. Arrows indicate the flow of control.
流程图使用标准符号：椭圆表示开始/停止，矩形表示处理，菱形表示决策，平行四边形表示输入/输出。箭头指示控制流程。
Trace tables are used to test algorithms manually. They record the values of variables at each step, helping to identify logic errors. A well‑designed trace table has a column for each variable and a column for output.
跟踪表用于手动测试算法。它们记录每一步的变量值，有助于发现逻辑错误。设计精良的跟踪表为每个变量设置一列，并为输出设置一列。
9. Programming Concepts | 编程概念
Variables are named storage locations that hold data which can change during program execution. A variable has a data type, such as integer, real (float), Boolean, char, or string. Declaring a variable before use is a good practice to improve code clarity and aid debugging.
变量是具有名称的存储位置，用于保存程序执行期间可以更改的数据。变量具有数据类型，例如整型、实数型（浮点）、布尔型、字符型或字符串型。在使用前声明变量是一种良好的实践，可提高代码清晰度并有助于调试。
Arrays (lists) store multiple values of the same data type under a single identifier. Elements are accessed using an index, typically starting at 0 or 1 depending on the language. A one‑dimensional array can represent a list of marks; a two‑dimensional array can represent a grid or timetable.
数组（列表）在单个标识符下存储相同数据类型的多个值。元素通过索引访问，通常索引从0或1开始，视语言而定。一维数组可以表示成绩列表；二维数组可以表示网格或时间表。
Conditional statements allow branching. The simple IF…THEN…ELSE construct executes one block if a condition is true and another if it is false. Nested IF statements can handle multiple mutually exclusive conditions. CASE (or SWITCH) statements provide a cleaner way to test a variable against several constant values.
条件语句允许分支。简单的 IF…THEN…ELSE 结构在条件为真时执行一个代码块，条件为假时执行另一个代码块。嵌套 IF 语句可以处理多个互斥的条件。CASE（或 SWITCH）语句提供了一种更清晰的方式来根据多个常量值测试变量。
Count‑controlled loops (FOR loops) repeat a set number of times using a counter variable. Condition‑controlled loops (WHILE and REPEAT…UNTIL) repeat as long as a condition remains true (WHILE) or until a condition becomes true (REPEAT…UNTIL). Understanding the difference in when the condition is tested is crucial: WHILE tests at the start, REPEAT…UNTIL tests at the end.
次数控制循环（FOR 循环）使用计数器变量重复执行指定次数。条件控制循环（WHILE 和 REPEAT…UNTIL）只要条件保持为真（WHILE）或直到条件变为真（REPEAT…UNTIL）就重复执行。理解条件检查时机的区别至关重要：WHILE 在循环开始时检查，REPEAT…UNTIL 在循环结束时检查。
10. High‑Level and Low‑Level Languages | 高级与低级语言
High‑level languages (HLLs) such as Python, Java, and C# are designed to be easy for humans to read and write. They are machine‑independent, meaning one program can be compiled to run on different types of processors. HLLs use English‑like keywords and abstract away hardware details.
高级语言（HLL）如 Python、Java 和 C#，旨在方便人类阅读和编写。它们是独立于机器的，意味着同一个程序可以编译以在不同类型的处理器上运行。高级语言使用类似英语的关键字，并抽象化了硬件细节。
Low‑level languages are closer to the hardware. Machine code consists of binary patterns directly executed by the CPU. Assembly language uses mnemonics (e.g., LDA, STA, ADD) that map to machine code instructions. Each CPU architecture has its own assembly language.
低级语言更接近硬件。机器码由 CPU 直接执行的二进制模式组成。汇编语言使用助记符（如 LDA、STA、ADD），这些助记符映射到机器码指令。每种 CPU 架构都有自己的汇编语言。
Translators convert code from one language to another. A compiler translates the entire HLL source code into machine code in one go, producing an executable file. An interpreter translates and executes HLL code line by line, without producing a standalone executable. An assembler translates assembly language into machine code.
翻译程序将代码从一种语言转换为另一种语言。编译器一次性将整个高级语言源代码转换为机器码，生成可执行文件。解释器逐行翻译并执行高级语言代码，不生成独立的可执行文件。汇编器将汇编语言转换为机器码。
Compiled programs generally run faster because the translation occurs before execution. Interpreted programs are easier to debug and test, as errors can be reported line by line, but they run more slowly due to real‑time translation.
编译后的程序通常运行更快，因为翻译在执行前完成。解释型程序更易于调试和测试，因为错误可以逐行报告，但由于实时翻译，运行速度较慢。
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