Core Knowledge Revision for Year 11 Edexcel Computer Science | Year 11 Edexcel 计算机核心知识点梳理

📚 Core Knowledge Revision for Year 11 Edexcel Computer Science | Year 11 Edexcel 计算机核心知识点梳理

This revision guide brings together the essential topics you need to master for the Edexcel GCSE Computer Science exam. It covers computer systems, data representation, networks, programming, algorithms, and the wider impact of technology. Each section pairs concise English explanations with Chinese versions to support bilingual learners and reinforce understanding of key concepts.

这份复习指南汇总了Edexcel GCSE计算机科学考试必须掌握的核心主题。涵盖计算机系统、数据表示、网络、编程、算法以及技术的影响。每个小节都用简洁的英文解释配以中文翻译，帮助双语学习，加深对关键概念的理解。

1. Computer Systems and Architecture | 计算机系统与架构

The central processing unit (CPU) is the ‘brain’ of the computer. It carries out the fetch-decode-execute cycle, repeatedly fetching an instruction from memory, decoding it to work out what is required, and then executing it. Key components include the control unit (CU), the arithmetic logic unit (ALU), and several registers.

中央处理器(CPU)是计算机的“大脑”。它执行“取指-解码-执行”周期，不断从内存中取出指令，解码以明确要求，然后执行。核心部件包括控制单元(CU)、算术逻辑单元(ALU)以及多个寄存器。

The main registers are the program counter (PC) holding the address of the next instruction, the memory address register (MAR) and memory data register (MDR) for accessing memory, the current instruction register (CIR), and the accumulator (ACC) for intermediate results. All these work together under the Von Neumann architecture, where program instructions and data share the same memory.

主要寄存器包括：存放下一指令地址的程序计数器(PC)，用于访问内存的内存地址寄存器(MAR)和内存数据寄存器(MDR)，当前指令寄存器(CIR)以及存放中间结果的累加器(ACC)。它们都在冯·诺依曼架构下协同工作，该架构中程序指令和数据共用同一内存。

CPU performance is influenced by clock speed (how many cycles per second, measured in Hz), the number of cores (allowing multiple instructions to be processed simultaneously), and cache size (fast memory close to the CPU that reduces the need to fetch from slower main memory).

CPU性能受时钟速度(每秒执行多少个周期，单位为Hz)、内核数量(允许多条指令同时处理)和缓存大小(靠近CPU的快速内存，减少从较慢主存取指令的需求)的影响。

2. Memory and Storage | 内存与存储

Primary memory consists of RAM (random access memory) and ROM (read-only memory). RAM is volatile — it loses all data when power is turned off — and holds the operating system, programs, and data that are currently in use. ROM is non-volatile and usually stores the boot program (BIOS) needed to start the computer.

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——断电后所有数据丢失——它保存当前正在使用的操作系统、程序和数据。ROM是非易失性的，通常存储启动计算机所需的引导程序(BIOS)。

RAM	随机存取存储器
Volatile	易失性
Read and write	可读写
Larger capacity than ROM	容量比ROM大
Holds currently running programs and data	存放当前运行的程序和数据

ROM	只读存储器
Non-volatile	非易失性
Read-only (or difficult to write to)	只读(或很难写入)
Small capacity	容量小
Stores firmware / boot instructions	存放固件/启动指令

Virtual memory allows the computer to use part of secondary storage as if it were RAM when main memory is full. However, accessing virtual memory is much slower and can lead to disk thrashing.

虚拟内存允许计算机在主存不足时将部分辅助存储器当作RAM使用。但访问虚拟内存速度慢得多，并可能造成磁盘抖动。

Secondary storage devices (magnetic, solid-state, optical) provide long-term, non-volatile storage. Capacity and speed vary: solid-state drives (SSDs) are faster and more robust than magnetic hard disks, while optical discs (CD, DVD) are portable but have lower capacity.

辅助存储设备(磁性、固态、光学)提供长期的非易失性存储。容量和速度各异：固态硬盘(SSD)比磁硬盘更快、更耐用，光盘(CD、DVD)便携但容量较小。

3. Data Representation | 数据表示

Computers use binary (base-2) to represent all data. Denary (base-10) numbers are converted using place values: for example, 8 4 2 1. Denary 13 = 1101₂. Binary addition follows similar rules to denary: 0+0=0, 1+0=1, 1+1=10₂ (carry 1), 1+1+1=11₂.

计算机使用二进制(基2)表示所有数据。十进制(基10)借助位权转换：例如8 4 2 1。十进制13 = 1101₂。二进制加法类似十进制：0+0=0, 1+0=1, 1+1=10₂(进1), 1+1+1=11₂。

1011₂ + 0110₂ = 10001₂

Hexadecimal (base-16) uses digits 0–9 and letters A–F, making binary shorter and easier to read. One hex digit represents four bits. For instance, 1101 1010₂ is DA₁₆. Binary shifts move bits left (multiply by 2) or right (divide by 2).

十六进制(基16)使用0–9和A–F，让二进制表示更短、更易读。一位十六进制数字代表四个二进制位。例如，1101 1010₂ = DA₁₆。二进制移位向左(乘2)或向右(除2)。

Text is represented using character sets: ASCII uses 7 or 8 bits per character, covering basic English letters and symbols. Unicode allows many more characters for international scripts and emojis, but requires more bits per character.

文本使用字符集表示：ASCII每个字符7或8位，覆盖基本英文字母符号。Unicode可表示更多字符，支持各国文字和表情符号，但每个字符需更多位。

Images are made of pixels; each pixel’s colour is stored as a binary value. Colour depth (bits per pixel) determines how many colours can be represented — e.g., 8-bit = 256 colours, 24-bit ≈ 16.7 million colours. Resolution (total pixel count) affects sharpness and file size.

图像由像素组成，每个像素的颜色存储为二进制值。颜色深度(每像素位数)决定可表示的颜色数——例如8位=256色，24位≈1670万色。分辨率(总像素数)影响清晰度和文件大小。

Image file size (bits) = width in pixels × height in pixels × colour depth (bits)

图像文件大小(位) = 宽度(像素) × 高度(像素) × 颜色深度(位)

Sound is captured by taking samples of an analogue signal at regular intervals. Sample rate (Hz) and bit depth affect quality and file size. Higher sample rate captures higher frequencies; greater bit depth gives more dynamic range.

声音通过定期对模拟信号采样来捕获。采样率(Hz)和采样位数影响质量和文件大小。采样率越高越能捕获高频音；采样位数越大动态范围越广。

Sound file size (bits) = sample rate (Hz) × bit depth × duration (s) × channels

声音文件大小(位) = 采样率(Hz) × 采样位数 × 时长(秒) × 声道数

Compression reduces file size. Lossless compression (e.g., run-length encoding, Huffman coding) allows perfect reconstruction; lossy compression (e.g., JPEG, MP3) permanently discards some data to achieve smaller sizes, acceptable when the loss is imperceptible.

压缩可减小文件体积。无损压缩(如游程编码、哈夫曼编码)能完整还原；有损压缩(如JPEG、MP3)会永久丢弃部分数据以换取更小体积，当丢失不易察觉时是可接受的。

4. Networks and Topologies | 网络与拓扑

A network connects computers to share resources and communicate. A LAN (local area network) covers a small geographical area, usually with owned infrastructure; a WAN (wide area network) spans large distances, often using leased telecommunication links.

网络连接计算机以共享资源和通信。局域网(LAN)覆盖较小地理区域，设施通常自建；广域网(WAN)跨越长距离，常租用电信链路。

Client-server networks have a central server providing services (file storage, email, web) to clients. Peer-to-peer (P2P) networks allow each device to share resources directly, with no central server. Client-server offers easier management and backup; P2P is simpler and cheaper but less secure.

客户-服务器网络由中央服务器为客户提供文件、邮件、网页等服务。对等网络(P2P)没有中央服务器，每台设备直接共享资源。客户-服务器更容易管理和备份；P2P更简单、更便宜但安全性较差。

Common topologies: star topology connects all nodes to a central switch or hub — failure of one cable does not affect others, but the central device is a single point of failure. Mesh topology connects every node to many others, giving high redundancy but high cabling cost.

常见拓扑：星型拓扑将所有节点连到中央交换机或集线器——某条电缆故障不影响其他节点，但中央设备是单点故障；网状拓扑每个节点与多个节点直连，冗余高但布线成本高。

Network hardware: NIC (network interface card) provides physical connection; switches send data only to the intended recipient; routers connect different networks and forward data packets using IP addresses; wireless access points (WAPs) allow Wi-Fi connection.

网络硬件：网卡(NIC)提供物理连接；交换机只将数据发到目标设备；路由器连接不同网络并基于IP地址转发数据包；无线接入点(WAP)提供Wi-Fi连接。

Protocols are sets of rules governing communication. The TCP/IP stack groups protocols into layers: application (e.g., HTTP, FTP, SMTP), transport (TCP), internet (IP), and link (Ethernet, Wi-Fi). Each layer provides services to the one above it, aiding independent development.

协议是通信的规则集合。TCP/IP协议栈将协议分为层：应用层(如HTTP、FTP、SMTP)、传输层(TCP)、互联网层(IP)、链路层(以太网、Wi-Fi)。每层为上层提供服务，便于独立开发。

5. Network Security | 网络安全

Common threats include malware (viruses, worms, trojans) that disrupt or damage systems; social engineering and phishing attacks that trick users into revealing credentials; brute-force attacks that try many password combinations; denial-of-service (DoS) attacks that overwhelm a server; and SQL injection that exploits poorly secured databases.

常见威胁包括：恶意软件(病毒、蠕虫、木马)破坏系统；社会工程和钓鱼攻击诱骗用户泄露凭证；暴力破解尝试众多密码组合；拒绝服务(DoS)攻击使服务器瘫痪；SQL注入利用不安全的数据库。

Protection methods: firewalls filter incoming and outgoing traffic based on rules; encryption (e.g., SSL/TLS) scrambles data so only authorised parties can read it; anti-malware software detects and removes malicious code; user access levels limit what different users can do; regular penetration testing identifies weaknesses before attackers do.

防护方法：防火墙按规则过滤进出流量；加密(如SSL/TLS)扰乱数据使只有授权方可读；反恶意软件检测并删除恶意代码；用户访问级别限制不同用户的操作；定期渗透测试在攻击者之前发现弱点。

6. Systems Software | 系统软件

The operating system (OS) manages hardware, runs applications, and provides a user interface. Its main roles are memory management, processor scheduling, file management, and handling input/output operations. It also provides security features such as user authentication.

操作系统(OS)管理硬件、运行应用并提供用户界面。其主要职责包括内存管理、处理器调度、文件管理以及输入/输出处理。它还提供用户认证等安全特性。

Utility software performs maintenance tasks: encryption utilities protect data; defragmentation reorganises fragmented files on magnetic hard disks to improve access speed; compression tools reduce file sizes; backup software automates data copies to prevent loss.

实用软件执行维护任务：加密实用程序保护数据；碎片整理重组磁硬盘上的碎片文件以提升访问速度；压缩工具缩小文件体积；备份软件自动复制数据以防丢失。

7. Ethical, Legal, Cultural and Environmental Issues | 伦理、法律、文化与环境影响

The Data Protection Act (2018) governs how personal data is collected, stored, and used, giving individuals rights to access and correct their data. The Computer Misuse Act (1990) makes unauthorised access, modification, and creation of malware illegal.

数据保护法(2018)规范个人数据的收集、存储和使用，赋予个人访问和更正数据的权利。计算机滥用法(1990)将未经授权访问、修改数据以及制作恶意软件定为非法。

Copyright law protects original work; software licences (proprietary, open source, freeware) dictate how software can be used. Open-source software allows users to view and modify the source code, while proprietary software restricts it.

版权法保护原创作品；软件许可(专有、开源、自由软件)规定软件的使用方式。开源软件允许查看和修改源代码，专有软件则加以限制。

The digital divide refers to the gap between those who have access to digital technology and the internet and those who do not, often due to economic, geographical, or educational barriers. Stakeholders must consider inclusivity when designing technology.

数字鸿沟指能够访问数字技术和互联网的人群与不能访问的人群之间的差距，通常由经济、地理或教育障碍造成。利益相关者在设计技术时必须考虑包容性。

Environmental impact: manufacturing devices consumes resources and energy; disposal creates e-waste containing toxic materials. Companies are encouraged to design for repairability, recycling, and energy efficiency.

环境影响：制造设备消耗资源和能源；废弃处理产生含有毒物质的电子垃圾。鼓励企业设计可维修、可回收和节能的产品。

8. Algorithms and Computational Thinking | 算法与计算思维

Computational thinking involves decomposition (breaking down a complex problem into smaller parts), pattern recognition, abstraction (removing unnecessary detail), and algorithmic thinking (creating a step-by-step solution). Flowcharts and pseudocode are standard ways to represent algorithms before coding.

计算思维包括分解(将复杂问题拆分为小部分)、模式识别、抽象(去除不必要细节)和算法思维(制定分步解决方案)。流程图和伪代码是在编程前表示算法的标准方式。

Searching algorithms: linear search checks each item in a list until the target is found; simple but inefficient for large datasets. Binary search repeatedly divides a sorted list in half, comparing the middle item to the target — much faster with O(log n) complexity, but requires sorted data.

搜索算法：线性搜索逐一检查列表中的项目直至找到目标；简单但大数据集效率低。二分搜索将已排序列表不断对半分，比较中间项与目标——时间复杂度为O(log n)，快得多，但要求数据已排序。

Sorting algorithms: bubble sort compares adjacent elements and swaps them if out of order, repeating until sorted;

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Core Knowledge Revision for Year 11 Edexcel Computer Science | Year 11 Edexcel 计算机核心知识点梳理