📚 Year 10 OCR Computer Science: Core Knowledge Review | Year 10 OCR 计算机：核心知识点梳理
Welcome to the Year 10 OCR Computer Science core knowledge review. This guide covers the essential topics from both Component 01 (Computer Systems) and Component 02 (Computational Thinking, Algorithms and Programming). Mastering these fundamentals will help you build a solid foundation for your GCSE examinations and future studies.
欢迎阅读 Year 10 OCR 计算机科学核心知识点梳理。本指南涵盖了组件 01（计算机系统）和组件 02（计算思维、算法与编程）的核心主题。掌握这些基础知识将帮助你为 GCSE 考试及未来的学习打下坚实基础。
1. Systems Architecture | 系统架构
The Central Processing Unit (CPU) is the brain of the computer. It follows the fetch-decode-execute cycle repeatedly. The main components inside the CPU include the Control Unit (CU), which directs operations, the Arithmetic Logic Unit (ALU) that performs calculations and logical operations, and several special-purpose registers.
中央处理器（CPU）是计算机的大脑。它不断重复取指-译码-执行循环。CPU 内部的主要组件包括：控制单元（CU）负责指挥操作，算术逻辑单元（ALU）执行计算和逻辑操作，以及若干专用寄存器。
Key registers: Program Counter (PC) holds the address of the next instruction to fetch; Memory Address Register (MAR) holds the address of the memory location to be read from or written to; Memory Data Register (MDR) temporarily stores data fetched from or to be written to memory; Accumulator (ACC) stores intermediate results of ALU operations.
关键寄存器：程序计数器（PC）保存下一条要取指的指令地址；内存地址寄存器（MAR）保存待读写的内存单元地址；内存数据寄存器（MDR）暂时存放从内存读取或待写入内存的数据；累加器（ACC）存储 ALU 运算的中间结果。
The Von Neumann architecture stores both instructions and data in the same memory. The CPU fetches instructions one at a time, decodes them, and then executes them. The performance of the CPU is affected by clock speed (the number of cycles per second), number of cores, and cache memory size.
冯·诺依曼架构将指令和数据存储在同一内存中。CPU 每次取出一条指令，进行译码，然后执行。CPU 的性能受时钟速度（每秒周期数）、内核数量以及高速缓存大小的影响。
2. Memory and Storage | 内存与存储
Primary memory consists of RAM and ROM. RAM (Random Access Memory) is volatile, meaning it loses its data when the power is turned off. It holds the operating system, programs, and data currently in use. ROM (Read Only Memory) is non-volatile and typically stores the BIOS or boot firmware that starts the computer.
主存储器包括 RAM 和 ROM。RAM（随机存取存储器）是易失性的，断电后数据会丢失，它保存当前使用的操作系统、程序和数据。ROM（只读存储器）是非易失性的，通常存储启动计算机的 BIOS 或引导固件。
Virtual memory is a technique that uses a portion of the hard disk as if it were RAM. When RAM is full, the operating system swaps out less-used data to virtual memory, but this is much slower than RAM, leading to performance degradation if overused.
虚拟内存是一种将部分硬盘空间当作 RAM 来使用的技术。当 RAM 满时，操作系统会把不常用的数据交换到虚拟内存中，但这远慢于 RAM，如果过度使用会导致性能下降。
Secondary storage devices include magnetic (e.g., hard disk drive), optical (e.g., CD, DVD), and solid-state (e.g., SSD, USB flash drive). These are non-volatile and used for long-term data storage. They vary in capacity, speed, portability, durability, and cost.
二级存储设备包括磁性存储器（如硬盘）、光学存储器（如 CD、DVD）和固态存储器（如 SSD、USB 闪存盘）。它们都是非易失性的，用于长期数据存储。它们在容量、速度、便携性、耐用性和成本上有所差异。
3. Data Representation | 数据表示
All data inside a computer is represented using binary (base-2) digits, 0 and 1. Denary (base-10) numbers can be converted to binary, and vice versa. Hexadecimal (base-16) is a more human-friendly shorthand for binary, using digits 0-9 and letters A-F.
计算机中的所有数据都使用二进制（基数为 2）数位 0 和 1 来表示。十进制（基数为 10）数可与二进制相互转换。十六进制（基数为 16）是二进制的一种更便于人阅读的简写，使用数字 0-9 和字母 A-F。
Character sets such as ASCII (7-bit, 128 characters) and Unicode (multiple bytes, covers many languages and symbols) assign binary codes to characters. Images are often represented as bitmaps, where each pixel's colour is stored as a binary pattern; higher resolution and colour depth increase file size. Sound is sampled at regular intervals, and the binary values of each sample are stored; sampling rate and bit depth affect quality and size.
字符集如 ASCII（7 位，128 个字符）和 Unicode（多字节，涵盖多种语言和符号）为字符分配二进制代码。图像通常用位图表示，每个像素的颜色存储为二进制模式；分辨率和颜色深度越高，文件体积越大。声音按固定间隔采样，存储每个样本的二进制值；采样率和位深度影响质量和文件大小。
Compression reduces file sizes. Lossy compression (e.g., JPEG, MP3) permanently removes some data to achieve smaller sizes, while lossless compression (e.g., PNG, ZIP) reduces size without losing any data, allowing exact reconstruction.
压缩可减小文件大小。有损压缩（如 JPEG、MP3）通过永久丢弃部分数据来减小体积；无损压缩（如 PNG、ZIP）在减小体积的同时不丢失任何数据，可以精确还原。
4. Networks and Topologies | 网络与拓扑
A network is two or more computers connected together to share resources. LANs (Local Area Networks) cover a small geographical area, such as a school or office, while WANs (Wide Area Networks) connect LANs over large distances, like the Internet.
网络是由两台或多台连接在一起的计算机，用以共享资源。局域网（LAN）覆盖小范围地理区域，如学校或办公室；广域网（WAN）则跨大距离连接局域网，如互联网。
Networks can be organised as client-server, where a central server provides services and clients request them, or peer-to-peer (P2P), where each computer has equal status and can share resources directly. Common topologies include star (devices connected to a central switch), bus (all devices on a single backbone), and mesh (each device interconnected for redundancy).
网络可以组织为客户端-服务器模式（中央服务器提供服务，客户端请求服务）或点对点（P2P）模式（每台计算机地位平等，直接共享资源）。常见拓扑结构有星型（设备连接到中央交换机）、总线型（所有设备共用一条主干线）和网状（设备间互连以实现冗余）。
Protocols are rules for communication. The TCP/IP model has four layers: Application (e.g., HTTP, FTP, SMTP), Transport (TCP ensures reliable delivery), Internet (IP handles addressing and routing), and Link (physical transmission). IP addresses uniquely identify devices on a network, and MAC addresses are hardware identifiers.
协议是通信的规则。TCP/IP 模型包含四层：应用层（如 HTTP、FTP、SMTP）、传输层（TCP 确保可靠传输）、互联网层（IP 处理寻址与路由）和链路层（物理传输）。IP 地址唯一标识网络中的设备，MAC 地址则是硬件标识符。
5. Network Security | 网络安全
Network security threats include malware (viruses, worms, trojans, ransomware), social engineering attacks such as phishing (fraudulent emails that trick users into giving away personal data), brute-force attacks (trying many passwords), SQL injection (inserting malicious SQL code into a database query), and Denial of Service (DoS) attacks that flood a server with traffic.
网络安全威胁包括恶意软件（病毒、蠕虫、特洛伊木马、勒索软件），社会工程攻击如网络钓鱼（欺诈邮件诱骗用户泄露个人信息），暴力攻击（反复尝试密码），SQL 注入（在数据库查询中插入恶意 SQL 代码），以及拒绝服务（DoS）攻击（通过大量流量使服务器瘫痪）。
Prevention methods: firewalls filter traffic based on rules; encryption scrambles data so that only authorised parties can read it; antivirus software detects and removes malware; strong passwords and multi-factor authentication reduce unauthorised access; patches and software updates fix vulnerabilities. Biometrics and two-factor authentication add extra layers of security.
防御方法：防火墙根据规则过滤流量；加密将数据打乱，仅授权方可读取；反病毒软件检测并清除恶意软件；强密码和多因素认证降低未经授权访问的风险；补丁和软件更新修复漏洞。生物识别和双因素认证增加了额外的安全层。
6. System Software | 系统软件
System software manages hardware and provides a platform for applications.
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