📚 Year 11 OCR Computer Science: Summer Bridging Course | Year 11 OCR 计算机暑期预习与衔接课程
Welcome to your Year 11 OCR Computer Science summer bridging guide. This resource is designed to strengthen your Year 10 foundations and introduce key Year 11 topics, ensuring you start the academic year with confidence.
欢迎使用 Year 11 OCR 计算机科学暑期衔接指南。本资源旨在巩固 Year 10 基础并介绍关键 Year 11 主题，确保你自信地开始新学年。
1. Revising CPU and Memory Fundamentals | 复习 CPU 与存储器基础
The CPU architecture comprises the Control Unit (CU), Arithmetic Logic Unit (ALU), and a set of registers including the Program Counter (PC), Memory Address Register (MAR), Memory Data Register (MDR), and Accumulator (ACC).
CPU 体系结构由控制单元 (CU)、算术逻辑单元 (ALU) 以及一组寄存器组成，包括程序计数器 (PC)、存储器地址寄存器 (MAR)、存储器数据寄存器 (MDR) 和累加器 (ACC)。
The fetch-decode-execute cycle is the process through which the processor retrieves an instruction from memory, translates it, and carries out the required operation.
取指-解码-执行周期是处理器从内存中取出指令、翻译指令并执行所需操作的过程。
Primary memory is divided into RAM (volatile, working memory) and ROM (non-volatile, stores boot instructions).
主存储器分为 RAM（易失性，工作内存）和 ROM（非易失性，存储启动指令）。
The concept of cache memory, located closer to the CPU, speeds up data access by storing frequently used instructions.
高速缓存位于更靠近 CPU 的位置，通过存储常用指令来加快数据访问速度。
2. Data Representation & Compression | 数据表示与压缩
Images are represented as a grid of pixels, where each pixel’s colour is stored as a binary value; the colour depth (bits per pixel) determines the number of available colours.
图像以像素网格表示，每个像素的颜色以二进制值存储；颜色深度（每像素位数）决定了可用颜色数量。
An image’s file size can be calculated using: File Size = Width × Height × Colour Depth (bits).
图像文件大小可用公式计算：文件大小 = 宽度 × 高度 × 颜色深度（位）。
Sound is sampled at regular intervals; the sample rate (Hz) and bit depth influence the quality and size of the audio file.
声音按固定间隔采样；采样率 (Hz) 和位深度影响音频文件的质量和大小。
Lossless compression (e.g., run-length encoding) reduces file size without losing any data, while lossy compression (e.g., JPEG, MP3) removes some data that is less perceptible.
无损压缩（如行程编码）可在不丢失任何数据的情况下减小文件大小，而有损压缩（如 JPEG、MP3）会移除一些不易察觉的数据。
3. Networks and Protocols Refresher | 网络与协议回顾
A network can be classified as a LAN (Local Area Network) covering a small geographical area, or a WAN (Wide Area Network) spanning large distances.
网络可分为覆盖小范围的局域网 (LAN) 和跨越长距离的广域网 (WAN)。
The TCP/IP stack is a layered protocol suite: Application, Transport, Internet, and Link layers, enabling reliable communication over the internet.
TCP/IP 协议栈是分层协议套件：应用层、传输层、互联网层和链路层，可实现互联网上可靠通信。
Protocols such as HTTP/HTTPS (web), FTP (file transfer), SMTP/IMAP (email), and Ethernet (wired connectivity) define rules for data exchange.
HTTP/HTTPS（网页）、FTP（文件传输）、SMTP/IMAP（电子邮件）和以太网（有线连接）等协议定义了数据交换的规则。
Packet switching breaks data into packets that travel independently and are reassembled at the destination; each packet includes a header with source and destination addresses.
分组交换将数据分割为独立传输的数据包，并在目的地重新组装；每个数据包包含带有源地址和目的地址的头部。
4. System Security Threats & Prevention | 系统安全威胁与防御
Malware encompasses viruses, worms, trojans, ransomware, and spyware, each designed to disrupt, damage, or gain unauthorised access to systems.
恶意软件包括病毒、蠕虫、特洛伊木马、勒索软件和间谍软件，旨在破坏、损坏或未经授权访问系统。
Social engineering attacks, such as phishing and pretexting, manipulate individuals into revealing confidential information.
社会工程攻击，如网络钓鱼和借口欺诈，操纵个人泄露机密信息。
Preventive measures include firewalls (filter incoming and outgoing traffic), anti-malware software, encryption, penetration testing, and regular software updates.
预防措施包括防火墙（过滤进出流量）、反恶意软件、加密、渗透测试和定期软件更新。
SQL injection is a code injection technique that exploits vulnerable input fields to manipulate a database; input validation and parameterised queries can prevent it.
SQL 注入是一种代码注入技术，利用脆弱的输入字段操纵数据库；输入验证和参数化查询可以防止它。
5. Ethical, Legal, Cultural and Environmental Issues | 伦理、法律、文化与环境影响
The UK’s Computer Misuse Act 1990 criminalises unauthorised access to computer material, unauthorised modification, and the creation of malware.
英国《1990年计算机滥用法》将未经授权访问计算机资料、未经授权修改及制造恶意软件定为刑事犯罪。
The Data Protection Act 2018 (incorporating GDPR) governs the collection, processing, and storage of personal data, requiring consent and the right to erasure.
《2018年数据保护法》（包含 GDPR）管理个人数据的收集、处理和存储，要求同意和删除权。
Copyright, Designs and Patents Act 1988 protects intellectual property in software, music, and images, making unlicensed copying illegal.
《1988年版权、设计和专利法》保护软件、音乐和图像中的知识产权，将未经许可的复制定为非法。
Cultural and environmental factors include the digital divide (unequal access to technology), e-waste, and the energy consumption of data centres.
文化和环境因素包括数字鸿沟（技术获取不均等）、电子废物和数据中心的能源消耗。
6. Algorithms: Searching and Sorting | 算法：搜索与排序
Linear search scans each element of a list sequentially until the target is found; it works on unsorted data with a worst-case time complexity of O(n).
线性搜索按顺序扫描列表的每个元素直到找到目标；它适用于未排序数据，最坏情况时间复杂度为 O(n)。
Binary search repeatedly divides a
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