📚 IB & Edexcel Computer Science: High-Frequency Exam Topics Summary | IB与Edexcel计算机科学高频考点总结
Understanding high-frequency exam topics is the key to effective revision for both IB and Edexcel Computer Science. This guide compiles the most commonly examined concepts, from system fundamentals to algorithm design, to help you focus your study and boost your exam performance.
理解高频考点是有效复习IB和Edexcel计算机科学的关键。本指南汇总了从系统基础到算法设计最常见的考查概念，帮助你集中复习，提升考试成绩。
1. Fundamentals of Computer Systems | 计算机系统基础
A computer system consists of hardware and software working together to process data. Hardware includes physical components like CPU, memory, and input/output devices, while software includes operating systems and applications.
计算机系统由协同处理数据的硬件和软件组成。硬件包括CPU、内存和输入/输出设备等物理组件，而软件则包括操作系统和应用程序。
Systems can be categorized as general-purpose (e.g., personal computers) or embedded systems (e.g., microcontrollers in appliances). Understanding the role of system software, such as utility programs and device drivers, is frequently tested.
系统可分为通用系统（如个人电脑）和嵌入式系统（如家电中的微控制器）。对系统软件（如实用程序和设备驱动程序）作用的理解常被考查。
Key exam topics include distinguishing between volatile and non-volatile memory (RAM vs ROM), and describing the function of the BIOS during booting.
关键考点包括区分易失性和非易失性存储器（RAM与ROM），以及描述BIOS在启动过程中的功能。
2. Data Representation & Storage | 数据表示与存储
All data in a computer is stored in binary. You must be able to convert between binary, denary, and hexadecimal. For example, the denary number 27 is represented as 00011011 in binary and 1B in hex.
计算机中所有数据都以二进制存储。你必须能够在二进制、十进制和十六进制之间转换。例如，十进制数27在二进制中表示为00011011，十六进制为1B。
27₁₀ = 11011₂ = 1B₁₆
Character encoding schemes like ASCII and Unicode map characters to numeric codes. ASCII uses 7 or 8 bits, while Unicode can use up to 32 bits to represent a vast range of symbols. Exams often ask about storage size calculations for text files.
字符编码方案如ASCII和Unicode将字符映射为数字代码。ASCII使用7或8位，而Unicode可使用多达32位来表示大量符号。考试常要求计算文本文件的存储大小。
Images are represented as a grid of pixels, with each pixel's colour encoded in binary (e.g., using RGB values). Sound is sampled at regular intervals to create a digital representation, and the concepts of sampling rate and bit depth are critical.
图像表示为像素网格，每个像素的颜色用二进制编码（如使用RGB值）。声音以固定间隔采样来生成数字表示，采样率和位深度的概念非常重要。
3. Computer Architecture & Organization | 计算机体系结构与组成
Von Neumann architecture is the foundation of most modern computers, featuring a single shared memory for data and instructions, a control unit (CU), arithmetic logic unit (ALU), and registers.
冯·诺依曼架构是大多数现代计算机的基础，其特点是数据和指令共享单一存储器、控制单元(CU)、算术逻辑单元(ALU)及寄存器。
The fetch-decode-execute cycle is a fundamental concept. The CPU fetches an instruction from memory, decodes it, and executes it, often involving the program counter (PC) and memory address register (MAR).
取指-解码-执行周期是基本概念。CPU从内存取指、解码并执行，通常涉及程序计数器(PC)和内存地址寄存器(MAR)。
Factors affecting CPU performance include clock speed, number of cores, and cache size. Pipelining and the role of the system bus (address bus, data bus, control bus) are also common exam topics.
影响CPU性能的因素包括时钟速度、核心数量和缓存大小。流水线技术以及系统总线（地址总线、数据总线、控制总线）的作用也是常见考点。
4. Networks & Communication | 网络与通信
Networks are classified by scale: Personal Area Network (PAN), Local Area Network (LAN), Wide Area Network (WAN). Typical topologies include star, bus, ring, and mesh. The star topology, with a central switch, is widely used due to its fault tolerance.
网络按规模分类：个人区域网(PAN)、局域网(LAN)、广域网(WAN)。典型拓扑包括星型、总线型、环型和网状。星型拓扑以中央交换机为核心，因其容错性而被广泛使用。
Protocols define rules for communication. The TCP/IP stack consists of four layers: Application (HTTP, FTP, SMTP), Transport (TCP, UDP), Internet (IP), and Link (Ethernet, Wi-Fi). Understanding packet switching and the role of routers is crucial.
协议定义了通信规则。TCP/IP协议栈分为四层：应用层(HTTP, FTP, SMTP)、传输层(TCP, UDP)、网络层(IP)和链路层(Ethernet, Wi-Fi)。理解分组交换和路由器的角色至关重要。
| Protocol | Full Name | Port |
|---|---|---|
| HTTP | HyperText Transfer Protocol | 80 |
| HTTPS | HTTP Secure | 443 |
| FTP | File Transfer Protocol | 21 |
| SMTP | Simple Mail Transfer Protocol | 25 |
Network security threats like malware, phishing, and denial-of-service attacks are high-frequency topics. Symmetric encryption (e.g., AES) and asymmetric encryption (e.g., RSA) are commonly compared.
网络安全威胁如恶意软件、钓鱼和拒绝服务攻击是高频考点。对称加密（如AES）和非对称加密（如RSA）常被比较。
5. Operating Systems & Resource Management | 操作系统与资源管理
An operating system (OS) manages hardware resources, provides a user interface, and enables multitasking. Core functions include memory management, process scheduling, and handling interrupts.
操作系统(OS)管理硬件资源、提供用户界面并实现多任务处理。核心功能包括内存管理、进程调度和处理中断。
Virtual memory allows the execution of programs larger than physical RAM by using disk space, but it can cause disk thrashing if overused. Paging and segmentation are common memory allocation techniques.
虚拟内存允许通过使用磁盘空间来执行大于物理RAM的程序，但过度使用会导致磁盘抖动。分页和分段是常见的内存分配技术。
In IB and Edexcel, you may be asked to explain the role of the scheduler, the difference between preemptive and non-preemptive scheduling, or how an OS handles a hardware interrupt.
在IB和Edexcel考试中，可能要求解释调度程序的作用、抢占式与非抢占式调度的区别，或操作系统如何处理硬件中断。
6. Programming Concepts & OOP | 编程概念与面向对象
Basic programming constructs include sequence, selection (if-else, switch), and iteration (for, while loops). You should be able to trace pseudocode and identify logic errors.
基本编程结构包括顺序、选择（if-else, switch）和循环（for, while）。你应该能够跟踪伪代码并找出逻辑错误。
Data types such as integer, float, char, string, and Boolean are fundamental. Arrays and 2D arrays are used to store collections, and string manipulation methods (e.g., concatenation, substring)
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