IB and WJEC Computer Science: High-Frequency Exam Topics Summary | IB与WJEC计算机高频考点总结

📚 IB and WJEC Computer Science: High-Frequency Exam Topics Summary | IB与WJEC计算机高频考点总结

Preparing for computer science exams across different exam boards can be daunting. This article highlights the most frequently examined topics in both IB Computer Science and WJEC Computer Science specifications, providing a concise revision guide for students aiming to master core concepts.

准备不同考试局的计算机考试可能令人生畏。本文提炼了IB计算机和WJEC计算机大纲中最常考的主题，为想要掌握核心概念的学生提供精炼的复习指南。

1. Data Representation and Storage | 数据表示与存储

Binary numbers are base-2, using digits 0 and 1. You must be able to convert between binary, denary and hexadecimal, and perform binary addition while identifying overflow errors.

二进制数是基数为2的数制，使用数字0和1。你必须能够在二进制、十进制和十六进制之间转换，并进行二进制加法同时识别溢出错误。

Negative integers are represented using two’s complement, a method that simplifies subtraction by turning it into addition. Both IB and WJEC exams require you to find the two’s complement of a given binary number.

负整数使用补码表示，这种方法通过将减法转换为加法来简化运算。IB和WJEC考试都要求你求出一个给定二进制数的补码。

Floating-point representation stores real numbers using a mantissa and an exponent. Normalised form ensures maximum precision. You should know how to convert between floating-point and denary and calculate the range of representable numbers.

浮点数表示使用尾数和指数来存储实数。规范化形式可确保最大精度。你应知道如何在浮点数与十进制之间转换，并计算可表示数的范围。

Character sets such as ASCII and Unicode map numbers to symbols. ASCII uses 7 or 8 bits, while Unicode supports thousands of characters for global languages. Understanding the difference is frequently examined.

字符集如ASCII和Unicode将数字映射为符号。ASCII使用7位或8位，而Unicode则支持数千种字符以适应全球语言。理解它们的区别是常考内容。

Bitmap images are stored as a grid of pixels, each assigned a colour value. Resolution and colour depth directly affect file size. Sound is digitised by sampling at regular intervals; the sample rate and bit depth determine quality and storage needs.

位图图像存储为像素网格，每个像素分配一个颜色值。分辨率和颜色深度直接影响文件大小。声音通过定期采样进行数字化；采样率和位深度决定了质量与存储需求。

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2. Computer Architecture | 计算机体系结构

The von Neumann architecture describes a system with a central processing unit, memory, input/output, and the stored program concept. You need to identify the roles of the control unit, ALU, and various registers.

冯·诺依曼体系结构描述了包含中央处理器、内存、输入/输出以及存储程序概念的系统。你需要识别控制单元、ALU和各种寄存器的作用。

The fetch-decode-execute cycle is the heartbeat of the CPU. The PC (program counter) holds the address of the next instruction, the MAR and MDR handle memory read/write, and the CIR stores the current instruction. You should be able to trace this cycle step by step.

取指-解码-执行周期是CPU的心跳。PC（程序计数器）保存下一条指令的地址，MAR和MDR处理内存读写，CIR存储当前指令。你应能逐步追踪这一周期。

Cache memory is a small, fast buffer between CPU and main memory, reducing the average access time. The concept of locality of reference explains why caching works effectively. Both syllabi expect you to discuss its impact on performance.

高速缓存是位于CPU与主存之间的一个小型快速缓冲区，可降低平均访问时间。局部性原理解释了为何缓存能有效工作。两个大纲都要求你讨论它对性能的影响。

RISC and CISC architectures differ in their instruction sets. RISC uses simple, fixed-length instructions while CISC includes complex, multi-step instructions. This comparison often appears in WJEC papers.

RISC和CISC架构的指令集不同。RISC使用简单、定长的指令，而CISC包含复杂、多步指令。这一对比常出现在WJEC试卷中。

Primary memory (RAM, ROM) and secondary storage (HDD, SSD, optical) have distinct characteristics regarding speed, volatility and cost. Exam questions may ask you to recommend storage for a given scenario.

主存储器（RAM、ROM）和辅助存储器（HDD、SSD、光盘）在速度、易失性和成本方面各有特点。考题可能会要求你针对某种场景推荐存储设备。

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3. Networking Fundamentals | 网络基础

Local area networks (LANs) and wide area networks (WANs) differ in geographical scope, ownership and technologies. You should be able to describe typical hardware such as switches, routers and access points.

局域网和广域网在地理范围、所有权和技术上有所不同。你应能描述交换机、路由器和接入点等典型硬件。

The OSI and TCP/IP models organise network communication into layers. Each layer performs specific functions: physical transmission, data link framing, routing, transport reliability, and application protocols. WJEC often expects candidates to compare the two models.

OSI和TCP/IP模型将网络通信组织为层次。每一层执行特定功能：物理传输、数据链路成帧、路由、传输可靠性和应用协议。WJEC常要求考生比较这两种模型。

Packet switching divides data into packets that travel independently through the network. Routers examine destination IP addresses to forward packets. You need to explain how this supports robust and efficient communication.

分组交换将数据分割成在网络上独立传输的数据包。路由器检查目的IP地址以转发数据包。你需要解释这如何支持稳健高效的通信。

Protocols like TCP, IP, HTTP, HTTPS, FTP and SMTP each serve a defined purpose. For instance, TCP provides reliable, connection-oriented delivery while IP handles addressing. Distinguishing between these is essential for both IB and WJEC exams.

TCP、IP、HTTP、HTTPS、FTP和SMTP等协议均有明确定义的功能。例如，TCP提供可靠的、面向连接的交付，而IP处理寻址。区分这些协议对IB和WJEC考试至关重要。

IP addresses identify devices on a network. Subnet masks determine which portion identifies the network and which identifies the host. DNS translates human-friendly domain names into IP addresses. Understanding these relationships is regularly tested.

IP地址标识网络上的设备。子网掩码决定哪部分标识网络、哪部分标识主机。DNS将易记的域名转换为IP地址。理解这些关系经常被测查。

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

Pseudocode and flowcharts allow algorithms to be expressed in a language-independent manner. Both IB and WJEC require you to interpret and write such representations for common problems like finding maximum, summing elements or sorting.

伪代码和流程图允许以与语言无关的方式表达算法。IB和WJEC都要求你为常见问题（如求最大值、求和元素或排序）解释和书写这类表示。

Linear search checks each element sequentially, while binary search requires a sorted array and halves the search space each step. You must be able to compare their efficiencies and trace through examples.

线性搜索顺序检查每个元素，而二分搜索要求排序数组，并且每一步将搜索空间减半。你必须能比较它们的效率并追踪实例。

Sorting algorithms, including bubble sort, insertion sort and merge sort, are core. IB HL may also include quicksort. Knowing their best- and worst-case time complexities (e.g., O(n²) for bubble, O(n log n) for merge) is essential.

排序算法，包括冒泡排序、插入排序和归并排序是核心。IB HL可能还包括快速排序。了解它们最好和最坏情况的时间复杂度（如冒泡排序O(n²)，归并排序O(n log n)）是必须的。

Big O notation describes how the runtime or memory usage grows with input size. O(1), O(n), O(n²), O(2ⁿ) are commonly assessed. You should be able to justify the complexity of a given algorithm.

大O表示法描述运行时间或内存使用量如何随输入规模增长而增长。常评估的有O(1)、O(n)、O(n²)、O(2ⁿ)。你应能论证给定算法的复杂度。

Recursion occurs when a function calls itself. Tracing recursive functions for tasks like factorial or Fibonacci is particularly important for IB HL. You should identify base cases and recursive calls.

递归发生在一个函数调用自身时。对于阶乘或斐波那契等任务追踪递归函数对IB HL尤其重要。你应识别基案和递归调用。

Computational thinking involves abstraction (ignoring unnecessary detail) and decomposition (breaking problems into smaller parts). These concepts underpin all problem-solving and are implicitly examined.

计算思维包括抽象（忽略不必要的细节）和分解（将问题分解为更小的部分）。这些概念是所有问题解决的基础且被隐含考察。

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5. Programming Techniques | 编程技术

Primitive data types such as integer, real (float), boolean, char and string must be used correctly. You need to know how operations and storage differ among them, especially regarding type casting.

原始数据类型如整数、实数（浮点）、布尔、字符和字符串必须正确使用。你需要知道它们的操作和存储方式有何不同，尤其是类型转换方面。

Control structures—sequence, selection (if-else, switch-case) and iteration (for loops, while loops)—form the logic of any program. Tracing and writing code that correctly implements these structures is fundamental.

控制结构——顺序、选择（if-else、switch-case）和迭代（for循环、while循环）——构成任何程序的逻辑。追踪和编写正确实现这些结构的代码是基础。

Arrays, both one-dimensional and two-dimensional, are heavily used to store collections of data. You should be able to traverse, search and manipulate array elements, often combined with loops.

一维和二维数组被广泛用于存储数据集合。你应能够遍历、搜索和操作数组元素，通常与循环结合使用。

File handling operations—opening,

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