📚 Year 10 WJEC Computer Science: Core Knowledge Organiser | WJEC 计算机核心知识点梳理
Mastering the fundamentals of WJEC GCSE Computer Science starts with a solid grasp of the key topics covered in Year 10. This article organises essential knowledge across data representation, hardware, software, networks, algorithms, and ethical considerations. Each section presents concepts in both English and Chinese to support bilingual learning and revision, ensuring you build a strong foundation for the Unit 1 and Unit 2 examinations.
掌握 WJEC GCSE 计算机科学的基础，首先要牢固掌握 Year 10 的核心主题。本文梳理了数据表示、硬件、软件、网络、算法和伦理议题等关键知识点。每个小节都以中英双语呈现，辅助双语学习与备考，帮助你在 Unit 1 和 Unit 2 考试中建立扎实基础。
1. Binary and Data Representation | 二进制与数据表示
All data in a computer is stored and processed as binary digits (bits) – 0s and 1s. A group of 8 bits forms a byte, which can represent 256 different values. We use binary because computers rely on transistors that have only two stable states, ON (1) and OFF (0). To convert a denary (decimal) number to binary, repeatedly divide by 2 and record the remainders. For example, the denary number 13 becomes 1101 in binary (reading remainders from bottom to top).
计算机中的所有数据都以二进制数字（位，bit）存储和处理——0 和 1。8 个位组成一个字节，可以表示 256 种不同的值。我们使用二进制是因为计算机依赖只有两种稳定状态的晶体管：开 (1) 和关 (0)。要将十进制数转换为二进制，反复除以 2 并记录余数。例如，十进制数 13 转换为二进制是 1101（从下往上读余数）。
Binary is also used to represent text, images, and sound. Text characters are assigned numeric codes (e.g., ‘A’ = 65 in ASCII). Images are broken into pixels, and each pixel’s colour is stored as a binary number – the more bits per pixel (colour depth), the more colours can be represented. Sound is captured by sampling the analogue signal at regular intervals and storing each sample as a binary value – the higher the sample rate and bit depth, the better the quality.
二进制还用于表示文本、图像和声音。文本字符被分配数字编码（例如 ASCII 中 ‘A’ = 65）。图像被分解为像素，每个像素的颜色以二进制数存储——每像素使用的位数（颜色深度）越多，可表示的颜色就越多。声音通过定期对模拟信号进行采样，并将每个样本存储为二进制值来捕捉——采样率和位深度越高，音质越好。
2. Hexadecimal and Character Sets | 十六进制与字符集
Hexadecimal (base‑16) is a shorthand for binary, using digits 0‑9 and letters A‑F. One hex digit represents a nibble (4 bits), so two hex digits represent a full byte. This makes it much easier to read long binary sequences – for example, the byte 11011010 is DA in hex. Programmers often use hex when working with memory addresses, colour codes (e.g., #FF0055 in HTML), and error codes.
十六进制（基数为 16）是二进制的一种简写，使用数字 0‑9 和字母 A‑F。一个十六进制数字代表一个半字节（4 位），因此两个十六进制数字就代表一个完整的字节。这使得长串二进制更易于阅读——例如字节 11011010 在十六进制中就是 DA。程序员在处理内存地址、颜色代码（如 HTML 中的 #FF0055）和错误代码时经常使用十六进制。
Character sets like ASCII and Unicode define the mapping between characters and their numeric codes. Standard ASCII uses 7 bits to represent 128 characters (English letters, digits, punctuation). Extended ASCII uses 8 bits (256 characters) to include some accented letters. Unicode, however, can represent characters from virtually all writing systems using up to 4 bytes per character; UTF‑8 is a variable‑length encoding that is backward‑compatible with ASCII.
像 ASCII 和 Unicode 这样的字符集定义了字符与数字编码之间的映射。标准 ASCII 使用 7 位来表示 128 个字符（英文字母、数字、标点符号）。扩展 ASCII 使用 8 位（256 个字符）来包含一些带重音的字母。而 Unicode 则可以使用每个字符最多 4 个字节来表示几乎所有书写系统的字符；UTF‑8 是一种可变长度编码，与 ASCII 向后兼容。
3. Binary Arithmetic and Overflow | 二进制算术与溢出
Computers perform arithmetic using binary addition. The rules are simple: 0+0=0, 0+1=1, 1+0=1, and 1+1=0 with a carry of 1 to the next column. When two 8‑bit numbers are added, the result may require 9 bits – this extra bit is called a carry‑out. If the CPU cannot store the 9th bit because the register size is fixed, an overflow error occurs, producing an incorrect result. Overflow flags in the status register can be checked to detect such errors.
计算机使用二进制加法执行算术运算。规则很简单：0+0=0，0+1=1，1+0=1，1+1=0 并向下一列进位 1。当两个 8 位数字相加时，结果可能需要 9 位——这个额外的位称为进位输出。如果 CPU 因为寄存器大小固定而无法存储第 9 位，则会发生溢出错误，产生错误结果。可以通过检查状态寄存器中的溢出标志来检测此类错误。
Understanding binary addition is essential for grasping how the Arithmetic Logic Unit (ALU) operates. It also explains why programming languages have limits on integer sizes (e.g., a 32‑bit integer can store values from about −2 billion to +2 billion). In negative number representation using two’s complement, the most significant bit acts as the sign bit (0 for positive, 1 for negative). Adding positive and negative numbers still follows the binary addition rules, and overflow is handled differently.
理解二进制加法对于掌握算术逻辑单元 (ALU) 的工作原理至关重要。它也解释了为什么编程语言对整数大小有限制（例如 32 位整数可以存储大约从 −20 亿到 +20 亿的值）。在使用二进制补码表示负数时，最高有效位充当符号位（0 为正，1 为负）。正数和负数相加仍然遵循二进制加法规则，并且溢出处理方式不同。
4. Logic Gates and Truth Tables | 逻辑门与真值表
Logic gates are the building blocks of digital circuits. The three fundamental gates are AND, OR, and NOT. An AND gate outputs 1 only if both inputs are 1. An OR gate outputs 1 if at least one input is 1. A NOT gate takes a single input and outputs its opposite. These can be combined to create more complex circuits such as half adders and full adders that perform binary addition.
逻辑门是数字电路的基本构建块。三种基本门是与门 (AND)、或门 (OR) 和非门 (NOT)。与门仅在两个输入都为 1 时输出 1。或门在至少一个输入为 1 时输出 1。非门接受单一输入并输出其相反值。它们可以组合起来创建更复杂的电路，例如执行二进制加法的半加器和全加器。
A truth table lists every possible combination of inputs and the corresponding output for a circuit. For a two‑input AND gate, the truth table has four rows: 00→0, 01→0, 10→0, 11→1. In the exam, you need to be able to complete truth tables for simple gate combinations and recognise how they correspond to Boolean expressions such as (A AND B) OR (NOT C).
真值表列出了电路所有可能的输入组合及其对应的输出。对于两输入与门，真值表有四行：00→0、01→0、10→0、11→1。在考试中，你需要能够完成简单门组合的真值表，并识别它们与布尔表达式（例如 (A AND B) OR (NOT C)）的对应关系。
5. Computer Architecture and the CPU | 计算机架构与中央处理器
The Central Processing Unit (CPU) is the brain of the computer. It follows the Von Neumann architecture, which stores both program instructions and data in the same memory. The CPU consists of the Control Unit (CU), which decodes instructions and directs operations; the Arithmetic Logic Unit (ALU), which performs calculations and logical operations; and a set of registers that provide fast storage for data and instructions during execution.
中央处理器 (CPU) 是计算机的大脑。它遵循冯·诺依曼架构，将程序指令和数据存储在同一内存中。CPU 由控制单元 (CU)（负责解码指令并指挥操作）、算术逻辑单元 (ALU)（执行计算和逻辑操作）以及一组寄存器组成，这些寄存器在执行期间为数据和指令提供快速存储。
Key registers include the Program Counter (PC) that holds the address of the next instruction; the Memory Address Register (MAR) that holds the address of the memory location to be read from or written to; the Memory Data Register (MDR) that holds the data transferred to or from memory; the Current Instruction Register (CIR) that holds the instruction currently being decoded; and the Accumulator (ACC) that stores intermediate results from the ALU. The fetch‑decode‑execute cycle repeats billions of times per second.
关键的寄存器包括：程序计数器 (PC) 存放下一条指令的地址；内存地址寄存器 (MAR) 存放要读写的内存位置地址；内存数据寄存器 (MDR) 存放传入或传出内存的数据；当前指令寄存器 (CIR) 存放正在被解码的指令；累加器 (ACC) 存放来自 ALU 的中间结果。取指-解码-执行周期每秒钟重复数十亿次。
6. Memory and Storage | 内存与存储
Primary memory (RAM and ROM) is directly accessible by the CPU. RAM (Random Access Memory) is volatile – it loses its contents when power is off – and holds the operating system, programs, and data currently in use. ROM (Read Only Memory) is non‑volatile and stores the BIOS or firmware needed to boot the computer. Cache memory is a small, high‑speed memory inside or near the CPU that stores frequently used instructions to speed up processing.
主内存（RAM 和 ROM）可由 CPU 直接访问。RAM（随机存取存储器）是易失性的——断电时丢失内容——它保存当前正在使用的操作系统、程序和数据。ROM（只读存储器）是非易失性的，存储启动计算机所需的 BIOS 或固件。缓存是一种位于 CPU 内部或附近的小型高速内存，用于存储常用指令以加快处理速度。
Secondary storage provides permanent, non‑volatile storage for programs and files. Magnetic hard disk drives (HDDs) use spinning platters and read/write heads; they offer high capacity at low cost but are slower and susceptible to physical shock. Solid‑state drives (SSDs) use flash memory with no moving parts, giving much faster access times and greater durability, though at a higher cost per gigabyte. Optical discs (CDs, DVDs) use lasers to read and write data but are now less common.
辅助存储为程序和文件提供永久性的非易失性存储。磁性硬盘驱动器 (HDD) 使用旋转盘片和读写磁头；它们以低成本提供高容量，但速度较慢且容易受到物理冲击。固态驱动器 (SSD) 使用闪存，无移动部件，存取时间更快，耐用性更高，但每 GB 成本更高。光盘 (CD、DVD) 使用激光读写数据，但现在已不太常见。
7. System Software | 系统软件
System software manages the hardware and provides a platform for application software. The operating system (OS) performs vital functions: memory management (allocating RAM to programs), processor scheduling (deciding which process runs at each moment), file management (organising and controlling access to files), and peripheral management (communicating with devices like printers via drivers). It also provides a user interface (GUI or command line) and handles security features such as user authentication.
系统软件管理硬件并为应用软件提供平台。操作系统 (OS) 执行重要功能：内存管理（为程序分配 RAM）、处理器调度（决定每个时刻运行哪个进程）、文件管理（组织并控制对文件的访问）以及外设管理（通过驱动程序与打印机等设备通信）。它还提供用户界面（图形界面或命令行）并处理诸如用户认证等安全功能。
Utility software is part of system software that helps maintain and protect the computer. Examples include disk defragmentation (reorganising files to improve access speed), backup software (creating copies of data to prevent loss), encryption software (scrambling data to keep it secure), compression tools (reducing file sizes), and anti‑malware programs (detecting and removing viruses and spyware). These are not part of the OS kernel but are essential for smooth operation.
实用工具软件是系统软件的一部分，用于维护和保护计算机。例子包括磁盘碎片整理（重新组织文件以提高访问速度）、备份软件（创建数据副本以防止丢失）、加密软件（对数据加扰以保安全）、压缩工具（减小文件大小）以及反恶意软件程序（检测并移除病毒和间谍软件）。它们并非 OS 内核的一部分，但对平稳运行至关重要。
8. Networks and Topologies | 网络与拓扑结构
A network connects two or more computers to share resources and communicate. Local Area Networks (LANs) cover a small geographical area like a school or office building, often using Ethernet cables or Wi‑Fi. Wide Area Networks (WANs) connect LANs over large distances – the Internet is the largest WAN. Key network hardware includes switches (connecting devices within a LAN), routers (connecting different networks and forwarding data packets), and network interface cards (NICs).
网络将两台或多台计算机连接起来，以共享资源和进行通信。局域网 (LAN) 覆盖较小地理区域，如学校或办公楼，通常使用以太网电缆或 Wi‑Fi。广域网 (WAN) 将远距离的局域网连接起来——因特网就是最大的广域网。关键的联网硬件包括交换机（连接局域网内的设备）、路由器（连接不同网络并转发数据包）以及网络接口卡 (NIC)。
Topology describes the physical or logical layout of a network. In a star topology, all devices are connected to a central switch; if one cable fails, only that device is affected, but the switch is a single point of failure. In a bus topology, all devices share a single backbone cable; it is cheap and easy to install but a break in the cable brings down the whole network. Ring topologies pass data in one direction around a loop, while mesh networks offer multiple redundant paths.
拓扑结构描述网络的物理或逻辑布局。星型拓扑中，所有设备都连接到一台中央交换机；如果一条电缆故障，只有该设备受影响，但交换机是单点故障。总线拓扑中，所有设备共享一条主干电缆；它便宜且易于安装，但电缆一处断裂会导致整个网络瘫痪。环型拓扑沿环路单向传递数据，而网状网络则提供多条冗余路径。
9. Network Security | 网络安全
Networks face numerous threats. Malware (malicious software) includes viruses (that replicate and attach to files), worms (that spread without user action), and trojans (that disguise themselves as legitimate software). Phishing attacks trick users into revealing sensitive information such as passwords and bank details. Denial‑of‑Service (DoS) attacks flood a server with traffic to make it unavailable. Other risks include packet sniffing, where data is intercepted as it travels across a network.
网络面临众多威胁。恶意软件包括病毒（复制并附着于文件）、蠕虫（无需用户操作即可传播）和特洛伊木马（伪装成合法软件）。网络钓鱼攻击诱骗用户泄露密码和银行详细信息等敏感信息。拒绝服务 (DoS) 攻击通过大量流量淹没服务器使其不可用。其他风险包括数据包嗅探，即在数据通过网络传输时将其拦截。
Organisations defend networks using a layered approach. Firewalls monitor incoming and outgoing traffic and block unauthorised access according to rules. Encryption scrambles data so that only intended recipients with the correct key can read it – HTTPS uses SSL/TLS encryption. Strong authentication methods, such as two‑factor authentication, add an extra security layer. Regular penetration testing and software updates (patching) are also vital to close vulnerabilities.
组织使用分层方法来保护网络。防火墙监控传入和传出的流量，并根据规则阻止未经授权的访问。加密对数据打乱，只有拥有正确密钥的预期接收者才能读取——HTTPS 使用 SSL/TLS 加密。强认证方法（如双因素认证）增加了一层额外的安全保护。定期的渗透测试和软件更新（打补丁）对于关闭漏洞也至关重要。
10. Algorithms and Programming Concepts | 算法与编程概念
An algorithm is a step‑by‑step procedure for solving a problem. Two fundamental searching algorithms are linear search (checking each element in order until the target is found, works on unsorted data) and binary search (repeatedly dividing a sorted list in half; much faster for large datasets). For sorting, bubble sort compares adjacent pairs and swaps them if they are in the wrong order, repeating the process until no swaps are needed. Understanding these algorithms helps with writing efficient code and answering trace table questions.
算法是逐步解决问题的过程。两种基本的搜索算法是线性搜索（按顺序检查每个元素直到找到目标，适用于未排序的数据）和二分搜索（反复将已排序的列表对半分；对于大型数据集快得多）。在排序方面，冒泡排序比较相邻对，如果顺序错误则交换它们，重复此过程直到不再需要交换。理解这些算法有助于编写高效的代码并回答跟踪表问题。
Programming fundamentals include variables (named storage locations whose values can change), constants (values that remain fixed), data types such as integer, float/real, Boolean, character, and string, and control structures. Sequence, selection (if‑else), and iteration (for and while loops) are the three building blocks of structured programming. Arrays (or lists) store multiple items of the same data type under one name. Effective use of these concepts enables a programmer to solve problems systematically.
编程基础包括变量（可改变值的命名存储位置）、常量（保持固定的值）、整型、浮点/实型、布尔型、字符和字符串等数据类型，以及控制结构。顺序、选择 (if‑else) 和迭代（for 和 while 循环）是结构化编程的三大构建块。数组（或列表）将多个相同数据类型的元素存储在一个名称下。有效地使用这些概念，程序员就能系统性地解决问题。
11. Ethical, Legal and Environmental Issues | 伦理、法律与环境议题
Computing technology raises important ethical and legal questions. The Data Protection Act requires organisations to handle personal data fairly and lawfully. The Computer Misuse Act makes unauthorised access to computer systems illegal. The Copyright, Designs and Patents Act protects intellectual property, preventing illegal copying of software and digital media. Plagiarism and the need to reference sources are also key academic ethics.
计算技术引发了重要的伦理和法律问题。《数据保护法》要求组织公平、合法地处理个人数据。《计算机滥用法》规定未经授权访问计算机系统为非法。《版权、设计和专利法》保护知识产权，防止非法复制软件和数字媒体。抄袭问题以及注明出处的必要性也是关键的学术伦理。
There are also environmental and social impacts. Manufacturing and disposing of electronic devices consumes energy and produces toxic e‑waste, so we should consider recycling and extending product lifespans. The digital divide refers to the gap between those who have access to digital technology and those who do not, which can exacerbate inequality. Additionally, increased screen time and the spread of misinformation through social media are modern challenges requiring responsible use of technology.
此外还有环境和社会影响。制造和处置电子设备会消耗能源并产生有毒的电子垃圾，因此我们应该考虑回收和延长产品寿命。数字鸿沟指的是能接触到数字技术与不能接触到数字技术的人群之间的差距，这可能会加剧不平等。此外，增加屏幕时间和通过社交媒体传播的错误信息是现代挑战，需要负责任地使用技术。
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