📚 Year 8 OCR Computer Science: Core Knowledge Summary | Year 8 OCR 计算机：核心知识点梳理
Welcome to your essential revision guide for Year 8 OCR Computer Science. This article gathers the most important concepts you need to master, from hardware basics to programming logic, networking, and cybersecurity. Each idea is explained clearly in both English and Chinese to support bilingual learners.
欢迎阅读 Year 8 OCR 计算机科学核心复习指南。本文汇集了你必须掌握的最重要概念，从硬件基础到编程逻辑、网络和网络安全。每个概念都用中英双语清晰解释，帮助双语学习者理解和记忆。
1. Computer Hardware and Software | 计算机硬件与软件
A computer system is made up of hardware and software. Hardware refers to the physical components you can touch, like the keyboard, mouse, monitor, motherboard, and hard drive. Software includes the programs and instructions that tell the hardware what to do, such as operating systems, word processors, and games.
计算机系统由硬件和软件组成。硬件是指你可以触摸到的物理部件，如键盘、鼠标、显示器、主板和硬盘。软件包括告诉硬件做什么的程序和指令，如操作系统、文字处理软件和游戏。
Hardware can be divided into input devices (e.g., keyboard, scanner), output devices (e.g., printer, speakers), and storage devices (e.g., SSD, USB flash drive). The motherboard connects all components and allows them to communicate.
硬件可分为输入设备（如键盘、扫描仪）、输出设备（如打印机、音箱）和存储设备（如固态硬盘、U盘）。主板连接所有组件并使它们能够相互通信。
Software is split into system software (operating system, utilities) and application software (web browsers, spreadsheet programs). The operating system manages hardware resources, provides a user interface, and runs other software.
软件分为系统软件（操作系统、实用工具）和应用软件（网页浏览器、电子表格程序）。操作系统管理硬件资源，提供用户界面，并运行其他软件。
2. The CPU and Its Role | 中央处理器及其作用
The Central Processing Unit (CPU) is often called the "brain" of the computer. It carries out instructions from programs by performing the fetch-decode-execute cycle. Modern CPUs contain multiple cores, which allow them to process several instructions at the same time.
中央处理器（CPU）常被称为计算机的“大脑”。它通过执行取指—译码—执行周期来运行程序指令。现代CPU包含多个核心，可以同时处理多条指令。
The CPU's speed is measured in gigahertz (GHz). A higher clock speed generally means faster processing. The CPU contains the arithmetic logic unit (ALU) for calculations and the control unit (CU) for directing operations.
CPU的速度以千兆赫兹（GHz）为单位。时钟频率越高通常意味着处理速度越快。CPU包含用于计算的算术逻辑单元（ALU）和用于指挥操作的控制单元（CU）。
Cache memory inside the CPU stores frequently used data for quick access. The CPU also uses registers—tiny, super-fast storage locations—to hold instructions temporarily.
CPU内部的缓存存储器保存常用数据以便快速访问。CPU还使用寄存器——极小的超快存储位置——来临时保存指令。
3. Memory and Storage | 内存与存储器
Primary memory includes RAM (Random Access Memory) and ROM (Read-Only Memory). RAM 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 is non-volatile and stores the boot-up instructions (BIOS).
主存储器包括RAM（随机存取存储器）和ROM（只读存储器）。RAM是易失性的，意味着断电时数据会丢失。它保存当前正在使用的操作系统、程序和数据。ROM是非易失性的，存储启动指令（BIOS）。
Secondary storage is used for long-term keeping of files and software. Hard disk drives (HDDs) use magnetic platters, while solid-state drives (SSDs) use flash memory with no moving parts, making them faster and more durable. Portable storage includes USB sticks and SD cards.
辅助存储器用于长期保存文件和软件。硬盘驱动器（HDD）使用磁性盘片，而固态硬盘（SSD）使用无移动部件的闪存，速度更快、更耐用。便携式存储包括U盘和SD卡。
yte (TB). 1 TB = 1000 GB; 1 GB = 1000 MB; 1 MB = 1000 KB; 1 KB = 1000 bytes approximately.
存储容量以字节为单位：千字节（KB）、兆字节（MB）、吉字节（GB）和太字节（TB）。1 TB = 1000 GB；1 GB = 1000 MB；1 MB = 1000 KB；1 KB ≈ 1000 字节。
4. Binary System and Conversions | 二进制系统与转换
Computers use binary (base‑2) because they are built from billions of tiny switches that can be either ON (1) or OFF (0). All data—numbers, text, images, sound—is represented using combinations of 0s and 1s.
计算机使用二进制（基数为2），因为它们由数十亿个微小开关构成，这些开关只有开（1）或关（0）两种状态。所有数据——数字、文本、图像、声音——都用0和1的组合表示。
, the binary number 1011 represents (1×2³)+(0×2²)+(1×2¹)+(1×2⁰) = 8+0+2+1 = 11 in decimal.
一个二进制数字是一位（bit）。8位组成一个字节（byte）。半字节（nibble）是4位。更大的数字通过增加位数来表示。例如，二进制数1011表示(1×2³)+(0×2²)+(1×2¹)+(1×2⁰) = 8+0+2+1 = 十进制11。
To convert from binary to denary (decimal), you can use a table of place values. For an 8‑bit number, the columns are 128, 64, 32, 16, 8, 4, 2, 1. Simply add up the values where a 1 appears.
从二进制转换为十进制时，可以使用位值表格。对于8位数字，列依次为128、64、32、16、8、4、2、1。只需将出现1的位置的数值相加即可。
| 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 |
|---|---|---|---|---|---|---|---|
| 0 | 1 | 0 | 0 | 1 | 1 | 0 | 1 |
The table above shows binary 01001101: 64 + 8 + 4 + 1 = 77 in denary.
上表显示二进制01001101：64 + 8 + 4 + 1 = 十进制77。
5. Data Representation: Text and Images | 数据表示：文本与图像
Characters such as letters and symbols are stored using binary codes. Two common character sets are ASCII and Unicode. ASCII uses 7 bits per character, allowing 128 characters. Extended ASCII uses 8 bits (256 characters). Unicode can represent characters from all writing systems and uses up to 32 bits per character.
字母和符号等字符使用二进制代码存储。两个常见的字符集是ASCII和Unicode。ASCII每个字符使用7位，可表示128个字符。扩展ASCII使用8位（256个字符）。Unicode可以表示所有书写系统的字符，每个字符最多使用32位。
red in 1 bit (0 = white, 1 = black). In a colour image, more bits per pixel are used to represent a wide range of colours. The resolution is the number of pixels in the image; higher resolution gives more detail but larger file size.
图像表示为称为像素的微小点组成的网格。每个像素有其颜色的二进制代码。在黑白图像中，1个像素可以用1位存储（0 = 白，1 = 黑）。在彩色图像中，每个像素使用更多位来表示广泛的颜色。分辨率是图像中的像素数量；分辨率越高，细节越多，但文件也越大。
urs. Metadata stores information about the image, such as width, height, and colour depth.
颜色深度（位深度）是每个像素使用的位数。例如，每个像素8位，可以有2⁸ = 256种颜色。元数据存储有关图像的信息，如宽度、高度和颜色深度。
6. Introduction to Algorithms | 算法简介
An algorithm is a step-by-step set of instructions designed to perform a specific task or solve a problem. Everyday examples include a recipe for baking a cake or a set of directions to a friend's house. In computing, algorithms must be precise, unambiguous, and finite.
算法是为执行特定任务或解决问题而设计的一组循序渐进的指令。日常生活中的例子包括烘焙蛋糕的食谱或去朋友家的路线指南。在计算机领域，算法必须精确、无歧义且有限。
Algorithms can be expressed in many forms: plain English, pseudocode, or flowcharts. A good algorithm is efficient—it uses minimal time and resources—and it should always produce a correct output for valid inputs.
算法可以用多种形式表达：普通英语、伪代码或流程图。一个好的算法是高效的——它使用最少的时间和资源——并且对于有效的输入应该总是产生正确的输出。
Abstraction is an important tool when designing algorithms. It means focusing on the important details while ignoring irrelevant information. For example, when designing a bus timetable app, you ignore the colour of the buses.
抽象化是设计算法时的重要工具。它意味着专注于重要细节，忽略无关信息。例如，设计公交时刻表应用时，你会忽略公交车的颜色。
7. Flowcharts and Pseudocode | 流程图与伪代码
Flowcharts use symbols to represent the steps of an algorithm visually. The main symbols are: oval for start/end, rectangle for a process or instruction, parallelogram for input/output, diamond for a decision, and arrows to show the flow of control.
流程图使用符号直观地表示算法的步骤。主要符号有：椭圆形表示开始/结束，矩形表示处理或指令，平行四边形表示输入/输出，菱形表示判断，箭头表示控制流。
Pseudocode is an informal, high-level description of an algorithm using a mixture of English and programming-like keywords. It does not follow strict syntax rules, making it easy for humans to read but not executable by a computer.
伪代码是对算法的非正式、高层次描述，使用英语与类似编程的关键词混合。它不遵循严格的语法规则，便于人类阅读，但计算机无法执行。
Typical pseudocode includes instructions like INPUT name, IF age > 12 THEN, PRINT "Hello", and loops such as WHILE count < 10 DO. It helps programmers plan before coding.
典型的伪代码包括诸如 INPUT name、IF age > 12 THEN、PRINT "Hello" 之类的指令，以及诸如 WHILE count < 10 DO 的循环。它帮助程序员在编码前进行规划。
8. Programming Concepts: Sequence, Selection, Iteration | 编程概念：顺序、选择和迭代
All programs are built using three fundamental control structures: sequence, selection, and iteration. Sequence means instructions are executed in the order they are written, one after the other.
所有程序都使用三种基本的控制结构构建：顺序、选择和迭代。顺序意味着指令按照它们编写的顺序依次执行。
Selection allows the program to make decisions. It uses IF, ELSE IF, and ELSE to run different blocks of code depending on whether a condition is true or false. For example, a weather app might display a rain warning if the precipitation chance is above 80%.
选择允许程序做出决定。它使用 IF、ELSE IF 和 ELSE，根据条件为真还是假来运行不同的代码块。例如，天气应用可能会在降水概率超过80%时显示下雨警告。
Iteration (looping) repeats a section of code. There are two main types: count‑controlled loops (e.g., FOR i = 1 TO 10) repeat a set number of times, while condition‑controlled loops (e.g., WHILE score < 100) repeat as long as a condition remains true.
迭代（循环）重复执行一段代码。主要有两种类型：计数控制循环（例如 FOR i = 1 TO 10）按设定次数重复，而条件控制循环（例如 WHILE score < 100）只要条件为真就继续重复。
9. Networks: LAN and WAN | 网络：局域网与广域网
A computer network connects two or more devices to share data and resources. A Local Area Network (LAN) covers a small geographical area, such as a school or office building. LANs offer high data transfer speeds and are usually owned and managed by the same organisation.
计算机网络连接两个或多个设备以共享数据和资源。局域网（LAN）覆盖较小的地理区域，如学校或办公楼。LAN提供高数据传输速度，通常由同一组织拥有和管理。
A Wide Area Network (WAN) spans a large geographical area, often a country or even the whole world. The internet is the largest WAN. WANs use infrastructure like telephone lines, fibre optic cables, and satellites, and are often created by connecting multiple LANs.
广域网（WAN）跨越较大的地理区域，通常是一个国家甚至全球。互联网是最大的广域网。WAN使用电话线、光纤和卫星等基础设施，通常通过连接多个LAN来构建。
Network hardware includes switches (connect devices in a LAN), routers (send data between different networks), and network interface cards (NICs) inside each device. Wi‑Fi uses radio waves to provide wireless connectivity.
网络硬件包括交换机（在LAN中连接设备）、路由器（在不同网络间传送数据）以及每个设备内的网络接口卡（NIC）。Wi‑Fi使用无线电波提供无线连接。
10. The Internet and the World Wide Web | 互联网与万维网
The Internet is a global network of networks that connects billions of devices. It provides the physical infrastructure and uses protocols like IP (Internet Protocol) to route data packets between computers.
互联网是一个连接数十亿设备的全球性网络之网络。它提供物理基础设施，并使用诸如IP（互联网协议）之类的协议在计算机之间路由数据包。
The World Wide Web (WWW) is a service that runs on top of the Internet. It consists of web pages accessed through a browser using HTTP or HTTPS. The web uses URLs (Uniform Resource Locators) to locate resources, and web servers store and deliver web pages to clients.
万维网（WWW）是运行在互联网之上的服务。它由通过浏览器使用HTTP或HTTPS访问的网页组成。Web使用URL（统一资源定位符）来定位资源，Web服务器存储网页并将其传递给客户端。
Search engines like Google use web crawlers to index pages and provide relevant results. The distinction between the Internet and the Web is a common exam question: the Internet is the network hardware and protocols, while the Web is the collection of information accessed via the Internet.
像Google这样的搜索引擎使用网络爬虫来索引网页并提供相关结果。互联网和Web的区别是常见的考试问题：互联网是网络硬件和协议，而Web是通过互联网访问的信息集合。
11. Cybersecurity Threats and Protection | 网络安全威胁与防护
Cybersecurity involves protecting computer systems, networks, and data from digital attacks. Common threats include malware (viruses, worms, trojans), phishing emails, social engineering, and denial-of-service (DoS) attacks.
网络安全涉及保护计算机系统、网络和数据免受数字攻击。常见威胁包括恶意软件（病毒、蠕虫、特洛伊木马）、网络钓鱼邮件、社会工程和拒绝服务（DoS）攻击。
A virus attaches itself to a legitimate program and spreads when that program runs. A worm can spread without user action by exploiting network vulnerabilities. Phishing uses fake emails or websites to trick people into revealing passwords or financial details.
病毒附着在合法程序上，并在该程序运行时传播。蠕虫无需用户操作即可通过利用网络漏洞进行传播。网络钓鱼使用虚假电子邮件或网站诱骗人们泄露密码或财务细节。
Protection measures include using strong passwords, keeping software updated, installing anti-malware software, and not opening suspicious attachments. Firewalls monitor incoming and outgoing network traffic and block unauthorised access. Encryption scrambles data so only authorised parties can read it.
防护措施包括使用强密码、保持软件更新、安装反恶意软件以及不打开可疑附件。防火墙监控传入和传出的网络流量并阻止未授权访问。加密将数据打乱，只有被授权方才能读取。
12. Responsible Use of Computers | 负责任地使用计算机
Using computers responsibly means following legal, ethical, and safety guidelines. The Computer Misuse Act (1990) makes it illegal to access computers without permission (hacking), to spread viruses, or to conduct cyber attacks. The Data Protection Act controls how personal data can be collected and used.
负责任地使用计算机意味着遵循法律、道德和安全准则。《计算机滥用法》（1990年）规定未经许可访问计算机（黑客行为）、传播病毒或进行网络攻击都是非法的。《数据保护法》控制个人数据的收集和使用方式。
Digital footprints are traces of your online activity, such as social media posts, search history, and comments. Once something is posted online, it can be difficult to remove completely. It is important to think before sharing.
数字足迹是在线活动的痕迹，如社交媒体帖子、搜索历史和评论。一旦在网上发布，就很难完全删除。分享之前要三思。
Good practice includes respecting copyright, citing sources, protecting your own privacy, and treating others with respect when communicating online. Cyberbullying is harmful and should be reported. The PEGI age ratings help you choose age‑appropriate games.
良好实践包括尊重版权、注明出处、保护个人隐私以及在网上交流时尊重他人。网络欺凌是有害的，应当举报。PEGI年龄分级帮助你选择适龄游戏。
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