📚 Year 11 SQA Computing: Core Knowledge Points Review | 核心知识点梳理
In the SQA National 5 Computing Science course, students explore how computers work, how to create software, and the impact of technology on society. This article provides a comprehensive review of the core knowledge points, structured for effective revision and bilingual understanding.
在SQA National 5 计算机科学课程中，学生探索计算机如何工作、如何创建软件以及技术对社会的影响。本文全面梳理核心知识点，兼顾双语理解，便于高效复习。
1. Data Representation and Units | 数据表示与单位
All data inside a computer is represented using binary digits (bits). A single bit can be 0 or 1, and 8 bits grouped together form a byte.
计算机内部所有数据都使用二进制数字（比特）表示。一个比特可以是0或1，8个比特组成一个字节。
Larger units include kilobyte (KB), megabyte (MB), gigabyte (GB), terabyte (TB), where each step is 1024 times the previous one (210 = 1024).
更大的单位有千字节(KB)、兆字节(MB)、吉字节(GB)、太字节(TB)，每一步是前一个的1024倍（210 = 1024）。
edly divide by 2 and read the remainders from bottom to top. For example, denary 13 → 11012.
将十进制数转换为二进制时，反复除以2，从下往上读取余数。例如十进制13 → 11012。
=1 carry 1. An overflow error occurs when the result exceeds the available number of bits.
二进制加法遵循简单规则：0+0=0, 0+1=1, 1+0=1, 1+1=10（进位1）, 1+1+1=11（进位1）。当结果超出可用位数时会发生溢出错误。
Hexadecimal (base-16) uses digits 0–9 and letters A–F. Each hex digit represents 4 bits, making it easier to read long binary values. For example, 1010 00112 = A316.
十六进制使用数字0–9和字母A–F。每个十六进制数字代表4个比特，使长二进制值更易读。例如1010 00112 = A316。
Text is stored by assigning a numeric code to each character. ASCII uses 7 bits (128 characters) while Unicode uses up to 32 bits, supporting global scripts and emoji.
文本通过为每个字符分配数字编码来存储。ASCII使用7位（128个字符），而Unicode最多使用32位，支持全球文字和表情符号。
Bitmap images are made of pixels, each assigned a binary colour value. Image quality depends on resolution (number of pixels) and colour depth (bits per pixel).
位图图像由像素组成，每个像素被赋予二进制颜色值。图像质量取决于分辨率（像素数量）和颜色深度（每像素位数）。
Vector graphics store shapes using mathematical descriptions such as coordinates, lines, and curves. They scale without losing quality and have smaller file sizes for simple diagrams.
矢量图形使用坐标、线条和曲线等数学描述来存储形状。它们可无损失地缩放，对于简单图形文件大小更小。
Sound is captured by sampling the analogue signal at regular intervals. The sampling rate (e.g. 44.1 kHz) and bit depth determine the accuracy and file size of the digital recording.
声音通过定期采样模拟信号来捕获。采样率（如44.1 kHz）和位深度决定了数字录音的精度和文件大小。
2. Computer System Components | 计算机系统组成
The central processing unit (CPU) executes instructions and consists of the control unit (CU), arithmetic logic unit (ALU), and registers. The CU fetches and decodes instructions, while the ALU performs calculations and logical operations.
中央处理器执行指令，由控制单元、算术逻辑单元和寄存器组成。控制单元负责取指和译码，算术逻辑单元执行计算和逻辑操作。
Registers are high-speed memory locations inside the processor, such as the program counter (PC), memory address register (MAR), and memory data register (MDR).
寄存器是处理器内部的高速存储位，例如程序计数器、内存地址寄存器和内存数据寄存器。
Random Access Memory (RAM) holds data and programs currently in use. It is volatile and loses its content when power is turned off. Read Only Memory (ROM) is non-volatile and stores startup instructions.
随机存取存储器保存当前正在使用的数据和程序。它是易失性的，断电后内容丢失。只读存储器是非易失性的，存储启动指令。
Cache memory is a very fast, small amount of memory located close to the CPU. It stores frequently used instructions and data to speed up processing.
高速缓存是非常快且容量小的存储器，放置在CPU附近。它储存频繁使用的指令和数据以加快处理速度。
Secondary storage devices retain data permanently. Hard disk drives (HDD) use magnetic platters, solid-state drives (SSD) use flash memory with no moving parts, and optical discs use lasers. Cloud storage allows data to be saved on remote servers accessed via the internet.
二级存储设备永久保存数据。硬盘驱动器使用磁性盘片，固态驱动器使用无活动部件的闪存，光盘使用激光。云存储允许将数据保存在通过互联网访问的远程服务器上。
Input devices (e.g. keyboard, mouse, touchscreen, microphone) feed data into the system, while output devices (e.g. monitor, printer, speaker) present information to the user. Some devices, like a touchscreen, act as both.
输入设备（如键盘、鼠标、触摸屏、麦克风）将数据送入系统，输出设备（如显示器、打印机、扬声器）向用户呈现信息。像触摸屏这样的设备兼具两者功能。
3. System Software and Application Software | 系统软件与应用软件
System software manages hardware and provides a platform for application software. The operating system (OS) is the most important system software, performing functions such as memory management, file management, input/output management, and user interface.
系统软件管理硬件并为应用软件提供平台。操作系统是最重要的系统软件，执行内存管理、文件管理、输入输出管理和用户界面等功能。
Application software performs specific tasks for the user, such as word processing, spreadsheet calculation, web browsing, and gaming. It relies on the OS to access hardware resources.
应用软件为用户执行特定任务，如文字处理、电子表格计算、网页浏览和游戏。它依赖操作系统来访问硬件资源。
Utility programs are system software designed to maintain or protect the computer. Examples include antivirus scanners, disk defragmenters, backup tools, and file compression utilities.
实用程序是旨在维护或保护计算机的系统软件。示例包括防病毒扫描程序、磁盘碎片整理程序、备份工具和文件压缩工具。
Proprietary software is owned by a company and users must purchase a licence. Open-source software is distributed with its source code, allowing users to modify and share it freely.
专有软件由公司拥有，用户必须购买许可证。开源软件随源代码分发，允许用户自由修改和分享。
4. Networks and the Internet | 网络与因特网
A computer network connects two or more devices to share resources and data. A Local Area Network (LAN) covers a small geographical area, while a Wide Area Network (WAN) connects LANs over large distances.
计算机网络连接两台或更多设备以共享资源和数据。局域网覆盖较小的地理区域，广域网则在远距离上连接局域网。
Client-server networks have a central server providing services, and clients request those services. Peer-to-peer networks have equal nodes that share resources directly without a central server.
客户端-服务器网络拥有提供服务的中央服务器，客户端请求这些服务。对等网络中的节点平等，无需中央服务器即可直接共享资源。
Essential network hardware includes network interface cards (NIC), switches, routers, and wireless access points. Routers direct data packets between different networks, often connecting a LAN to the internet.
基本的网络硬件包括网络接口卡、交换机、路由器和无线接入点。路由器在不同网络之间引导数据包，通常将局域网连接到因特网。
Protocols are sets of rules that govern data communication. TCP/IP is the core protocol suite of the internet. TCP ensures reliable data delivery, while IP handles addressing and routing.
协议是管理数据通信的规则集。TCP/IP是因特网的核心协议簇。TCP确保可靠的数据传送，IP负责寻址和路由。
Every device on the internet has an IP address (IPv4 e.g. 192.168.1.1; IPv6 e.g. 2001:0db8::1). The Domain Name System (DNS) translates human-friendly domain names into IP addresses.
因特网上的每个设备都有一个IP地址（IPv4 例如 192.168.1.1；IPv6 例如 2001:0db8::1）。域名系统将人类友好的域名转换为IP地址。
5. Web Technologies | 网页技术
Web pages are built using Hypertext Markup Language (HTML), which defines the structure and content through elements like headings, paragraphs, images, and hyperlinks.
网页使用超文本标记语言构建，它通过标题、段落、图像和超链接等元素定义结构和内容。
Cascading Style Sheets (CSS) control the presentation and layout of web pages, separating content from design. Selectors target HTML elements, and declarations set properties like colour, font, and margin.
层叠样式表控制网页的外观和布局，将内容与设计分离。选择器指向HTML元素，声明设置颜色、字体和边距等属性。
Responsive design ensures websites adapt to different screen sizes using flexible grids, media queries, and scalable images. This improves user experience on mobile devices.
响应式设计确保网站通过弹性网格、媒体查询和可缩放图像适应不同的屏幕尺寸，提升移动设备上的用户体验。
Search engines index web content by crawling pages and ranking them based on relevance and authority. SEO (Search Engine Optimisation) techniques help pages appear higher in search results.
搜索引擎通过爬取网页并基于相关性和权威性进行排名来索引网页内容。SEO技术有助于页面在搜索结果中显示在更靠前的位置。
Web hosting stores website files on a server connected to the internet. Hosting packages vary in storage, bandwidth, and support for server-side technologies like PHP and databases.
网站托管将网站文件存储在连接到因特网的服务器上。托管套餐在存储、带宽以及PHP和数据库等服务器端技术支持方面各有不同。
6. Databases and SQL | 数据库与SQL
A relational database organises data into tables, each consisting of records (rows) and fields (columns). Each field holds a specific type of data, such as text, number, or date.
关系数据库将数据组织成表，每个表由记录（行）和字段（列）组成。每个字段保存特定类型的数据，如文本、数字或日期。
A primary key is a field that uniquely identifies each record in a table. A foreign key is a field in one table that links to the primary key of another, creating a relationship between tables.
主键是唯一标识表中每条记录的字段。外键是一个表中的字段，它链接到另一个表的主键，在表之间建立关系。
tabases. The SELECT statement retrieves data: SELECT name, age FROM Students WHERE grade = 'A' ORDER BY age DESC;
结构化查询语言用于管理和查询数据库。SELECT语句检索数据：SELECT name, age FROM Students WHERE grade = 'A' ORDER BY age DESC;
Other SQL commands include INSERT INTO to add records, UPDATE to modify existing data, and DELETE FROM to remove records. Conditions in WHERE clauses filter the affected rows.
其他SQL命令包括INSERT INTO添加记录，UPDATE修改现有数据，DELETE FROM删除记录。WHERE子句中的条件用于过滤受影响的行。
Data validation in databases helps ensure accuracy, using checks such as presence check, length check, range check, and format check. Validation is performed before data is stored.
数据库中的数据验证有助于确保准确性，使用存在性检查、长度检查、范围检查和格式检查等方法。验证在存储数据之前执行。
7. Programming Fundamentals | 编程基础
Variables are named storage locations in a program. Each variable has a data type: integer (whole numbers), real/float (decimal numbers), string (text), and Boolean (TRUE or FALSE).
变量是程序中命名的存储位置。每个变量都有数据类型：整数、实数/浮点数、字符串和布尔值。
Assignment statements give a value to a variable, e.g. score = 0 or name = "Alex". Arithmetic operators include +, -, *, /, ^ (exponent) and mod (remainder).
赋值语句将值赋给变量，例如 score = 0 或 name = "Alex"。算术运算符包括 +、-、*、/、^（指数）和 mod（余数）。
ion structures make decisions. An IF statement tests a condition: IF age >= 18 THEN output "Adult" ELSE output "Minor" END IF. Complex conditions use AND, OR, NOT.
选择结构进行决策。IF语句测试条件：IF age >= 18 THEN output "Adult" ELSE output "Minor" END IF。复杂条件使用AND、OR、NOT。
ng as a condition is true, and a REPEAT UNTIL loop runs at least once before checking the condition.
迭代重复执行一段代码。FOR循环运行已知次数：FOR i = 1 TO 10。WHILE循环在条件为真时重复，REPEAT UNTIL循环在检查条件之前至少运行一次。
Arrays store multiple values under a single name, accessed by an index. A 1D array holds a list, while a 2D array holds a table of values. Indices usually start at 0.
数组在单一名称下存储多个值，通过索引访问。一维数组保存列表，二维数组保存表格值。索引通常从0开始。
Subprograms break code into manageable pieces. A procedure performs a task without returning a value, while a function returns a value. Parameters allow data to be passed into the subprogram.
子程序将代码分解为可管理的部分。过程执行任务而不返回值，函数则返回一个值。参数允许将数据传入子程序。
8. Software Development Process | 软件开发流程
The software development process typically follows stages: analysis, design, implementation, testing, evaluation, and documentation. This iterative approach helps create reliable software.
软件开发流程通常遵循以下阶段：分析、设计、实现、测试、评估和文档编写。这种迭代方法有助于创建可靠的软件。
During analysis, the problem is defined through requirements gathering. A clear software specification lists inputs, processes, and outputs, often obtained from stakeholders.
在分析阶段，通过需求收集定义问题。清晰的软件规格说明书列出输入、处理和输出，通常从利益相关者处获取。
Design involves planning the solution. Tools include pseudocode (structured written steps), flowcharts (graphical symbols for steps), and structure diagrams showing modular hierarchy.
设计阶段包括规划解决方案。工具包括伪代码（结构化编写步骤）、流程图（步骤的图形符号），以及显示模块层次的结构图。
Implementation is the coding stage, where the design is translated into a programming language. A good implementation follows coding conventions and is easy to maintain.
实现是编码阶段，将设计翻译成编程语言。良好的实现遵循编码规范并易于维护。
Testing verifies that the program works correctly. Normal test data tests expected values, extreme data tests boundary limits, and exceptional data tests invalid input. Errors are corrected before release.
测试验证程序是否正常运行。正常测试数据测试预期值，边界数据测试边界极限，异常数据测试无效输入。在发布之前修正错误。
Evaluation reviews the completed solution against the original requirements. It checks fitness for purpose, efficiency, readability, and user feedback to suggest improvements.
评估阶段对照原始需求审查完成的解决方案。检查适用性、效率、可读性和用户反馈，以提出改进建议。
Documentation provides written information about the program, including a user guide and technical guide. This assists future maintenance and training.
文档提供关于程序的书面信息，包括用户指南和技术指南。这有助于未来的维护和培训。
9. Computer Security | 计算机安全
Common security threats include malware (viruses, worms, trojans), phishing (fraudulent emails to steal credentials), denial of service (DoS) attacks, and social engineering (tricking people into giving information).
常见安全威胁包括恶意软件（病毒、蠕虫、特洛伊木马）、网络钓鱼（欺诈性电子邮件窃取凭据）、拒绝服务攻击和社会工程学（诱骗人们泄露信息）。
Encryption scrambles data by applying an algorithm and a key, making it unreadable without the correct decryption key. It protects data at rest and in transmission.
加密通过施加算法和密钥对数据进行置乱，没有正确的解密密钥就无法读取。它保护静态数据和传输中的数据。
A firewall monitors incoming and outgoing network traffic based on security rules. It blocks unauthorised access while permitting legitimate communication.
防火墙根据安全规则监控传入和传出的网络流量。它在阻止未经授权访问的同时允许合法通信。
Strong authentication methods verify identity. Passwords should be complex and changed regularly. Two-factor authentication (2FA) adds an extra layer, such as a code sent to a mobile phone. Biometrics uses unique physical traits like fingerprints.
强身份验证方法验证身份。密码应复杂并定期更改。双因素身份验证增加了额外一层防护，例如发送到手机的验证码。生物识别使用指纹等独有物理特征。
Security protocols such as HTTPS (HTTP over SSL/TLS) encrypt data between a browser and a web server, indicated by a padlock icon. Regular software updates patch known vulnerabilities.
安全协议如HTTPS（基于SSL/TLS的HTTP）加密浏览器与网页服务器之间的数据，由挂锁图标表示。定期软件更新修补已知漏洞。
10. Legal, Ethical and Environmental Impacts | 法律、伦理与环境影响
The Computer Misuse Act makes unauthorised access to computer material, intent to commit further offences, and unauthorised modification of data illegal. This deters hacking and spreading malware.
《计算机滥用法》将未经授权访问计算机材料、意图犯进一步罪行以及未经授权修改数据定为非法。这威慑了黑客行为和恶意软件传播。
The Data Protection Act (and GDPR) governs how personal data is collected, stored, and used. Organisations must follow principles such as lawfulness, purpose limitation, data minimisation, and security.
《数据保护法》（以及GDPR）规定了如何收集、存储和使用个人数据。组织必须遵循合法、目的限制、数据最小化和安全等原则。
The Copyright, Designs and Patents Act protects intellectual property. It is illegal to copy or distribute software, music, or images without permission, giving creators control over their work.
《版权、设计和专利法》保护知识产权。未经许可复制或分发软件、音乐或图像是非法的，使创作者能控制其作品。
Ethical computing involves respecting privacy, avoiding discrimination in algorithms, ensuring accessibility, and preventing the digital divide between those with and without technology access.
伦理计算涉及尊重隐私、避免算法歧视、确保可访问性以及防止有技术访问和无技术访问人群之间的数字鸿沟。
Environmental concerns include e-waste from discarded devices, toxic materials in landfills, and high energy consumption of data centres. Green computing promotes recycling, energy-efficient hardware, and virtualisation to reduce carbon footprint.
环境问题包括废弃设备产生的电子垃圾、垃圾填埋场的有毒材料以及数据中心的高能耗。绿色计算倡导回收、节能硬件和虚拟化以降低碳足迹。
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