📚 Year 9 AQA Computer Science: Core Knowledge Review | Year 9 AQA 计算机：核心知识点梳理
This article consolidates the essential topics for Year 9 students following the AQA Computer Science pathway. You will revisit key concepts in computational thinking, programming fundamentals, data representation, computer systems, networking, cybersecurity, and responsible use of technology. Each section pairs English explanations with their Chinese counterparts to strengthen bilingual understanding and prepare you for both classroom assessments and future GCSE study.
本文梳理了 AQA 计算机课程 Year 9 阶段的核心知识要点。内容涵盖计算思维、编程基础、数据表示、计算机系统、网络、网络安全以及技术的负责任使用。每个小节都采用中英双语对照讲解，帮助你巩固理解，为课堂测评和未来的 GCSE 学习做好准备。
1. Computational Thinking and Algorithms | 计算思维与算法
Computational thinking is a problem-solving approach that involves breaking down complex problems into smaller, manageable parts. It relies on three main techniques: decomposition, pattern recognition, and abstraction. Decomposition means splitting a large problem into sub-problems, making it easier to solve each part and then combine the solutions. Pattern recognition involves spotting similarities with other problems you have already solved, while abstraction focuses on hiding unnecessary details and keeping only the relevant information.
计算思维是一种解决问题的方法，强调将复杂问题拆解为更小、可管理的部分。它主要依赖三种技术：分解、模式识别和抽象。分解是指把一个大的问题分成若干子问题，从而更容易地解决每个部分再合并方案；模式识别是发现当前问题与已有问题的相似之处；抽象则关注隐藏不必要的细节，只保留相关信息。
- An algorithm is a step-by-step set of instructions designed to perform a specific task.
- 算法 是为完成特定任务而设计的一组有序步骤。
- Algorithms can be represented using flowcharts or pseudocode.
- 算法可以用 流程图 或 伪代码 表示。
- A good algorithm must be precise, finite, and produce correct output for all valid inputs.
- 好的算法必须精确、有限，并且对所有有效输入都能产生正确输出。
2. Programming Fundamentals – Variables, Data Types, and Operators | 编程基础——变量、数据类型和运算符
In programming, a variable is a named storage location that holds a value which can change during execution. You declare a variable and assign it a value using an assignment statement, for example score = 0. Every variable has a data type that determines what kind of data it can hold and what operations can be performed on it.
在编程中，变量 是一个命名的存储位置，保存着程序运行期间可以改变的值。你通过赋值语句声明变量并赋予其值，例如 score = 0。每个变量都有一种数据类型，决定了它可以保存何种数据以及可执行的操作。
| Data Type / 数据类型 | Description / 描述 | Example / 例子 |
|---|---|---|
| Integer / 整型 | Whole numbers / 整数 | 5, -12, 0 |
| Real (Float) / 实数型 | Numbers with decimals / 带小数点的数 | 3.14, -0.5 |
| Boolean / 布尔型 | True or False / 真或假 | True, False |
| Character / 字符型 | Single symbol / 单个符号 | 'A', '7' |
| String / 字符串 | Sequence of characters / 字符序列 | "Hello" |
Operators are symbols that tell the computer to perform specific mathematical or logical manipulations. Arithmetic operators include + (addition), - (subtraction), * (multiplication), / (division), and MOD (remainder after division). Comparison operators – such as ==, !=, <, >, <=, >= – return a Boolean result.
运算符是指示计算机执行特定数学或逻辑操作的符号。算术运算符包括 +（加）、-（减）、*（乘）、/（除）和 MOD（取余）。比较运算符——如 ==、!=、<、>、<=、>=——返回布尔值。
3. Control Structures – Sequence, Selection, and Iteration | 控制结构——顺序、选择和迭代
Programs execute statements in order by default, which is called sequence. Selection allows the program to choose different paths based on conditions. The most common selection statements are IF, ELSE IF, and ELSE. For example: IF temperature > 30 THEN output "Hot".
程序默认按顺序执行语句，这被称为顺序结构。选择结构允许程序根据条件选择不同的执行路径。最常见的选择语句有 IF、ELSE IF 和 ELSE。例如：IF temperature > 30 THEN output "Hot"。
Iteration (looping) repeats a block of code. Definite iteration uses a FOR loop when the number of repetitions is known ahead of time. Indefinite iteration uses a WHILE or REPEAT...UNTIL loop when the loop continues until a condition becomes false or true. Infinite loops must be avoided by ensuring the condition eventually changes.
迭代（循环）重复执行一段代码。确定次数迭代 使用 FOR 循环，适用于事先知道重复次数的情况。不确定次数迭代 使用 WHILE 或 REPEAT...UNTIL 循环，直到某个条件变为假或真。必须保证循环条件最终会改变，以避免无限循环。
4. Data Structures – Arrays and Lists | 数据结构——数组与列表
An array is a collection of elements of the same data type, stored in contiguous memory locations. Each element can be accessed using its index, which usually starts at 0. Arrays are useful when you need to process many related values, such as a list of test scores.
数组 是一组相同数据类型的元素的集合，存储在连续的内存位置中。可以通过索引（通常从 0 开始）访问每个元素。当需要处理大量相关值时，例如一系列测试分数，数组非常有用。
- One-dimensional array:
scores = [12, 18, 24, 9] - 一维数组：
scores = [12, 18, 24, 9] - Two-dimensional arrays are like tables with rows and columns.
- 二维数组如同带有行和列的表格。
A list (in Python or similar languages) is a more flexible structure that can hold mixed data types and change size dynamically. Common list operations include append, remove, sort, and iterating through the list with a FOR loop.
列表（在 Python 等语言中）是一种更灵活的结构，可存放混合数据类型并动态调整大小。常用列表操作包括 append（追加）、remove（移除）、sort（排序）以及用 FOR 循环遍历列表。
5. Subroutines – Procedures and Functions | 子程序——过程和函数
A subroutine is a named block of code that performs a specific task. It promotes code reuse and makes programs easier to read and debug. There are two main types: procedures and functions.
子程序 是一个执行特定任务的命名代码块。它能促进代码重用，让程序更易阅读和调试。主要有两种类型：过程 和 函数。
- Procedure: performs actions but does not return a value. Example:
PROCEDURE display_menu() - 过程：执行操作但不返回值。例：
PROCEDURE display_menu() - Function: performs actions and returns a single value. Example:
FUNCTION calculate_area(radius) RETURNS Real - 函数：执行操作并返回一个值。例：
FUNCTION calculate_area(radius) RETURNS Real
Parameters are variables that allow you to pass values into subroutines, making them more general. Local variables are declared inside subroutines and cannot be seen outside; global variables are declared in the main program and can be accessed anywhere.
参数（parameters）是允许向子程序传递值的变量，使子程序更具通用性。局部变量在子程序内部声明，外部不可见；全局变量在主程序中声明，任何地方都可以访问。
6. Data Representation – Binary and Hexadecimal | 数据表示——二进制与十六进制
Computers use binary (base‑2) because they rely on switches that are either ON (1) or OFF (0). A single binary digit is called a bit. Eight bits make one byte. Binary numbers are written with a subscript 2 or preceded by 0b. For example, the decimal number 13 is 1101₂.
计算机使用二进制（基数为 2），因为其内部开关只有开（1）和关（0）两种状态。一个二进制位称为比特（bit）。八个比特构成一个字节（byte）。二进制数以角标 2 或前缀 0b 标记。例如，十进制数 13 的二进制表示为 1101₂。
Hexadecimal (base‑16) uses sixteen symbols: 0‑9 and A‑F. It is a compact way to represent large binary values, because one hex digit corresponds to four bits (a nibble). The binary value 1101 1010₂ becomes DA₁₆.
十六进制（基数为 16）使用 0‑9 和 A‑F 共十六个符号。它是一种紧凑表示大二进制值的方式，因为一个十六进制位对应四个比特（半字节）。二进制值 1101 1010₂ 转换为十六进制就是 DA₁₆。
You should be able to convert between binary, denary (decimal), and hexadecimal, and understand how negative integers can be represented using two's complement. To find the two's complement, invert all the bits of the positive binary number and add 1.
你需要掌握二进制、十进制和十六进制之间的转换，并理解用补码（two's complement）表示负整数的方法。求一个数的补码需要先将对应正数的二进制位全部取反，然后加上 1。
7. Computer Hardware and Storage | 计算机硬件与存储
The von Neumann architecture describes a system where the CPU fetches instructions from memory, decodes them, and executes them. The CPU contains the control unit (CU), arithmetic logic unit (ALU), and registers such as the program counter (PC) and memory address register (MAR). The clock speed, number of cores, and cache size all affect performance.
冯·诺依曼架构 描述了 CPU 从内存中取出指令、译码并执行的系统。CPU 包含控制单元（CU）、算术逻辑单元（ALU）以及寄存器，如程序计数器（PC）和存储器地址寄存器（MAR）。时钟速度、核心数量和缓存大小都会影响性能。
Primary storage (RAM and ROM) is directly accessible by the CPU. RAM is volatile and used for currently running programs and data; ROM is non-volatile and holds the firmware needed to start the computer. Secondary storage holds data permanently and includes magnetic hard drives, solid-state drives (SSD), and optical discs. The choice of storage device depends on capacity, speed, portability, durability, and cost.
主存储器（RAM 和 ROM）可由 CPU 直接访问。RAM 是易失性的，用于存放正在运行的程序和数据；ROM 是非易失性的，保存着启动计算机所需的固件。辅助存储器 永久保存数据，包括磁性硬盘、固态硬盘（SSD）和光盘。存储设备的选择取决于容量、速度、便携性、耐用性和成本。
8. Networking Basics | 网络基础
A network is two or more devices connected together to share resources and data. LAN (Local Area Network) covers a small geographical area, such as a school; a WAN (Wide Area Network) connects LANs over large distances, the internet being the prime example. Wired connections use Ethernet cables, while wireless uses Wi‑Fi or Bluetooth.
网络是将两个或多个设备连接在一起以共享资源和数据的系统。LAN（局域网）覆盖较小的地理区域，如学校；WAN（广域网）则连接远距离的局域网，互联网就是典型的广域网。有线连接使用以太网线缆，无线连接则使用 Wi‑Fi 或蓝牙。
The TCP/IP protocol stack divides network communication into four layers: Application, Transport, Internet, and Network Interface. IP addresses uniquely identify devices, and routers forward data packets between networks. A domain name system (DNS) converts human-friendly website names into IP addresses.
TCP/IP 协议栈将网络通信分为四层：应用层、传输层、互联网层和网络接口层。IP 地址唯一标识设备，路由器负责在网络之间转发数据包。域名系统（DNS）将人类友好的网站名称转换为 IP 地址。
9. Cybersecurity Threats and Prevention | 网络安全威胁与防护
Cybersecurity protects systems, networks, and data from digital attacks. Common threats include malware (viruses, worms, trojans, ransomware), phishing (fake emails designed to steal credentials), social engineering (tricking people into revealing information), and brute force attacks (repeatedly trying passwords).
网络安全旨在保护系统、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、勒索软件）、网络钓鱼（用于窃取凭证的虚假邮件）、社会工程学（欺骗人们泄露信息）以及暴力破解（反复尝试密码）。
- Prevention measures / 防护措施:
- Use firewalls to filter incoming and outgoing traffic.
- 使用防火墙过滤进出流量。
- Install and update anti-malware software.
- 安装并更新反恶意软件。
- Apply encryption to protect data confidentiality.
- 使用加密保护数据机密性。
- Use strong passwords and two-factor authentication (2FA).
- 使用强密码和双重认证（2FA）。
- Keep software up to date with patches.
- 通过补丁保持软件更新。
It is vital to recognise that the weakest link in security is often the human user. Regular training and following acceptable use policies greatly reduce risk.
要认识到安全中最薄弱的环节往往是用户本身。定期培训和遵守可接受使用策略可以大大降低风险。
10. Digital Literacy and Ethical Issues | 数字素养与伦理问题
Digital literacy involves the ability to use technology safely, critically evaluate online information, and understand the implications of digital footprints. Your personal data has value; many online services collect data to target advertisements. The Data Protection Act (2018) and GDPR set rules for how organisations must handle personal data fairly and transparently.
数字素养涉及安全使用技术、批判性地评估在线信息以及理解数字足迹影响的能力。你的个人数据具有价值；许多在线服务会收集数据以投放定向广告。《数据保护法》（2018 年）和 GDPR 规定了组织必须公平、透明地处理个人数据的规则。
Ethical issues include plagiarism, copyright infringement, and the responsible use of artificial intelligence. Always credit sources and respect intellectual property. When using AI tools, you remain accountable for the work you submit.
伦理问题包括剽窃、侵犯版权以及负责任地使用人工智能。始终注明引用来源并尊重知识产权。使用人工智能工具时，你仍需对自己提交的成果负责。
The digital divide refers to the gap between those who have access to modern technology and those who do not. Addressing this gap is important for equality in education and employment.
数字鸿沟指的是能够使用现代技术的人与不能使用的人之间的差距。缩小这一差距对于教育和就业的公平至关重要。
Published by TutorHao | AQA Computer Science Revision Series | aleveler.com
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