📚 Core Concepts in Year 8 WJEC Computer Science | Year 8 WJEC 计算机：核心知识点梳理
This article covers the essential topics you will meet in Year 8 WJEC Computer Science, helping you build a solid foundation in how computers work, how we write instructions for them, and how digital systems connect and stay safe. We explore binary representation, computational thinking, programming essentials, hardware and software, networks, and online safety — all aligned with the WJEC curriculum for Key Stage 3.
本文梳理了 Year 8 WJEC 计算机课程的核心知识点，帮助你稳固理解计算机的工作原理、如何编写指令，以及数字系统如何连接并保持安全。内容涵盖二进制表示、计算思维、编程基础、硬件与软件、网络以及在线安全，紧扣 WJEC 关键阶段三课程大纲。
1. Binary Basics: Why Computers Use 0 and 1 | 二进制基础：为什么计算机只用 0 和 1
All digital devices store and process data using the binary number system, which has only two digits: 0 and 1. This is because the tiny switches inside a computer — transistors — can only be in two states, off (0) or on (1). By grouping these bits together, we can represent numbers, letters, images, and sound.
所有数字设备都使用二进制数制存储和处理数据，它只有两个数字：0 和 1。这是因为计算机内部的微型开关——晶体管——只能处于两种状态，关（0）或开（1）。把这些二进制位组合起来，我们就可以表示数字、字母、图像和声音。
A single binary digit is called a bit. Eight bits make one byte. With one byte, we can store 256 different values (from 00000000 to 11111111, which is 0 to 255 in denary). Larger units include kilobyte (KB, 1024 bytes), megabyte (MB, 1024 KB), and gigabyte (GB, 1024 MB).
一个二进制数字称为比特（bit）。8 个比特组成一个字节（byte）。一个字节可以存储 256 种不同的值（从 00000000 到 11111111，对应的十进制是 0 到 255）。更大的单位有千字节（KB，1024 字节）、兆字节（MB，1024 KB）和千兆字节（GB，1024 MB）。
To convert a binary number to denary (our normal base‑10 system), we use place values that are powers of two:
把二进制数转换成十进制（我们常用的基数 10 系统）时，我们使用以 2 为底的位权：
128 64 32 16 8 4 2 1
For example, the binary number 01011010 (1×64) + (0×32) + (1×16) + (1×8) + (0×4) + (1×2) + (0×1) = 64 + 16 + 8 + 2 = 90 in denary.
例如，二进制数 01011010 的计算方法是 (0×128) + (1×64) + (0×32) + (1×16) + (1×8) + (0×4) + (1×2) + (0×1) = 64 + 16 + 8 + 2 = 十进制 90。
2. Data Representation: Bits and Beyond | 数据表示：比特之上的世界
Besides numbers, computers represent text characters using standard codes like ASCII (American Standard Code for Information Interchange). In ASCII, each character is assigned a unique 7‑bit binary number. For instance, the uppercase letter 'A' is 65 in denary, which is 1000001 in binary. Extended ASCII uses 8 bits to include more symbols and accented letters.
除了数字，计算机还用标准编码表示文本字符，比如 ASCII（美国信息交换标准代码）。在 ASCII 中，每个字符被赋予一个唯一的 7 位二进制数。例如，大写字母 'A' 的十进制是 65，二进制是 1000001。扩展 ASCII 使用 8 位，可以包含更多符号和带重音的字母。
Images are stored as a grid of tiny squares called pixels. In a black‑and‑ our information; a common method is RGB (Red, Green, Blue), where each colour channel is given a value, often 8 bits each, allowing 256×256×256 ≈ 16.7 million colours.
图像以一个个小方格的网格形式存储，每一个小格称为像素。黑白图像中，每个像素用一个比特表示（0 代表白，1 代表黑）。彩色图像中，每个像素使用多个比特存储颜色信息；常见的方法是 RGB（红、绿、蓝），每个颜色通道被赋予一个值，通常各占 8 比特，从而可以表现 256×256×256 ≈ 1670 万种颜色。
The resolution of an image is the total number of pixels (e.g. 1920×1080), and the colour depth is the number of bits used for each pixel. Higher resolution and higher colour depth give better quality but require more storage space.
图像的分辨率是像素总数（如 1920×1080），颜色深度是每个像素使用的比特数。分辨率和颜色深度越高，画质越好，但需要的存储空间也越大。
Sound is analogue in the real world, so to store it digitally we must take samples at regular intervals. The sample rate (measured in hertz, Hz) tells us how many samples are taken per second, and the bit depth determines the number of possible amplitude levels. A typical CD quality uses a sample rate of 44.1 kHz and a bit depth of 16.
声音在现实世界中是模拟的，所以要用数字方式存储，就必须以固定间隔采样。采样率（以赫兹 Hz 为单位）告诉我们每秒采集多少个样本，比特深度决定了可能的振幅等级数。典型的 CD 音质使用 44.1 kHz 的采样率和 16 位的比特深度。
3. Computational Thinking: Breaking Down Problems | 计算思维：分解问题
Computational thinking is a set of problem‑solving skills that involve decomposition, pattern recognition, abstraction, and algorithm design. These skills help us tackle complex problems by breaking them into smaller, more manageable parts.
计算思维是一套解决问题的技能，包括分解、模式识别、抽象和算法设计。这些技能帮助我们通过将复杂问题分解成更小、更易处理的部分来解决它们。
Decomposition means splitting a big problem into smaller sub‑problems. For example, creating a school website can be divided into designing the homepage, writing the news page, coding the contact form, and testing the links.
分解是指把一个大问题拆分成若干小问题。例如，创建学校网站可以分解为设计主页、编写新闻页、编写联系表单代码和测试链接。
Pattern recognition is about noticing similarities among problems or within data. If you spot that a game character's movement follows a repeated sequence of steps, you can reuse the same code block instead of writing it again.
模式识别是注意问题之间或数据内部的相似之处。如果你发现游戏角色的移动遵循重复的步骤序列，就可以重复使用同一个代码块，而不必再次编写。
Abstraction involves focusing on the important details and ignoring irrelevant information. When drawing a map of the London Underground, we keep the order of stations and their connections but ignore geographical distances and exact locations — this makes the map easier to read.
抽象是指关注重要细节，忽略无关信息。在绘制伦敦地铁图时，我们保留车站的顺序和连接关系，但忽略地理距离和精确位置——这使地图更易于阅读。
Finally, algorithm design is the process of creating a step‑by‑step plan to solve a problem. Algorithms can be written in plain English (pseudocode) or shown as a flowchart with symbols like ovals for start/end, rectangles for processes, and diamonds for decisions.
最后，算法设计是创建逐步解决问题方案的过程。算法可以用通俗英语（伪代码）写出，也可以用流程图表示，流程图中圆角矩形表示开始/结束，矩形表示处理步骤，菱形表示决策判断。
4. Algorithms in Practice: Sequence, Selection, Iteration | 实际算法：顺序、选择、迭代
Every algorithm is built from three basic constructs: sequence, selection, and iteration. Understanding these is key to writing programs in any language, including block‑based environments like Scratch or text‑based ones like Python.
所有算法都由三种基本结构构建：顺序、选择和迭代。理解这些结构是使用任何语言（包括像 Scratch 这样的积木式环境或像 Python 这样的文本语言）编写程序的关键。
Sequence means performing one instruction after another, in the order they are written. For example, making a cup of tea: 1. Boil water, 2. Put tea bag in cup, 3. Pour hot water, 4. Wait, 5. Remove tea bag, 6. Add milk.
顺序是指按照书写顺序，一条接一条地执行指令。例如，泡一杯茶：1. 烧水，2. 把茶包放进杯子，3. 倒入热水，4. 等待，5. 取出茶包，6. 加牛奶。
Selection allows the program to make decisions and choose different paths based on conditions. This uses if‑then‑else logic. For instance, if a user's age is greater than or equal to 18, display 'You can vote'; otherwise, display 'You are too young to vote'.
选择允许程序根据条件做出决定并选择不同路径。它使用如果-那么-否则逻辑。例如，如果用户的年龄大于或等于 18，显示“你可以投票”；否则显示“你年龄太小不能投票”。
Iteration is repeating a set of instructions. There are two main types: count‑controlled loops (e.g. repeat 10 times) and condition‑controlled loops (e.g. repeat until a condition is met). In a game, a character might keep moving forward until it hits a wall — that is an example of condition‑controlled iteration.
迭代是重复执行一组指令。主要有两种类型：计数控制循环（例如重复 10 次）和条件控制循环（例如重复直到满足某个条件）。在游戏中，角色可能会一直向前移动直到碰到墙壁——这就是条件控制迭代的一个例子。
5. Introduction to Programming: Variables and Data Types | 编程入门：变量与数据类型
When we write programs, we store information in variables. A variable is like a named box in the computer's memory that holds a value, and that value can change while the program runs. For example, score = 0 creates a variable called score and gives it the starting value 0.
我们编写程序时，信息存储在变量中。变量就像计算机内存中有名字的盒子，里面保存一个值，在程序运行过程中这个值可以改变。例如，score = 0 创建了一个名为 score 的变量，并赋予初始值 0。
Different kinds of data are given different data types. The most common are integer (whole numbers, e.g. 7, -3), float or real (decimal numbers, e.g. 3.14), string (text, e.g. 'Hello'), and Boolean (True or False). In many programming languages, you need to be careful about using the correct data type, because trying to add a string to an integer may cause an error.
不同类型的数据被赋予不同的数据类型。最常见的有整型（整数，如 7、-3）、浮点型或实型（小数，如 3.14）、字符串（文本，如 'Hello'）和布尔型（True 或 False）。在许多编程语言中，需要注意使用正确的数据类型，因为试图把字符串和整数相加可能会导致错误。
Programs also use operators: arithmetic operators (+, -, *, /) for calculations; comparison operators (==, ! lues, giving a Boolean result; and logical operators (AND, OR, NOT) to combine conditions.
程序还会使用运算符：算术运算符（+、-、*、/）用于计算；比较运算符（==、!=、<、>、<=、>=）用于比较值，得出布尔结果；逻辑运算符（AND、OR、NOT）用于组合条件。
6. Scratch and Block‑Based Programming | Scratch 与积木式编程
In Year 8, you will often use block‑based environments like Scratch to bring algorithms to life without worrying about typing syntax errors. Scratch programs are built by snapping together coloured blocks that represent commands, events, and controls.
在 Year 8，你经常会使用像 Scratch 这样的积木式环境来实现算法，而不用担心拼写语法错误。Scratch 程序通过将代表不同命令、事件和控制的结构化彩色积木拼接在一起来构建。
Key blocks include event blocks (like 'when green flag clicked'), motion blocks ('move 10 steps'), looks blocks ('say Hello!'), control blocks ('repeat 10', 'if then else'), and sensing blocks ('ask and wait', 'touching colour?' ). Variables can be created and used to keep score or count lives.
关键的积木模块包括事件积木（例如“当点击绿旗”）、运动积木（“移动 10 步”）、外观积木（“说 你好！”）、控制积木（“重复执行 10 次”、“如果 那么 否则”）以及侦测积木（“询问 并等待”、“碰到颜色？”）。可以创建变量并用于计分或统计生命值。
Scratch encourages logical thinking and creativity. Even complex games can be built by applying sequence, selection, and iteration, along with broadcasting messages between sprites to coordinate actions.
Scratch 鼓励逻辑思维和创造力。即使是复杂的游戏，也可以通过应用顺序、选择和迭代，并在角色之间广播消息以协调动作来构建。
7. Text‑Based Programming: Python Fundamentals | 文本编程：Python 基础
Moving beyond blocks, Year 8 students are introduced to Python, a text‑based language that is widely used in industry and education. Python code is written line by line and executed from top to bottom.
除了积木式编程，Year 8 学生会初步接触 Python，这是一种在工业和教育领域广泛使用的文本语言。Python 代码逐行编写，从上到下执行。
A simple program might ask for the user's name and then greet them:
一个简单的程序可能会询问用户的名字并问候：
name = input('What is your name? ')print('Hello, ' + name)
Here input() is a function that reads text entered by the user, and print() displays output on the screen. The plus sign joins (concatenates) strings.
这里 input() 是一个函数，读取用户输入的文本，print() 则在屏幕上显示输出。加号用于连接（拼接）字符串。
Selection in Python uses if, elif, and else. For example:
Python 中的选择结构使用 if、elif 和 else。例如：
age = int(input('Enter your age: '))if age >= 18:
print('You are an adult.')else:
print('You are a child.')
Notice the colon at the end of the if and else lines, and the indentation (usually four spaces) that tells Python which lines belong to the if block. Iteration uses for loops when we know how many times to repeat, and while loops when we want to repeat based on a condition.
请注意 if 和 else 行末尾的冒号，以及缩进（通常为四个空格），它告诉 Python 哪些行属于 if 代码块。迭代方面，当我们知道重复次数时使用 for 循环，当根据条件重复时使用 while 循环。
for i in range(5): print(i) will print numbers 0 to 4. while score < 10: keeps looping while the condition is true.
for i in range(5): print(i) 将打印数字 0 到 4。while score < 10: 会在条件为真时一直循环。
8. Hardware and Software: The Physical and the Programs | 硬件与软件：物理实体与程序
A computer system can be divided into hardware — the physical components you can touch — and software — the programs and data that instruct the hardware.
计算机系统可分为硬件——你可以触摸到的物理部件——和软件——指挥硬件的程序和数据。
Key hardware components inside a typical computer include the CPU (Central Processing Unit), which executes instructions and performs calculations; RAM (Random Access Memory), which holds data and programs currently in use (it is volatile, meaning it loses its contents when the power is turned off); storage devices like hard disk drives (HDD) or solid‑state drives (SSD) for long‑term data keeping; and input/output devices such as keyboard, mouse, monitor, and printer.
典型计算机内部的关键硬件部件包括中央处理器（CPU），它执行指令并进行计算；随机存取存储器（RAM），存储当前正在使用的数据和程序（它是易失性的，意为掉电后内容会丢失）；存储设备，如硬盘驱动器（HDD）或固态驱动器（SSD），用于长期保存数据；以及输入/输出设备，如键盘、鼠标、显示器和打印机。
The motherboard is the main circuit board that connects all components together. Data travels between components along buses — groups of tiny parallel wires.
主板是连接所有部件的主电路板。数据通过总线——一组细小的并行导线——在部件之间传输。
Software can be divided into system software and application software. System software includes the operating system (like Windows, macOS, or Linux), which manages hardware and provides a user interface, and utility programs (antivirus, backup tools). Application software are the programs you use to perform specific tasks, such as word processors, web browsers, and games.
软件可分为系统软件和应用软件。系统软件包括操作系统（如 Windows、macOS 或 Linux），它管理硬件并提供用户界面，以及实用程序（杀毒软件、备份工具）。应用软件是用于完成具体任务的程序，如文字处理软件、网页浏览器和游戏。
9. The CPU and the Fetch‑Decode‑Execute Cycle | CPU 与取指-解码-执行周期
The CPU is often called the 'brain' of the computer. To process an instruction, it repeatedly performs the fetch‑decode‑execute cycle.
CPU 常被称为计算机的“大脑”。为处理指令，它不断重复取指-解码-执行周期。
In the fetch stage, the CPU collects the next instruction from RAM, using the program counter to know the address. In the decode stage, the control unit works out what the instruction means. In the execute stage, the arithmetic logic unit (ALU) carries out the required operation, which could be a calculation or a logical comparison. The result is then stored, and the program counter moves to the next instruction.
在取指阶段，CPU 从 RAM 中获取下一条指令，借助程序计数器得知地址。在解码阶段，控制单元解读指令的含义。在执行阶段，算术逻辑单元（ALU）执行所需的操作，可能是计算或逻辑比较。结果随后被存储，程序计数器移动到下一条指令。
The speed of the CPU is measured in hertz (Hz), which indicates how many cycles it can perform per second. Modern CPUs run at several gigahertz (GHz), meaning billions of cycles per second.
CPU 的速度以赫兹（Hz）为单位，表示每秒可执行多少个周期。现代 CPU 的主频可达数吉赫兹（GHz），即每秒执行数十亿个周期。
10. Networks: Connecting Devices Together | 网络：把设备连接起来
A computer network is formed when two or more devices are connected to share data and resources. The internet is the world's largest network, connecting millions of devices globally.
当两个或更多设备连接在一起以共享数据和资源时，就形成了计算机网络。互联网是全球最大的网络，连接了数以百万计的设备。
Networks can be classified by their geographical size: a LAN (Local Area Network) covers a small area like a school or home; a WAN (Wide Area Network) connects LANs over large distances, often using public infrastructure. The internet is a WAN.
网络可按地理范围分类：局域网（LAN）覆盖如学校或家庭这样的小范围；广域网（WAN）通过长距离连接局域网，通常使用公共基础设施。互联网就是一个广域网。
Devices on a network need a unique IP address to identify themselves, much like a postal address. Data is sent in small units called packets, which travel across the network independently and are reassembled at the destination. This is called packet switching.
网络上的设备需要唯一的IP 地址来标识自己，就像邮寄地址一样。数据以称为数据包的小单元发送，这些数据包在网络中独立传输，并在目的地重新组装。这称为分组交换。
Network hardware includes routers that direct packets between networks, switches that connect devices within a LAN, and wireless access points for Wi‑Fi connections. The World Wide Web is a service that runs over the internet, using protocols like HTTP and HTTPS to transfer web pages.
网络硬件包括在不同网络之间引导数据包的路由器、在局域网内连接设备的交换机，以及用于 Wi‑Fi 连接的无线接入点。万维网是运行在互联网上的一项服务，使用 HTTP 和 HTTPS 等协议来传输网页。
11. E‑Safety: Protecting Yourself and Your Information | 网络安全：保护自己和你的信息
As we spend more time online, it is crucial to understand how to stay safe. E‑safety covers protecting personal information, recognising online risks, and behaving responsibly.
随着我们在网上花费越来越多的时间，了解如何保持安全至关重要。网络安全涵盖保护个人信息、识别网络风险以及负责任地行事。
Personal information (name, address, school, phone number, passwords) should never be shared with strangers online. Once something is posted, it can be difficult to remove completely — this is known as a digital footprint. Think carefully before you share photos or opinions.
个人信息（姓名、地址、学校、电话号码、密码）绝不要与网上陌生人分享。一旦发布某些内容，就很难彻底删除——这被称为数字足迹。在分享照片或观点之前，请三思。
Common online threats include malware (malicious software like viruses, worms, and trojans), phishing (fake emails or messages that try to steal your login details), and cyberbullying (using technology to harass or embarrass someone). Always keep your software up to date, use strong passwords combining upper‑case, lower‑case, numbers, and symbols, and tell a trusted adult if something makes you uncomfortable.
常见的网络威胁包括恶意软件（如病毒、蠕虫和木马等恶意软件）、网络钓鱼（试图窃取你登录信息的虚假邮件或消息）以及网络欺凌（利用技术骚扰或使人难堪）。始终让软件保持最新，使用包含大小写字母、数字和符号的强密码，并且如果有什么让你感到不舒服，一定要告诉可信赖的成年人。
Encryption is used to scramble data so that only the intended recipient can read it — look for the padlock symbol in the address bar when browsing, indicating a secure connection (HTTPS).
加密用于打乱数据，只有预期的接收者才能读取——浏览网页时，请注意地址栏中的挂锁符号，它表示安全连接（HTTPS）。
12. Boolean Logic and Truth Tables | 布尔逻辑与真值表
At the heart of computer decision‑making lies Boolean logic, named after mathematician George Boole. Boolean expressions evaluate to either TRUE or FALSE, and logic gates are the physical circuits that implement these operations.
计算机决策的核心是布尔逻辑，以数学家乔治·布尔的名字命名。布尔表达式的结果只能是真（TRUE）或假（FALSE），而逻辑门是实现这些运算的物理电路。
The three fundamental gates are AND, OR, and NOT.
三种基本门是与（AND）、或（OR）和非（NOT）。
- AND: outputs TRUE only if both inputs are TRUE.
- 与门：仅当两个输入都为 TRUE 时，输出才为 TRUE。
- OR: outputs TRUE if at least one input is TRUE.
- 或门：只要至少一个输入为 TRUE，输出就为 TRUE。
- NOT: reverses the input (TRUE becomes FALSE, and vice versa).
- 非门：反转输入（TRUE 变成 FALSE，反之亦然）。
We can summarise the behaviour of a gate using a truth table. For example, the AND gate truth table:
我们可以用真值表总结门的行为。例如，与门的真值表：
| Input A | Input B | Output (A AND B) |
|---|---|---|
| 0 | 0 | 0 |
| 0 | 1 | 0 |
| 1 | 0 | 0 |
| 1 | 1 | 1 |
Boolean logic is used in programming conditions, database searches, and even in simple electronic circuits.
布尔逻辑被用于编程中的条件判断、数据库搜索，甚至简单的电子电路中。
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