IGCSE Computer Science: The Internet & Its Applications | IGCSE计算机：互联网及其应用场景

📚 IGCSE Computer Science: The Internet & Its Applications | IGCSE计算机：互联网及其应用场景

The Internet is one of the most transformative technologies ever created. For CIE IGCSE Computer Science, you must understand not only what the Internet is, but also how data travels across it, how addresses and domain names work, and the range of everyday applications it powers. This guide covers every key point you need to revise, written in clear bilingual pairs to help you master both the concepts and the exam vocabulary.

互联网是人类历史上最具变革性的技术之一。在 CIE IGCSE 计算机科学考试中，你不仅需要知道互联网是什么，还必须理解数据如何在互联网上传输、IP 地址与域名如何工作，以及互联网驱动的各类日常应用场景。本篇指南以中英双语配对的方式，覆盖所有需要复习的考点，帮助你同时掌握核心概念与考试词汇。

1. What Is the Internet? | 什么是互联网？

The Internet is a global network of interconnected computers and networks that communicate using a standardised set of rules called protocols. No single organisation owns the entire Internet; instead, it is a decentralised system made up of millions of public and private networks. These networks are linked by cables, fibre optics, satellites, and wireless connections.

互联网是一个由全球互联的计算机和网络组成的体系，它们通过一套标准化的规则（即“协议”）进行通信。没有任何单一组织拥有整个互联网；相反，它是一个由数百万公共和私有网络组成的去中心化系统。这些网络通过电缆、光纤、卫星和无线连接互相联通。

The most important protocol suite used on the Internet is TCP/IP. TCP (Transmission Control Protocol) is responsible for breaking data into packets and reassembling them in the correct order at the destination. IP (Internet Protocol) handles addressing, ensuring each packet is routed to the correct device. Together, TCP/IP provides the “rules of the road” that make reliable communication across the global network possible.

互联网上最重要的协议族是 TCP/IP。TCP（传输控制协议）负责将数据拆分成数据包，并在目的地按正确顺序重新组装。IP（互联网协议）负责寻址，确保每个数据包被路由到正确的设备。TCP/IP 共同构成了“道路规则”，使全球网络上的可靠通信成为可能。

It is essential to distinguish between the Internet and the World Wide Web. The Internet is the physical and logical infrastructure — the cables, routers, servers, and the TCP/IP protocols — while the World Wide Web is one of the services that runs on top of the Internet, consisting of web pages and hyperlinks. The Internet also carries email, file transfer, VoIP, gaming, and many other services.

必须区分互联网与万维网。互联网是物理和逻辑基础设施——包括电缆、路由器、服务器以及 TCP/IP 协议；而万维网是运行在互联网之上的服务之一，由网页和超链接组成。互联网还承载电子邮件、文件传输、网络电话、游戏以及许多其他服务。

2. IP Addresses and MAC Addresses | IP 地址与 MAC 地址

Every device connected to the Internet must have a unique address so that data packets can be delivered correctly. An IP address is a unique identifier assigned to a device on a network. In IPv4, the address is a 32-bit number written as four decimal numbers separated by dots, such as 192.168.1.10. IPv4 supports about 4.3 billion unique addresses, which is no longer enough for the modern world.

连接到互联网的每一台设备都必须有一个唯一的地址，以便数据包能够被正确送达。IP 地址是分配给网络中设备的一个唯一标识符。在 IPv4 中，地址是一个 32 位数字，写成四个用点分隔的十进制数，例如 192.168.1.10。IPv4 最多支持约 43 亿个唯一地址，已不足以满足当今世界的需求。

IPv6 was introduced to solve this shortage. It uses a 128-bit address, written as eight groups of hexadecimal digits, for example 2001:db8::ff00:42:8329. IPv6 provides an astronomically large number of addresses, more than enough for every device on Earth. At IGCSE level, you need to be able to recognise the difference between IPv4 and IPv6 formats and understand why the transition was necessary.

为解决地址短缺问题，IPv6 被引入。它使用 128 位地址，写成八组十六进制数字，例如 2001:db8::ff00:42:8329。IPv6 提供的地址数量极为庞大，足以满足地球上每一台设备的需求。在 IGCSE 阶段，你需要能够识别 IPv4 和 IPv6 格式的区别，并理解过渡到 IPv6 的必要性。

A MAC address (Media Access Control address) is different from an IP address. A MAC address is a 48-bit hardware address burned into a device’s network interface card, such as 00:1A:2B:3C:4D:5E. It identifies the physical device on a local network, while the IP address identifies the device’s logical location on the wider Internet. MAC addresses are fixed by the manufacturer, whereas IP addresses can change.

MAC 地址（介质访问控制地址）与 IP 地址不同。MAC 地址是烧录在设备网卡中的 48 位硬件地址，例如 00:1A:2B:3C:4D:5E。它在局域网中标识物理设备，而 IP 地址标识设备在更大范围互联网中的逻辑位置。MAC 地址由制造商固定，而 IP 地址可以改变。

3. URLs and DNS | 统一资源定位符与域名系统

A URL (Uniform Resource Locator) is the full web address used to locate a resource on the Internet. A typical URL contains several parts: the protocol (such as http:// or https://), the domain name (such as http://www.example.com), the path to a specific file or page, and sometimes parameters. For example, in https://www.aleveler.com/computer-science, the protocol is HTTPS, the domain is http://www.aleveler.com, and the path is /computer-science.

URL（统一资源定位符）是用于在互联网上定位资源的完整网址。一个典型的 URL 包含几个部分：协议（如 http:// 或 https://）、域名（如 http://www.example.com）、指向特定文件或页面的路径，有时还包括参数。例如，在 https://www.aleveler.com/computer-science 中，协议是 HTTPS，域名是 http://www.aleveler.com，路径是 /computer-science。

The domain name itself is hierarchical. The top-level domain (TLD) is the last part, such as .com, .org, or .uk. The second-level domain is the name before the TLD, such as “aleveler”. Subdomains, like www or blog, can precede the second-level domain. This hierarchy helps organise the domain name space and makes addresses easier for humans to remember than numeric IP addresses.

域名本身是分层的。顶级域（TLD）是最后一部分，如 .com、.org 或 .uk。二级域是 TLD 之前的名称，如 “aleveler”。子域名（如 www 或 blog）可以位于二级域之前。这种层级结构有助于组织域名空间，并且比数字形式的 IP 地址更容易记忆。

The DNS (Domain Name System) acts like the “phonebook of the Internet”. When you type a URL into a browser, the DNS resolution process translates the human-readable domain name into a machine-readable IP address. A DNS server looks up the requested name in its database and returns the corresponding IP address. If the local DNS server does not know the address, it forwards the query to other DNS servers until an authoritative answer is found. This process is transparent to the user and typically takes only milliseconds.

DNS（域名系统）就像“互联网的电话簿”。当你在浏览器中输入一个 URL 时，DNS 解析过程会将人类可读的域名转换为机器可读的 IP 地址。DNS 服务器在其数据库中查找所请求的名称，并返回对应的 IP 地址。如果本地 DNS 服务器不知道该地址，它会把查询转发给其他 DNS 服务器，直到找到权威答案为止。这个过程对用户完全透明，通常只需几毫秒。

For the exam, remember the order: user types URL → browser asks DNS for IP address → DNS returns IP → browser sends HTTP/HTTPS request to that IP → web server responds with the page. Candidates frequently lose marks by confusing the roles of DNS and IP addresses, so practise this sequence until it is automatic.

考试时请记住这一顺序：用户输入 URL → 浏览器向 DNS 请求 IP 地址 → DNS 返回 IP → 浏览器向该 IP 发送 HTTP/HTTPS 请求 → Web 服务器响应页面内容。考生经常因混淆 DNS 与 IP 地址的职责而失分，请反复练习这一流程直至熟练。

4. HTTP, HTTPS and Web Browsers | HTTP、HTTPS 与网页浏览器

HTTP (Hypertext Transfer Protocol) is the protocol used to transfer web pages from a server to a browser. When the browser requests a page, the server responds by sending HTML code and other resources. HTTP is stateless, meaning each request is independent and the server does not remember previous requests without additional mechanisms such as cookies or sessions.

HTTP（超文本传输协议）用于将网页从服务器传输到浏览器。当浏览器请求一个页面时，服务器会响应并发送 HTML 代码及其他资源。HTTP 是无状态协议，意味着每个请求都是独立的；如果没有 Cookie 或会话等额外机制，服务器不会记住之前的请求。

HTTPS (HTTP Secure) is the encrypted version of HTTP. It uses TLS/SSL encryption to scramble data during transmission, so that eavesdroppers cannot read the content. The padlock symbol in a browser address bar indicates that the connection is secure. HTTPS protects sensitive information such as passwords, credit card numbers, and personal data, and is essential for online banking, shopping, and login systems.

HTTPS（安全超文本传输协议）是 HTTP 的加密版本。它使用 TLS/SSL 加密技术在传输过程中对数据进行打乱处理，使窃听者无法读取内容。浏览器地址栏中的挂锁图标表示该连接是安全的。HTTPS 可保护密码、信用卡号和个人数据等敏感信息，对网上银行、购物和登录系统至关重要。

A web browser is a software application used to access and display web pages. Common examples include Google Chrome, Mozilla Firefox, Microsoft Edge, and Safari. The browser interprets HTML, CSS, and JavaScript from the server and renders them as a visual page. Browsers also manage cookies, store favouritess, maintain history, and provide developer tools for inspecting underlying code.

网络浏览器是用于访问和显示网页的软件应用。常见示例包括 Google Chrome、Mozilla Firefox、Microsoft Edge 和 Safari。浏览器解析来自服务器的 HTML、CSS 和 JavaScript，并将其渲染为可视化页面。浏览器还管理 Cookie、收藏夹、历史记录，并提供用于检查底层代码的开发者工具。

5. Email Systems and Protocols | 电子邮件系统与协议

Email (electronic mail) is one of the oldest and most widely used Internet applications. It allows users to send messages, files, and images to other users across the world almost instantly. An email message consists of a header (containing the sender’s address, recipient’s address, subject, and date) and a body (the actual message content). The structure of an email address is username@domain, for example student@aleveler.com.

电子邮件是互联网上最古老、使用最广泛的应用之一。它允许用户向世界各地的其他用户几乎即时地发送消息、文件和图片。一封电子邮件由邮件头（包含发件人地址、收件人地址、主题和日期）和邮件正文（实际消息内容）组成。电子邮件地址的结构是用户名@域名，例如 student@aleveler.com。

Email relies on several protocols to function correctly. SMTP (Simple Mail Transfer Protocol) is used for sending emails from a client to a server and for transferring mail between servers. POP (Post Office Protocol), now commonly POP3, downloads emails from the server to a single local device and usually deletes them from the server afterwards. IMAP (Internet Message Access Protocol) synchronises emails across multiple devices; messages remain stored on the server, allowing access from different locations.

电子邮件的正常运行依赖多个协议。SMTP（简单邮件传输协议）用于将邮件从客户端发送到服务器，以及在服务器之间传输邮件。POP（邮局协议），现在通常指 POP3，将邮件从服务器下载到单个本地设备，并通常在之后从服务器上删除。IMAP（互联网消息访问协议）可在多个设备之间同步邮件；邮件保留在服务器上，因此可以从不同地点访问。

When you are asked about SMTP, POP, and IMAP in the exam, think of SMTP as the “sending” protocol, POP as “download and remove”, and IMAP as “sync and keep”. A useful revision table is shown below:

当考试中遇到 SMTP、POP 和 IMAP 时，可以把 SMTP 理解为“发送”协议，POP 是“下载并删除”，IMAP 是“同步并保留”。下面的复习表格对你有帮助：

Protocol / 协议	Port / 端口	Function / 功能
SMTP	25	Sending email / 发送邮件
POP3	110	Download and delete from server / 下载并从服务器删除
IMAP	143	Synchronise across devices / 多设备同步

6. VoIP and Video Conferencing | 网络电话与视频会议

VoIP (Voice over Internet Protocol) is a technology that allows voice communication to be transmitted over the Internet as digital data packets, rather than through traditional telephone lines. Services such as Skype, WhatsApp voice calls, and Zoom all use VoIP. Voice signals are digitised, compressed, split into packets, sent across the Internet, and reassembled at the destination before being converted back to sound.

VoIP（基于互联网协议的语音传输）是一种允许语音通过互联网以数字数据包形式传输的技术，而不是通过传统电话线路。Skype、WhatsApp 语音通话和 Zoom 等服务都使用 VoIP。语音信号被数字化、压缩、拆分成数据包，在互联网上传输，在目的地重新组装，然后再转换回声音。

Video conferencing extends VoIP by adding live video streams to the audio stream. Participants can see and hear each other in real time using cameras, microphones, and speakers connected to their computers or mobile devices. Video conferencing requires significantly more bandwidth than audio-only calls because video frames carry much more data. Modern platforms also offer screen sharing, virtual backgrounds, interactive whiteboards, and live chat features.

视频会议在 VoIP 的基础上增加了实时视频流。参与者可以使用连接到电脑或移动设备的摄像头、麦克风和扬声器实时看到和听到彼此。视频会议需要的带宽远高于纯语音通话，因为视频帧携带的数据量更大。现代平台还提供屏幕共享、虚拟背景、互动白板和实时聊天等功能。

There are several advantages of VoIP over traditional telephony. VoIP calls are often cheaper or free, especially for international calls. The same network can carry voice, video, and data simultaneously. However, VoIP depends on a stable Internet connection; poor connectivity can cause delay, echo, or dropped calls. A power failure also disables VoIP unless backup power is available, whereas traditional telephone lines may still work.

与传统电话相比，VoIP 具有多项优势。VoIP 通话通常更便宜甚至免费，尤其是国际电话。同一网络可以同时承载语音、视频和数据。然而，VoIP 依赖稳定的互联网连接；连接质量差会导致延迟、回声或通话中断。停电时 VoIP 也会失效（除非有备用电源），而传统电话线路在停电时仍可能正常工作。

7. Cloud Computing and Cloud Storage | 云计算与云存储

Cloud computing refers to the delivery of computing services — including servers, storage, databases, networking, software, and analytics — over the Internet (“the cloud”). Instead of buying and maintaining physical hardware, users rent computing resources from providers such as Amazon Web Services, Microsoft Azure, or Google Cloud. There are three main service models: IaaS (Infrastructure as a Service), PaaS (Platform as a Service), and SaaS (Software as a Service).

云计算是指通过互联网（“云”）提供计算服务——包括服务器、存储、数据库、网络、软件和分析。用户无需购买和维护物理硬件，而是从 Amazon Web Services、Microsoft Azure 或 Google Cloud 等提供商处租用计算资源。主要有三种服务模式：IaaS（基础设施即服务）、PaaS（平台即服务）和 SaaS（软件即服务）。

Cloud storage is a specific application of cloud computing that allows users to save data to remote servers over the Internet. Popular services include Google Drive, iCloud, Dropbox, and OneDrive. Files can be uploaded, downloaded, edited, and shared from any device with an Internet connection. Cloud storage separates the physical location of data from the user’s device, providing flexibility and accessibility.

云存储是云计算的一种具体应用，允许用户通过互联网将数据保存到远程服务器。流行的服务包括 Google Drive、iCloud、Dropbox 和 OneDrive。只要有互联网连接，用户就可以在任何设备上上传、下载、编辑和共享文件。云存储将数据的物理位置与用户设备分离开来，提供了灵活性和可访问性。

Advantages of cloud computing include scalability (resources can be increased or decreased on demand), cost savings (you only pay for what you use), automatic updates, and remote accessibility. Disadvantages include reliance on a stable Internet connection, potential security and privacy risks, data sovereignty concerns (data may be stored in another country with different laws), and the possibility of vendor lock-in.

云计算的优势包括可扩展性（资源可按需增减）、成本节约（只按使用量付费）、自动更新以及远程可访问性。劣势包括依赖稳定的互联网连接、潜在的安全与隐私风险、数据主权问题（数据可能存储在法律法规不同的其他国家），以及可能被供应商锁定。

8. E-Commerce and Online Banking | 电子商务与网上银行

E-commerce (electronic commerce) is the buying and selling of goods and services over the Internet. Online retail platforms such as Amazon, Alibaba, and eBay allow customers to browse product catalogues, compare prices, read reviews, and make purchases without leaving their homes. E-commerce also includes business-to-business (B2B) transactions, online auctions, and digital goods such as software, e-books, and streaming subscriptions.

电子商务（electronic commerce）是通过互联网买卖商品和服务。Amazon、Alibaba、eBay 等在线零售平台允许顾客在家中浏览产品目录、比较价格、阅读评论并完成购买。电子商务还包括企业对企业（B2B）交易、在线拍卖以及软件、电子书和流媒体订阅等数字商品。

The online payment process is a critical part of e-commerce. When a customer enters their payment details, the information must be encrypted (typically using HTTPS) to prevent interception. Payment gateway providers, such as PayPal or Stripe, verify the transaction and transfer funds securely. Additional security measures include two-factor authentication (2FA), CAPTCHA, and fingerprint or face recognition on mobile devices.

在线支付流程是电子商务的关键环节。当顾客输入支付信息时，该信息必须被加密（通常使用 HTTPS）以防止被截获。PayPal 或 Stripe 等支付网关提供商负责验证交易并安全地转移资金。额外的安全措施包括双重身份验证（2FA）、CAPTCHA 验证码，以及移动设备上的指纹或人脸识别。

Online banking allows customers to manage their finances through a bank’s website or mobile application. Users can check account balances, transfer money, pay bills, and apply for loans. Online banking offers convenience and 24/7 availability, but it also introduces risks such as phishing attacks, keylogging, and identity theft. Banks therefore implement robust security protocols, including real-time fraud detection, secure sessions, and customer education.

网上银行允许客户通过银行的网站或移动应用管理财务。用户可以查询账户余额、转账、支付账单和申请贷款。网上银行提供了便利性和全天候服务，但也引入了网络钓鱼攻击、键盘记录和身份盗窃等风险。因此，银行实施严格的安全协议，包括实时欺诈检测、安全会话和客户教育。

9. Social Media, Forums and Instant Messaging | 社交媒体、论坛与即时通讯

Social media platforms such as Facebook, Instagram, X (formerly Twitter), and TikTok allow users to create profiles, share content, follow other users, and interact through likes, comments, and direct messages. Social media relies on large server farms to store user-generated content and sophisticated algorithms to recommend content to users. These platforms generate revenue primarily through targeted advertising based on user data analysis.

Facebook、Instagram、X（原 Twitter）和 TikTok 等社交媒体平台允许用户创建个人资料、分享内容、关注其他用户，并通过点赞、评论和私信进行互动。社交媒体依赖大型服务器集群来存储用户生成的内容，并使用复杂的算法向用户推荐内容。这些平台主要通过基于用户数据分析的定向广告来获取收入。

Online forums (such as Reddit or subject-specific discussion boards) are structured around topics and threads, allowing asynchronous discussions that remain available for future reference. Instant messaging services (such as WhatsApp, WeChat, and Telegram) provide real-time, one-to-one or group text communication. Modern messaging often includes end-to-end encryption, meaning only the sender and receiver can read the messages — the service provider itself cannot access the content.

在线论坛（如 Reddit 或特定学科的讨论板）围绕主题和帖子线程组织，允许非实时（异步）讨论，并且这些讨论内容长期保留供后续查阅。即时通讯服务（如 WhatsApp、微信和 Telegram）提供实时的一对一或群组文本通信。现代消息应用通常包含端到端加密，即只有发送方和接收方可以阅读消息内容——服务提供商本身也无法访问。

A key concept for the exam is the difference between synchronous and asynchronous communication. Instant messaging and VoIP are synchronous because both parties communicate at the same time; email and forums are asynchronous because there is a delay between sending and reading. Social media spans both categories: live streams are synchronous, while posts and comments are asynchronous.

考试中的一个关键概念是同步通信与异步通信的区别。即时通讯和 VoIP 是同步通信，因为双方在同一时间进行交流；电子邮件和论坛是异步通信，因为发送与阅读之间存在时间差。社交媒体同时涵盖两种类型：直播是同步的，而帖子和评论是异步的。

10. Data Packets and Packet Switching | 数据包与分组交换

Data on the Internet is not sent as a single continuous block. Instead, it is broken down into small units called packets. Each packet contains three main parts: the header (which includes the sender’s IP address, the destination IP address, and the packet number), a payload (the actual data fragment), and a trailer (which contains error-checking information, such as a checksum, used to verify that the packet arrived intact).

互联网上的数据并不是作为一个连续的整体一次性发送的。相反，它被拆分称为“数据包”的小单元。每个数据包包含三个主要部分：头部（包含发送方 IP 地址、目标 IP 地址和包编号）、数据负载（实际的数据片段）和尾部（包含用于验证包完整到达的差错校验信息，如校验和）。

Packet switching is the method by which these packets are routed across the network. Each packet travels independently and may take a different route to reach the destination, moving through routers that examine the destination address and forward the packet to the next link. At the destination, the TCP layer reorders the packets using their sequence numbers, discards any corrupted packets and requests retransmission, and reassembles the original data.

分组交换是这些数据包在网络上的路由方式。每个数据包独立传输，可能经过不同路由到达目的地；数据包通过路由器时，路由器检查目标地址并将其转发到下一个链路。在目的地，TCP 层根据包编号对数据包重新排序，丢弃损坏的数据包并请求重传，最后重组原始数据。

Packet switching offers two major advantages over circuit switching (used in traditional telephone networks): efficient use of bandwidth because links are only used when packets are sent, and resilience because packets can be rerouted if a link fails. However, packets can arrive out of order or be delayed, which is why TCP’s sequencing and error-checking responsibilities are so important.

与传统电话网络使用的电路交换相比，分组交换具有两大优势：带宽利用率高，因为链路仅在发送数据包时被占用；抗故障能力强，因为链路失败时数据包可以被重新路由。然而，数据包可能乱序到达或发生延迟，这正是 TCP 的排序和差错校验职责如此重要的原因。

11. Security Threats on the Internet | 互联网安全威胁

Whenever you use the Internet, you are exposed to potential security threats. Malware is malicious software that includes viruses, worms, trojans, spyware, and ransomware. A virus attaches itself to a legitimate program and spreads when that program is run; a worm spreads independently across networks; a trojan disguises itself as useful software while performing hidden harmful actions.

每当你使用互联网，都会面临潜在的安全威胁。恶意软件（malware）是包含病毒、蠕虫、木马、间谍软件和勒索软件在内的恶意程序。病毒附着在合法程序上并在该程序运行时传播；蠕虫可以独立在网络中传播；木马伪装成有用的软件，同时在后台执行恶意的隐蔽操作。

A phishing attack is a social engineering technique in which an attacker sends a fraudulent email or message that pretends to be from a trustworthy source, tricking the victim into revealing passwords, credit card numbers, or other sensitive information. Phishing messages often contain urgent language and links to spoofed websites that look almost identical to real ones.

网络钓鱼（phishing）是一种社会工程学攻击手段：攻击者发送伪装成可信来源的欺诈性电子邮件或消息，诱骗受害者泄露密码、信用卡号或其他敏感信息。钓鱼信息通常包含紧急措辞，并附上指向与真实网站几乎一模一样的仿冒网站的链接。

To protect against these threats, users and organisations use antivirus software, firewalls, encryption, secure connections (HTTPS), automatic software updates, and strong password policies. For the examiner, remember that you should also mention good user practices: never click unknown links, verify the sender’s identity, and avoid sharing passwords. A layered approach — combining technical controls with user awareness — is the most effective defence.

为防范这些威胁，用户和组织使用杀毒软件、防火墙、加密、安全连接（HTTPS）、自动软件更新和强密码策略。请记住，考试中还应提及良好的用户习惯：不点击不明链接、核实发件人身份以及不共享密码。将技术手段与安全意识相结合的纵深防御是最有效的防线。

12. Advantages and Disadvantages of the Internet | 互联网的优点与缺点

For a balanced exam answer, you should be able to discuss both the benefits and drawbacks of Internet use, and give an example for each point where possible.

为了在考试中给出均衡的答案，你应该能够讨论互联网使用的好处与弊端，并尽可能为每一点给出具体示例。

Advantages: instant global communication (email, VoIP); access to a vast amount of information and educational resources; e-commerce enables convenient 24/7 shopping; cloud computing provides flexible and scalable resources; social media enables connection with people worldwide.

优点：即时全球通信（电子邮件、VoIP）；获取海量信息和教育资源；电子商务实现全天候便捷购物；云计算提供灵活可扩展的资源；社交媒体使人能够与世界各地的人联系。
Disadvantages: privacy and security risks (data theft, hacking, phishing); digital divide between those with and without Internet access; spread of misinformation and harmful content; dependence on Internet connectivity; potential negative impact on mental health and social skills from excessive use.

缺点：隐私与安全风险（数据窃取、黑客攻击、网络钓鱼）；有互联网接入与无接入人群之间的数字鸿沟；错误信息和有害内容的传播；对互联网连接的依赖；过度使用可能对心理健康和社交技能产生负面影响。

In a six-mark “discuss” question, always structure your answer into two clear sections (advantages and disadvantages), define the terms you use, and give specific, differentiated examples rather than repeating the same idea in different words.

在 6 分的“讨论”题中，请务必把答案分成两个清晰的部分（优点和缺点），定义你使用的术语，并给出具体且不同的示例，而不是用不同措辞重复同一个观点。

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IGCSE Computer Science: The Internet & Its Applications | IGCSE计算机：互联网及其应用场景