📚 Computer | 计算机
A computer is an electronic device that processes data and executes instructions, working through the close cooperation of hardware and software. It performs a huge range of functions by accepting input, processing information, storing data and outputting results, and it has become an indispensable tool in modern daily life.
计算机是一种能够处理数据并执行指令的电子设备，由硬件和软件共同配合工作。它通过接收输入、处理信息、存储数据和输出结果来实现各种功能，如今已成为人们日常生活离不开的重要工具。
1. What a Computer Is | 计算机的定义
At its simplest, a computer is a programmable machine. The word "programmable" matters: unlike a calculator that only adds numbers, a computer can be given a new set of instructions and then perform a completely different job without any change to its physical parts. This flexibility is what separates a computer from a single-purpose tool such as a toaster or a digital watch.
最简单地说，计算机是一台可编程的机器。"可编程"这个词很关键：与只会做加法的计算器不同，计算机只要被赋予一套新的指令，就能在物理部件完全不变的情况下执行完全不同的任务。正是这种灵活性，把计算机与烤面包机、电子手表这类单一用途的工具区分开来。
Every computer, from a smartwatch to a supercomputer, carries out the same four basic operations, often remembered as the IPOS cycle.
从智能手表到超级计算机，每一台计算机都在执行同样的四个基本操作，通常被概括为 IPOS 循环。
Input - data and commands enter the system through devices such as keyboards, mice, touchscreens, scanners and microphones.
输入——数据与命令通过键盘、鼠标、触摸屏、扫描仪、麦克风等设备进入系统。
Process - the processor performs arithmetic and logical operations on the data according to the program.
处理——处理器按照程序对数据进行算术运算和逻辑运算。
Storage - data and programs are kept in main memory while in use and in secondary storage for the long term.
存储——数据与程序在使用期间保存在内存中，长期则保存在辅助存储器里。
Output - results are presented through monitors, printers, speakers or transmitted to other devices over a network.
输出——结果通过显示器、打印机、扬声器呈现，或经网络传输给其他设备。
Because these four steps repeat endlessly and very quickly, users rarely notice them. Yet understanding the cycle is the foundation for every later topic in computer science, from CPU design to database management.
由于这四个步骤以极快的速度不断循环，使用者几乎察觉不到它们的存在。然而理解这一循环，是后续学习 CPU 设计、数据库管理等所有计算机科学主题的基础。
2. Hardware and Software Working Together | 硬件与软件的协同
Hardware refers to the physical components you can touch, while software refers to the programs and data that tell the hardware what to do. Neither is useful alone: a processor with no program is a lump of silicon, and a program with no processor is a set of ideas with nowhere to run.
硬件指可以触摸到的物理部件，软件指告诉硬件该做什么的程序与数据。两者单独存在都没有意义：没有程序的处理器只是一块硅片，没有处理器的程序只是一堆无处运行的想法。
The main hardware components of a typical computer are listed below.
典型计算机的主要硬件部件如下所示。
CPU (Central Processing Unit) - fetches, decodes and executes instructions; contains the arithmetic logic unit and the control unit.
CPU（中央处理器）——取指、译码并执行指令，内部包含算术逻辑单元和控制单元。
Main memory (RAM) - fast, volatile storage that holds programs and data currently in use; its contents disappear when power is cut.
主存（RAM）——速度快、易失的存储器，保存正在使用的程序和数据；断电后内容消失。
Secondary storage - solid-state drives and hard disk drives that keep files permanently.
辅助存储器——固态硬盘和机械硬盘，用于永久保存文件。
Motherboard - the circuit board that connects the processor, memory, storage and peripherals.
主板——连接处理器、内存、存储和外设的电路板。
GPU (Graphics Processing Unit) - handles images, video and, increasingly, parallel computing tasks.
GPU（图形处理器）——负责图像、视频处理，并越来越多地承担并行计算任务。
Software is normally divided into two broad categories. System software, such as the operating system, manages hardware resources, memory allocation, file systems and security. Application software, such as word processors, browsers and games, is written to solve specific user tasks. The operating system sits between the two, providing the platform on which applications run.
软件通常分为两大类。系统软件（如操作系统）负责管理硬件资源、内存分配、文件系统与安全；应用软件（如文字处理程序、浏览器、游戏）则为解决特定用户任务而编写。操作系统位于二者之间，为应用程序提供运行平台。
3. How Data Is Represented | 数据的表示方式
Inside a computer there is no such thing as a letter, a photograph or a song. Everything is reduced to binary digits, or bits, each of which is either 0 or 1. The reason is physical: a circuit is most reliable when it only has to distinguish between two states, such as high and low voltage, or magnetised and non-magnetised.
在计算机内部，并不存在字母、照片或歌曲这样的东西。一切都化约为二进制数字，即位（bit），每一位非 0 即 1。原因在于物理层面：当电路只需区分两种状态（如高电压与低电压、有磁性与无磁性）时，它最可靠。
A single bit can represent only two values, so bits are grouped. Eight bits form one byte, which is enough to represent 256 different patterns - more than enough for the letters of the English alphabet and common punctuation.
单独一位只能表示两个值，因此位需要成组使用。八位构成一个字节（byte），足以表示 256 种不同组合——对于英文字母和常用标点来说绰绰有余。
Storage and memory capacities are measured with the following units.
存储与内存容量使用以下单位衡量。
| Unit | 单位 | Size | 大小 | Typical example | 典型例子 |
| bit | 位 | 0 or 1 | one binary digit |
| byte (B) | 字节 | 8 bits | one character of text |
| kilobyte (KB) | 千字节 | 2¹⁰ B = 1024 B | a short email |
| megabyte (MB) | 兆字节 | 2¹⁰ KB ≈ 1.05 × 10⁶ B | a minute of MP3 audio |
| gigabyte (GB) | 吉字节 | 2¹⁰ MB ≈ 1.07 × 10⁹ B | a standard DVD |
| terabyte (TB) | 太字节 | 2¹⁰ GB ≈ 1.10 × 10¹² B | a large external drive |
Different kinds of content need different encoding rules. Text is mapped to numeric codes such as ASCII or Unicode; images are stored as grids of pixels, each with colour values; sound is stored as a series of samples taken thousands of times per second. Video combines both, storing many images plus an audio track.
不同类型的内容需要不同的编码规则。文本被映射为 ASCII 或 Unicode 等数值编码；图像以像素网格形式存储，每个像素带有颜色值；声音则是每秒数千次采样得到的一系列样本。视频兼而有之，存储大量图像外加一条音轨。
4. From Room-Sized Machines to Pocket Devices | 从庞然大物到掌上设备
The history of computing can be traced back to the 1940s, when the first electronic computers were built. Those machines were enormous, filling whole rooms, and operating them was a complicated business: programmers had to rewire plugboards or feed in punched cards, and early machines used thousands of vacuum tubes that generated great heat and failed frequently.
计算机的历史可以追溯到 20 世纪 40 年代，那时的机器体积庞大、操作复杂。它们占满整个房间，操作起来十分麻烦：程序员必须重新连接插线板或输入打孔卡片，早期机器使用成千上万个真空管，发热量大且频繁损坏。
Three inventions changed everything. The transistor replaced the vacuum tube in the late 1940s, making machines smaller and far more reliable. The integrated circuit, developed at the end of the 1950s, placed many transistors on a single chip. The microprocessor, introduced in the early 1970s, put an entire processor on one chip and made the personal computer possible.
三项发明改变了一切。20 世纪 40 年代末，晶体管取代真空管，使机器更小、可靠得多；50 年代末出现的集成电路把许多晶体管集成到一块芯片上；70 年代初问世的微处理器把整个处理器放到一块芯片上，让个人计算机成为可能。
Since then, the number of transistors on a chip has roughly doubled every two years - an observation known as Moore's Law. The result is that a modern smartphone, which fits in a pocket, holds far more computing power than the room-sized machines that launched the digital age.
此后，一块芯片上的晶体管数量大约每两年翻一番，这一观察被称为摩尔定律。结果是，装进口袋的现代智能手机，其计算能力远远超过当年开启数字时代的房间大小的机器。
Today computers appear in many forms, each suited to different needs.
如今计算机拥有多种形态，各自适应不同需求。
Desktop computers - powerful, upgradeable and cost-effective, but fixed in one place.
台式机——性能强、可升级、性价比高，但只能固定在一处使用。
Laptops - portable and self-contained, a compromise between power and mobility.
笔记本电脑——便携且自成一体，在性能与移动性之间取得平衡。
Tablets - touch-driven, ideal for reading, drawing and light productivity.
平板电脑——以触控操作为主，适合阅读、绘图和轻量办公。
Smartphones - always connected, combining communication, camera, navigation and computing in one device.
智能手机——始终联网，把通信、相机、导航与计算功能集于一身。
5. Computers in Education | 教育中的计算机
In education, computers help students acquire knowledge and create interactive learning experiences. A single device can hold an entire library, play explanatory animations, run simulations of chemical reactions or physics experiments, and mark exercises instantly. Learners can pause, repeat and revisit material at their own pace, which is difficult to achieve in a large class.
在教育中，计算机帮助学生获取知识，营造互动式学习体验。一台设备就能装下整座图书馆，播放讲解动画，运行化学反应或物理实验的模拟，并即时批改练习。学习者可以按自己的节奏暂停、重听、回顾内容，这在大型班级里很难做到。
Online platforms extend the classroom beyond the school gate. Students in remote areas can attend live lessons, submit homework electronically and receive feedback within hours. Teachers can use data dashboards to see which topics the class has misunderstood and adjust the next lesson accordingly.
在线平台把课堂延伸到校门之外。偏远地区的学生可以参加直播课、以电子方式提交作业，并在数小时内收到反馈。教师可以借助数据看板了解全班在哪些知识点上出错，据此调整下一节课。
There are, however, conditions for these benefits to appear. Reliable internet access, well-designed software and teachers who know how to integrate technology into their subject teaching are all essential. Used carelessly, a computer in the classroom becomes a distraction rather than a tool.
不过，这些好处需要一定条件才能显现。稳定的网络接入、精心设计的软件，以及懂得如何把技术融入学科教学的教师，缺一不可。若使用不当，教室里的计算机会变成干扰而非工具。
6. Computers in Medicine | 医疗中的计算机
In medicine, computers assist doctors in diagnosis and process and analyse medical images, effectively raising the standard of care. A CT or MRI scanner produces thousands of cross-sectional images; software reconstructs them into clear three-dimensional views that a radiologist can examine slice by slice.
在医疗上，计算机辅助医生诊断，对医学图像进行处理分析，有效提升了诊疗水平。CT 或核磁共振扫描仪会产生成千上万张断层图像，软件将其重建为清晰的三维视图，供放射科医生逐层查看。
Beyond imaging, computers support patient monitoring, where sensors track heart rate, blood pressure and oxygen saturation continuously and raise an alarm when values leave a safe range. They manage appointment systems, prescriptions and electronic health records, reducing the paperwork that once consumed hours of clinical time.
除影像之外，计算机还支持病人监护：传感器持续追踪心率、血压和血氧饱和度，一旦数值超出安全范围便发出警报。它们还管理预约系统、处方和电子健康档案，减少了曾经耗费大量临床时间的文书工作。
More recently, machine learning models have been trained to spot patterns in scans or test results that may be easy to miss. Such systems are decision-support tools rather than replacements for doctors, and their output must always be checked by a qualified clinician, because a wrong recommendation can have serious consequences.
近年来，机器学习模型被训练用于识别扫描图像或检验结果中容易被忽略的模式。这类系统是决策支持工具，而不是医生的替代品；其输出必须由合格的临床医生复核，因为错误的建议可能带来严重后果。
7. Computers in Industry | 工业中的计算机
In industry, computers allow production line tasks to be automated and significantly improve efficiency. Programmable controllers coordinate robotic arms, conveyor belts and inspection cameras, so that a car body can be welded, painted and checked with very little human intervention.
在工业里，计算机让生产线任务实现自动化，显著提高工作效率。可编程控制器协调机械臂、传送带和检测摄像头，使汽车车身在极少人工干预下完成焊接、喷漆和检验。
Automation brings clear advantages: consistent quality, round-the-clock operation, and the removal of workers from dangerous or repetitive environments. It also brings challenges. Jobs that consist mainly of routine physical or clerical tasks are the most exposed, and the workers affected often need retraining in new skills such as machine maintenance, quality data analysis or programming.
自动化带来明显优势：质量稳定、可以全天候运行，并让工人远离危险或高度重复的环境。它也带来挑战。以常规体力或事务性任务为主的工作最容易受到冲击，受影响的工人往往需要接受再培训，学习设备维护、质量数据分析或编程等新技能。
Computers are equally important before production begins. Designers use computer-aided design to model parts in three dimensions, engineers simulate stress and airflow before a single component is made, and planners use scheduling software to balance stock levels against demand. This shortens development cycles and reduces costly physical prototypes.
在生产开始之前，计算机同样重要。设计人员用计算机辅助设计对零件进行三维建模，工程师在制造任何部件之前就模拟受力与气流，计划人员用排程软件平衡库存与需求。这缩短了开发周期，也减少了昂贵的实物样机。
8. Transport, Communication and Entertainment | 交通、通信与娱乐
Beyond these fields, computers have a profound influence on transport, communication and entertainment. In transport they control traffic lights, adjust signal timing according to real-time flow, and optimise route planning, so that city journeys become smoother and less fuel is wasted in queues.
除了上述领域，计算机在交通、通信和娱乐方面同样影响深远。在交通方面，它控制交通信号灯，根据实时车流调整配时，并优化路线规划，让城市出行更加顺畅，也减少了排队时浪费的燃油。
In communication, computers support high-speed network communication and data transmission, bringing people closer together. Messages, photographs and video calls cross continents in fractions of a second, and cloud services let colleagues in different countries edit the same document at the same time.
在通信方面，计算机支撑高速网络通信与数据传输，拉近人与人之间的距离。消息、照片和视频通话在零点几秒内跨越各大洲，云服务让身处不同国家的同事可以同时编辑同一份文件。
In entertainment, computers deliver rich and varied leisure experiences through games, music, film and virtual reality. Streaming platforms recommend content based on listening and viewing habits, game engines render physically accurate worlds in real time, and virtual reality headsets place the user inside a simulated environment for training, therapy or pure enjoyment.
在娱乐方面，计算机通过游戏、音乐、电影和虚拟现实等形式，带来丰富多彩的休闲体验。流媒体平台依据收听收视习惯推荐内容，游戏引擎实时渲染符合物理规律的世界，虚拟现实头显则把用户置于模拟环境中，用于培训、治疗或纯粹的娱乐。
These three areas are increasingly connected. A navigation app uses the same mobile network that carries video calls, and the same device that plays music also books a train ticket. This convergence is one reason why computers have become so deeply embedded in daily routine.
这三个领域正日益相互连接。导航应用使用的移动网络同样承载视频通话，播放音乐的设备也能预订火车票。这种融合正是计算机如此深入日常生活的部分原因。
9. Algorithms and Programming | 算法与编程
A computer can only do what it is told, and the telling is done through algorithms and programs. An algorithm is a finite sequence of unambiguous steps that solves a problem; a program is that algorithm written in a language a machine can execute, such as Python, Java or C++.
计算机只能做被要求做的事，而"要求"是通过算法和程序传达的。算法是解决问题的有限、无歧义的步骤序列；程序则是用机器可执行的语言（如 Python、Java 或 C++）写出的算法。
Good algorithms are judged by more than correctness. Efficiency matters, because the same task may be solved by a method that finishes in a second and by one that takes an hour. Programmers therefore compare how running time grows with input size, and prefer designs that stay manageable as data volumes increase.
好的算法不只看是否正确。效率同样重要，因为同一个任务，可能有一种方法一秒完成，另一种方法却要一小时。因此程序员会比较运行时间随输入规模增长的方式，倾向于选择在数据量增大时仍然可控的设计。
Programs are built from a small set of constructs: sequence, selection and iteration, plus variables, data structures and subprograms.
程序由少量基本结构搭建而成：顺序、选择与循环，再加上变量、数据结构和子程序。
Sequence - instructions are carried out one after another.
顺序——指令依次执行。
Selection - conditions such as if / else choose between alternative paths.
选择——if / else 等条件语句在不同分支之间做出取舍。
Iteration - loops repeat a block of code while a condition holds or for a fixed number of times.
循环——在条件成立期间或固定次数内重复执行一段代码。
Data structures - arrays, lists, stacks and queues organise data so it can be searched and updated efficiently.
数据结构——数组、列表、栈和队列用于组织数据，以便高效查找与更新。
Testing and debugging are as important as writing code. A program that has not been tested against normal, boundary and invalid inputs is not finished, and clear documentation helps the next programmer understand the reasoning behind each decision.
测试与调试同编写代码一样重要。没有针对正常值、边界值和非法输入进行测试的程序不算完成，而清晰的文档能帮助下一位程序员理解每项决策背后的理由。
10. Networks, the Internet and the Cloud | 网络、互联网与云计算
A standalone computer is useful; a connected one is transformative. A network links devices so that they can share files, printers and an internet connection. Local area networks cover a single building, while wide area networks span cities and countries, and the internet is the global network of networks that joins them all.
单机有用，联网则带来变革。网络把设备连接起来，使它们能够共享文件、打印机和互联网连接。局域网覆盖单栋建筑，广域网跨越城市与国家，而互联网则是把这一切连接起来的全球性网络之网。
Communication over a network relies on protocols - agreed rules for how data is packaged, addressed and checked. Data is split into packets, each carrying a destination address; routers forward these packets along different paths, and the receiving device reassembles them in the correct order. If a packet is lost, it is simply requested again.
网络通信依赖协议，即关于数据如何打包、寻址和校验的共同规则。数据被拆分成数据包，每个包都带有目的地址；路由器沿不同路径转发这些数据包，接收设备再按正确顺序重新组装。如果某个包丢失，只需请求重发即可。
Cloud computing extends this idea. Instead of running software on a local machine, users access services provided over the network: storage, databases, virtual machines and artificial intelligence tools. The advantages include access from any device, automatic backup and payment only for what is used. The trade-offs are dependence on a stable connection and questions about where personal data is stored and who can access it.
云计算把这一思路进一步延伸。用户不再在本地机器上运行软件，而是通过网络访问服务：存储、数据库、虚拟机和人工智能工具。其优势包括可从任意设备访问、自动备份以及按用量付费；代价则是依赖稳定连接，以及个人数据存储在哪里、谁能访问等问题。
11. Risks and Challenges | 风险与挑战
However, computers also bring problems that cannot be ignored. Overuse may lead people to become absorbed in virtual worlds, weakening real-life communication and experience. Hours spent scrolling or gaming displace conversation, outdoor activity and sleep, and the effects on concentration and mood are now widely studied.
不过，计算机也带来了一些不可忽视的问题。过度使用可能让人沉迷虚拟世界，削弱现实中的交流与体验。长时间刷屏或打游戏占据了交谈、户外活动和睡眠的时间，其对注意力和情绪的影响如今已被广泛研究。
In addition, information security faces constant challenges, and hacker attacks and cybercrime pose a serious threat to society. Common dangers include malware, phishing emails that imitate trusted organisations, ransomware that encrypts files and demands payment, and data breaches that expose personal records.
此外，信息安全不断面临挑战，黑客攻击和网络犯罪对社会构成严重威胁。常见危险包括恶意软件、冒充可信机构的钓鱼邮件、加密文件并索要赎金的勒索软件，以及泄露个人记录的数据入侵。
Basic protective habits reduce most of the risk.
养成基本的防护习惯可以消除大部分风险。
Use long, unique passwords and enable two-factor authentication.
使用足够长且各不相同密码，并开启双重验证。
Keep operating systems and applications updated so known weaknesses are patched.
及时更新操作系统和应用程序，修补已知漏洞。
Be cautious with links and attachments, even when a message appears to come from a friend.
对链接和附件保持警惕，即使消息看似来自熟人。
Back up important files offline or in a second location.
将重要文件离线备份，或保存在第二个位置。
There are wider concerns too. Automated decisions can inherit bias from the data used to train them, algorithms can create filter bubbles that narrow what users see, and the energy consumed by large data centres raises environmental questions. Awareness of these issues is the first step towards managing them.
还有一些更广泛的担忧。自动化决策可能继承训练数据中的偏见，算法可能制造"过滤气泡"、缩窄用户所见，大型数据中心的能耗也引发环境问题。意识到这些问题，是加以管理的第一步。
12. Using Computers Wisely and Looking Ahead | 理性使用与未来展望
We therefore need to use computers rationally and to see their advantages and disadvantages clearly. While enjoying the convenience they bring, we should also value face-to-face communication and protect personal information. Only by applying their strengths sensibly can we better open up new possibilities for our lives and work.
因此，我们需要理性地使用计算机，清醒看待它的利与弊。在享受它带来的便捷时，也要重视面对面交流、保护好个人信息等重要事项。只有合理运用其长处，才能更好地拓展我们生活和工作的新可能。
In practice this means setting sensible limits on screen time, keeping devices out of bedrooms and meals, and treating technology as a means rather than an end. Schools and families both have a role: schools can teach digital literacy and responsible behaviour, while families can model balanced habits at home.
在实践中，这意味着为屏幕时间设定合理限度，让设备远离卧室和餐桌，并把技术当作手段而非目的。学校和家庭都有责任：学校可以教授数字素养与负责任的行为，家庭则可以在日常中示范有节制的习惯。
Looking forward, several trends are already visible. Artificial intelligence is moving from narrow tasks into everyday tools that draft text, translate speech and assist diagnosis. Quantum computing promises to solve certain problems far beyond classical machines. Edge computing processes data near where it is created, reducing delay. Each advance will raise new ethical and regulatory questions alongside its benefits.
展望未来，若干趋势已经显现。人工智能正从狭窄任务走向日常工具，可以起草文本、翻译语音、辅助诊断；量子计算有望解决经典机器远远无法处理的某些问题；边缘计算在数据产生地附近完成处理，从而降低延迟。每一次进步在带来益处的同时，也会引出新的伦理与监管问题。
Overall, computers play an indispensable role in modern society. This great invention has created enormous convenience for people's lives and work, and as technology continues to advance, we have good reason to expect that it will keep evolving and open up an even better future for us.
总的来说，计算机在现代社会中扮演着
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