📚 IGCSE OCR Computer Science: Final Revision Guide | IGCSE OCR 计算机：期末复习提纲
Welcome to your final revision guide for IGCSE OCR Computer Science. This article brings together all the essential topics you need to master, from binary logic to cybersecurity, presented clearly so you can review efficiently. Whether you are brushing up on data representation or perfecting your programming logic, this guide will help you consolidate key concepts and exam techniques.
欢迎阅读 IGCSE OCR 计算机科学的期末复习提纲。本文汇总了你需要掌握的所有核心主题，从二进制逻辑到网络安全，以清晰的方式呈现，让你能够高效复习。无论你是在巩固数据表示还是在完善编程逻辑，这份提纲都能帮助你整合关键概念和考试技巧。
1. Data Representation | 数据表示
Understand how computers represent numbers, text, images, and sound using binary. Binary is base-2, using only 0s and 1s. Denary (base-10) numbers are converted to binary through successive division by 2. Hexadecimal (base-16) is used as a shorthand for binary, with digits 0–9 and letters A–F. You must be able to convert between denary, binary, and hexadecimal, and know why hex is used (shorter, less error-prone).
理解计算机如何使用二进制表示数字、文本、图像和声音。二进制是基数为 2 的系统，只使用 0 和 1。十进制（基数为 10）通过连续除以 2 转换为二进制。十六进制（基数为 16）用作二进制的简写，数字为 0–9 和字母 A–F。你必须能在十进制、二进制和十六进制之间转换，并了解为什么使用十六进制（更短、不易出错）。
Two’s complement is used to represent negative integers. The most significant bit (MSB) acts as a sign bit. To find the negative of a number, invert all bits and add 1. Binary addition and overflow must be understood. An overflow error occurs when a calculation produces a result that exceeds the available bits.
补码（two’s complement）用于表示负整数。最高有效位 (MSB) 充当符号位。要求一个数的负数，将所有位取反再加 1。必须理解二进制加法和溢出。当运算结果超出可用位数时，就会发生溢出错误。
Character representation uses ASCII (7 bits, 128 characters) and Unicode (up to 32 bits, covering many languages). Unicode allows global text encoding but requires more storage. Images are stored as bitmaps (grid of pixels, each pixel assigned a binary colour value). Metadata stores width, height, and colour depth. Sound is sampled at regular intervals; sample rate and bit depth affect quality and file size. File size formulas are: text file size = bits per character × number of characters; image size = width × height × colour depth; sound size = sample rate × bit depth × duration (in seconds) × channels.
字符表示使用 ASCII（7 位，128 个字符）和 Unicode（最多 32 位，涵盖多种语言）。Unicode 支持全球文本编码，但需要更多存储空间。图像以位图形式存储（像素网格，每个像素分配一个二进制颜色值）。元数据存储宽度、高度和颜色深度。声音以固定间隔采样；采样率和位深度影响质量和文件大小。文件大小计算公式为：文本文件大小 = 每字符位数 × 字符数；图像大小 = 宽度 × 高度 × 颜色深度；声音大小 = 采样率 × 位深度 × 时长（秒）× 声道数。
Data compression can be lossy (some data permanently removed, e.g., JPEG, MP3) or lossless (original data fully restored, e.g., ZIP, PNG). Run-length encoding (RLE) is a simple lossless method for repeated values.
数据压缩可以分为有损（部分数据永久删除，如 JPEG、MP3）或无损（原始数据完全恢复，如 ZIP、PNG）。游程编码 (RLE) 是一种简单的针对重复值的无损方法。
2. Systems Architecture | 系统架构
The central processing unit (CPU) is the ‘brain’ of the computer. It consists of the control unit (CU), arithmetic logic unit (ALU), and registers. Von Neumann architecture stores both data and instructions in the same memory. Registers include: Program Counter (PC) holding the address of the next instruction; Memory Address Register (MAR) holding the address to read/write; Memory Data Register (MDR) holding the data being transferred; Accumulator (ACC) holding intermediate ALU results; and Current Instruction Register (CIR) holding the instruction being decoded.
中央处理器 (CPU) 是计算机的“大脑”。它由控制单元 (CU)、算术逻辑单元 (ALU) 和寄存器组成。冯·诺依曼架构将数据和指令存储在同一个内存中。寄存器包括：程序计数器 (PC)，存放下一条指令的地址；内存地址寄存器 (MAR)，存放待读写地址；内存数据寄存器 (MDR)，存放正在传输的数据；累加器 (ACC)，存放 ALU 的中间结果；以及当前指令寄存器 (CIR)，存放正在解码的指令。
The fetch-decode-execute cycle runs continuously. Fetch: PC → MAR, instruction from memory to MDR → CIR, PC incremented. Decode: CU interprets opcode. Execute: instruction carried out, e.g., ALU operation or data load.
取指-解码-执行循环持续运行。取指：PC → MAR，指令从内存到 MDR → CIR，PC 递增。解码：CU 解释操作码。执行：执行指令，例如 ALU 运算或数据加载。
CPU performance depends on clock speed (cycles per second, GHz), number of cores (parallel processing possible), and cache size (fast memory for frequently used data). More cache and higher clock speed typically improve performance but generate more heat.
CPU 性能取决于时钟速度（每秒周期数，GHz）、核心数量（可实现并行处理）以及缓存大小（用于频繁访问数据的快速内存）。更大的缓存和更高的时钟速度通常会提升性能，但也会产生更多热量。
Embedded systems are dedicated computers within larger devices (e.g., washing machines, microwaves). They typically have reduced functionality, low power consumption, and are often based on microcontrollers.
嵌入式系统是大型设备中的专用计算机（例如洗衣机、微波炉）。它们通常功能精简、功耗低，且大多基于微控制器。
3. Memory and Storage | 内存与存储
Primary storage is directly accessed by the CPU. RAM (Random Access Memory) is volatile and holds data/instructions currently in use. ROM (Read Only Memory) is non-volatile and contains boot instructions (BIOS). Virtual memory uses hard disk space as RAM when RAM is full, but is much slower.
主存储器由 CPU 直接访问。RAM（随机存取存储器）是易失性的，保存当前正在使用的数据/指令。ROM（只读存储器）是非易失性的，包含引导指令 (BIOS)。当 RAM 满时，虚拟内存使用硬盘空间作为 RAM，但速度慢得多。
Secondary storage is non-volatile and used for long-term data retention. Magnetic storage (HDD) uses spinning platters; large capacity, low cost, but sensitive to movement. Optical storage (CD, DVD, Blu-ray) uses lasers; portable but limited capacity. Solid-state storage (SSD, USB flash) uses NAND flash; fast, durable, no moving parts, but higher cost per gigabyte.
辅助存储是非易失性的，用于长期数据保留。磁性存储 (HDD) 使用旋转盘片；大容量、低成本，但易受移动影响。光存储（CD、DVD、蓝光）使用激光；便携但容量有限。固态存储（SSD、USB 闪存）使用 NAND 闪存；速度快、耐用、无移动部件，但每 GB 成本较高。
Storage capacity is measured in bytes: kilobyte (KB), megabyte (MB), gigabyte (GB), terabyte (TB). Data transfer rate depends on the interface (e.g., SATA, USB). Cloud storage offers remote access via the internet but requires connectivity and raises security concerns.
存储容量以字节为单位：千字节 (KB)、兆字节 (MB)、千兆字节 (GB)、太字节 (TB)。数据传输速率取决于接口（例如 SATA、USB）。云存储通过互联网提供远程访问，但需要网络连接，并引发安全问题。
4. Networks and Topologies | 网络与拓扑
A network is two or more connected computers. LAN (Local Area Network) covers a small geographical area, usually privately owned. WAN (Wide Area Network) connects LANs over large distances, often using public infrastructure. Factors affecting network performance include bandwidth (maximum data transfer rate), latency (delay), and number of users.
网络是由两台或以上计算机连接而成。LAN（局域网）覆盖小范围地理区域，通常为私有。WAN（广域网）通过远距离连接 LAN，常使用公共基础设施。影响网络性能的因素包括带宽（最大数据传输速率）、延迟（时延）和用户数量。
Client-server networks have a central server providing services (file storage, authentication), while clients request them. Peer-to-peer (P2P) networks have equal machines sharing resources directly; no central server. Network hardware includes switches (connect devices in a LAN, intelligent forwarding), routers (connect different networks, forward data based on IP addresses), and NICs (network interface cards).
客户端-服务器网络有一个中央服务器提供服务（文件存储、身份验证），客户端则请求这些服务。点对点 (P2P) 网络中的机器地位平等，直接共享资源；没有中央服务器。网络硬件包括交换机（连接 LAN 中的设备，智能转发）、路由器（连接不同网络，基于 IP 地址转发数据）和 NIC（网络接口卡）。
Topologies: Star topology has each device connected to a central switch; if one cable fails, others unaffected, but switch failure brings whole network down. Mesh topology provides multiple routes between devices; robust but expensive due to cabling. Wireless networks use Wi-Fi (IEEE 802.11) standards, with frequencies 2.4 GHz and 5 GHz. Encryption like WPA2/WPA3 is essential.
拓扑结构：星型拓扑中，每台设备连接到中央交换机；一条电缆故障不影响其他设备，但交换机故障会导致整个网络瘫痪。网状拓扑在设备间提供多条路径；鲁棒但布线成本高。无线网络使用 Wi-Fi (IEEE 802.11) 标准，频率为 2.4 GHz 和 5 GHz。WPA2/WPA3 等加密至关重要。
Protocols are rules for communication. Key protocols: TCP/IP (transmission/Internet), HTTP/HTTPS (web), FTP (file transfer), SMTP/POP3/IMAP (email). The 4-layer TCP/IP model: Application, Transport, Internet, Network Access.
协议是通信规则。关键协议：TCP/IP（传输/互联网）、HTTP/HTTPS（网页）、FTP（文件传输）、SMTP/POP3/IMAP（电子邮件）。四层 TCP/IP 模型：应用层、传输层、互联网层、网络接入层。
5. Network Security | 网络安全
Malware includes viruses (self-replicate, attach to files), worms (self-spread without host files), Trojans (disguised as legitimate software), spyware (covertly monitors activity), and ransomware (encrypts files for ransom). Phishing uses deceptive emails/websites to steal credentials. Social engineering manipulates people into divulging information.
恶意软件包括病毒（自我复制，附着于文件）、蠕虫（无需宿主文件自行传播）、特洛伊木马（伪装成合法软件）、间谍软件（秘密监视活动）和勒索软件（加密文件以勒索赎金）。网络钓鱼利用欺骗性邮件/网站窃取凭证。社会工程学操纵人们泄露信息。
Brute force attacks try all possible passwords. Denial of Service (DoS) floods a server with traffic to make it unavailable. SQL injection inserts malicious SQL code into data inputs. Cross-site scripting (XSS) injects client-side scripts into web pages.
暴力破解尝试所有可能的密码。拒绝服务攻击 (DoS) 用流量淹没服务器使其不可用。SQL 注入将恶意 SQL 代码插入数据输入中。跨站脚本攻击 (XSS) 将客户端脚本注入网页。
Protection measures: firewalls (filter incoming/outgoing traffic based on rules), encryption (scrambling data so only intended recipient can read it), anti-malware software (detection and removal), penetration testing (simulating attacks to find vulnerabilities), and user access levels (restricting rights). Physical security includes locks, CCTV, and biometric systems.
防护措施：防火墙（基于规则过滤进出流量）、加密（将数据置乱，只有目标接收者才能读取）、反恶意软件（检测与移除）、渗透测试（模拟攻击查找漏洞）以及用户访问级别（限制权限）。物理安全包括锁具、闭路电视和生物识别系统。
6. Systems Software | 系统软件
Operating systems (OS) manage hardware resources, provide a user interface, manage files, handle multitasking, memory management, and peripheral communication via drivers. Examples: Windows, macOS, Linux, Android. Utility software performs specific maintenance tasks: defragmentation (reorganises fragmented files), compression, backup, encryption, antivirus.
操作系统 (OS) 管理硬件资源、提供用户界面、管理文件、处理多任务、内存管理，并通过驱动程序与外设通信。示例：Windows、macOS、Linux、Android。实用工具软件执行特定的维护任务：碎片整理（重组碎片文件）、压缩、备份、加密、防病毒。
Backup types: full (complete copy), incremental (only changes since last backup), differential (changes since last full backup). The OS manages user accounts with differing permissions (admin vs standard).
备份类型：完全备份（完整复制）、增量备份（仅上次备份以來的更改）、差异备份（自上次完全备份以来的更改）。操作系统管理具有不同权限的用户账户（管理员与标准用户）。
7. Ethical, Legal, and Environmental Issues | 伦理、法律与环境问题
Computing technology raises ethical dilemmas around privacy, surveillance, automation replacing jobs, and the digital divide. Legal frameworks include the Data Protection Act (governs use of personal data), Computer Misuse Act (makes unauthorised access or hacking illegal), Copyright Designs and Patents Act (protects intellectual property), and Freedom of Information Act (right to access public organisation data).
计算机技术引发了关于隐私、监控、自动化取代就业以及数字鸿沟的伦理困境。法律框架包括《数据保护法》（规范个人数据的使用）、《计算机滥用法》（将未经授权的访问或黑客行为定为非法）、《版权、设计和专利法》（保护知识产权）以及《信息自由法》（有权访问公共机构数据）。
Environmental impact: e-waste from disposed electronics contains toxic materials; energy consumption of data centres and devices contributes to carbon emissions. Sustainable practices include recycling, energy-efficient components, and responsible manufacturing.
环境影响：废弃电子产品的电子垃圾含有有毒物质；数据中心和设备的能耗导致碳排放。可持续实践包括回收利用、节能组件和负责任制造。
8. Algorithms | 算法
An algorithm is a step-by-step procedure to solve a problem. Key concepts: sequence, selection (IF-THEN-ELSE), iteration (loops). Algorithms can be expressed in pseudocode or flowcharts. Common searching algorithms: linear search (checks each element sequentially; O(n)) and binary search (works on sorted lists, repeatedly dividing search interval; O(log n)).
算法是解决问题的一步一步的过程。关键概念：顺序、选择（IF-THEN-ELSE）、迭代（循环）。算法可以用伪代码或流程图表达。常见搜索算法：线性搜索（按顺序检查每个元素；O(n)）和二分搜索（适用于有序列表，反复划分搜索区间；O(log n)）。
Sorting algorithms: bubble sort (compares adjacent elements and swaps; O(n²)), merge sort (divide and conquer, splits list into sublists; O(n log n)), insertion sort (builds sorted list one item at a time; O(n²)). Understand how each works and their efficiencies.
排序算法：冒泡排序（比较相邻元素并交换；O(n²)）、归并排序（分治法，将列表分成子列表；O(n log n)）、插入排序（一次构建一个排序项；O(n²)）。理解每种算法的工作原理及其效率。
9. Programming Concepts | 编程概念
Programming involves writing instructions for a computer. High-level languages (Python, Java) are human-readable and need translation. Low-level languages include assembly (mnemonics, processor-specific) and machine code (binary). Translators: compiler (translates whole program at once, produces executable), interpreter (translates line by line, no executable produced), assembler (assembly to machine code).
编程涉及为计算机编写指令。高级语言（Python、Java）人类可读，需要翻译。低级语言包括汇编语言（助记符，特定于处理器）和机器码（二进制）。翻译器：编译器（一次性翻译整个程序，生成可执行文件）、解释器（逐行翻译，不生成可执行文件）、汇编器（汇编转机器码）。
Variables hold data that can change; constants remain fixed. Data types: integer, real (float), Boolean, character, string. String manipulation: concatenation, substrings, length. Basic operators: arithmetic (+, -, *, /, MOD, DIV), relational (==, !=, <, >, <=, >=), logical (AND, OR, NOT).
变量保存可变化的数据；常量保持不变。数据类型：整型、实数（浮点）、布尔型、字符、字符串。字符串操作：拼接、子串、长度。基本运算符：算术（+, -, *, /, MOD, DIV）、关系（==, !=, <, >, <=, >=）、逻辑（AND, OR, NOT）。
Control structures: IF-ELSE, nested IF, switch/case. Loops: FOR (definite iteration, repeat a set number of times), WHILE (pre-condition, may never run), REPEAT-UNTIL (post-condition, runs at least once). Nested loops and tracing values are exam staples.
控制结构：IF-ELSE、嵌套 IF、switch/case。循环：FOR（确定迭代，重复指定次数）、WHILE（前置条件，可能根本不执行）、REPEAT-UNTIL（后置条件，至少运行一次）。嵌套循环和追踪值是考试常考内容。
10. Producing Robust Programs | 编写健壮程序
Robust programs handle unexpected inputs without crashing. Input validation checks: range check, type check, presence check, format check, length check. Input sanitisation removes unwanted characters. Testing is vital: test data should include normal (expected), boundary (edge values), invalid (wrong type/range), and erroneous (incorrect but acceptable) data. Iterative testing happens during development; final/terminal testing at the end.
健壮的程序能处理意外输入而不崩溃。输入验证检查：范围检查、类型检查、存在检查、格式检查、长度检查。输入净化去除不需要的字符。测试至关重要：测试数据应包括正常（预期）、边界（边缘值）、无效（错误类型/范围）和异常（不正确但可接受）的数据。迭代测试在开发过程中进行；最终/终端测试在结束时进行。
Logic errors cause incorrect output but the program runs; syntax errors prevent translation. Trace tables help find logic flaws by tracking variable values. Maintainability is improved by comments, meaningful identifiers, and indentation.
逻辑错误导致输出不正确但程序仍运行；语法错误阻止翻译。跟踪表通过追踪变量值帮助发现逻辑缺陷。通过注释、有意义的标识符和缩进来提高可维护性。
11. Boolean Logic | 布尔逻辑
Logic gates are the building blocks of digital circuits: AND, OR, NOT, NAND, NOR, XOR. Truth tables show all possible input combinations and corresponding outputs. Boolean expressions can be simplified using laws like De Morgan’s: NOT (A AND B) = NOT A OR NOT B, and NOT (A OR B) = NOT A AND NOT B.
逻辑门是数字电路的基本构件：AND、OR、NOT、NAND、NOR、XOR。真值表展示所有可能的输入组合及对应的输出。布尔表达式可以利用定律进行化简，例如德摩根定律：NOT (A AND B) = NOT A OR NOT B，以及 NOT (A OR B) = NOT A AND NOT B。
Logic circuits can be drawn from expressions and vice versa. Combining gates produces more complex operations. Understanding how to construct a truth table for a given circuit is essential.
可以根据表达式绘制逻辑电路，反之亦然。组合门可以产生更复杂的操作。理解如何为给定电路构建真值表是必不可少的。
12. Integrated Development Environment (IDE) | 集成开发环境 (IDE)
An IDE provides tools to aid programming: code editor (with syntax highlighting), error diagnostics (underlines errors), run-time environment (executes code), debugger (step through, breakpoints, watch variables), and translators. Know the difference between an IDE and a simple text editor.
IDE 提供辅助编程的工具：代码编辑器（带语法高亮）、错误诊断（下划线标出错误）、运行时环境（执行代码）、调试器（单步执行、断点、监视变量）以及翻译器。了解 IDE 与简单文本编辑器的区别。
Version control (e.g., Git) tracks changes and allows collaboration. Not always part of an IDE but often integrated.
版本控制（如 Git）可跟踪更改并支持协作。不一定总是 IDE 的一部分，但常被集成。
Published by TutorHao | Computer Science Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
屏轩国际教育cambridge primary/secondary checkpoint, cat4, ukiset,ukcat,igcse,alevel,PAT,STEP,MAT, ibdp,ap,ssat,sat,sat2课程辅导，国外大学本科硕士研究生博士课程论文辅导Cancel reply