GCSE CIE Computer Science: End-of-Term Revision Guide | GCSE CIE 计算机：期末复习提纲

📚 GCSE CIE Computer Science: End-of-Term Revision Guide | GCSE CIE 计算机：期末复习提纲

Preparing for your GCSE CIE Computer Science exam can feel overwhelming, but a structured revision guide can help you focus on the key concepts. This article serves as a comprehensive end-of-term review covering all the essential topics from the syllabus, including data representation, hardware, software, networking, security, algorithms, and programming fundamentals. Use it to consolidate your knowledge and identify areas that need more practice.

准备GCSE CIE计算机科学考试可能让人感到不知所措，但一份结构清晰的复习提纲可以帮助你聚焦关键概念。本文是一份全面的期末复习指南，涵盖了教学大纲中的核心主题，包括数据表示、硬件、软件、网络、安全、算法和编程基础。用它来巩固知识，并找出需要更多练习的薄弱环节。

1. Data Representation | 数据表示

All data in a computer is represented using binary (base 2), which uses only the digits 0 and 1. To convert a decimal number to binary, you can repeatedly divide by 2 and note the remainders. For example, 157 in binary is 10011101.

计算机中的所有数据都使用二进制（基数为2）表示，仅使用数字0和1。要将十进制数转换为二进制，可以反复除以2并记录余数。例如，157的二进制是10011101。

Hexadecimal (base 16) uses digits 0–9 and letters A–F to represent groups of four binary bits, making long binary strings shorter and easier to read. Each hex digit corresponds directly to a nibble (4 bits), so 1010 1111 in binary becomes AF in hex.

十六进制（基数为16）使用数字0–9和字母A–F来表示四个二进制位的组，使长二进制字符串更短且更易读。每个十六进制数字直接对应一个半字节（4位），因此二进制1010 1111变成十六进制的AF。

File sizes are measured in bytes. Standard units include: 1 KB = 2¹⁰ bytes = 1024 bytes, 1 MB = 2²⁰ bytes, 1 GB = 2³⁰ bytes, and 1 TB = 2⁴⁰ bytes. When storing text, character sets like ASCII use 7 or 8 bits per character, while Unicode can use up to 16 or 32 bits to represent symbols from many languages.

文件大小以字节为单位。标准单位包括：1 KB = 2¹⁰字节 = 1024字节，1 MB = 2²⁰字节，1 GB = 2³⁰字节，1 TB = 2⁴⁰字节。存储文本时，像ASCII这样的字符集每个字符使用7或8位，而Unicode可以使用多达16或32位来表示多种语言的符号。

Images are stored as a bitmap grid of pixels. The colour of each pixel is encoded as a binary number; higher colour depth (e.g., 24 bits) allows more colours. Resolution is the number of pixels per inch (PPI) or the total pixels in width × height. Increasing either colour depth or resolution improves image quality but increases file size.

图像存储为像素的位图网格。每个像素的颜色编码为二进制数；更高的颜色深度（例如24位）允许更多颜色。分辨率是每英寸像素数（PPI）或宽度×高度的总像素数。增加颜色深度或分辨率可提高图像质量，但会增大文件大小。

2. Data Transmission | 数据传输

Data can be transmitted serially (one bit at a time over a single wire) or in parallel (multiple bits simultaneously over several wires). Serial transmission is better over long distances because it avoids skew; parallel is faster over short distances but suffers from crosstalk and clock skew.

数据可以串行传输（一次一位通过单根线）或并行传输（通过多根线同时传输多位）。串行传输更适合长距离，因为它避免了偏斜；短距离内并行速度更快，但存在串扰和时钟偏斜问题。

Transmission can be simplex (one-way, like a keyboard to CPU), half-duplex (two-way but only one direction at a time, like a walkie-talkie), or full-duplex (simultaneous two-way, like a telephone).

传输可以是单工（单向，如键盘到CPU）、半双工（双向但一次只能一个方向，如对讲机）或全双工（同时双向，如电话）。

Error detection methods include parity bits, checksums, and echo

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