Year 12 CAIE Computer Science: Core Knowledge Points | Year 12 CAIE 计算机：核心知识点梳理

📚 Year 12 CAIE Computer Science: Core Knowledge Points | Year 12 CAIE 计算机：核心知识点梳理

The CAIE AS Computer Science syllabus (9618) covers a wide range of foundational topics that bridge hardware, software, theory, and programming. This article provides a structured overview of the core knowledge points that every Year 12 student should master, from data representation to algorithm design.

CAIE AS 计算机科学（9618）课程涵盖硬件、软件、理论与编程等广泛的基础知识。本文系统梳理 Year 12 学生必须掌握的核心知识点，从数据表示到算法设计逐一说明。

1. Data Representation | 数据表示

Computers process data in binary form, using bits (0 and 1). A group of 8 bits forms a byte, which can represent integers, text, images, or sound.

计算机以二进制形式处理数据，使用比特（0 和 1）。8 个比特组成一个字节，可以表示整数、文本、图像或声音。

Denary (base‑10) numbers are converted to binary through repeated division by 2. Hexadecimal (base‑16) uses digits 0‑9 and A‑F, providing a compact representation of binary values; each hex digit corresponds to 4 bits.

十进制数通过连续除以 2 转换为二进制。十六进制采用 0‑9 和 A‑F，提供紧凑的二进制表示法；每个十六进制位对应 4 个比特。

In integer representation, unsigned integers use all bits for magnitude, while signed integers employ two’s complement. In two’s complement, the most significant bit is negative. For an n‑bit number, the range is −2ⁿ⁻¹ to 2ⁿ⁻¹−1.

在整数表示中，无符号整数用全部位表示数值，有符号整数采用补码。补码中最左位为负权。对于 n 位数字，范围是 −2ⁿ⁻¹ 到 2ⁿ⁻¹−1。

Character data uses character sets: ASCII encodes 128 characters using 7 bits; extended ASCII uses 8 bits for 256 characters. Unicode uses up to 4 bytes per character, supporting global scripts and emojis.

字符数据使用字符集：ASCII 用 7 位编码 128 个字符；扩展 ASCII 用 8 位编码 256 个字符。Unicode 每个字符最多 4 字节，支持全球文字与表情符号。

Images are stored as bitmaps: each pixel’s colour is represented by a binary code. The calculation of image file size is:

Image size (bits) = width × height × colour depth

Colour depth (e.g. 24‑bit for true colour) determines the number of colours per pixel.

图像以位图存储：每个像素的颜色用二进制编码表示。图像文件大小计算公式：

图像大小（比特）= 宽度 × 高度 × 色深

色深（如真彩色 24 位）决定了每像素的颜色数量。

Sound is digitised by sampling the analogue signal at regular intervals. The file size for uncompressed audio is:

Sound size (bits) = sampling rate × bit depth × duration × number of channels

声音通过定期采样模拟信号实现数字化。未压缩音频文件大小计算公式：

声音大小（比特）= 采样率 × 位深 × 时长 × 声道数

2. Communication and Internet Technologies | 通信与互联网技术

Networks can be classified by scale: LAN (Local Area Network) covers a small area, WAN (Wide Area Network) spans large geographical distances. The Internet is a global WAN using the TCP/IP protocol suite.

网络可按规模分类：局域网覆盖小范围，广域网跨越大地理距离。互联网是使用 TCP/IP 协议簇的全球广域网。

Packet switching breaks data into packets, each carrying source/destination IP addresses and sequence numbers. Routers direct packets independently, reassembling them at the destination.

分组交换将数据分割成数据包，每个包携带源/目的 IP 地址和序号。路由器独立转发数据包，在目的地重新

Published by TutorHao | Year 12 Computer Science Revision Series | aleveler.com

更多咨询请联系16621398022（同微信）