Year 12 CCEA Computer Science: Core Concepts Review | CCEA 12年级计算机科学：核心知识点梳理

📚 Year 12 CCEA Computer Science: Core Concepts Review | CCEA 12年级计算机科学：核心知识点梳理

As a Year 12 student following the CCEA specification, building a solid foundation across all core topics is essential for success in both AS examinations and future studies. This article reviews the key knowledge areas you need to master, from data representation and computer architecture to programming, databases, and ethical issues. Each section provides a concise explanation to help you consolidate your understanding and prepare effectively.

作为学习 CCEA 课程大纲的 12 年级学生，在所有核心主题上打下扎实基础对于在 AS 考试和未来学习中取得成功至关重要。本文回顾了你需要掌握的关键知识领域，从数据表示和计算机体系结构到编程、数据库以及伦理问题。每个部分都提供了简洁的解释，帮助你巩固理解并有效备考。

1. Data Representation | 数据表示

All data inside a computer is stored and processed in binary (base‑2). A single binary digit is called a bit; eight bits form a byte. Binary numbers use only 0 and 1. For example, the binary number 1010₂ represents the decimal value 10.

计算机内部的所有数据都以二进制（基数为 2）形式存储和处理。一个二进制数字称为一个比特；八个比特组成一个字节。二进制数仅使用 0 和 1。例如，二进制数 1010₂ 表示十进制值 10。

Hexadecimal (base‑16) is often used as a shorthand for binary because one hex digit corresponds to exactly four bits. Hex digits range from 0–9 and A–F. Converting between binary and hexadecimal is straightforward: group bits into nibbles of four. For instance, 1101 0110₂ becomes D6₁₆.

十六进制（基数为 16）经常用作二进制的简写，因为一个十六进制数字正好对应四个二进制位。十六进制数字范围是 0–9 和 A–F。二进制与十六进制互相转换十分简单：将二进制位每四位一组进行分组。例如，1101 0110₂ 转换为 D6₁₆。

Characters are represented using standard codes such as ASCII (7‑bit, 128 characters) and Unicode (up to 32 bits, covering many languages). ASCII is sufficient for basic English text, while Unicode supports global character sets, including emojis.

字符使用标准编码表示，如 ASCII（7 位，128 个字符）和 Unicode（最高 32 位，涵盖多种语言）。ASCII 足以表示基本英文文本，而 Unicode 支持包括表情符号在内的全球字符集。

Images are stored as a grid of pixels. In a bitmap image, each pixel has a colour value; the colour depth (bits per pixel) determines the number of available colours. A higher resolution provides more detail but requires more storage. Sound is sampled at regular intervals; the sampling rate and bit depth affect the quality and file size of digital audio.

图像以像素网格的形式存储。在位图图像中，每个像素有一个颜色值；颜色深度（每像素位数）决定了可用颜色的数量。更高的分辨率提供更多细节，但需要更多存储空间。声音按固定间隔采样；采样率和位深度影响数字音频的质量和文件大小。

2. Computer Architecture | 计算机体系结构

The Von Neumann architecture describes a system where both instructions and data are stored in the same memory unit. Key components include the CPU, main memory (RAM), input/output devices, and the system bus carrying data, addresses, and control signals.

冯·诺依曼体系结构描述了一种指令和数据存储在同一存储单元中的系统。关键部件包括 CPU、主存储器（RAM）、输入/输出设备以及传输数据、地址和控制信号的系统总线。

The CPU consists of the control unit (CU), which directs operations, and the arithmetic logic unit (ALU), which performs calculations and logical comparisons. Registers such as the program counter (PC), memory address register (MAR), memory data register (MDR), and accumulator (ACC) hold temporary data during the fetch‑decode‑execute cycle.

CPU 由控制单元（CU）和算术逻辑单元（ALU）组成，CU 指挥操作，ALU 执行计算和逻辑比较。寄存器如程序计数器（PC）、存储器地址寄存器（MAR）、存储器数据寄存器（MDR）和累加器（ACC）在取指－解码－执行周期中保存临时数据。

The fetch‑decode‑execute cycle is the fundamental process by which the CPU processes instructions. Fetch: the address in PC is copied to MAR, the instruction is read from memory into MDR, then into the current instruction register (CIR). PC is incremented. Decode: the CU interprets the instruction. Execute: the ALU performs the required operation, involving other registers if necessary.

取指－解码－执行周期是 CPU 处理指令的基本过程。取指：PC 中的地址被复制到 MAR，指令从内存读入 MDR，再进入当前指令寄存器（CIR），PC 递增。解码：CU 解释指令。执行：ALU 执行所需的操作，必要时涉及其他寄存器。

Factors affecting CPU performance include clock speed (number of cycles per second), number of cores (allowing parallel processing), and cache memory (high‑speed access to frequently used data).

影响 CPU 性能的因素包括时钟速度（每秒周期数）、内核数量（允许并行处理）以及高速缓存（对常用数据的高速访问）。

3. Logic Gates and Boolean Algebra | 逻辑门与布尔代数

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