📚 Year 11 WJEC Computer Science: Core Essentials Summary | Year 11 WJEC 计算机：核心知识点梳理
This article summarises the core knowledge areas for Year 11 students following the WJEC GCSE Computer Science specification. It provides a concise yet comprehensive review of key concepts, from data representation to programming techniques, to support your revision and examination preparation.
本文为遵循 WJEC GCSE 计算机科学大纲的 Year 11 学生梳理核心知识领域。它提供了从数据表示到编程技术等关键概念的简明而全面的回顾，以支持你的复习和考试准备。
1. Data Representation | 数据表示
All data in a computer is stored and processed in binary form (base-2), using only the digits 0 and 1. A single binary digit is called a bit; 8 bits make a byte. Larger units include kilobyte (KB), megabyte (MB), gigabyte (GB), and terabyte (TB).
计算机中的所有数据都以二进制形式（基数为2）存储和处理，只使用数字0和1。单个二进制数字称为一个比特 (bit)；8个比特组成一个字节 (byte)。更大的单位包括千字节 (KB)、兆字节 (MB)、吉字节 (GB) 和太字节 (TB)。
₀. Decimal to binary conversion uses successive division by 2, reading remainders upwards.
要将二进制数转换为十进制，将出现1的位权（2的幂）相加。例如，1011₂ = 1×8 + 0×4 + 1×2 + 1×1 = 11₁₀。十进制转二进制使用连续除以2取余，并从下往上读余数。
One hex digit represents four binary digits (a nibble), making it a compact way to represent long binary strings. Conversion between hex and binary involves grouping bits in nibbles.
十六进制 (base-16) 使用数字 0-9 和字母 A-F（A=10, ..., F=15）。一个十六进制数字代表四个二进制位（一个半字节），这使其成为表示长二进制串的紧凑方式。十六进制与二进制之间的转换涉及按半字节分组。
Characters are represented using binary codes such as ASCII and Unicode. Standard ASCII uses 7 bits to represent 128 characters, while Extended ASCII uses 8 bits. Unicode uses up to 32 bits to encode characters from all major writing systems, ensuring global compatibility.
字符使用二进制编码表示，如 ASCII 和 Unicode。标准 ASCII 使用7位表示128个字符，扩展 ASCII 使用8位。Unicode 使用最多32位来编码所有主要书写系统的字符，确保全球兼容性。
Images are stored as a grid of pixels. Bitmap images record the colour value of each pixel. Colour depth (bits per pixel) determines the number of available colours; for instance, 24-bit colour allows over 16 million colours. Resolution is the number of pixels in the image, and higher resolution means more detail but larger file size.
图像存储为像素网格。位图图像记录每个像素的颜色值。颜色深度（每像素位数）决定可用的颜色数量；例如，24位真彩色可允许超过1600万种颜色。分辨率是图像中的像素数量，更高的分辨率意味着更多细节但文件
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