📚 8C Unit 5: Data Representation – Binary, Text, Images and Sound | 8C 第5单元：数据表示——二进制、文本、图像与声音
In 8C Unit 5, students explore how all forms of data are represented inside a computer system. From numbers and text to images and sound, everything is ultimately stored as patterns of binary digits. This unit builds the essential knowledge needed for understanding how digital devices store, process and transmit information.
在八年级C单元第五课中，学生将探索计算机系统内部如何表示各种形式的数据。从数字、文本到图像和声音，所有信息最终都以二进制数字的模式存储。本单元为理解数字设备如何存储、处理和传输信息打下必要基础。
1. Why Computers Use Binary | 为什么计算机使用二进制
All digital computers use binary because electronic circuits can only reliably represent two states: on or off. These states are written as 1 and 0, and they map naturally to voltage levels in transistors and memory cells.
所有数字计算机都使用二进制，因为电子电路只能可靠地表示两种状态：开或关。这些状态写作 1 和 0，它们自然地对应晶体管和存储单元中的电压电平。
A single binary digit is called a bit. The word bit comes from 'binary digit'. Bits can be grouped into larger units such as nibbles and bytes.
一个二进制数字称为一个比特（bit）。bit 一词来自 'binary digit'。比特可以组合成更大的单位，例如半字节和字节。
- 0 = off, false, low voltage | 0 = 关、假、低电压
- 1 = on, true, high voltage | 1 = 开、真、高电压
Because binary uses only two symbols, it is very reliable in noisy electronic environments. A small change in voltage is less likely to make a 0 look like a 1 when there are only two widely separated states.
由于二进制只使用两个符号，它在有噪声的电子环境中非常可靠。当只有两个相距很远的状态时，电压的微小变化不太可能使 0 看起来像 1。
2. Bits, Nibbles, Bytes and Storage Units | 位、半字节、字节与存储单位
A bit is the smallest unit of data. Four bits make a nibble, and eight bits make one byte. A byte can represent 256 different values, from 00000000₂ to 11111111₂.
位是最小的数据单位。四个位组成一个半字节，八个位组成一个字节。一个字节可以表示 256 种不同的值，从 00000000₂ 到 11111111₂。
1 byte = 8 bits
1 nibble = 4 bits
Larger storage units are based on powers of two but are often approximated in decimal for marketing. You need to know the exact binary multiples for IGCSE and GCSE assessment.
更大的存储单位以二的幂为基础，但在市场上通常用十进制近似。你需要知道IGCSE和GCSE评估中的精确二进制倍数。
| Unit | 单位 | Exact bytes | 精确字节数 | Common approximation | 常见近似 |
|---|---|---|
| 1 KiB | 2¹⁰ = 1024 bytes | 1 thousand bytes |
| 1 MiB | 2²⁰ = 1,048,576 bytes | 1 million bytes |
| 1 GiB | 2³⁰ = 1,073,741,824 bytes | 1 billion bytes |
Always write bit with a lowercase b and byte with an uppercase B. This difference is important in file size and data transfer rate questions.
始终用小写 b 表示位，用大写 B 表示字节。这个区别在文件大小和数据传输速率问题中非常重要。
3. Binary to Denary Conversion | 二进制转十进制
Denary, also called decimal, uses base 10 with digits 0 to 9. Binary uses base 2 with digits 0 and 1. To convert binary to denary, write the binary number under a set of place values starting from 1 on the right and
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